Using Stereo Analyst For Arcgis: Geographic Imaging by Leica Geosystems Gis & Mapping

Using Stereo Analyst for ArcGIS
Geographic Imaging by Leica Geosystems GIS & Mapping

Kris Curry
Using Stereo Analyst for ArcGIS
Copyright © 2003 Leica Geosystems GIS & Mapping, LLC

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and other international copyright treaties and conventions. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying and recording, or by any information storage or retrieval system, as expressly permitted in writing by Leica Geosystems GIS & Mapping, LLC. All
requests should be sent to Attention: Manager of Technical Documentation, Leica Geosystems GIS & Mapping, LLC, 2801 Buford Highway NE, Suite 400, Atlanta, GA,
30329-2137, USA.
The information contained in this document is subject to change without notice.
CONTRIBUTORS
Contributors to this book and On-line Help for Stereo Analyst for ArcGIS include: Sam Megenta, Frank Obusek, Jay Pongonis, Russ Pouncey, Mladen Stojic′, Ryan Strynatka,
and Lori Zastrow of Leica Geosystems GIS & Mapping, LLC.
U.S. GOVERNMENT RESTRICTED/LIMITED RIGHTS
Any software, documentation, and/or data delivered hereunder is subject to the terms of the License Agreement. In no event shall the U.S. Government acquire greater than
RESTRICTED/LIMITED RIGHTS. At minimum, use, duplication, or disclosure by the U.S. Government is subject to restrictions set forth in FAR §52.227-14 Alternates I,
II, and III (JUN 1987); FAR §52.227-19 (JUN 1987), and/or FAR §12.211/12.212 (Commercial Technical Data/Computer Software); and DFARS §252.227-7015 (NOV
1995) (Technical Data) and/or DFARS §227.7202 (Computer Software), as applicable. Contractor/Manufacturer is Leica Geosystems GIS & Mapping, LLC, 2801 Buford
Highway NE, Suite 400, Atlanta, GA, 30329-2137, USA.
ERDAS, ERDAS IMAGINE, IMAGINE OrthoBASE, and Stereo Analyst for ArcGIS are registered trademarks. IMAGINE OrthoBASE Pro and IMAGINE VirtualGIS are
trademarks.
SOCET SET is a registered trademark of BAE Systems Mission Solutions.
ERDAS® is a wholly owned subsidiary of Leica Geosystems GIS & Mapping, LLC.
Other companies and products mentioned herein are trademarks or registered trademarks of their respective trademark owners.
Contents
Contents Contents iii

Foreword vii
Getting started
1 Introducing Stereo Analyst for ArcGIS 3
What can you do with Stereo Analyst for ArcGIS? 4
Learning about Stereo Analyst for ArcGIS 11
2 Quick-start tutorial 13
Exercise 1: Starting Stereo Analyst for ArcGIS 14
Exercise 2: Adding oriented images 18
Exercise 3: Converting features—3D to 2D and 2D to 3D 31
Exercise 4: Collecting features in 3D 42
Exercise 5: Editing existing features 58
What’s next? 66
Working in stereo
3 Working with oriented images 69
Creating oriented images 70
Using IMAGINE OrthoBASE to create oriented images 76
Using Image Analysis for ArcGIS to create oriented images 78
Importing IMAGINE OrthoBASE block files 79
Importing SOCET SET ® files 82
What’s next? 85
4 Working with 3D data 87

Comparing 3D features and 3D models 88
III
Using Virtual 2D To 3D 89
Setting Virtual 2D To 3D options 90
Using the 2D to 3D converter 93
Using advanced conversion options 95
Using the 3D to 2D converter 103
What’s next? 104
5 Visualizing in stereo 105

Introducing stereo visualization 106
Using Stereo Window views 108
Learning about the Stereo Analyst toolbar 111
Learning about the Stereo View toolbar 112
Learning about the Stereo Enhancement toolbar 113
Using Stereo Analyst for ArcGIS with ArcMap 119
Setting stereo display options 124
What’s next? 129
6 Applying the 3D Floating Cursor 131

Using the 3D Floating Cursor 132
Adjusting the position of the 3D Floating Cursor 133
Selecting 3D Floating Cursor options 136
Using the Terrain Following Mode 138
Applying other Terrain Following Mode options 141
Checking accuracy of 3D information 146
Using the 3D Floating Cursor 147
Using keyboard shortcuts 149
What’s next? 151
IV USING STEREO ANALYST FOR ARCGIS

Working with features
7 Capturing GIS data 155
Collecting features in different modes 156
Using 3D Snap 162
Using Squaring 167
Using the Monotonic Mode 172
Using digitizing devices 173
What’s next? 176
Appendices
A Capturing data using imagery 179
Collecting data for a GIS 180
Preparing imagery for a GIS 182
Using traditional approaches 186
Applying geographic imaging 188
Moving from imagery to a 3D GIS 190
Identifying workflow 191
Getting 3D GIS data from imagery 195
B Understanding stereo viewing 199

Learning principles of stereo viewing 200
Understanding stereo models and parallax 202
Understanding scaling, translation, and rotation 205
Understanding the epipolar line 206
C Applying photogrammetry 209

Learning principles of photogrammetry 210
Acquiring images and data 214
CONTENTS V
Scanning aerial photography 216
Understanding interior orientation 223
Understanding exterior orientation 226
Using digital mapping solutions 229
Glossary 233
References 249
Index 251
VI USING STEREO ANALYST FOR ARCGIS

Foreword
An image of the earth’s surface is a wealth of information. Images capture a

permanent record of buildings, roads, rivers, trees, schools, mountains, and other
features located on the earth’s surface. But images go beyond simply recording
features. Images also record relationships and processes as they occur in the real
world. Images are snapshots of geography, but they are also snapshots of reality.
Images chronicle our earth and everything associated with it; they record a specific
place at a specific point in time. They are snapshots of our changing cities, rivers,
and mountains. Images are snapshots of life on earth.
The data in a GIS needs to reflect reality, and snapshots of reality need to be
incorporated and accurately transformed into instantaneously ready, easy-to-use
information. From snapshots to digital reality, images are pivotal in creating and
maintaining the information infrastructure used by today’s society. Today’s
geographic information systems have been carefully created with features,
attributed behavior, analyzed relationships, and modeled processes.
There are five essential questions that any GIS needs to answer: Where, What,
When, Why, and How. Uncovering Why, When, and How are all done within the
GIS; images allow you to extract the Where and What. Precisely where is that
building? What is that parcel of land used for? What type of tree is that? The new
extensions developed by Leica Geosystems GIS & Mapping, LLC use imagery to
allow you to accurately address the questions Where and What, so you can then
derive answers for the other three.
But our earth is changing! Urban growth, suburban sprawl, industrial usage and
natural phenomena continually alter our geography. As our geography changes, so
VII
does the information we need to understand it. Because an
image is a permanent record of features, behavior,
relationships, and processes captured at a specific moment in
time, using a series of images of the same area taken over
time allows you to more accurately model and analyze the
relationships and processes that are important to our earth.
The new extensions by Leica Geosystems are technological

breakthroughs which allow you to transform a snapshot of
geography into information that digitally represents reality in
the context of a GIS. Image Analysis™ for ArcGIS and
Stereo Analyst® for ArcGIS are tools built on top of a GIS to
maintain that GIS with up-to-date information. The
extensions provided by Leica Geosystems reliably transform
imagery directly into your GIS for analyzing, mapping,
visualizing, and understanding our world.
On behalf of the Image Analysis for ArcGIS and Stereo

Analyst for ArcGIS product teams, I wish you all the best in
working with these new products and hope you are
successful in your GIS and mapping endeavors.
Sincerely,
Mladen Stojic′
Product Manager
Leica Geosystems GIS & Mapping, LLC
VIII USING STEREO ANALYST FOR ARCGIS

Getting started
Section 1
2 USING STEREO ANALYST FOR ARCGIS
Introducing Stereo Analyst
1Introducing Stereo Analyst for ArcGIS
for ArcGIS 1
IN THIS CHAPTER Welcome to Stereo Analyst® for ArcGIS, the stereo feature collection extension
for ArcGIS™. Stereo Analyst for ArcGIS adds unique image viewing and feature
• What can you do with Stereo collection capabilities to your ArcGIS desktop and uses the existing feature editing
Analyst for ArcGIS?
and collection capabilities available in ArcMap™.
• Learning about Stereo Analyst for
ArcGIS With Stereo Analyst for ArcGIS, you can access image and feature datasets
directly from a geodatabase. You can also collect new feature datasets accurately
using oriented imagery as a reference backdrop. If you already have some feature
datasets, you can edit them reliably in stereo using ArcMap editing tools.
Using a three-dimensional (3D) digital view of the earth’s surface created with
oriented imagery, you can collect true, real-world 3D geographic information. By
analyzing oriented imagery with Stereo Analyst for ArcGIS, even more
information can be extracted from imagery. Geographic information system (GIS)
professionals are no longer limited to collecting two-dimensional (2D) GIS data.
This data can be used to build relationships into a GIS. Also, you can collect mass
points with X, Y, and Z coordinates for the creation of a digital terrain model
(DTM).
3
What can you do with Stereo Analyst for ArcGIS?
Stereo Analyst for ArcGIS supplies you with the tools you’ll need The 3D Floating Cursor has a 3D coordinate associated with it. As
to update and create accurate and reliable feature datasets for use in a result, wherever you move the 3D Floating Cursor, a new 3D
a GIS. You can use Stereo Analyst for ArcGIS in conjunction with coordinate is displayed. To ensure the accuracy of GIS feature data
two applications you’re probably already familiar with, collected in Stereo Analyst for ArcGIS, the 3D Floating Cursor is
ArcCatalog™ and ArcMap. These applications allow you to easily positioned so that it rests on the feature being collected. When the
manage all of your raster and feature datasets used in Stereo 3D Floating Cursor rests on the ground or feature of interest, a new
Analyst for ArcGIS. 3D coordinate is computed and then the feature can be accurately
collected. (See “Adjusting the position of the 3D Floating Cursor”
Creati ng your wo rld in 3 D on page 133 for information about placing the 3D Floating Cursor
on the feature of interest.)
Stereo Analyst for ArcGIS creates an accurate 3D digital
representation of the earth’s surface and geography using imagery.
Using GIS-ready images, the contents of an image are recreated and
represented in a 3D view. This 3D digital representation of the earth
is displayed on the screen.
By adding feature datasets to ArcMap, the features are

superimposed on top of the 3D digital representation. Using the 3D
digital picture of the earth’s surface as a reference source, the
feature data is updated to “fit” the earth and its associated
geography. Once updates to the feature data have been made, the
information can be saved or checked back into the geodatabase.
Ga i n i n g m o r e a c c u r a cy i n G IS d a t a
collectio n
During the collection of accurate GIS feature data using Stereo

Analyst for ArcGIS, a unique 3D Floating Cursor “floats” within
the 3D digital depiction of the earth’s surface as displayed on the
screen. This 3D Floating Cursor is also referred to as a ground This IMAGINE VirtualGIS™ scene shows a 3D world.
point. (See chapter 6, “Applying the 3D Floating Cursor” on
page 131 for more information about the 3D Floating Cursor.) Automated techniques have been developed in Stereo Analyst for
ArcGIS to place the 3D Floating Cursor on the geographic feature
The 3D Floating Cursor floats until you place it on the feature of of interest. This feature, Terrain Following Mode, is used to
interest. You can move the 3D Floating Cursor anywhere within facilitate accurate feature collection and editing. (See “Using the
this 3D digital representation. The 3D Floating Cursor can float Terrain Following Mode” on page 138 for information about the
above, below, or rest on the earth’s surface or feature of interest. Terrain Following Cursor.)
Acc e s s i n g i m ag e a n d fea tu r e d a t a
Stereo Analyst for ArcGIS supports all of the raster and feature
dataset formats currently supported by ArcMap. For example,
raster format support includes: ArcSDE rasters, ERDAS® 7.5
LAN, ERDAS IMAGINE® (.img), ERDAS Raw, ESRI Image
Catalogs, GRID, GRID Stack, and Windows BMP.
New feature datasets can be created using ArcCatalog. In addition

to this, existing CAD formats such as DGN, DWG, and DXF are
also supported by ArcMap for use in Stereo Analyst for ArcGIS.
Personal and multiuser geodatabases created using ArcCatalog can
be maintained to include up-to-date feature data.
Editing fe atures
Using the editing tools you’re already familiar with in ArcMap, you
can edit features that you create and features that you have imported
in Stereo Analyst for ArcGIS. Simply display the Editor toolbar and
choose the edit tools you need to modify feature datasets.
Attribution information is updated accordingly.
You can easily update feature vertices to greater accuracy.
INTRODUCING STEREO ANALYST FOR ARCGIS 5

Up datin g feature d ata
Using Stereo Analyst for ArcGIS, feature datasets can be updated to reflect the geography on the earth’s surface as recorded by an image.
Highly accurate oriented images are used as a reference source for updating feature datasets. (See “Creating oriented images” on page 70
for information about oriented imagery.) Using Stereo Analyst for ArcGIS, updates to feature datasets are not only in 3D, but are also
accurate 2D (planimetric) updates.
In the picture on the left, before editing, this road is not positioned correctly. In the picture on the right, the road clearly follows the feature.

Co llecting features
Using the Editor tools you’re probably already familiar with in ArcMap, Stereo Analyst for ArcGIS allows you to collect new features. To
ensure the accuracy of the GIS data collected using Stereo Analyst for ArcGIS, the 3D Floating Cursor must rest on the feature of interest
being collected.
The picture on the left shows features collected in ArcMap; the picture on the right shows the same features collected in the Stereo Window.

Co llecting points for the crea tion of elevati on mo dels
Stereo Analyst for ArcGIS allows you to collect elevation information directly from oriented imagery without requiring a digital elevation
model (DEM). Since an accurate 3D digital representation of the earth’s surface is created on the screen using imagery, accurate 3D point
feature datasets can be collected. With mass point data, you can easily create DEMs using Spatial Analyst™, 3D Analyst™, or ERDAS
IMAGINE.
The picture on the left shows mass points collected in Stereo Analyst for ArcGIS. The DTM on the right was generated from the mass points collected in Stereo
Analyst for ArcGIS. ERDAS IMAGINE was used to create the DTM.

U s i n g A rc M a p a n d S t e r e o A n a ly s t for A rc G I S
Stereo Analyst for ArcGIS adds three toolbars and several new features to ArcMap when it is installed. The three toolbars include the Stereo
Analyst toolbar, the Stereo View toolbar, and the Stereo Enhancement toolbar. The Stereo Analyst toolbar is the main toolbar and provides
access to importers and exporters as well as preference settings. The Stereo View toolbar provides tools to manipulate data in the Stereo
Window. The Stereo Enhancement toolbar controls the operation of image enhancement in the Stereo Window.
The Stereo Window, which is the middle window in the above picture, can be docked inside the ArcMap application, or can be undocked.

Using these tools, you can perform actions such as selecting an
image pair from a graphic display and modifying the behavior of
the Stereo Window.
You also have the option of embedding the Stereo Window within
the ArcMap window. The Stereo Window is an extension to the
ArcMap window and is used as the workspace for updating and
collecting new feature datasets. Work conducted in the Stereo
Window is simultaneously reflected in the ArcMap data view.
Stereo Analyst for ArcGIS adds additional functionality to

ArcMap. This includes a new Stereo Analyst for ArcGIS footprint
layer and 3D snap options for feature editing. (See “Using Stereo
Analyst for ArcGIS with ArcMap” on page 119 for information on
the footprint layer and “Using 3D Snap” on page 162 for
information about the 3D snap options.)
W h a t c a n you d o w i t h A rc C a t a l o g ?
As you know, ArcCatalog is an application with which you can

create and manage GIS data. ArcCatalog’s ability to create layers is
also applicable to Stereo Analyst for ArcGIS functionality. Use
ArcCatalog to manage the feature datasets that often accompany a
GIS mapping project.

Learning about Stereo Analyst for ArcGIS
If you are just learning about geographic information systems Contacting Leica Geosystems GIS &
(GISs), you may want to read the books about ArcCatalog and Mappi ng
ArcMap: Using ArcCatalog and Using ArcMap. Knowing about
these applications makes your use of Stereo Analyst for ArcGIS If you need to contact Leica Geosystems for technical support, see
much easier. the product registration and support card you received with Stereo
Analyst for ArcGIS. You can also contact Customer Support at
If you’re ready to learn about how Stereo Analyst for ArcGIS 1-404-248-9777. You may also visit Leica Geosystems on the Web
works, refer to chapter 2, “Quick-start tutorial”. In chapter 2 you’ll at <www.gis.leica-geosystems.com>.
learn how to change image pairs’ display using enhancement tools,
navigate in a 3D digital space in the Stereo Window, create three- Contac ting ESRI
dimensional (3D) feature datasets from 2D feature datasets and vice
versa, collect feature datasets, and edit feature datasets. The tutorial If you need to contact ESRI for technical support refer to “Getting
is written so that you can do the exercises using your computer and technical support” in the On-line Help system’s “Getting more
the example data supplied with Stereo Analyst for ArcGIS. If you’d help” section. The telephone number for Technical Support is
rather, you can simply read the tutorial to learn about the 1-909-793-3774. You may also visit ESRI on the Web at
functionality of Stereo Analyst for ArcGIS. <www.esri.com>.
Find ing answ ers to qu estio ns Lei ca Geosy stems GI S & Mapp ing
Ed ucati on Solutions
This book describes the typical workflow involved in creating and
updating GIS data for mapping projects. The chapters are set up so Leica Geosystems offers instructor-based training about Stereo
that you first learn the theory behind certain applications, then you Analyst for ArcGIS. For more information, go to the Web site
are introduced to the typical workflow you’d apply to get the results <www.gis.leica-geosystems.com> and follow the Training link to
you want. A glossary is provided to help you understand any terms Training Centers, Course Schedules, and Course Registration.
you haven’t seen before.
ESRI educ atio n sol utio ns
Getti ng he lp on your compu ter
ESRI provides educational opportunities related to GISs, GIS
Useful information can be found in the On-line Help system. applications, and technology. You can choose among instructor-led
Consult it to learn how to use Stereo Analyst for ArcGIS. To learn courses, Web-based courses, and self-study workbooks to find
how to use Help, see the Using ArcMap book. educational solutions that fit your learning style and pocketbook.
For more information, visit the Web site <www.esri.com/
education>.

2 Quick-start tutorial
2
IN THIS CHAPTER This chapter provides the hands-on training you’ll need to use Stereo Analyst for
ArcGIS to complete your own mapping projects.
• Exercise 1: Starting Stereo
Analyst for ArcGIS In “Exercise 1: Starting Stereo Analyst for ArcGIS” on page 14, you’ll learn how
to set up the work environment to run Stereo Analyst for ArcGIS.
• Exercise 2: Adding oriented
images In “Exercise 2: Adding oriented images” on page 18, you’ll learn about populating
the Stereo Window with raster data and how to best examine the imagery.
• Exercise 3: Converting features—
3D to 2D and 2D to 3D
In “Exercise 3: Converting features—3D to 2D and 2D to 3D” on page 31, you’ll
learn about how to create a 2D feature dataset from a 3D feature dataset. You’ll
• Exercise 4: Collecting features in
3D also learn how to create a 3D feature dataset from a 2D dataset using an elevation
source.
• Exercise 5: Editing existing
features In “Exercise 4: Collecting features in 3D” on page 42, you’ll learn how to use
editing tools to collect 3D feature data in the Stereo Window.
Finally, in “Exercise 5: Editing existing features” on page 58, you’ll learn how to
update existing features.
To start this tutorial, you must have Stereo Analyst for ArcGIS and ArcGIS
installed on your system. Also, you must have access to the tutorial data that
accompanies the installation CD. Ask your administrator for the location of the
tutorial data if you can’t find it in the default installation directory.
13
Exercise 1: Starting Stereo Analyst for ArcGIS
In the following exercises, we’ve assumed that you are using
a single-monitor workstation that is configured for use with
ArcMap and Stereo Analyst for ArcGIS.
If you have a dual-monitor configuration, you may spread out
the applications so that the ArcMap application is displayed 1
on one monitor and the Stereo Window and the Stereo
Analyst for ArcGIS toolbars are displayed on the other
monitor. This type of setup is ideal for productive feature
collection. 2
In this scenario, the ArcMap display serves as the
cartographic station for verifying features that have been A dd i n g t h e S t e r e o A n a ly st for A rc G I S
collected or edited, and the Stereo Window display serves as ex tensi on
the main focus for collecting and editing feature datasets.
1. If the ArcMap dialog opens, keep the option to create a
In this exercise, you’ll learn how to start Stereo Analyst for new map, then click OK.
ArcGIS and display all of the toolbars associated with Stereo
Analyst for ArcGIS. You’ll be able to use the toolbars to gain
access to all of the key functionality in Stereo Analyst for
ArcGIS.
Preparing
This exercise assumes that you have already successfully
completed installing Stereo Analyst for ArcGIS on your
computer. If you haven’t installed Stereo Analyst for
ArcGIS, do so now.
S t a r t i n g A rc M a p
1. Click the Start button on your desktop, then point to
Programs, then point to ArcGIS. 1
2. Click ArcMap to start the application.
2. In the ArcMap window, click the Tools menu, then click
Extensions.

3
3. On the Extensions dialog, click the check box for Stereo

Analyst to add the extension to ArcMap. 4
Once the Stereo Analyst check box has been selected,

the extension is activated.
4. Click Close on the Extensions dialog.
Addin g to olbars
1. Click the View menu, then point to Toolbars, then click
Stereo Analyst to add that toolbar to the ArcMap
window.
QUICK-START TUTORIAL 15
With the Stereo View toolbar, you can enable many of
the special Stereo Analyst for ArcGIS modes, such as
the Terrain Following Mode and Fixed Cursor Mode.
Additionally, you can use the Continuous Zoom Mode
and the image Roam Tool to adjust the extent of the
image pair display in the Stereo Window.
Other tools allow the ability to synchronize the ArcMap
and Stereo Window displays, input coordinates to drive
to a specific location, reverse the left and right images,
1 and update the feature display.
With the Stereo Analyst toolbar, you can choose image

pairs to view, open the Stereo Window, import and
export data, and much more. 3. Click the View menu, then point to Toolbars, then click
Stereo Enhancement to add that toolbar to the ArcMap
window.
2. Click the View menu, then point to Toolbars, then click

Stereo View to add that toolbar to the ArcMap window.
With the Stereo Enhancement toolbar, you can change

the contrast and brightness display of both the individual
2

images that make up the image pair as well as whole
image pairs in the Stereo Window.
4. Arrange the toolbars in the ArcMap window so that you

can easily access each of them.
Cl osing the appl icati ons
If you plan to continue on to “Exercise 2: Adding oriented
images”, then proceed to “Adding image pairs” on page 18.
Otherwise, you may exit ArcMap, which also closes Stereo
Analyst for ArcGIS.
What’s next?
In “Exercise 2: Adding oriented images”, you’ll add oriented
images to ArcMap and learn how to use some of the Stereo
Analyst for ArcGIS tools in the Stereo Window.
Exercise 2: Adding oriented images
In this exercise, you’ll learn how to add multiple oriented 2. In the Add Data dialog, navigate to the folder called
images (rasters) to ArcMap and the Stereo Window. The \ArcTutor\StereoAnalyst\Images.
oriented images you’ll be using were created by importing 3. Shift-click to select the images named strip1_1.img and
data from the SOCET SET® digital photogrammetry strip2_2.img. This selects all of the raster images in the
software product. list.
4. Click Add to add the images to the ArcMap data view.
Using overlapping, GIS-ready images
In order to view or update existing features or collect new 2

features, at least two overlapping GIS-ready rasters must be
added to ArcMap. See chapter 3 “Working with oriented
images” on page 69 to learn more about GIS-ready images.
3
Preparing
If you’re continuing the tutorial from “Exercise 1: Starting
Stereo Analyst for ArcGIS”, you may proceed to the section
named “Adding image pairs” below.
4
If you’re starting this exercise from scratch, you should have
ArcMap running with an empty data view, and Stereo
Analyst for ArcGIS should also be loaded and running. You
should also have the three Stereo Analyst for ArcGIS The photographs you’re adding were recorded with a
toolbars displayed. Proceed to “Adding image pairs” below. specially-fitted camera used to capture photography
Adding imag e pai rs from aircraft. Then, they were digitally scanned. Each
pixel represents 0.16458 meters (approximately 16.5
1. Click the Add Data button to select the rasters to add to centimeters by 16.5 centimeters) on the earth’s surface.
ArcMap.

Creati ng pyramid layers
C r e a t i n g p y r a m id l a y e r s
A pyramid layer is a version of the original raster that has
been resampled at a lower resolution. A raster dataset Once pyramid layers have been created for a raster dataset, they
commonly has eight pyramid layers. Pyramid layers make do not need to be created again unless they are deleted. Pyramid
navigation and display of large raster datasets much faster at layers are contained in files with an .rrd extension and are
any resolution. Therefore, you should build pyramid layers typically located in the same directory as the rasters with which
for each of the raster images in this dataset. they are associated.
1. Click OK on the Create pyramids dialog to build
pyramid layers for the first raster image, strip1_1.img. 3. Click OK on the dialog alerting you about the absence
of spatial reference information.
3
1
You get this message if the images lack a projection, as
A progress meter displays to show the status of the in the case of these images.
pyramid layer generation.
2. Click OK on the next three Create pyramids dialogs to

generate pyramid layers for all of the images you’ll be
using in this exercise.
Once you’ve added the rasters, you can see that the data
view shows two overlapping strips of photography, and
each strip contains two overlapping photographs. The
aircraft that recorded the imagery flew south-east to
north-west, and as a result the images appear diagonal
within ArcMap.
Viewing overlapping areas
Two adjacent rasters that overlap are referred to as an image

pair. The overlapping portion of the two rasters is what is most
useful in the Stereo Window. It is this overlapping portion of
two raster images that is used to recreate the earth’s surface
digitally and in 3D within the Stereo Window.
Because the images are diagonal, but their bounding

boxes are squares, they have dark background values
that may be distracting as you view them in ArcMap.
Once the four raster images are added to ArcMap, they You’ll fix that next.
display with each raster footprint (red) and overlap area
(yellow) indicated by graphical borders. Changi ng pro per ti es
You can alter the properties of each image so that the
Changing footprint and overlap display background values are transparent in the data view. To make
the change, make a simple adjustment to the Layer Properties
By default, the display color for image footprints is red, and the for each raster image.
display color for overlap areas is yellow. If you would like to
In these example images, the background value is 0 (which
use different colors, you can change the defaults on the Stereo
you can determine using the Identify tool) and displays in
Analyst Options dialog.
black. If you set the 0 value to No Color, those areas appear
To access the options, on the Stereo Analyst toolbar click the transparent in the data view.
Stereo Analyst dropdown list, then select Options. On the 1. Right-click the title of the first image in the Table of
ArcMap Display tab, use the dropdown lists to access and apply
contents, then select Properties.
different colors for the Oriented image footprint color and the
Selected Image Pair highlight color. Then click OK to accept
the changes.

4. Click OK and the image redisplays in ArcMap with the
background value 0 set to display transparently.
5. Repeat step 1 through step 4 under “Changing
properties” for the remaining three images listed in the
Table of contents.
Now, only the raster images, their vector footprints, and
overlap boundaries display in ArcMap.
2. On the Symbology tab of the Layer Properties dialog,

click the check box for Display Background Value.
Make sure the value is set to 0 (zero).
3. Make sure that the Display Background Value as color
block is set to No Color.
C h a n g i n g t h e A rc M a p d i s p l ay
It is often helpful to have the orientation of the display in
ArcMap match that of the display in the Stereo Window. To
ensure that this is always the case within the same ArcMap
session, you can set an option on the Stereo Analyst Options
dialog.
1. On the Stereo Analyst toolbar, click the Stereo Analyst
dropdown list, then click Options.
2 4 3
3 2
2. Click the ArcMap Display tab of the Stereo Analyst

Options dialog.
3. Click the check box for Orient ArcMap document to
Image Pair when Image Pair changes.
4. Click OK to apply the orientation setting and close the

Stereo Analyst Options dialog.
The display of the images in ArcMap changes. You’ll
see how the change compliments the images’ display in
the Stereo Window in the section called “Working with
the Stereo Window” on page 24.

1
The yellow overlap graphic changes position to indicate

the new active area of overlap for the image pair
strip1_1.img/strip1_2.img.
The new image pair is the active image pair and is used
to recreate a 3D digital representation of the earth’s
surface in the Stereo Window.
Ch angin g th e imag e pair

One or more image pairs consisting of two overlapping raster
images may display in ArcMap. When you need to change
the geographic extent displayed within the Stereo Window,
you can easily select a different image pair in ArcMap.
You can change an active image pair whose overlap portion
is highlighted in yellow in two ways. Either use the Image
Pairs dropdown list or use the Image Pair Selection Tool (on
the Stereo Analyst toolbar) to choose the image pair you want
to work with.
1. On the Stereo Analyst toolbar, click the Image Pairs 2. Click the Image Pair Selection Tool to graphically select
dropdown list and select a different pair to make active, the original area of overlap—strip2_1.img/strip2_2.img.
strip1_1.img/strip1_2.img. The button appears recessed when it is active.
2 5
3. Move your cursor into the data view and position it over Workin g with the Ste reo Wind ow
the original area of overlap. Notice that the area
The Stereo Window is where the image pair displays to
becomes highlighted in yellow as you move your cursor
recreate a 3D digital representation of the specific area of
inside the overlap area.
interest as recorded in the oriented images. You’ll learn how
4. Click to select the overlap area of strip2_1.img/ to open it next.
strip2_2.img and make it the active image pair.
Using graphics cards
3
If your computer system doesn’t have a graphics card that
supports quad-buffered stereo, Stereo Analyst for ArcGIS uses
anaglyph rendering techniques to recreate and display the 3D
digital representation of the area of interest. In this case, you
need red/blue anaglyph glasses to view the image pairs in 3D.
See the Web site <http://support.erdas.com/specs/specs.html>

for a list of supported graphics cards.
1. On the Stereo Analyst toolbar, click the Stereo Window

button.
The ArcMap window contents adjust to include the

Stereo Window. The Stereo Window can be docked
5. To disable the Image Pair Selection Tool, click the
either inside or outside the ArcMap window.
ArcMap Select Elements button.

Initially, the Stereo Window opens in 3-Pane View: one
pane for the primary stereo scene, which displays the
active image pair; and one pane each for the left and
right oriented images of the image pair (the 2-Pane 2. On the Stereo View toolbar, click the Fixed Cursor
View). Mode button.
2. Undock the Stereo Window from the ArcMap display by
clicking on the window’s title bar and dragging it 2
outside the ArcMap display.
3. Resize the Stereo Window to your liking. The cursor
becomes a double-headed arrow at the extents of the
window indicating that you can click, hold, and drag the When Fixed Cursor Mode is active, the 3D Floating
window to a new size. Cursor maintains its position in the center of the Stereo
Window while the image pair moves “beneath” it.
Ad j u s ti n g t h e d i s p l ay
3. Click and hold on the Z thumb wheel located on the
1. Put on your stereo or anaglyph glasses. right-hand side of the Stereo Window, then move it
You’ll notice that the Stereo Window display is 3D. slightly up and/or down until the same features overlap
in both the right and left images. In the following
picture, the images have been adjusted so that the area 4. Click the 1-Pane View button located at the bottom of
around the 3D Floating Cursor, which is circled in red, the Stereo Window to remove the 2-Pane View from the
is set for optimal stereo viewing. Stereo Window configuration.
This enlarges the area of stereo display.
3
4
The cursor in the Stereo Window is called the 3D
Floating Cursor because it can float on, below, or above
a feature. 5. Click the Fixed Cursor Mode button again to exit that
mode.
By adjusting the Z thumb wheel, the height of the 3D
Floating Cursor is modified via the movement of the When you have exited Fixed Cursor Mode, the button
images of the image pair. You can see the elevation no longer appears recessed on the Stereo View toolbar.
change in the coordinates of the location of the 3D A dju s t ing t h e z o om rat i o
Floating Cursor, which are displayed in the lower-left
status bar located within the Stereo Window. 1. Click the Zoom to Data Extent button to see the entire
extent of the image pair displayed in the Stereo Window.
2. On the Stereo View toolbar, click the Zoom In By 2
1 button a number of times until you can comfortably see
features on the earth’s surface displayed in 3D within
the Stereo Window.
3. Click the Roam Tool button, then move your cursor
If you are viewing in anaglyph mode, the left image of (which appears as a hand) into the Stereo Window and
the image pair appears red for nonoverlap areas; the double-click to activate Auto Roam Mode.
right image appears blue for nonoverlap areas; and the
overlap area is grey.
3 2
If you are viewing in quad-buffered stereo, the entire
area appears grey, but you can see in 3D only in the
overlap area.
4. The hand changes into an arrow in Auto Roam Mode.
Move your mouse in any direction to adjust the image
pair’s position in the Stereo Window.
Adjusting bri ghtne ss an d con tra st
4 You can adjust the brightness and contrast of the image pair
displayed in the Stereo Window to suit your viewing and
feature collection needs.
By default, both images are adjusted together; however, you
can also adjust each image separately by changing the setting
in the Adjust dropdown list.
1. On the Stereo Enhancement toolbar, make sure that the
Adjust dropdown list shows Both Images.
2. On the Stereo Enhancement toolbar, click, hold, and

move the Brightness thumb wheel right and left to see
the changes in the image pair displayed in the Stereo
Window.
2
The arrow’s proximity to the center of the Stereo
Window determines the speed of the Auto Roam Mode.
If you are close to the center of the Stereo Window, the
speed is slow; if you are close to the edges of the Stereo The following picture shows the image pair with
Window, the speed is fast. decreased brightness.
5. Once you find an area that interests you, double-click in
the Stereo Window again to return to normal Roam
Mode.
Notice that the 3D Floating Cursor recenters in the
middle of the Stereo Window when you exit Auto Roam
Mode.

4
The following picture shows the image pair with

increased contrast.
3. Click the Reset Brightness button.
4. On the Stereo Enhancement toolbar, click, hold, and

move the Contrast thumb wheel right and left to see the 5. Click the Reset Contrast button.
changes in the image pair displayed in the Stereo
Window.
5
6. Close the Stereo Window by clicking the Close button in
the top right corner of the window.

If you plan to continue on to “Exercise 3: Converting
features—3D to 2D and 2D to 3D”, do not remove any of the
images currently displayed in ArcMap.
Otherwise, you may Exit ArcMap, which also closes Stereo
Analyst for ArcGIS.
What’s next?
In “Exercise 3: Converting features—3D to 2D and 2D to
3D”, you’ll learn how to use Stereo Analyst for ArcGIS tools
to convert your 3D features to 2D features and vice versa.

E x e r c i s e 3 : C o n v e r t i n g f e a tu r e s — 3 D t o 2 D a n d 2 D t o 3 D
Two options are available for converting feature datasets— 5. If necessary, click OK on the dialog alerting you about
one is actual and one is virtual. The actual option converts 3D the absence of spatial reference information.
features to 2D features, or converts 2D features to 3D If the display of the background values in ArcMap
features. In either case, the result is a new, separate file. bothers you, refer to “Changing properties” on page 20
The virtual option converts a 2D feature dataset to 3D, but a for instructions about how to fix the images’ display.
separate file is not created. For more information on Virtual
C o nv e r t in g 3 D fe a t u res t o 2 D
2D To 3D, please refer to “Using Virtual 2D To 3D” on page
89. The features, which are in the example geodatabase that
In this exercise, first you’ll learn how to convert 3D features comes with Stereo Analyst for ArcGIS, are 3D. Stereo
to 2D. Then, you’ll learn how to convert 2D features to 3D Analyst for ArcGIS provides you with a utility that quickly
using an elevation source. converts 3D feature data to 2D. You’ll learn how to use that
utility in the next series of steps.
Preparing
If you’re continuing the tutorial from “Exercise 2: Adding dropdown list and choose Convert 3D Features to 2D.
oriented images”, you may progress to the section named
“Converting 3D features to 2D” on page 31.
If you’re starting this exercise from scratch, you should have
ArcMap and Stereo Analyst for ArcGIS running with an 1
empty data view. You should have the Stereo Analyst and
Stereo View toolbars displayed. Proceed to “Adding image
pairs” below.
Adding imag e pai rs
1. Click the Add Data button to select the rasters to add to
ArcMap.
2. In the Add Data dialog, navigate to the folder called
\ArcTutor\StereoAnalyst\Images. The Convert Features to 2D dialog opens. In this dialog,
you can define input options and modify the parameters
3. Shift-click to select the images named strip1_1.img and
associated with converting 3D features to 2D features.
strip2_2.img. This selects all of the images in the list.
2. On the Convert Features to 2D dialog, click the Open
4. Click Add to add the images to ArcMap.
button.
5. Click Open on the Input Features dialog to add the
feature classes in the geodatabase to the Convert
2 Features to 2D dialog.
Selecting feature classes to make 2D
1. Scroll to the top of the Select classes window, then
position your cursor inside the window and click to
select the feature class named CONTOUR_INDEX.
2. Hold the Ctrl key on the keyboard and click to select the
classes: CONTOUR_INTERMEDIATE,
FREEWAY, HOUSE, PAVED_ROAD, RAILROAD,
RIVER, and SPOTHEIGHT.
1
3. In the Input Features dialog, navigate to the folder
named \ArcTutor\StereoAnalyst\Geodatabase. 2
4. Click to select the geodatabase file named
sampleAltdorfFME.mdb.
3
4
Choosing other settings and converting features

1. Notice that the Output dataset name is automatically
5 entered for you.
By default, it is named like the input dataset, but with
the additional element “_2D”. As a result, the contents

of the original dataset are not changed, and a new file is 4. When the process is complete, indicated by the status
generated. Unless you select a different location, the bar’s closure in the lower-left corner of the ArcMap
new file is placed in the same location as the input window, click Done on the Convert Features to 2D
dataset. dialog to close it.
2. Notice that the Add converted 2D feature classes to The new, 3D feature classes display over the oriented
ArcMap document check box is selected by default. images in ArcMap.
This option adds the converted feature datasets to the 5. Use the ArcMap Fixed Zoom In and Pan buttons to
ArcMap Table of contents and data view immediately clearly view the features in ArcMap.
after conversion. If this box is not checked, then you
may add the 2D dataset to ArcMap at a later time like
5
any other file.
3. Click Convert on the Convert Features to 2D dialog to
begin the conversion process.
A status bar displays at the bottom of the ArcMap
window. You can view the percentage complete there as You can use the ArcMap Identify tool to get information
the process runs. about individual features.
1
2
3 4
Confirming features are 3D
You can use the Virtual 2D To 3D tab of the Stereo Analyst 2
Options dialog to determine whether or not features are 2D.
3D features are not eligible for use in Virtual 2D To 3D and
will not display on the Virtual 2D To 3D tab of the Stereo
Analyst Options dialog. Since this tool is only operational
with 2D features; therefore, you’ll use it in this case to
confirm that the features were converted to 2D.
For more information, see “Using Virtual 2D To 3D” on page
89 in chapter 4 “Working with 3D data”.
1. From the Stereo Analyst toolbar, click the Stereo
Analyst dropdown list and choose Options.
3 4
1
4. Click OK to close the Stereo Analyst Options dialog.

C onv e r t ing 2 D fe a t u res t o 3 D
Next, you’ll use the 2D feature dataset you just created,
sampleAltdorfFME_2D.mdb, and see how you can convert it
2. On the Stereo Analyst Options dialog, click the Virtual back to a 3D feature dataset using an elevation source.
2D To 3D tab. 1. On the Stereo Analyst toolbar, click the Stereo Analyst
3. Notice that all of the features you chose for 3D to 2D dropdown list and choose Features to 3D.
conversion in the previous section of this exercise are
listed in the Selected features window of the Virtual 2D
To 3D tab.

3. In the Input Features dialog, navigate to the folder
named \ArcTutor\StereoAnalyst\Geodatabase.
1
4. Click to select the geodatabase file you created in the
previous section of this exercise, “Converting 3D
features to 2D”, sampleAltdorfFME_2D.mdb.
The Convert Features to 3D dialog opens. In this dialog,

you can define input options and modify the parameters
associated with converting 2D features to 3D features.
button. 5
2
5. Click Open on the Input Features dialog to add the
feature classes in the geodatabase to the Convert
Features to 3D dialog.
Selecting feature classes to make 3D
By selecting a geodatabase, all the feature classes associated
with the geodatabase are automatically listed in the Select
classes list of the Convert Features to 3D dialog.
1. Notice that all of the classes you chose to convert from
3D to 2D in the previous section of this exercise are
listed in the Select classes window.
Those classes include: CONTOUR_INDEX,
CONTOUR_INTERMEDIATE, FREEWAY, HOUSE,
PAVED_ROAD, RAILROAD, RIVER, and
SPOTHEIGHT.
2. Make sure that all of the classes are selected
(highlighted) in the list.
2 1 2
3. In the Raster or Tin Surface dialog, navigate to the

directory \ArcTutor\StereoAnalyst\DEM folder.
S e l e c t i n g a n e le v a t i o n s o u r c e 4. Select the file Altdorf_1m_dem.img.
The elevation source is where Stereo Analyst for ArcGIS
gets the elevation information for the 2D features in order to
convert them to 3D features. 3
1. Under Elevation Source, click the Raster or TIN surface 4

option.
2. Click the Open button for the Raster or TIN surface
option.

5. Click Open on the Raster or Tin Surface dialog to accept
the DEM raster file as the elevation source.
Ensuring accuracy
The accuracy of the elevation source used to convert a feature

dataset to 3D impacts the quality and the amount of editing
required to ensure that the features reflect what is on the earth’s
surface. The more an elevation source reflects the topography
on the ground, the less feature editing is required.
Choosing other settings and converting features 1

2
1. Notice that the Output dataset name is automatically
entered for you.
By default, it is named like the input dataset, but with 3 4
the additional element “_3D”. As a result, the contents
of the original dataset are not changed, and a new file is
4. When the process is complete, indicated by the status
generated.
bar’s closure in the lower-left corner of the ArcMap
2. Notice that the Add converted 3D feature classes to window, click Done on the Convert Features to 3D
ArcMap document check box is selected by default. dialog to close it.
This option adds the converted feature datasets to the The new, 3D feature classes display over the oriented
ArcMap Table of contents and data view immediately images (and 2D features you’ve already created) in
after conversion. If this box is not checked, then you ArcMap.
may add the 3D dataset to ArcMap at a later time like
5. Use the ArcMap Fixed Zoom In and Pan buttons to
any other file.
clearly view the features in ArcMap.
3. Click Convert on the Convert Features to 3D dialog to
begin the conversion process.
5
A status bar displays at the bottom of the ArcMap
window. You can view the percentage complete there as
the process runs.
You might want to use the Source tab of the Table of View ing 3D features in the Ste reo Wind ow
contents to confirm which feature classes are the 2D
Now that you’ve successfully updated the feature datasets
feature classes, and which are the 3D feature classes.
using a raster DEM as your elevation source, you can view
the features in the 3D representation of the area, which is
created using an image pair.
button to open a Stereo Window.
Make sure you put on the appropriate viewing glasses

(anaglyph or stereo). The ArcMap display adjusts to
accommodate the Stereo Window, which displays the
3D feature data. If you undocked the Stereo Window in
the previous exercise, that undocked setting is retained.
2. On the Stereo View toolbar, click the Zoom Out By 2
button until you see the extent of the raster and feature
data displayed in the Stereo Window.
Aligning features 2
The features may not entirely align with the oriented images in
ArcMap. This is common since the raw pixels in the oriented
images have not been transformed and then projected to create
a new raster dataset. This process is commonly referred to as All of the features you chose in the Convert Features to
orthorectification. 3D dialog display in the ArcMap data view and the
Stereo Window.
Viewing the same features and oriented images in the Stereo
Window yields better results since Stereo Analyst for ArcGIS
resamples raw pixels on the fly. To learn more about this, refer
to “Applying epipolar correction” on page 124.

3. On the Stereo View toolbar, click the Default Zoom U s i n g t o o l s t o v i ew fe a t u r e s
button to display the oriented images at a 1 image pixel
Stereo Analyst for ArcGIS comes with tools that allow you
to a 1 screen pixel resolution. This is referred to as 1 to 1
to rapidly view the data in the Stereo Window. You’ve
Zoom.
already tried the Roam Tool and are familiar with its
functionality, so apply it again to view other portions of the
3 image pair.
1. Click the Roam button, then hold the left mouse button
and drag the image pair in the Stereo Window to view a
different area.
Make sure you stay within the area of overlap between
the left and right image of the image pair to maintain the
3D view in the Stereo Window.
E n t e r i n g a n d e xi t i n g A u t o R o a m M o d e
Remember, you can double-click with the left mouse button

when in Roam Mode to enable Auto Roam Mode. Double-click
again to return to normal Roam Mode.
2. Click the Zoom In Tool button and click inside the

Stereo Window until you see a feature of interest.
You can also draw a rectangle in the Stereo Window
with the Zoom In Tool to select an area to view.
2 1
When Zoom In Mode is applied, the feature that you

clicked on is automatically repositioned so that it
displays in the center of the Stereo Window. You may
continue to click inside the Stereo Window until the
feature is displayed at the resolution you want, which is 4. With the Zoom In Tool button still active, click and hold
indicated in the Scale window of the Stereo View the mouse scroll wheel, then drag the mouse towards
toolbar. and away from you. This is another way to adjust the
3. If necessary, use the Z thumb wheel in conjunction with display, called the Continuous Zoom Mode.
Fixed Cursor Mode to align the left and right images so 5. On the Stereo View toolbar, click the Manually Toggle
that features overlap properly. Once they are aligned, 3D Floating Cursor button to deselect the Zoom In Tool
make sure that Fixed Cursor Mode is turned off. button.

6. On the Stereo View toolbar, click the Default Zoom Closin g th e appl ications
button to display the oriented images at a 1 image pixel
If you plan to proceed to “Exercise 4: Collecting features in
to a 1 screen pixel resolution.
3D”, then perform the next series of steps. Otherwise, you
may exit the ArcMap application at this time. This closes
6 Stereo Analyst for ArcGIS as well.
1. Shift-click all of the feature classes displayed in the
ArcMap Table of contents, then right-click and choose
Remove.
The image pair display in the Stereo Window updates.
2. Shift-click the images named strip1_1.img and
strip1_2.img in the ArcMap Table of contents, then
right-click and choose Remove.
Only the image pair strip2_1.img/strip2_2.img remains
in the Table of contents.
W h a t’s n ex t ?
Now that you’re familiar with some of the tools used to
manipulate the image pair’s display in Stereo Analyst for
ArcGIS, you’re ready to start collecting features.
Exercise 4: Collecting features in 3D
To collect features in Stereo Analyst for ArcGIS, you use If the display of the background values in ArcMap
tools in the ArcMap Editor you’re probably already familiar bothers you, refer to “Changing properties” on page 20
with. You can use these tools to collect features in the Stereo for instructions about how to fix the images’ display.
Window—the difference, of course, is that you’re collecting
features in 3D. Enhancing performance
Collecting features in 3D can be made easier by using the
2-Pane View of the Stereo Window. This method is If you want to enhance the performance of ArcMap, you can
turn off the display of the oriented images in the ArcMap Table
described in detail in this exercise.
of contents. The footprint and overlap extents remain displayed.
Preparing
You can also do this via the Stereo Analyst Options. Click the
If you’re continuing the tutorial from “Exercise 3: Stereo Analyst dropdown list and choose Options. Click the
Converting features—3D to 2D and 2D to 3D”, proceed to ArcMap Display tab, then click to select the Footprints of
the section named “Accessing device settings” on page 42. oriented images option, then click OK.
If you’re starting from scratch, you should have both ArcMap
and Stereo Analyst for ArcGIS running on your machine. Accessin g device settings
You should have an empty data view and Stereo Window,
and the Stereo Analyst and Stereo View toolbars displayed. To configure the system mouse, you need to access the
Proceed to “Adding images” below. Devices dialog.
Adding imag es
dropdown list.
1. Click the Add Data button to select the rasters.
2. Click the Devices option.
2. In the Add Data dialog, navigate to the folder named
\ArcTutor\StereoAnalyst\Images.
1
3. Ctrl-click to select the images named strip2_1.img and
strip2_2.img.
4. Click Add to load the rasters in the Stereo Window and
ArcMap.
2
5. If necessary, click OK on the dialog alerting you about
the absence of spatial reference information.

Co nfig uri ng th e sys tem mo use This opens the System Mouse Properties dialog where
settings that control mouse performance can be
Before collecting new features, it’s important to configure
changed.
your input device for optimal use. An input device is the
computer system’s peripheral device that is used to control One of the most important settings is Axis-To-Ground.
the 3D Floating Cursor in Stereo Analyst for ArcGIS. In this The settings in this section of the dialog control the
exercise, you’ll be using the system mouse. sensitivity of mouse movement in X, Y, and Z
(elevation).
Using input (digitizing) devices Usually, the X and Y settings of 1.00 are acceptable for
digitizing. Increasing these values increases the 3D
Possible input devices include: Immersion’s SoftMouse, ITAC Floating Cursor’s amount of movement in ground space
Systems’ Mouse-Track Professional, Leica Geosystems’ in the Stereo Window relative to movement of the
TopoMouse, and the standard system mouse. mouse (or other digitizing device) in the X, Y, and Z
See the Stereo Analyst for ArcGIS On-line Help for more directions and vice versa.
information. For this exercise, you should alter the value for the
scroll wheel (that affects Z elevation), which is 1.00 by
Setting properties default.
1. On the Devices dialog, click to highlight System Mouse 3. Type the value 0.005 in the ScrollWheel window that
from the Device Selection list. corresponds to Z.
2. Click Properties on the Devices dialog. This means that every movement of the scroll wheel
(either up or down) results in a +/- 0.005 map unit
adjustment of the elevation of the 3D Floating Cursor.
All other default system mouse properties are
1 2 appropriate for this exercise.
Controlling Z movement
In addition to the ScrollWheel setting on the System Mouse

Properties dialog, you can also control Z movement by
changing a setting on the Mouse Properties dialog. You access
this dialog through the Control Panel of your system.
3 On the Buttons tab of the Mouse Properties dialog, there is a

setting for the Scrolling Size (indicated by the red box, below)
that affects the scroll wheel of the mouse. For best results, this
value should be set to 1 line. The 1 line setting equals 32 points,
which is equivalent to 32 units in ground space in the Stereo
Window. Therefore, each “click” of the scroll wheel moves the
3D Floating Cursor up or down 32 ground units.
If the Scrolling Size is set to 3 lines, then movement of the scroll

wheel equals 96 points, which is equivalent to 96 units in
ground space, and so on.
4. Click OK to return to the Devices dialog.

Mapping buttons 3. Notice that the Currently assigned to window shows
It’s also possible to change the functions of the mouse Start Feature Collection.
buttons. 4. Click the Press/Select device dropdown list and check
1. With the System Mouse still selected on the Devices the settings for the other mouse buttons.
dialog, click Button Mappings to open the System The middle mouse button (that is, the scroll wheel)
Mouse Button Mapping dialog. remains unassigned so that it can function as the
elevation control in the Stereo Window.
For this exercise, you’ll be using the default settings.
However, it is useful to know that you can easily change
the button mappings via this dialog.
1
The System Mouse Button Mapping dialog has three

components. These are: Categories, Commands/ 2
Buttons, and Customize Button Assignment. Categories
lists the various ArcMap function categories, the 3
Commands/Buttons window shows the commands
5
within each of the Categories, and the Customize Button
Assignment section of the dialog is where the current
button assignments can be viewed and changed.
5. Click Close to exit the System Mouse Button Mapping
The Customize Button Assignment area contains a
dialog.
Press/Select device button dropdown list that can be
used to display the different mouse button assignments.
When a selection is made, the button’s function is listed
in the Currently assigned to window.
2. Click the Press/Select device dropdown list and choose
Mouse Left Button.
1
6. Click Close on the Devices dialog. 2. Click the 3D Floating Cursor tab of the Stereo Analyst
Options dialog.
Restoring default settings 3. Click the Cursor color dropdown list and choose a color
other than white, which is the default, for the 3D
The default settings files for the system mouse and all other Floating Cursor.
supported devices are contained in the following location:
4. Click the up arrow to increase the Line width of the 3D
\arcexe83\Raster\ButtonMappings\StereoAnalyst. You can also
Floating Cursor, which is measured in pixels (points), to
click Reset All on the corresponding Button Mapping dialog to
return to the original, default settings. 6.00.
5. Click the Cursor shape dropdown list and choose
Ch angin g th e 3D Floa ting Cu rs or another 3D Floating Cursor shape from the list, such as
Open X with dot.
You can easily change the way the 3D Floating Cursor looks
in the Stereo Window. This may make features easier to
collect. C h a n g i n g 3 D F lo a t i n g C u r s o r s h a p e s
1. On the Stereo Analyst toolbar, click the Stereo Analyst For more information about 3D Floating Cursor shapes, please
dropdown list and choose Options. refer to “Selecting 3D Floating Cursor options” on page 136 in
chapter 6 “Applying the 3D Floating Cursor”.

When the Stereo Window is in 3-Pane View, it includes
3 4 2 the 2-Pane View at the bottom of the Stereo Window.
The 2-Pane View, which shows the left and right images
of the image pair, is very helpful when digitizing
features to make sure that the 3D Floating Cursor rests
on the same feature in each image.
2. On the Stereo View toolbar, click the Scale dropdown
list and choose 150%.
A dd i n g fe a t u r e cla s s e s
In this exercise, you’ll learn some of the common techniques
used in the collection of features. First, you add the feature
classes.
5 7 6
1. On the ArcMap toolbar, click the Add Data button.
2. In the Add Data dialog, navigate to the
6. Click Apply on the 3D Floating Cursor tab of the Stereo \ArcTutor\StereoAnalyst\Geodatabase folder.
3. Double-click the file sampleAltdorfFME.mdb.
7. Click OK to close the Stereo Analyst Options dialog.
4. Ctrl-click to select the datasets named Buildings,
Set t i n g u p th e S t e r e o W indow Ground Points, Hydrography, and Transportation.
1. If the Stereo Window is not in 3-Pane View, click the
3-Pane View button at the bottom of the Stereo Window.
Collecting a po lygo n fe ature
3 Polygon features are created by collecting a number of
vertices, which are eventually closed to create a shape. For
example, a rectangular building may be represented by four
4 connected vertices.
Locating the polygon feature
The easiest way to locate the first polygon you’ll be
digitizing is to use the 3D Position Tool. The coordinates
you’re going to enter correspond to the image pair
5 strip2_1.img/strip2_2.img, so make sure it is active.
1. On the Stereo View toolbar, click the 3D Position Tool
button.
The Buildings feature dataset has the layers HOUSE,

1
HOUSE_EXTENSION, and STORAGE_TANKS.
The Ground Points feature dataset has the layers
FULL_CONTROL_POINT and SPOTHEIGHT.
The Hydrography feature dataset has the layers DRAIN, 2. In the X window of the 3D Position Tool dialog, type
POND, RIVER, STORM_DRAIN, and STREAM. the X coordinate 691121.3.
The Transportation feature dataset has the layers 3. Type the Y coordinate 191339.7.
FOOTPATH, FREEWAY, PAVED_ROAD, You don’t need to enter a value in the Z window.
RAILROAD, and TRACK.
4. Click Apply on the 3D Position Tool dialog.
5. Click Add on the Add Data dialog.
Di splaying the Edi tor too lbar
The ArcMap editing tools let you collect and edit features 2
quickly in the Stereo Window. If you don’t have the Editor 3
toolbar displayed, click the View menu, then point to
Toolbars, then click Editor to display the toolbar.
4

The position of the 3D Floating Cursor adjusts to reflect
the coordinates you enter in the 3D Position Tool. This Orienting the ArcMap display
is the first building you’ll digitize.
While the location displayed in the ArcMap data view
approximates that in the Stereo Window, the orientation of the
image pair in ArcMap may appear different than the display in
the Stereo Window.
To orient the ArcMap display to match the display in the Stereo

Window, select the Stereo Analyst dropdown menu on the
Stereo Analyst toolbar, then click Options. On the ArcMap
Display tab, click the check box for Orient ArcMap document
to Image Pair when Image Pair changes. Then click OK.
Note, however, if you uncheck this check box, the display in

ArcMap won’t return to the original rotation. To unrotate the
display, use the ArcMap Data Frame Tools.
Preparing to collect the feature

1. Using the Fixed Cursor Mode and the Z thumb wheel,
adjust the position of the images until the roof of the
5. On the Stereo View toolbar, click the Synchronize building feature overlaps in the right image and the left
Geographic Displays button so that the view in the image. Make sure you deselect Fixed Cursor Mode
ArcMap data view approximates that in the Stereo when you are finished.
Window. 2. Click the Editor dropdown list and choose Start Editing.
5
2
3. On the Editor toolbar, make sure that the Task window

displays Create New Feature.
4. On the Editor toolbar, click the Target dropdown list and
choose HOUSE.
7. Adjust the scroll wheel on the mouse up and down until
the 3D Floating Cursor appears to rest on the same
portion of the building in the 2-Pane View (the roof of
3 4 which is approximately 456 meters).
If you are new to working in stereo, you may want to
5. On the Editor toolbar, click the Sketch Tool button. use the 2-Pane View frequently. It shows the individual
left and right images of the image pair. When the
position of the 3D Floating Cursor in the left pane
5
matches the identical position in the right pane, you are
at the correct X, Y, Z location.
6. On the Stereo View toolbar, click the Auto Toggle 3D

Floating Cursor button, then move the cursor into the
Stereo Window where it immediately transitions to the
3D Floating Cursor.
When you are in Auto Toggle 3D Floating Cursor

Mode, it isn’t necessary to toggle in and out of the
Stereo Window (using the F3 key).
An important distinction must be made here. It should
be understood that, once in the Stereo Window, the
mouse can no longer be thought of as a typical 2D
mouse. It now controls the 3D Floating Cursor in three
dimensions.
It is also worth noting that, when in Auto Toggle 3D
Floating Cursor Mode, the images are fixed. That is, you
adjust the elevation value using the separation of the 3D 7
Floating Cursor rather than the parallax of the images.

Collecting the polygon feature 3. Examine the ArcMap display—you should now see a
1. Using the left mouse button, to click to collect the 2D display of the 3D feature you just collected.
building vertices (the HOUSE layer is a polygon feature
layer) around the roof’s perimeter.
Always remember that you must make accurate
collections in X, Y, and Z. A good strategy is to move
close to the building corners, and then adjust Z with the
mouse scroll wheel to get the correct X, Y, Z location.
2. Double-click to finish collecting the polygon (or press
F2 on the keyboard).
The ArcMap display updates in real time. Any

collections made in the Stereo Window are immediately
reflected in the ArcMap display.
4. On the Stereo View toolbar, click the Manually Toggle
3D Floating Cursor button.
2 C o lle c t ing a n o t h e r p olygon feat ure

The next polygon you’ll collect is located in the same area,
but has a different elevation.
Locating the polygon feature Collecting the polygon feature
1. In the X window of the 3D Position Tool dialog, type 1. Move the scroll wheel on the mouse up and down until
the X coordinate 691119.9. the roof overlaps in both the left and right image of the
2. Type the Y coordinate 191376.2. image pair, and the 3D Floating Cursor appears to rest
on the same portion of the roof in the 2-Pane View. The
You don’t need to enter a value in the Z window. building’s roof is approximately 457 meters.
3. Click Apply on the 3D Position Tool dialog. 2. Click to select vertices corresponding to the corners of
the building.
3. Double-click to finish collecting the building (or press
1 F2 on the keyboard).
2
Preparing to collect the feature

1. On the Stereo View toolbar, click the Fixed Cursor
Mode button.
2 1
2. Notice that clicking the Fixed Cursor Mode button

disables the Auto Toggle 3D Floating Cursor Mode.
In Fixed Cursor Mode, the 3D Floating Cursor does not
appear to be moving as it was in Auto Toggle 3D
Floating Cursor Mode. Instead, the elevation of the 3D
Floating Cursor is controlled by moving the images,
which is also known as adjusting parallax. 3
3. Move the cursor over the Stereo Window and click
inside the window. Then press F3 on the keyboard to 4. If you want to collect other building features, do so.
activate the 3D Floating Cursor in the Stereo Window.
5. Press the F3 key to toggle off the 3D Floating Cursor. 6. Click Open on the Raster or TIN Surface dialog.
Co llecting a polylin e fe ature You could specify the Use image correlation option
instead, which would use a correlation algorithm to
Like polygon features you collect using Stereo Analyst for
place the 3D Floating Cursor on the feature of interest.
ArcGIS, polyline features have an elevation component. In
For more information about that, see “Using image
the next example, you’ll see how you can use the Terrain
correlation” on page 138.
Following Mode to simplify collection of a road feature.
7. Make sure that Apply continuous terrain following is
S e t t i n g T e r r a i n F o l lo w i n g M o d e o p t i o n s
not enabled since you still want to be able to manually
In this portion of the exercise, you’ll use Snap To Ground and navigate in Z.
the Terrain Following Mode in conjunction with a raster
8. Click Apply on the Terrain Following Cursor tab.
elevation data source.
dropdown list and choose Options. 2 3 4
2. Click the Terrain Following Cursor tab of the Stereo

3. In the Elevation type section, check the option to Use
external elevation information. 7 9 8
4. Select the Raster or TIN surface option, then click the

Open button. 9. Click OK on the Stereo Analyst Options dialog to accept
the changes and close the dialog.
5. Navigate to \ArcTutor\StereoAnalyst\DEM and select
the Altdorf_1m_dem.img raster surface.
Locating the polyline feature 4. Notice the current elevation of the 3D Floating Cursor,
1. In the X window of the 3D Position Tool dialog, type which displays at the bottom of the Stereo Window.
the X coordinate 691265.5.
2. Type the Y coordinate 191653.8.
You don’t need to enter a value in the Z window.
1
2
Collecting a polyline feature

In this part of the exercise, you’ll be collecting a 3D line
feature for the PAVED_ROAD layer. You should still be in
Fixed Cursor Mode, and the Manually Toggle 3D Floating
Cursor Mode should still be active.
1. Click the Target dropdown list and choose
4 3
PAVED_ROAD.
5. Press the “s” key on the keyboard to snap the 3D

Floating Cursor to the ground.
1
Using Snap To Ground moves the elevation of the 3D
Floating Cursor to the ground level elevation
(approximately 454 meters). This elevation is obtained
2. Move your cursor into the Stereo Window and click, from the elevation data source you specified on the
then press the F3 key on the keyboard to activate the 3D Terrain Following Cursor tab of the Stereo Analyst
Floating Cursor. Options dialog.
3. Move in X and Y to the part of the road just within the
image pair overlap boundary.

6. Notice that the elevation of the area beneath the 3D 10. Continue to collect the road feature until you reach the
Floating Cursor updates in the lower portion of the approximate coordinates X: 691225.9 and Y: 191446.9.
Stereo Window. 11. Double-click to finish collecting the road (or press F2 on
the keyboard).
6 12. Press “t” on the keyboard to toggle off Terrain
Following Mode.
7. Press the “t” key on the keyboard to enter Terrain 13. Toggle off Fixed Cursor Mode by pressing “c” on the
Following Mode. keyboard.
Entering Terrain Following Mode forces the 3D 14. Press F3 to toggle off Manually Toggle 3D Floating
Floating Cursor to constantly acquire an elevation value Cursor Mode.
from the elevation source. Using the Terrain Following
Mode is the same as constantly applying the Snap To
Ground operation. Notice that, on the Stereo View
toolbar, the Terrain Following Mode button is toggled
on.
8. While still in Terrain Following Mode, begin collecting

vertices for the road feature.
9. As you digitize, notice the CE90 and LE90 readings and
associated colorblock at the bottom of the Stereo
Window.
A green colorblock indicates that the 3D Floating
Cursor is on the ground or feature of interest; a red
colorblock indicates that the 3D Floating Cursor is not
resting on the feature. If the colorblock is red, adjust the
position of the 3D Floating Cursor slightly until it
changes to green, then collect the next vertex. 10 9
For more information about LE90 and CE90, see
“Checking accuracy of 3D information” on page 146.
If you want to see the new feature in the ArcMap data 2. On the Editor toolbar, click the Target dropdown list and
view, you can click the Synchronize Geographic choose SPOTHEIGHT.
Displays button on the Stereo View toolbar.
Co llecting point fe atures
You collect point features, each of which has an X, Y, and Z
2
coordinate, with a single click. You can use keyboard
shortcuts and other tools you’ve learned about so far in the
collection of point features. 3. Make sure the Manually Toggle 3D Floating Cursor
button is selected.
Locating the area for point features
1. In the X window of the 3D Position Tool dialog, type
the X coordinate 691350.4. 4

3. Click Apply on the 3D Position Tool dialog. Collecting point features
1. Click inside the Stereo Window, then press the F3
button on the keyboard to toggle on Manually Toggle
1
3D Floating Cursor Mode.
2 2. Use a combination of procedures outlined in the
previous examples (such as Snap To Ground [“s”] and
Terrain Following Mode [“t”]) to collect individual spot
3 4 heights with a single click.
3. Collect approximately 10 spot heights in the area.
4. Click Close on the 3D Position Tool dialog.
Preparing to collect point features
Spot heights are point features; therefore, one click both
starts and completes digitizing a spot height.
1. Use a combination of the Fixed Cursor Mode and the Z
thumb wheel to adjust the overlap of the images so that
features overlap. Make sure you exit Fixed Cursor Mode
when you are finished.

1
2. Click Yes on the Save dialog to save your edits.
Closin g th e appl ications

If you plan to proceed directly to “Exercise 5: Editing
existing features”, keep the raster images and the feature
datasets displayed in the ArcMap and Stereo Analyst for
ArcGIS applications.
Otherwise, you may exit ArcMap, which also closes Stereo
Analyst for ArcGIS.
2
W h a t’s n ex t ?
4. If you used it, make sure that you have exited Terrain In the final exercise, “Exercise 5: Editing existing features”,
Following Mode. (The Terrain Following Mode button you’ll learn how to edit individual vertices and move entire
does not appear recessed on the Stereo View toolbar.) features in the Stereo Window.
5. Press F3 to toggle off Manually Toggle 3D Floating
Cursor Mode.
If you want to see the new features in the ArcMap data
view, you can click the Synchronize Geographic
Displays button on the Stereo View toolbar.
Saving features
1. Click the Editor dropdown list and choose Stop Editing.
Exercise 5: Editing existing features
Feature editing in Stereo Analyst for ArcGIS differs from 2. In the Add Data dialog, navigate to the folder named
traditional ArcMap feature editing by operating in 3D. In \ArcTutor\StereoAnalyst\Images.
Stereo Analyst for ArcGIS, existing features can be edited 3. Ctrl-click to select the images named strip2_1.img and
using a 3D digital representation of the earth’s surface strip2_2.img.
(created using overlapping, oriented images) as a reference
backdrop for updating the existing dataset. 4. Click Add to load the rasters in the Stereo Window and
ArcMap.
While it is still possible to edit features solely in X and Y, you
can no longer ignore elevation. All data collected and edited 5. If necessary, click OK on the dialog alerting you about
in Stereo Analyst for ArcGIS is 3D. In Stereo Analyst for the absence of spatial reference information.
ArcGIS, each vertex of every feature has an X, Y, and Z If the display of the background values in ArcMap
(elevation) value associated with it. bothers you, refer to “Changing properties” on page 20
This section focuses on editing polygon features, which for instructions about how to fix the images’ display.
involves editing vertices associated with a polygon and A ddin g fe a t ur e da t a
moving an entire polygon. The same editing procedures in
Stereo Analyst for ArcGIS can be used regardless of the type 1. On the ArcMap toolbar, click the Add Data button.
of feature data (point, line, or polygon). 2. In the Add Data dialog, navigate to the
Preparing \ArcTutor\StereoAnalyst\Geodatabase folder.
3. Double-click the file sampleAltdorfFME.mdb.
This exercise assumes you’re using a standard computer
mouse (with a scroll wheel). 4. Click to select the layer named Buildings.
If you’re continuing the tutorial from “Exercise 4: Collecting The Buildings feature dataset has the layers HOUSE,
features in 3D”, then you can proceed to “Adjusting a HOUSE_EXTENSION, and STORAGE_TANKS.
polygon feature” on page 58. 5. Click Add on the Add Data dialog.
If you’re starting this exercise from scratch, you should have Adjusting a polygon fea ture
an empty ArcMap data view and Stereo Window displayed.
Also, you should have the Stereo Analyst, Stereo View, and Locating an existing polygon feature
Editor toolbars displayed. Then, proceed to “Adding images” The first feature to be edited is in the HOUSE feature
below. category in image pair strip2_1.img/strip2_2.img, so make
Adding imag es sure it’s active. You’ll use the 3D Position Tool to find the
first feature quickly.
1. Click the Add Data button to select the rasters.
1. On the Stereo View toolbar, click the Scale dropdown
list and select 150%.

1
2. On the Stereo View toolbar, click the 3D Position Tool

button.

6. On the Stereo View toolbar, click the Synchronize

3
Geographic Displays button so that the view in the
4 ArcMap data view approximates that in the Stereo
Window.
5
6
After the new coordinates are applied, the portion of the
image pair shown in the Stereo Window changes. Also,
the 3D Floating Cursor moves to the coordinate location
you entered. As you can see, two vertices (which are
circled in yellow in the following picture) for this
feature are not positioned on the building corners.
Orienting the ArcMap display 5
To orient the ArcMap display to match the display in the Stereo
Window, select the Stereo Analyst dropdown menu on the
Stereo Analyst toolbar, then click Options. On the ArcMap
Display tab, click the check box for Orient ArcMap document 6. Click inside the Stereo Window, then press F3 on the
to Image Pair when Image Pair changes. Then click OK. keyboard to toggle on the 3D Floating Cursor.
Remember that, while in the Stereo Window, this cursor
Preparing to adjust the polygon feature is a 3D cursor that no longer functions as a regular 2D
1. Click the Editor dropdown list and choose Start Editing. Windows cursor.
7. Press the “c” key on the keyboard to enter Fixed Cursor
Mode.
1 8. Using the scroll wheel on the mouse, adjust parallax so
that the 3D Floating Cursor is at the same elevation as
the roof of the building (approximately 463 meters).
2. On the Editor toolbar, set the Task to Modify Feature.
9. Press “c” again to exit Fixed Cursor Mode after you
3. On the Editor toolbar, set the Target to the HOUSE have removed parallax.
layer.
1 3
4. Click the Edit Tool button.
5. Click the Manually Toggle 3D Floating Cursor button.

8 10
Adjusting vertex position

If you look at the 2-Pane View at the bottom of the
Stereo Window, you’ll know you’re at the correct 1. Position the 3D Floating Cursor over the right-most
elevation when the 3D Floating Cursor is in the same erroneous vertex.
position in both panes. 2. Using the scroll wheel, adjust the Z elevation of the 3D
10. When the 3D Floating Cursor is at the correct elevation, Floating Cursor to match that of the right erroneous
position it in the middle of the polygon and click the left vertex (approximately 467 meters).
mouse button once. 3. Notice how the 3D Floating Cursor changes to a squared
This selects the polygon. Notice how a dark blue square crosshair, shown in the following illustration, when you
is positioned at the center of the polygon in the Stereo are within the snap radius of a vertex.
Window, and the polygon outline color is light blue in
ArcMap.
The following series of steps makes use of the 2-Pane
View to ensure that the 3D Floating Cursor is located at
the same position in both the left and right images.
7. When the 3D Floating Cursor is in the correct X, Y, and

4 Z location, release the left mouse button. Notice that the
original feature outline (blue) still reflects the old
4. To move the vertex, position the 3D Floating Cursor location, even though the vertex is in its new location.
within the snap radius of a vertex, then click and hold 8. Using the same steps, proceed to correct the location of
the left mouse button. the left-most erroneous vertex, which is at an incorrect
5. Move the 3D Floating Cursor in X and Y while holding elevation of approximately 470 meters.
down the left mouse button until its location 9. If you are satisfied with the adjusted vertices locations,
corresponds to the appropriate corner of the building. click the right mouse button. This launches a dialog with
several options.
10. Choose the Finish Sketch option. Notice that the
polygon outlines update and the vertices are in the
correct locations.
6. While continuing to hold the left mouse button, use the

scroll wheel on your mouse to adjust the elevation of the
3D Floating Cursor. The elevation of the building is
approximately 463 meters.
10

11. Click outside the polygon to exit feature editing. You don’t need to enter a value in the Z window.
12. Press F3 to toggle off Manually Toggle 3D Floating 3. Click Apply on the 3D Position Tool dialog.
Cursor Mode.
When you’re done, the building should look similar to
the one shown in the following picture. 1
2
3 4
4. Click Close on the 3D Position Tool dialog.

You’ll notice a house polygon which is incorrectly
located offset from the actual building.
Movi ng a polygon feature

In this section of an exercise, you’ll learn how to move a
polygon in X, Y, and Z.
Locating an existing polygon feature
Preparing to move the polygon feature 4. Click and hold the left mouse button, and move the
1. On the Editor toolbar, click the Task dropdown list and polygon to the correct building location in the X and Y
select Reshape Feature. direction.
2. On the Editor toolbar, confirm that the Target layer is Again, it is easiest to judge the correct location by
still HOUSE. looking at the corners of the building in the 2-Pane
View.
Since you already adjusted the 3D Floating Cursor
elevation to the building’s roof, there is no need to make
1 2 further adjustments in Z.
Adjusting polygon position

1. Click in the Stereo Window, then press F3 to toggle on
Manually Toggle 3D Floating Cursor Mode.
2. Adjust the position of the 3D Floating Cursor using the
scroll wheel on your mouse so that it rests on the roof of
the house polygon (approximately 461 meters).
This is easiest to accomplish at the corner of the
building. You could also use the “s” keyboard shortcut
to snap the 3D Floating Cursor to the roof.
3. Left-click inside of the misplaced polygon to select it. 4

The polygon outline color turns to light blue. This
means that the polygon is selected. 5. Release the left mouse button.

6. Once the polygon has been placed in its correct position,
left-click anywhere outside the polygon to exit the
editing task.
7. Press F3 to toggle off Manually Toggle 3D Floating
Cursor Mode.
If you want to see the new feature position in the
ArcMap data view, you can click the Synchronize
Geographic Displays button on the Stereo View toolbar.
Editing a number of features
The same procedure described here, in “Moving a polygon

feature” on page 63, can be used to edit a number of polygons
that are displaced by the same amount in the X, Y, and/or Z.
direction.
1
Saving feature modi fica tion s
1. Click the Editor dropdown list and choose Stop Editing. 2. Click Yes to save your changes to an ArcMap document
if you want; otherwise, click No.
2. Click Yes on the Save dialog to save your edits.
2 Both the ArcMap application and the Stereo Analyst for

ArcGIS application exit.
1. Click the File menu in the ArcMap window, then click
Exit.
What’s next?
This tutorial has introduced you to some of the basic
functions you can perform using Stereo Analyst for ArcGIS.
The following chapters go into more detail about each
element of the Stereo Analyst for ArcGIS suite of tools, and
include instructions on how to use them to your advantage.

Working in stereo
Section 2
3 Working with oriented images
3
IN THIS CHAPTER Oriented images serve the most important role in collecting accurate and reliable
information from imagery. In this chapter, you’ll learn about oriented images:
• Creating oriented images where they come from, how to create them, and how to import them into the
ArcGIS environment.
• Using IMAGINE OrthoBASE to
create oriented images
• Using Image Analysis for ArcGIS

to create oriented images
• Importing IMAGINE OrthoBASE

block files
• Importing SOCET SET® files
69
Creating oriented images
To understand an oriented image, it is helpful to look at the process
used to create one.
St ar tin g with raw imag er y
On a day-to-day, minute-to-minute basis, our eyes record people,

places, and interactions. The images our eyes record are
subsequently associated with features, relationships, and processes
we maintain in our brains.
Subconsciously, we automatically associate intelligence with a

feature. Once intelligence has been associated with a feature,
relationships and processes between that feature and other features
can be deduced.
Now, apply this concept to imagery.
Two raw and overlapping images can be derived from an airborne

A Stereo Window can display features in a set of oriented images.
sensor, satellite sensor, or even a hand-held digital camera. A raw
image serves as a permanent record of the state of the world at the
time the image was captured. Images record:
• Features such as houses, roads, rivers, schools

• Relationships between features such as distance from the post
office to your office
• Processes such as the amount of water flowing in a river
• Information such as the monetary value of a foreststand
This is the same relative area as depicted in the previous illustration, with
only feature outlines displayed.

Raw imagery is an untapped resource for creating and updating all A raw image knows nothing about geography, geographical
of the data used in a GIS. Stereo Analyst for ArcGIS transforms the relationships, processes on the earth’s surface, scale, or how it was
permanent record stored in a raw image into information directly recorded—it’s a raster with pixels in it, plain and simple.
stored in the geodatabase. Essentially, it’s a “stupid” image that is not GIS-ready since it
knows nothing about geography.
To get accurate, valuable information from a raw image, you have

to process it to make it “intelligent”. Creating an intelligent image
involves associating it with the earth. This means defining the
relationship between an image (as it existed when the image was
recorded) and the earth’s surface. Once a raw image has
intelligence associated with it, it is GIS-ready.
By making an image intelligent, features on the earth’s surface can

be collected. When features have been collected, they can be stored
within a database in multiple layers, and relationships between
features can be defined. Once relationships between features are
defined, processes associated with features and their relationships
to other features can be derived.
Multiple levels of information can be extracted from imagery, but

the foundation for information extraction is in the oriented image.
Prior to extracting any information from imagery, an image must be
oriented and made intelligent. An intelligent image is the map of the
future.
Understan ding imag e-to -ear th ass ociation
An image-to-earth association is the result of defining the 3D

mathematical relationship between an image and the earth’s
surface. This process is referred to as aerial triangulation (AT) and
is commonly done in digital photogrammetry products such as
SOCET SET® and IMAGINE OrthoBASE®. These products are
factories since they provide a series of step-by-step processes that
are required to transform the stupid image into an intelligent,
oriented image.
The top image is a simple TIF image; the bottom is a stereo view of the area.
WORKING WITH ORIENTED IMAGES 71

Oriented Image = + Intelligence
Stupid raster image
Intelligence is defined as spatial reference plus a sensor model.
Modified from Asher and Adams, 1976
The factory adds information to the stupid image to make it intelligent.

Intelligence = + Sensor Model
Once a raw image has been transformed inside the factory,

information such as projection, units, and a sensor model is
available for each intelligent, oriented image. A sensor model is the
3D mathematical relationship between the sensor used to record the Spatial Reference
image, the ground, and the image itself. These are the three general (projection/units)
variables characterized by a sensor model.
A sensor model, which is a 3D mathematical relationship, is
Proc essing inside the fa ctor y
defined by an image-to-earth association.
Inside the factory, either IMAGINE OrthoBASE or SOCET SET®

is busily adding intelligence to the raw image. This involves
integrating information from a variety of sources to compute the
image-to-earth association. The following deductions can be made
to better understand an oriented image. Sensor Model =
An oriented image is defined as a stupid raster image plus

intelligence.
Image-to-earth Association

The image-to-earth association is defined as the position of the These variables are computed by measuring 3D ground control
satellite at the time of image capture, plus the image, plus the points (GCPs) within the raw image. In order to establish the
image’s location on the earth. image-to-earth association, the internal characteristics associated
with the sensor as reflected on the raw image must be defined. This
is referred to as interior orientation. This involves defining sensor
properties such as focal length.
Defini ng an oriented im ag e
Satellite images recorded and prepared by Space Imaging and

+
DigitalGlobe are referred to as oriented images. Stereo Analyst for
ArcGIS can directly use overlapping oriented images provided by
Space Imaging and DigitalGlobe.
Image-to-earth
Association = These oriented images contain metadata referred to as rational
polynomial coefficients (RPCs). RPCs are coefficients that contain
information defining the relationship between the image and the
+
earth’s surface. Both the imagery and the metadata are most
commonly stored in NITF or GeoTIFF format.
Other examples of oriented images include aerial triangulation data

created by SOCET SET® or IMAGINE OrthoBASE. SOCET
SET® creates project and support files that store all of the metadata
required to create an oriented image. IMAGINE OrthoBASE block
The image-to-earth association yields a transformation that files serve as metadata storage containers used to create oriented
consists of a series of coefficients describing the 3D mathematical images.
relationship between the image, the sensor that captured it, and the
ground it has recorded. This process estimates the exact 3D position
(X, Y, Z) and rotation (three rotation angles) of the sensor that was
used to record the image at the time of capture. These parameters
are also referred to as exterior orientation parameters.

Un ifyin g imag es, feature s, relationsh ips, process es, a nd in formation
A GIS serves as a container for the feature datasets that have been extracted from oriented images. A GIS also maintains all of the
relationships, processes, and information associated with a feature dataset.
By tracing the ancestry of spatial information, it is evident that the reliability of information in a GIS is dependent on the accuracy of feature
data derived from oriented imagery. The following example illustrates the ancestry of information derived from imagery used to assess
what impact a residential housing development may have on a watershed drainage system.

In this example, a factory is used to transform a raw image to create
a GIS-ready, oriented image. Stereo Analyst for ArcGIS then uses
the oriented imagery to extract all of the feature data required to
assess the impact on the drainage system. This includes vegetation
(location and type), roads, rivers, trees, and terrain. An additional
layer of information can be derived from each feature dataset (that
is, use Spatial Analyst™ to delineate a drainage system), and
relationships can be built between multiple layers of information in
the geodatabase.
ArcGIS uses these feature datasets in combination with other

information layers (such as annual precipitation) to conduct
hydrological analysis to assess the overall impact on water quality
and quantity on the watershed of interest. Without imagery, the data
required to assess the impact would not be available. Without
accurate and up-to-date feature data, a reliable study could not be
done. This example illustrates how intelligent information relies on
accurate, oriented imagery.

Using IMAGINE OrthoBASE to create oriented images
IMAGINE OrthoBASE can be thought of as a process-driven The final process of creating an oriented image involves associating
factory that creates oriented images and other first and second the sensor model metadata with the original image. In IMAGINE
generation data layers. These layers are stored and used in a GIS. OrthoBASE, this process is referred to as orthocalibration. The
original image is not resampled or modified. IMAGINE
In order to create oriented images in IMAGINE OrthoBASE, you OrthoBASE simply saves intelligent sensor model information and
must complete the first five steps associated with processing raw associates it with the original raw image.
imagery.
To create the oriented image in IMAGINE OrthoBASE, first
choose the Process menu. From there, you select Ortho
Rectification, then Calibration, and the following dialog opens.
This is the IMAGINE OrthoBASE interface.
The processing steps include:
1. Adding images to your project.

2. Defining the sensor and properties associated with the sensor.
3. Measuring GCPs.
4. Performing automatic tie point collection. This is the Ortho Calibration dialog in IMAGINE OrthoBASE.
5. Performing image-to-earth association (aerial triangulation). You have the option of creating one oriented image at a time or
creating multiple oriented images simultaneously. In order to create
Once the image-to-earth association has been completed, the
multiple oriented images simultaneously, select the OK to all
information required to create an oriented image is available.
option. It is important to note that at least two overlapping oriented
IMAGINE OrthoBASE allows you to create one oriented image at
images are required in order to perform feature collection and
a time, or multiple oriented images simultaneously.
editing using Stereo Analyst for ArcGIS.

In IMAGINE OrthoBASE, you are asked to define an elevation
source. However, an elevation source is not always required in Using spatial database engine files
order to create an oriented image, as in the case of importing using
the IMAGINE OrthoBASE and SOCET SET® importers. An If you use the SDE converter to create an SDE raster file from
elevation source is required in this case since this interface also a raster file calibrated in IMAGINE OrthoBASE, the converted
serves the purpose of creating orthocalibrated images. This process file will not retain the map model.
requires an elevation source to account for the effects of
In order to use SDE raster files in Stereo Analyst for ArcGIS,
topographic relief displacement on the image. Thus, this interface
first convert the original raster file to an SDE raster file, then
now serves two purposes: creating oriented images and creating
attach the SDE raster file to an IMAGINE OrthoBASE block
orthocalibrated images.
file, then calibrate the file. The resulting SDE raster file retains
Once the oriented images have been created, you can directly add the map model and can be used in Stereo Analyst for ArcGIS.
the images to ArcMap for use in Stereo Analyst for ArcGIS.
ArcMap automatically recognizes that the images are oriented
images.
For more information on using IMAGINE OrthoBASE, please

refer to the IMAGINE OrthoBASE User’s Guide.
Using data from IMAGINE OrthoBASE
Stereo Analyst for ArcGIS supports digital camera, frame

camera, IKONOS, IRS-1C, QuickBird, and SPOT oriented
images created by IMAGINE OrthoBASE. Oriented images
cannot be created for terrestrial or close-range images.

Using Image Analysis for ArcGIS to create oriented images
Another extension to ArcGIS, Image Analysis for ArcGIS, also In order to create oriented images using Image Analysis for
allows you to create oriented images. You can access this ArcGIS, the following steps must be completed.
functionality via the Data Preparation menu in the Image Analysis
toolbar. 1. Add raster dataset(s) to ArcMap.
2. In the Image Analysis toolbar, select the appropriate sensor
The process of creating an oriented image in Image Analysis for model.
ArcGIS overlaps with the process of creating an orthorectified 3. Within the GeoCorrection properties:
image. The following models can be used to create oriented images
using Image Analysis for ArcGIS: camera, SPOT, QuickBird, and a. If using aerial camera imagery, define camera properties
IKONOS. and measure fiducial marks.
b. Define the elevation source.
Creating an oriented image in Image Analysis for ArcGIS involves
associating sensor model information (metadata) to a raw image. c. Measure links between the raw raster dataset and the
The original raw image is not modified, but the sensor model reference dataset. This involves locating reference GCPs
information is added as metadata which is required and used by in the reference dataset and linking them to the same
Stereo Analyst for ArcGIS for accurate feature collection. location on the raw image.
d. Define sensor properties. For camera imagery, this
involves defining initial approximations for exterior
orientation, if known. For satellite sensors, this involves
defining parameters associated with the image forming
satellite sensor geometry.
4. Solve and save the solution.
5. Repeat steps 1 through 4 for the next overlapping raster
dataset.
The GeoCorrection tool in Image Analysis for ArcGIS allows you to create
oriented images that can be used by Stereo Analyst for ArcGIS.

Importing IMAGINE OrthoBASE block files
One of the data formats you can use in Stereo Analyst for ArcGIS Block files, which are binary files, have the .blk extension, and may
to create oriented images is the IMAGINE OrthoBASE block file. contain information associated with one image, a strip of images
Created in IMAGINE OrthoBASE or IMAGINE OrthoBASE that overlap or are adjacent to one another, or several strips of
Pro™, the block file is a data container that stores all of the imagery. In the block file is all the information associated with the
necessary metadata information required to create oriented images. block including imagery locations on your system, camera/sensor
information, fiducial mark measurements, ground control point
information, image measurements, projection, spheroid, and datum
information.
Understan ding blo ck impor t requiremen ts
Stereo Analyst for ArcGIS initially reads the block file to determine
the location of the related images for importing. If the images are in
the location specified in the block file, they can be oriented and
imported immediately.
If the files are not located in the directory specified by the block
file, Stereo Analyst for ArcGIS looks in the same directory as the
block file. If the images are not in that location, you’ll be prompted
to locate them with the following dialog.
This is the Import IMAGINE OrthoBASE Block File dialog.
The import process opens the block file, identifies the images
referenced in the block file, verifies that the images are located in
the directory specified by the block file, and then associates the
intelligent metadata to the original images. Once this process has
been completed, the oriented images can be added to ArcMap for
use by Stereo Analyst for ArcGIS.
A block file, altdorf.blk, is included with the example data that

This is the IMAGINE OrthoBASE importer file locator dialog.
comes with Stereo Analyst for ArcGIS. You can find it in the
following directory: \ArcTutor\StereoAnalyst\BlockFile. The dialog functions like any other file chooser. Just click the Open
button and browse to locate the file in question, then click OK. If
Definin g a block file all the other files in the block are in the same location, they are
automatically attached to the block, then you only have to rename
A block file is data in a container storing all of the photogrammetric
the block file. If other files are still unavailable, you’ll be prompted
data associated with a strip or block of imagery. to select the appropriate location for them as well.

Because selecting a new image location changes the block file,
which contains the location of the files, you’ll be prompted to save
the block file with a new name in the following dialog.
Use this dialog to create a new block with the correct file location.

Impo r tin g a n I M AG INE Or thoBASE block file
You can import and orient block files derived from frame
camera images, digital camera images, and sensors into
Stereo Analyst for ArcGIS using the IMAGINE OrthoBASE
block file importer.
1
dropdown list and choose Import IMAGINE OrthoBASE
Block File.
2. On the Import IMAGINE OrthoBASE Block File dialog,
click the Open button and navigate to the directory
containing the block file you want to import.
The Select images to orient window displays each image
in the block file. You must select the images you want to
orient. If you do not select any images, no importing
occurs.
2
3. Use the Shift and/or Ctrl keys on the keyboard to select
the files you want to orient and import from the IMAGINE 3
OrthoBASE block file. You don’t have to select all of the
images in the block file.
4. If you would like to view the images immediately, make
sure the Add imported oriented images to ArcMap
document check box is checked.
5. Click OK to start the import process.
The imported, oriented images display in the ArcMap
data view and the Stereo Window. 4 5

Importing SOCET SET® files
SOCET SET® is a digital photogrammetry software product that is files to indicate the correct location. Otherwise, you cannot import
used to create oriented images, DTMs, and orthorectified images. and orient the example files. You can correct the location, indicated
Once aerial triangulation has been completed (using either ORIMA by DATA_PATH in the project file and IMAGE_FILE_NAME in
the support files, using a text editor.
or SOCET SET®), the information required to create oriented
images for use in Stereo Analyst for ArcGIS is available.
A SOCET SET® project file is typically structured as follows:
PROJECT_FILE f
DATA_PATH D:\Data\StereoAnalyst\
Socetset\escon_demo
COORD_SYS 6
XY_UNITS 1
Z_UNITS 1
MINIMUM_X_OR_LAT 0.00000000000000e+000
MINIMUM_Y_OR_LON 0.00000000000000e+000
MINIMUM_Z 2.00000000000000e+002
MAXIMUM_X_OR_LAT 0.00000000000000e+000
MAXIMUM_Y_OR_LON 0.00000000000000e+000
MAXIMUM_Z 4.00000000000000e+002
GP_ORIGIN_Y 0.00000000000000e+000
GP_ORIGIN_X 0.00000000000000e+000
GP_ORIGIN_Z 0.00000000000000e+000
This is the Import SOCET SET Project File import dialog. GP_SCALE_Y 1.00000000000000e+000
GP_SCALE_X 1.00000000000000e+000
GP_SCALE_Z 1.00000000000000e+000
A SOCET SET® project file (.prj) contains general project ELLIPSOID WGS_84
information associated with a photogrammetric mapping project. VERTICAL_REFERENCE 0
This file is an American Standard Code for Information A_EARTH 6.37813700000000e+006
Interchange (ASCII) file that is used as part of the import process. E_EARTH 8.18191912720360e-002
ELLIPSOID_CENTER 0.00000000000000e+000
The project file contains general mapping information associated 0.00000000000000e+000
with a project such as projection, units used, and so on. The .prj file 0.00000000000000e+000
is what you select for import. PROJECTION_TYPE UTM_PROJECTION
ZONE 11
FALSE_NORTHING_POS 0.00000000000000e+000
A SOCET SET® project file, altdorf.prj, is included with the FALSE_NORTHING_NEG 0.00000000000000e+000
example data that comes with Stereo Analyst for ArcGIS. You can FALSE_EASTING_POS 5.00000000000000e+005
find it in the directory: \ArcTutor\StereoAnalyst\SocetSet. Note FALSE_EASTING_NEG 5.00000000000000e+005
that if you load the project and support example data in a place other GRID_NAME UTM_11N
than the default, C:\arcgis\ArcTutor\StereoAnalyst\SocetSet, you IMAGE_LOCATION escon
will have to manually edit the SOCET SET® project and support

The project file also contains references to raw images. Each raw
image used in SOCET SET® has a corresponding support file
(.sup) associated with it. A support file is an ASCII file that
contains the detailed photogrammetric metadata associated with a
raw image.
This is part of a support file.
The import process accesses all of the metadata (interior and

exterior orientation parameters) associated with the image and uses
this information to create an oriented image.
Understanding importing limitations
SOCET SET® files in the geographic projection cannot be

imported by Stereo Analyst for ArcGIS unless the system on
which you’re working also has SOCET SET® installed and
licensed.

I m p o r ti n g a S O C E T S E T ® proj ect file
You can import and orient SOCET SET® projects into Stereo
Analyst for ArcGIS using the SOCET SET® importer.

dropdown list and choose Import SOCET SET Project 1
File.
2. On the Import SOCET SET Project File dialog, click the
Open button and navigate to the directory containing the
project file you want to orient and import.
The Select images to orient window displays each file in
the project file. You must select the files you want to
orient. If you do not select any images, no importing
occurs.
3. Use the Shift and/or Ctrl keys on the keyboard to select
the files you want to orient and import from the SOCET 2
SET® project file.
3
4. If you would like to view the images immediately, make
sure the Add imported oriented images to ArcMap
document check box is checked.
5. Click OK to start the import process.
The imported, oriented images display in the ArcMap
data view and the Stereo Window.
4 5

What’s next?
In the next chapter, “Working with 3D data”, you’ll learn about
methods for working with 3D data. These methods include Virtual
2D To 3D, conversion of 2D feature datasets to 3D, and exporting
3D datasets to 2D datasets.

4 Working with 3D data
4
IN THIS CHAPTER Using two overlapping, oriented images, an accurate 3D digital representation of
the earth’s surface is created when displayed in the Stereo Window and viewed
• Comparing 3D features and 3D with stereo hardware. Many existing GIS databases are 2D. In order to update
models existing GIS datasets (2D or 3D) using Stereo Analyst for ArcGIS, the feature
dataset must be superimposed on the 3D digital earth created using two
• Using Virtual 2D To 3D overlapping oriented images. In order to superimpose an existing feature dataset
on the 3D digital earth, the feature dataset must be 3D. If it is not 3D, it must be
• Setting Virtual 2D To 3D options transferred to 3D.
• Using the 2D to 3D converter This process of transforming a feature dataset to 3D can be either virtual or
physical. The virtual option temporarily transforms a feature dataset to 3D while
• Using advanced conversion
working in the Stereo Window. When the data updates have been completed, the
options
original feature dataset is restored, but with more accurate 2D feature data. The
• Using the 3D to 2D converter physical option transforms an existing 2D feature dataset and creates an entirely
new 3D feature dataset that both supports and contains 3D data.
Regardless of which option is used, an elevation source (either a constant elevation

or external elevation file) is referenced to obtain a Z (elevation) coordinate for a
particular X, Y coordinate derived from the feature dataset. Once the Z coordinate
source has been provided, it is then associated with each vertex in the dataset.
87
Comparing 3D features and 3D models
Ch arac terizing 3D features Chara cterizing 3D model s
A 3D feature can be a 3D point, 3D line, or a 3D polygon. A 3D A 3D model not only has 3D coordinates in X, Y, and Z, but it also
feature has an X, Y, and Z coordinate associated with each vertex has volumetric information. The following is an example of a scene
of that feature. The Z coordinate is the elevation value of that with many 3D building models (shown in grey, orange, and
vertex. For example, a vertex corresponding to the corner of a yellow).
house may have the X, Y, and Z coordinate values of 691402.4,
191111.6, and 466.6, respectively.
A 3D model has volumetric information.
A 3D model normally has a height attribute associated with the

feature. For example, a 3D polygon feature can have a height
A 3D feature has X, Y, and Z coordinates for each vertex. associated with it. In this case, it can be used as a 3D model in 3D
GIS applications.
A 3D feature has 3D coordinate values associated with each vertex,
but it does not have volumetric information as is the case with a 3D Stereo Analyst for ArcGIS allows you to collect 3D feature datasets
model. such as 3D points, 3D lines, and 3D polygons; however, Stereo
Analyst for ArcGIS does not allow for the collection of 3D models.

Using Virtual 2D To 3D
Virtual 2D To 3D conversion is useful when you want to improve If you need them, there are more advanced options that increase the
the accuracy of an existing feature dataset, but are not interested in accuracy of the conversion. These options include feature draping,
actually capturing 3D information from the dataset. That is, you can inclusion of planar features, and a choice of how to handle invalid
improve the X, Y coordinate values of feature vertices. elevations. Those options are discussed in “Using advanced
conversion options” on page 95.
However, in order to improve the reliability and quality of the
feature dataset, stereo feature collection and editing techniques Note that if a 3D feature dataset has been added to ArcMap, it won’t
must be used. As a result, the feature dataset must be superimposed be considered for use in Virtual 2D To 3D since it is already in 3D.
on top of the 3D digital representation of the earth’s surface. In In this case, use the Features to 3D utility to update elevation
order for this to occur, the feature dataset must have 3D coordinate information. See “Using the 2D to 3D converter” on page 93 for
information associated with it. additional details.
The Virtual 2D To 3D capability temporarily transforms a dataset Understan ding how it wo rks
to 3D so that it can be superimposed on the 3D digital earth’s
surface displayed in the Stereo Window. This is achieved by Once you define an input feature dataset and an elevation source,
referencing a user-defined elevation source at a particular X, Y the Z coordinate associated with a vertex node in the feature layer
location for Z coordinate information. The X, Y location of the is assigned the elevation value located within the corresponding
vertex is obtained from the original feature dataset. elevation source. The supported elevation sources include: constant
elevation value, DEM, and ESRI-type triangulated irregular
The Virtual 2D To 3D function does not create a new feature network (TIN) files.
dataset. Rather, it simply references and queries an elevation source
for Z coordinate information and then associates that information The conversion of the data to 3D is performed virtually, that is, your
with each vertex in the feature dataset. This Virtual 2D To 3D data is not actually edited. Stereo Analyst for ArcGIS simply uses
process only occurs when the feature dataset is being displayed in elevation information contained in a DTM file or a constant
the Stereo Window. Once all edits have been made and saved, only elevation to project your feature datasets in 3D. The initialized Z
2D (X and Y) coordinate information is written back to the original value is for viewing purposes only. The feature data you display in
feature dataset. the Stereo Window can be edited, but only X and Y information is
saved.
To successfully perform the virtual conversion of a dataset from 2D
to 3D, you need (1) a list of feature classes for conversion and (2) If you want the elevation information with a feature dataset to be
an elevation source such as a constant elevation value or an external retained, the Features to 3D option in the Stereo Analyst toolbar
elevation file. should be used. Refer to “Using the 2D to 3D converter” on page
93 for more information about this capability.
WORKING WITH 3D DATA 89

Setting Virtual 2D To 3D options
You can define the options that control the application of Virtual Se ttin g th e elevation source
2D To 3D to your data. To access these options, click the Stereo
Analyst dropdown list on the Stereo Analyst toolbar, then click The Elevation Source section of the Virtual 2D To 3D tab is where
Options. On the Stereo Analyst Options dialog, click the Virtual 2D you define the reference elevation source used by Stereo Analyst
To 3D tab. for ArcGIS to associate a Z coordinate with each vertex of a feature
in a feature class.
A raster surface can be an ERDAS IMAGINE .img file or a GRID

file. In this case, the raster dataset is an elevation model wherein
each pixel in the raster dataset has an elevation value associated
with it.
A constant elevation value is a user-defined value that

approximates the elevation of the study or working area. Using a
constant elevation value is less accurate than an elevation source
since it may not accurately reflect the topography on the earth’s
surface.
If either the Raster/TIN or Constant elevation source is selected,

then 2D feature datasets are displayed, and dynamic 2D geometry
is converted to 3D using the specified elevation source.
Selecting the None option disables the display of 2D feature

datasets in the Stereo Window. This option also forces ArcMap
dynamic 2D geometry (such as the selection box) displayed in the
The Virtual 2D To 3D tab allows you to create temporary 3D feature data. Stereo Window to assume the same elevation as the 3D Floating
Cursor.
U s in g T I N f i le s Se lecting featu res
You can only use ESRI-type TIN files with Stereo Analyst for The Selected features list shows all of the current 2D feature layers
ArcGIS. TINs generated in other applications, such as in the ArcMap Table of contents. If multiple feature datasets have
IMAGINE OrthoBASE Pro, cannot be used by Stereo Analyst been added to ArcMap, all of the 2D feature classes associated with
for ArcGIS. the feature datasets are shown in the list.

Setting advanc ed op tion s
The Advanced Options button is used to access the Feature to 3D

Options dialog. There, you can define detailed parameters
associated with the 2D to 3D conversion. This button is only
enabled if a raster or TIN surface is selected as the elevation source.
For more information on the advanced options, refer to “Using
advanced conversion options” on page 95.

Usi ng Vir t ual 2 D To 3 D
The following workflow describes how to use Virtual 2D To

3D.
1. Start ArcMap and Stereo Analyst for ArcGIS.

2. Add image pairs and 2D features to an empty data view.
3. On the Stereo Analyst toolbar, click the Stereo Analyst 3
dropdown list and choose Options.
4. On the Stereo Analyst Options dialog, click the Virtual 2D
To 3D tab.
5. Click the option corresponding to the elevation source
you wish to use for virtual conversion.
6. If you choose the Raster or TIN surface option, click the
Open button to select the file. If you select Constant
elevation, type an elevation value.
4
Notice that the 2D features you added and displayed in
step 2 are all listed in the Selected features window of the
Virtual 2D To 3D tab.
7. If you’re using a Raster or TIN as the elevation source,
click Advanced Options to make additional choices if you
wish.
Using advanced options
The advanced options for Virtual 2D To 3D are explained in

“Using advanced conversion options” on page 95.
8. Click Apply on the Stereo Analyst Options dialog.

9. Click OK on the Stereo Analyst Options dialog to close it.
5 7 9 6 8

Using the 2D to 3D converter
The Convert Features to 3D option works with the following types U s ing t h e c onv e r t e r
of input feature data:
Initially, you choose the 2D source that contains the feature data
• A workspace, which can consist of a collection of shapefiles or you want to convert to 3D. Once you have selected that source,
a geodatabase; eligible 2D features are listed in the Select classes window. To
• A feature dataset within a geodatabase, which might contain select them, you can use the Shift-click or Ctrl-click method to
multiple feature classes; select contiguous or noncontiguous classes, respectively.
• Standalone feature classes, which may consist of a feature In the Elevation Source section, you can choose to give your 2D
class stored within a geodatabase; and data elevation from either an external raster or ESRI TIN surface,
• A feature class within a feature dataset. or a constant elevation that you supply.
The output dataset is placed in the same folder as the input dataset
unless you specify otherwise. The output file is given the
designation “_3D” to distinguish it from the input file.
Geodatabases, feature datasets, and feature classes can be converted to

3D in Stereo Analyst for ArcGIS.
Up datin g Z valu es of 3D fea ture datasets
While the Convert Features to 3D dialog is most often used to add

elevation information to 2D features, you can also use it to update
existing 3D features with new elevation values.
The process to convert the data is the same—the only difference is

the input dataset. In this case, the data is already three-dimensional.
You are supplying a raster or ESRI TIN file, or a constant elevation
to update the elevation (Z) component of each vertex of each The Convert Features to 3D dialog is where you begin the conversion
feature. process.

Co nv er tin g 2D features to 3D
The following is an example workflow of how to convert 2D

features to 3D.
2
1. Start ArcMap and Stereo Analyst for ArcGIS.
dropdown list and choose Features to 3D.
button and browse to locate the 2D file.
4. In the Select classes window, click to select the classes
you want to convert to 3D.
5. Click the option corresponding to the elevation source
you wish to use for conversion.
6. If you choose the Raster or TIN surface option, click the
Open button to select the file. If you select Constant
elevation, type an elevation value.
3
7. Type a name for the Output dataset in the window if you
don’t want the default name.
4
Naming the output dataset
When an input feature dataset is selected, the output dataset 5 6

defaults to the original input dataset name with “_3D” appended
to the name. You can change the default name by typing it in the
Output dataset window. It defaults to the same directory and 7
folder location as the input dataset. 8
8. The check box next to Add converted 3D feature classes

to ArcMap document is selected by default. Uncheck it if 9 10
you don’t want the features to display after conversion.
9. Click Convert on the Convert Features to 3D dialog.
10. Click Done when the status bar at the bottom of the
ArcMap window indicates the process is complete.

Using advanced conversion options
When you convert features to 3D, you can accept the default
settings that are provided on the Convert Features to 3D dialog, Using advanced options
which you’ve already learned about in “Using the 2D to 3D
converter” on page 93, or you can use additional options in the Advanced options are only available if you select a raster or
processing of your data. These options are available to you whether TIN surface as an elevation source during the 3D conversion
you are using Virtual 2D To 3D or actually converting features to process. If you enter a constant elevation, you don’t have access
3D and creating a new file. to the advanced options.
The accuracy of the conversion process can be increased by using

U s ing fe a t u r e dr a p ing
accurate elevation surfaces and by defining advanced conversion
parameters. These options are available to you on the Feature to 3D
By using draping, you set the condition that the feature follows the
Options dialog. This section describes each of those options so you
subtle changes in elevation of the terrain surface in the height
can make the most appropriate selections for your data.
dimension. This is made possible by (1) interpolating new vertices
based on the location of existing vertices and (2) applying the
elevation source used to perform the 3D conversion. If a high-
resolution elevation source is used, the reliability of the newly
sampled (interpolated) points is higher.
In the diagram on page 96, the points reflect the vertices associated
with the features. The bottom layer is the original feature dataset
assuming a zero (sea level) elevation is applied to the feature
dataset. The top layer illustrates an elevation source applied to the
original feature dataset.
When draping is turned on, additional vertices associated with the

dataset can be inserted as a function of point spacing. In this
instance, the feature dataset is densified to include more vertices.
Refer to “Using thinning tolerance” on page 98 for more
information about densifying a feature dataset to include more
vertices.
The Feature to 3D Options dialog provides advanced settings.

Draping off
Original point
Interpolated point
Draping on

U s i n g p oi n t s p a c i n g
Point spacing is the distance between points used (sampled) during the interpolation process. The distance between the points is measured
in the same units as the image pair displayed in the Stereo Window. The distance you specify in the Point spacing window is not exceeded
when points are selected for interpolation.
Point spacing = 20
80 Units 100 Units
Original point
Interpolated point
Point spacing = 10
80 Units 100 Units

Usi n g t h i n n in g t o l e r a n c e Creating plana r featu res
The line thinning tolerance is only active when the Drape linear A planar feature is a feature in which all vertices associated with
features on the terrain surface option is active. This option removes the feature have the same elevation. These features are commonly
redundant points contained within the feature dataset based on a flat features such as building roofs.
thinning tolerance defined by you. It’s useful when the variation in
topography is minimal. In the Planar Features section of the Feature to 3D Options dialog,
you can select certain classes to which a single elevation value is
By setting a thinning tolerance, Stereo Analyst for ArcGIS checks applied to all features contained within that feature class. For
to make sure that there aren’t any duplicate points in collinear example, if a building feature is converted to 3D, you may want to
sections. If you don’t want thinning, simply set the value to 0. constrain the building polygon to be flat so that all vertices
associated with the polygon have the same elevation value.
In the following diagrams, the green circle represents the current
point, the black circles represent adjacent points, and the red line The elevation value applied to each vertex for a particular feature
terminating in an arrow represents the thinning tolerance. can be determined in several ways. In the Elevation dropdown list
of the Planar Features section, you have the option to select one of
the following techniques to be used for computing the elevation
value: At centroid, Minimum interpolated, Maximum interpolated,
and Average interpolated.
Each method of interpolation is described in the following sections.

In each diagram, the points reflect the vertices associated with the
features. The bottom layer (which has the red circles representing
sea level elevation) is the original feature dataset assuming a zero
(sea level) elevation is applied to the feature dataset.
Here, the point is outside the thinning tolerance and is retained.
Here, the point is inside the thinning tolerance and will be eliminated.

Using the At centroid option Using the Maximum interpolated option
The At centroid option takes the elevation from the physical center If you select the Maximum interpolated option, elevations are
of the feature, the centroid. For example, in a polygon, the center interpolated for each vertex making up the feature, then the largest
pixel is used for the elevation value. The following illustration value is used to assign the elevation to the feature. The following
shows the At centroid option. illustration shows the Maximum interpolated value.
Z
Z
value at centroid maximum value
Using the Average interpolated option

U s i n g t h e M in im u m i n t e r p o l a t e d o p t i o n
If you choose the Average interpolated option, elevations are
If you select the Minimum interpolated option, elevations are interpolated for each vertex, added, then divided by the number of
interpolated for each vertex making up the feature, then the smallest vertices, which yields an average elevation. This elevation is
value is used to assign the elevation value. The following assigned to the feature. The following illustration shows the
illustration shows the Minimum interpolated option. Average interpolated value.
Z
Z
maximum value
average value
minimum value
minimum value

Res olvin g invalid elevati ons
In some instances, invalid elevations may exist during the 3D

conversion and interpolation process. Stereo Analyst for ArcGIS
provides several options to resolve invalid elevations during the
interpolation and conversion process.
Using the original elevation value
By default, the selected option is Keep the original elevation value.

In case of an invalid elevation value, Stereo Analyst for ArcGIS
uses the original elevation value if the feature is 3D. The elevation
values of any questionable points are not changed.
Using a default elevation value
If you’re familiar with the terrain in your data, you can enter an
elevation value to apply to all questionable points.
U s i n g a m in i m u m v a l i d e l e v a ti o n v a l u e
Click the Use minimum elevation value check box and input the
value of the lowest possible elevation in your data. For example, if
you enter 30, then invalid elevation values are assigned a value no
lower than 30 map units, such as meters.

Ap plying adva nced 3 D c onversion
paramete rs
You begin the advanced 3D conversion process by selecting

the 2D feature dataset and an associated elevation source. 1

dropdown list and select Features to 3D.
button and navigate to the directory that contains the 2D
data.
3. On the Import Features dialog, select the data file and
click Open. X

4. Position your cursor inside the Select classes window
and choose the classes you want to convert to 3D. You
may use the Shift and Ctrl keys on the keyboard to select
neighboring and non-neighboring classes. Selected
classes have a blue background. 4
5. In the Elevation Source section, either click the Open
button and select a raster or a TIN file to use for
elevation, or enter a constant elevation for conversion.
5
6. If you wish, click the Open button and navigate to a
different directory for the output file (by default, the output
file is placed in the same directory as the input file). Give 6
it a different name if you wish.
7. By default, the Add converted 3D feature classes to
ArcMap document check box is selected. 8
8. Click the Options button on the Convert Features to 3D
dialog.
9. Click the check box for Feature Draping and type the
Point Spacing and Thinning Tolerance values. 7 14 15
10. Click inside the Planar Features window and select the
classes you want to use an interpolated value.
11. Specify how you want elevation to be assigned to 9
questionable areas.
12. Enter a minimum valid elevation value if you wish.
13. Click OK on the Feature to 3D Options dialog.
10
14. Click Convert on the Convert Features to 3D dialog.
15. Click Done when the status bar at the bottom of the
ArcMap window indicates that the process is complete.
11
12
13

Using the 3D to 2D converter
Stereo Analyst for ArcGIS also provides you with the ability to take For complete instructions about how to use this tool, refer to the
your 3D feature datasets and easily convert them to 2D using the section called “Converting 3D features to 2D” on page 31 in
Convert Features to 2D dialog. The process is the same as the 2D to chapter 2 “Quick-start tutorial”.
3D converter—you simply select the input 3D dataset, and Stereo
Analyst for ArcGIS produces a 2D dataset without the elevation (Z)
component.
The Convert Features to 2D dialog allows you to remove the height attribute
from feature datasets.
At the end of the export process, a new file is generated that is

named like the input file, but with an “_2D” designation. Of course,
if you want that file to be named something else and placed in a
different directory, you can click the Open button and make those
changes in an Output Features dialog.

What’s next?
Next, you’ll learn how to view in stereo (3D). You do so in the
Stereo Window, which has three possible configurations—the
1-Pane View, the 2-Pane View, and the 3-Pane View. You’ll also
learn about the toolbars that come with Stereo Analyst for ArcGIS
and how to best use the tools to your advantage.

5 Visualizing in stereo
5
IN THIS CHAPTER Stereo Analyst for ArcGIS provides you with tools so that you can easily view and
interpret your data—you do this using typical stereo visualization methods. This
• Introducing stereo visualization chapter introduces you to those methods and gives you tips for their most effective
use in Stereo Analyst for ArcGIS.
• Using Stereo Window views
In this chapter, you’ll learn about viewing imagery in 3D using stereo viewing
• Learning about the Stereo Analyst techniques. These techniques include using different Stereo Window views.
toolbar
You’ll also learn how to use tools found on the Stereo Analyst, Stereo View, and
• Learning about the Stereo View Stereo Enhancement toolbars.
toolbar
In the Stereo Window, you’ll see how to apply various tools regardless of whether
• Learning about the Stereo or not it is docked to or undocked from the ArcMap window.
Enhancement toolbar
Finally, you’ll learn about the best application of the stereo display options for
• Using Stereo Analyst for ArcGIS your application.
with ArcMap
• Setting stereo display options
105
Introducing stereo visualization
On a daily basis, we unconsciously perceive and measure depth using our eyes. Persons using both eyes to view an object have binocular
vision. Persons using one eye to view an object have monocular vision. The perception of depth through binocular vision is referred to as
stereoscopic viewing.
This anaglyph image shows a 1:1 image pixel to screen pixel ratio. With red/blue glasses, the drastic elevation differences in the region are obvious.

View ing imag er y in 3D • The collection of 3D coordinate information using stereo
viewing and feature collection techniques doesn’t depend on a
With stereoscopic viewing, depth information can be perceived DEM as an input source. Changes and variations in depth
with great detail and accuracy. Stereo viewing allows the human perception can be perceived and automatically transformed
brain to judge and perceive changes in depth and volume. In using the sensor model information associated with raw
photogrammetry, stereoscopic depth perception plays a vital role in imagery. Therefore, DTMs containing errors are not
using imagery to create and view 3D representations of the earth’s introduced into the collected GIS data. When compared to
surface. As a result of viewing overlapping images in stereo, orthorectified images (which require the use of an external
geographic information can be collected to a greater accuracy. This elevation source), a 3D digital stereo model (DSM) created
is because a true 3D representation of the earth’s surface is used using imagery is more accurate since an elevation model is not
instead of the traditional monoscopic techniques that use only one required as input.
image. • Digital photogrammetric techniques used in Stereo Analyst for
ArcGIS extend the perception and interpretation of depth to
Stereo feature collection techniques using oriented imagery provide include the measurement and collection of accurate 2D and 3D
greater GIS data collection and update accuracy when compared to GIS feature data.
other data collection and capture techniques. The following reasons
support why stereo feature collection techniques provide greater For more detailed information about stereoscopic viewing, see
data capture reliability and quality: appendix B, “Understanding stereo viewing” on page 199.
• Sensor model information derived from photogrammetric

block triangulation processing eliminates errors associated
with the uncertainty of sensor model position and orientation.
Accurate image position and orientation information (that is,
sensor model information) are required for the highly accurate
determination of 3D information. Sensor model information is
used together with imagery to create a 3D digital
representation of the earth’s surface.
• Systematic errors associated with raw photography and
imagery are considered and minimized during the block
triangulation process.
VISUALIZING IN STEREO 107

Using Stereo Window views
Stereo Analyst for ArcGIS provides three different Stereo Window
configurations for the collection of reliable GIS data using imagery.
U s i n g t h e 1 - Pan e V i ew
If the graphics card used by the computer does not support stereo
In this view, the sensor model information associated with each viewing, Stereo Analyst for ArcGIS automatically reverts to
oriented image in an image pair is used to visually superimpose the anaglyph stereo mode. See the Web site <http://support.erdas.com/
oriented images on one another, thereby creating a 3D digital specs/specs.html> for a list of graphics cards supported for use with
representation of the earth’s surface when viewed with the Stereo Analyst for ArcGIS.
appropriate stereo viewing hardware.
Viewing in quad-buffered stereo requires special hardware, such as an

emitter and stereo glasses.
If you do not have a stereo graphics card, you can work in anaglyph mode.
The 1-Pane View button is located within the lower-left portion of In anaglyph, shown above, Stereo Analyst for ArcGIS displays the
the Stereo Window. oriented images in red, green/blue to create a stereo view.

U s i n g t h e 2 - Pan e V i ew The 2-Pane View can be enabled by selecting the 2-Pane View
button located within the lower-left portion of the Stereo Window.
In the 2-Pane View, the left and right oriented images associated
with an image pair are separately displayed within the left and right
mono panes of the Stereo Window, respectively.
Using the 3 -Pane View
In the 3-Pane View, the 1-Pane View and the 2-Pane View are
embedded within the Stereo Window. This configuration was
designed so that you can collect feature data in the Stereo Window
while verifying data collected within the left and right mono panes.
The 2-Pane View shows the left image and the right image of the image pair.
The 2-Pane View is useful when stereo viewing hardware is not

available for stereo visualization. The 2-Pane View is also useful if
you cannot properly view overlapping oriented images in stereo. In
this case, positioning the 3D Floating Cursor on the same feature in
both panes during collection allows you to collect GIS data reliably
and accurately.
The 3-Pane View displays the stereo view and both mono images.

If the 3D Floating Cursor has been accurately placed on the feature
being collected, then the 3D Floating Cursor should reference the
same geographic location for that feature collected within the left
and right mono panes. The 3-Pane View is intended to provide a
simple setup for quick quality assurance during feature collection
and data update.
The 3-Pane View is the default Stereo Window setup used in Stereo
Analyst for ArcGIS. The 3-Pane View can be enabled by selecting
the 3-Pane View button located within the lower-left portion of the
Stereo Window.
Swit chin g lef t an d right imag es
If you need to switch the left and right images, you can do so by
using the Invert Stereo Model button, which is located on the Stereo
View toolbar.
Use of Invert Stereo Model is appropriate when areas of elevation

appear recessed in the Stereo Window and vice versa. Switching
the left and right images corrects this problem.

Learning about the Stereo Analyst toolbar
The Stereo Analyst toolbar is used to access functions and options associated with Stereo Analyst for ArcGIS, select the image pair to
display in the Stereo Window, and to open the Stereo Window.
.
Image Pairs list
Lets you choose
which image pair
to display in the
Stereo Window
from a dropdown list
Stereo Window
Click to open the
Stereo Window
The Stereo Analyst Image Pair Selection Tool

Dropdown Menu Click to select an image pair
Gives you access from the ArcMap data view
to a number of functions

L e a r n i n g a b o u t t h e S te r e o V i e w t o o l b a r
The Stereo View toolbar contains a number of tools used to efficiently operate within the Stereo Window.
Roam Zoom In By 2 Refresh Features Tool

Click to view Click for 1-time Click to refresh the
a different area application of zoom display of features
of the image pair in the Stereo Window
in real time
Manually Toggle Zoom to Data Extent 3D Position Tool

3D Floating Cursor Click to display Click to enter X, Y,
Click to use the all data in the and Z coordinates
F3 key to turn Stereo Window of a particular point
the 3D Floating Cursor and drive to that
on/off in the location
Stereo Window
Fixed Cursor Mode Scale Tool
Click so that the Click to select
cursor remains a predefined scale
stationary
Auto Toggle 3D
Zoom Out By 2 Synchronize Geographic Displays
Floating Cursor
Click to collect Click for 1-time Click so that the Stereo Window
features without toggling application of zoom and the ArcMap data view display
the same data coverage
Zoom In Tool Default Zoom
Click to magnify Click for a 1:1
by a power of 2 image pixel to
screen pixel ratio Invert Stereo Model
Zoom Out Tool Click so that the left image
Click to reduce of the image pair displays as
by a power of 2 the right image and vice versa
Terrain Following Mode

Click so that the 3D Floating
Cursor is automatically placed
on the ground or feature
of interest

Learning about the Stereo Enhancement toolbar
The Stereo Enhancement toolbar provides tools that allow you to control the contrast and brightness levels of the imagery displayed in the
Stereo Window.
Image Selector Reset Brightness Reset Contrast

Click to select Click to reset the Click to reset the
whether to apply amount of light amount of difference
enhancement to in the image pair between light and dark
the left, right, or to when it was in the image pair
to both images originally loaded to when it was
of the image pair originally loaded
Thumb Wheel Thumb Wheel
Increase brightness, right; Increase contrast, right;
decrease brightness, left decrease contrast, left
Increase Brightness Increase Contrast

Click to raise the Click to raise the
amount of light apparent difference
in the image pair between light and dark
in the image pair
Decrease Brightness Decrease Contrast

Click to lower the Click to lower the
amount of light apparent difference
in the image pair between light and dark
in the image pair

Openin g th e Stere o Win dow
The Stereo Window is where an image pair is displayed to

create a 3D digital representation of the earth’s surface. In the
Stereo Window, you can view your 3D features as well as
update and digitize features accurately. To open the Stereo
Window, perform the following steps.
1. Display the Stereo Analyst toolbar by clicking the ArcMap

View menu, then Toolbars, then checking the Stereo
Analyst toolbar.
2. Click the Stereo Window button on the Stereo Analyst
toolbar to open the Stereo Window. 1
Docking Stereo Analyst for ArcGIS windows

2
By default, when you first open a Stereo Window, it is
incorporated into the ArcMap workspace. You can undock it,
however, by clicking and holding on the bar at the top of the
Stereo Window and then dragging it outside the ArcMap
environment. The 2-Pane View works in the same fashion, but
the bar that controls docking is on the left side.
Docking the Stereo Window outside of the ArcMap workspace

is advantageous if a dual monitor configuration is being used for
feature collection. In this scenario, the Stereo Window is used
as the interface for collecting and editing features while the
ArcMap workspace is used as the cartographic station for
feature verification, attribution, and analysis.

Ap plyi ng tools in the Stereo W indow
Several tools designed to work in conjunction with the Stereo

Window can be used to increase the performance and 1
productivity of feature collection and editing.
1. Add data to the Stereo Window.

2
button to open a Stereo Window.
The Stereo Window opens with the setup displaying the
3
image pair in the top portion of the window, and the left
and right images of the image pair in the bottom portion
of the window—the 3-Pane View. In this example, the
Stereo Window is undocked from the ArcMap application.
3. On the Stereo View toolbar, click the Roam Mode button.
4. Move your cursor (which appears as a hand) into the
Stereo Window and hold down the left mouse button.
While the cursor is in the Stereo Window, drag the image
pair to a new position. X

5. Double-click inside the Stereo Window to enter the
Continuous Roam Mode.
The cursor changes from a hand to an arrow. As you
change the location of your mouse, the arrow changes
direction and speed accordingly.
6. Double-click inside the Stereo Window to exit the
Continuous Roam Mode.
You can also use the Zoom In/Out Tool in the Continuous
Zoom Mode.
7. Click the Zoom Out (or Zoom In) Tool button on the
Stereo View toolbar. X

8. Click and hold the scroll wheel inside the Stereo Window,
then move your mouse towards and/or away from you to
activate the Continuous Zoom Mode.
9. Release the scroll wheel to exit Continuous Zoom Mode.
10. Click the Default Zoom button to return the display to a
1:1 default zoom.
11. On the Stereo Enhancement toolbar, click the Adjust
dropdown arrow and select Right Image.
12. On the Stereo Enhancement toolbar, click the Image
Brightness Wheel and drag it all the way to the right to
change the display of the right image.
13. On the Stereo Enhancement toolbar, click the Image
Contrast Wheel and drag it to the right to change the
display of the right image. X
10
11
12 13

14. Observe the changes in the display.
Usually, you won’t make such drastic changes to the
appearance of the images in the Stereo Window. If you
don’t like the results, you can always reset the display of
the image pair to its original brightness and contrast.
15. On the Stereo Enhancement toolbar, click the reset
buttons both for Brightness and for Contrast.
The display returns to the original settings.
15

Using Stereo Analyst for ArcGIS with ArcMap
Most of the time, you’ll be using Stereo Analyst for ArcGIS in Ori entin g di splays
conjunction with ArcMap.
The Stereo Window and the ArcMap data view can be set to the
There are a few advanced options you can set so that the Stereo same orientation to make visualization and feature collection
Window and ArcMap data view compliment one another during easier. Stereo Analyst for ArcGIS also allows you to synchronize
feature collection and editing. You can set these options by the two displays (using the Synchronize Geographic Displays
accessing the Stereo Analyst toolbar, then clicking the Stereo button on the Stereo View toolbar).
Analyst dropdown list. From the list, select Options, then click on
the ArcMap Display tab. With both ArcMap and the Stereo Window displaying the data at
the same resolution and rotation, you can easily locate the same
feature in both applications. The orientation setting is retained for
ArcMap documents (.mxd) that you save and reopen in future
Stereo Analyst for ArcGIS sessions. Similarly, the orientation
setting is retained if you open different image pair in the same
ArcMap session. However, if you exit ArcMap, the orientation
setting must be reset when you resume your work.
Note that if you uncheck the Orient ArcMap document to Image

Pair when Image Pair changes check box, the display in the
ArcMap data view does not return to the original rotation. If you
want the image pair to unrotate, use the Data Frame Tools provided
by ArcMap.
Se lecting imag e p airs
Within ArcMap, an image pair can be interactively selected and

then displayed in the Stereo Window using oriented image
footprints.
The ArcMap Display tab is where you choose settings that control image pair
A footprint is a graphical representation of the boundary of an
behavior in the ArcMap data view.
individual oriented image. By default, Stereo Analyst for ArcGIS
displays the footprint in red. When two images overlap, that region
is again represented graphically, but in yellow. The overlap
portions of two oriented images is called an image pair, but can also
be referred to as a stereo pair.

If these colors don’t suit your needs, you can easily change them The overlap percentage of two photographs between two strips
using the dropdown arrows on the ArcMap Display tab of the (also referred to as sidelap) is commonly 20 percent. An image pair
Stereo Analyst Options dialog. The color changes are retained for created from two overlapping images in adjacent strips is not ideal
ArcMap documents (.mxd) that you save and reopen in future for stereo viewing and feature collection.
Stereo Analyst for ArcGIS sessions. Similarly, the footprint and
overlap colors are retained if you open a different image pair in the
same ArcMap session. However, if you exit ArcMap, the default
colors are reinstated when you resume your work.
Optimi zing d ispl ay p erformance
In cases where a mapping project uses many images (more than five
images) or large images (greater than 85 MB), the display of
oriented images in the ArcMap data view may be slow. Rather than
display each raster in ArcMap, Stereo Analyst for ArcGIS allows
you to display only the footprints of the oriented images. Selecting
this option on the ArcMap Display tab improves the display
performance in ArcMap.
Cal culating usable im ag e pa irs
Stereo Analyst for ArcGIS automatically computes valid image

pairs by determining whether or not two oriented images overlap.
Since each oriented image contains sensor model information (3D
position and orientation), Stereo Analyst for ArcGIS can determine
whether or not the two images overlap. In cases where multiple
images are being used in a project, Stereo Analyst for ArcGIS may
identify many image pairs, although not all of them may be suitable
for stereo viewing and feature collection.
During the collection of raw aerial photographs, flight plans are

purposely coordinated so that resulting photographs along a strip The top, left illustration shows a maximum overlap of 100 and a minimum
properly overlap so as to create an optimum 3D digital overlap of 60. With these settings, you can choose all overlapping images.
representation of the area of interest. The overlap percentage The bottom, right illustration shows a maximum overlap of 100 and a
minimum overlap of 25. With these settings, you can even choose the
between two photographs in a strip (also referred to as endlap) is sidelap area of image pairs. If you lower your minimum value, there are more
commonly 60 percent. This type of image pair is ideal for stereo possible image pairs from which to choose.
viewing and feature collection.
Stereo Analyst for ArcGIS computes image pairs based on an
Image Pair threshold percent setting on the ArcMap Display tab.
For example, if the threshold is set to 50 percent, the two images
considered must share at least half of the same geographic area to
be considered an image pair.
Depending on the type of data you use, the minimum and maximum
values may necessarily be different. For example, you might be
working with images that have only a 30 percent overlap; therefore,
you would change the minimum threshold value to ensure that you
get image pairs you can use in Stereo Analyst for ArcGIS.

Usi n g th e Ste r e o W in d ow w it h A rc M a p
2
When you use the Stereo Window in conjunction with
ArcMap, your ability to verify, assess, and analyze collected
features improves. Two important tools are Orient ArcMap
document to Image Pair when Image Pair Changes and
Synchronize Graphic Displays.
1. You may already have an image pair displayed in

ArcMap and the Stereo Window. This way, you can see
the change in orientation more clearly.
2. Click the Zoom to Data Extent Button to see all of the
image pair in the Stereo Window.
3. Note the position of the image pairs in ArcMap.
The overlap portion of the current image pair is
represented by the yellow border; image footprints are
represented by the red border.
If you are working in anaglyph mode, the overlap portion
of the current image pair displays in gray color, and the
left and right images of the image pair display in red and
blue, respectively.
If your graphics card supports quad-buffered stereo, the
entire display, both overlap and nonoverlap areas, 3
appears gray, but you can only see in stereo in the
overlap area.
You can get details about your graphics card by
accessing the Stereo Analyst toolbar, then clicking the
Stereo Analyst dropdown list, then clicking Graphics
Card Information. 4
4. From the Stereo Analyst toolbar, click the Stereo Analyst

dropdown list, and then select Options. X

5. Click the ArcMap Display tab.
6 5 8 7
6. Check the Orient ArcMap document to Image Pair when
Image Pair changes check box.
By choosing this option, you ensure that the rotation of
the image pair in ArcMap matches that of the image pair
displayed in the Stereo Window. As a result, the
orientation of the image pair in the Stereo Window is
used as a reference for orienting the ArcMap display.
This may help you locate features in both the Stereo
Window and the data view.
7. Click Apply on the Stereo Analyst Options dialog.
8. Click OK on the Stereo Analyst Options dialog.
9. Notice that the display of the image pair in ArcMap has
changed to reflect the same north-south orientation as
that in the Stereo Window.
Now, when you use tools such as Synchronize Graphic
Displays and Default Zoom, which are both located on
the Stereo View toolbar, the Stereo Window and ArcMap
both display the image pair in the same orientation. This
can help you as you digitize features.

Setting stereo display options
Like the options you can set affecting the display of data in Apply ing e pipol ar correction
ArcMap, there are also options you can set that affect the display of
oriented images in the Stereo Window. You can set these options The Use epipolar correction check box, when checked, removes
by accessing the Stereo Analyst toolbar, then clicking the Stereo Y-parallax from the image pair displayed in the Stereo Window.
Analyst dropdown list. Select Options from the list, then click on This leaves only X-parallax, which can be adjusted when the 3D
the Stereo Display tab on the Stereo Analyst Options dialog. Floating Cursor is in Fixed Cursor Mode. This ensures a more
accurate and visually comfortable stereo view.
For more information on Fixed Cursor Mode, see “Using Fixed

Cursor Mode” on page 156.
Using sensor model information, each oriented image in an image

pair is displayed so that, when viewed in stereo, a 3D digital
representation of the earth is perceived. In order to optimally
perceive imagery and features in 3D using stereo viewing
techniques, the images must be properly aligned. A feature
appearing on both the left and right image must be positioned along
the epipolar line.
At times a feature may not be properly displayed along the epipolar

line in both the left and right images. If the same feature appearing
in two overlapping oriented images does not appear along the
epipolar line, it is difficult to view the images in stereo and the
accuracy of the collected feature may not be as reliable.
By selecting the Use epipolar correction option, Stereo Analyst for

This is the Stereo Display tab. ArcGIS determines what correction needs to be made in order for
the feature to be positioned on the epipolar line for both the left and
Ch oosin g th e dis play area right images.
By default, Stereo Analyst for ArcGIS displays the entire image For more detailed information, see “Understanding the epipolar
pair in the Stereo Window. However, if you only want to see the line” on page 206.
overlap region common to the two images of an image pair, you can
select the Image Pair overlap region option. This only changes the
display in the Stereo Window, not the ArcMap data view.

Modifying screen do t pi tch The screen physical dimensions are approximate, and actual
dimensions may vary due to monitor settings. If an exact
The screen dot pitch is the size of the pixels on the screen. The X measurement is required, then measure the viewable area on the
screen dot pitch value is measured horizontally; the Y screen dot monitor and divide by the current screen pixel resolution.
pitch is measured vertically. This value is automatically computed
and is used for scaling in the Stereo Window. The more accurate the A p p ly in g c o n t r a s t st ret ch
screen dot pitch values are, the more accurate the scaling is in the
Stereo Window. Since the data file values in raster images often represent raw data
(such as elevation or an amount of reflected light), the range of data
To determine the appropriate screen dot pitch size for your display, file values is often not the same as the range of brightness values of
divide the screen physical size by the screen pixel resolution for the display.
each dimension. This information may be found on the Screen tab
of the Graphics Information dialog, which you access from the A contrast stretch, as the name implies, stretches the values of the
Stereo Analyst dropdown menu by clicking Graphics Card raster image to fit the range of the display. This results in a more
Information. crisp looking image in the Stereo Window.
You can choose from the following types of contrast stretches: Two
standard deviations, Min/max, Linear, or None.
Information about your system is readily available on the Graphics

Information dialog.
See the Web site <http://support.erdas.com/specs/specs.html> for a

list of graphics cards supported for use with Stereo Analyst for
ArcGIS.

Using a Two standard deviations stretch U s i n g a M in / m a x c o n t r a s t s t r e t c h
A Two standard deviations stretch uses the data that are between A Min/max contrast stretch makes the range of the data values vary
-2 and +2 standard deviations from the mean of the file values and linearly from the minimum statistics value to the maximum
stretches them to the complete range of output screen values. statistics value in the input direction, and from 0 to the maximum
brightness value in the output direction.
Output data
Output data
Input data
Input data
Output data
Histogram is yellow
Output data
Histogram is yellow
Input data
Original histogram is grey Input data
Original histogram is grey

Using a Linear contrast stretch In most raw data, the data file values fall within a narrow range—
usually a range much narrower than the display device is capable of
A Linear contrast stretch is a simple way to improve the visible displaying. The range can be expanded to use the total range of the
contrast of an image. It is often necessary to contrast-stretch raw display device. Note that you can only see a difference in images
image data so that they can be seen on the display. greater than 8 bits with this type of contrast stretch.
U s i n g n o s t r e t c h a t a ll
If you select None, the data is displayed in raw form without any
contrast adjustment.
Recente rin g th e ste reo cursor

Output data
The Automatic recenter of stereo cursor option automatically
recenters the 3D Floating Cursor to the center of the Stereo
Window. This occurs when Fixed Cursor Mode is not on and after
you have completed collecting or editing a feature. This option
helps minimize uncertainty as to where the 3D Floating Cursor is
Input data located and establishes a consistent position for the 3D Floating
Cursor while not forcing you to operate in Fixed Cursor Mode.
Displaying polygon outlines

Output data
Histogram is yellow
If a large feature dataset is being edited, performance may decrease.
One option for increasing the display speed of polygon features is
displaying only the outline of polygon features and not the texture
(fill) of the polygon itself. Selecting the Display Polygon Outlines
Only option displays the polygon but not the texture of the polygon.
This option is only applicable to the display of polygon features in
the Stereo Window and not the ArcMap display.
Input data
Original histogram is grey If this check box isn’t checked, then all polygon features are filled,
which masks the feature below it. If you aren’t concerned with the
details of features beneath polygons (such as trees in a large area
identified as a parcel of land), then filled polygons are acceptable in
addition to the outlines.

The top illustration shows filled polygons representing houses. The bottom
illustration shows the same polygons in the same area, but unfilled.

What’s next?
In the next chapter, you’ll learn all about what the 3D Floating
Cursor is, how to adjust it, how to use it in conjunction with
different modes, and some keyboard shortcuts.

6 Applying the 3D Floating Cursor
6
IN THIS CHAPTER Since Stereo Analyst for ArcGIS creates a 3D digital representation of the earth’s
surface using imagery, a standard cursor (2D) cannot be used to collect data. As a
• Using the 3D Floating Cursor result, Stereo Analyst for ArcGIS uses a 3D Floating Cursor that can be positioned
in all three dimensions (X, Y, and Z). This way, the 3D Floating Cursor can
• Adjusting the position of the 3D properly rest on the feature that is being collected or edited.
Floating Cursor
This 3D Floating Cursor gets its name because the cursor can float on, below, or
• Selecting 3D Floating Cursor above a feature. The cursor can also be referred to as a ground point, but in this
options document, the cursor is referred to as a 3D Floating Cursor. Understanding the
operation of the 3D Floating Cursor is very important since it is used to collect and
• Using the Terrain Following Mode edit features reliably in the Stereo Window.
• Applying other Terrain Following In this chapter, you’ll learn about using the different 3D Floating Cursor modes
Mode options
such as the Terrain Following Mode. You’ll also learn how to work with and
determine the accuracy of the 3D Floating Cursor in the Stereo Window. Plus,
• Checking accuracy of 3D
information keyboard shortcuts are described that can help you quickly view images and collect
features.
• Using the 3D Floating Cursor
• Using keyboard shortcuts
131
Using the 3D Floating Cursor
A 3D Floating Cursor consists of an independent cursor displayed The left and right cursors for the left and right images reference a
for the left image and an independent cursor displayed for the right location. When a feature is being collected in stereo, the image
image of an image pair. position of the cursor for the left and right image must be at the
exact same feature and location. If this does not occur, the feature
When images are not viewed in stereo, the 3D Floating Cursor cannot be reliably collected. For example, if a road along a rolling
simply appears to be two separate cursors that may or may not rest hill is being collected, the elevation of the 3D Floating Cursor must
on the same feature. However, when viewed in stereo, the two be adjusted so that the 3D Floating Cursor rests on the surface of
cursors fuse to create the perception of a 3D Floating Cursor. the road each time a point (vertex) for the road is collected.
It is referred to as a 3D Floating Cursor since the cursor commonly

floats above, below, or on a feature while viewing in stereo. The 3D
Floating Cursor is the primary measuring mark used in Stereo
Analyst for ArcGIS to collect and measure accurate 3D geographic
information.
While collecting or editing of features, the 3D Floating Cursor must

be positioned on the feature being collected. While viewing in
stereo, the 3D Floating Cursor is positioned on the feature being
collected by adjusting the X, Y, and Z coordinates of the 3D
Floating Cursor until it is perceived to be at the right location. The
X, Y, and Z position of the 3D Floating Cursor is adjusted using a
digitizing device such as the system mouse, the ITAC Systems
Mouse-Trak Professional, the Leica Geosystems TopoMouse, or
the Immersion SoftMouse.
This anaglyph image of an area in Laguna Beach, CA illustrates the 3D

Floating Cursor resting on top of a mountain ridge.

Adjusting the position of the 3D Floating Cursor
The position of the 3D Floating Cursor can be adjusted using a To observe this process, use Stereo Analyst for ArcGIS with the
digitizing device. For example, a system mouse with a scroll wheel Stereo Window in the 3-Pane View and turn on Terrain Following
can be moved to adjust the X and Y location while the scroll wheel Mode. Use the digitizing device to change the location of the 3D
can be adjusted up or down to either increase or decrease the Floating Cursor. While viewing in stereo, also notice how the left
elevation (Z) of the 3D Floating Cursor. Therefore, using the and right image positions of the cursors are being continuously
digitizing device, you actually have full control over the 3D adjusted so that they reference the same geographic area (this is
Floating Cursor, and can position it accurately and reliably within obvious in the 2-Pane View at the bottom of the Stereo Window).
the Stereo Window.
Every time the 3D Floating Cursor is adjusted, new 3D coordinates

are computed for the 3D Floating Cursor. 3D coordinates are
computed using the sensor model information associated with each
oriented image in the image pair. It is important to note that an
elevation model is not required to collect reliable 3D GIS data as
long as oriented images are being used.
Getting the best accuracy
If the 3D Floating Cursor is not accurately placed on the feature

of interest, the accuracy of the elevation of the feature won’t be
good. Manually adjusting the position of the 3D Floating
Cursor requires your continuous attention.
Pla cing the 3D F loating Cursor

auto matic ally
Stereo Analyst for ArcGIS uses an approach referred to as

automated terrain following to automatically adjust the position of
the 3D Floating Cursor so that it rests on the feature of interest as
the digitizing device is moved about in the Stereo Window. This
approach uses digital image correlation techniques to accurately
place the 3D Floating Cursor on the feature of interest.
The correlated 3D Floating Cursor is indicated by the green colorblock.
APPLYING THE 3D FLOATING CURSOR 133

Correlation is occurring automatically as the digitizing device is Another category that has tools you might want to customize is the
used to modify the position of the 3D Floating Cursor. Make sure Leica Feature Editing category. You can also drag these commands
you check the colorblock located at the bottom right of the Stereo to any existing toolbar.
Window. If it is green, the 3D Floating Cursor is accurately
positioned; if it is red, the 3D Floating Cursor has failed to correlate
and is not resting on the same feature in both the right and left
images of the image pair.
Usi ng c ustom tool s
Stereo Analyst for ArcGIS provides you with some custom tools for
use in controlling the position of the 3D Floating Cursor in the
Stereo Window. You can access these tools by selecting the Tools
menu, then Customize, then Commands. Click the Stereo Analyst
category to see the commands. You can drag the commands to any
existing toolbar.
The other category you can choose from is Leica Feature Editing.
Some notable Stereo Analyst for ArcGIS tools are described in the
following sections.
Decreasing elevation of the 3D Floating Cursor
Use the Decrease the elevation of the 3D Floating Cursor command

to lower the 3D Floating Cursor by one unit, such as meters.
Use the Customize dialog to add commands that do not already appear on
toolbars.

Increasing the elevation of the 3D Floating Cursor
Use the Increase the elevation of the 3D Floating Cursor command

to raise the 3D Floating Cursor by one unit, such as meters.
Recentering the 3D Floating Cursor
Use the Recenter the 3D Floating Cursor command to reposition the

3D Floating Cursor in the middle of the Stereo Window.
Completing feature collection or editing
Use the Complete editing feature command to finish collection of a

feature in the Stereo Window.

Selecting 3D Floating Cursor options
You can specify settings for the 3D Floating Cursor that provide A d j u s t i n g 3 D F lo a t i n g C u rso r s i z e
optimum viewing for your application. To set these options, access
the Stereo Analyst toolbar, then click the Stereo Analyst dropdown When referring to the 3D Floating Cursor size and width, a point
list, then choose Options. Click the 3D Floating Cursor tab. The 3D equals a pixel. Depending on the resolution of the images you are
Floating Cursor color, size, width, and shape can be modified there. working with, you may find that the size needs to be larger or
smaller. An optimum size is 28 points. Adjusting the size of the 3D
Floating Cursor refers to adjusting the linear size of the entire 3D
Floating Cursor.
A d jus t in g 3 D F loa t in g Cursor l i ne w i d th
Adjusting the line width of the 3D Floating Cursor adjusts the

thickness of the lines used to construct it. A point equals a pixel.
A d jus t in g 3 D F loa t in g Cursor sh apes
By default, the 3D Floating Cursor shape used in the Stereo

Window is a shaped like a cross (+). Certain 3D Floating Cursor
shapes are better for different applications—you can change the
shape quickly to see which works best for you.
The following table lists the different 3D Floating Cursor shapes.
The 3D Floating Cursor tab of the Stereo Analyst Options dialog is where you
make changes to the appearance of the 3D Floating Cursor in the Stereo
Window.
Ad justi ng 3D Fl oati ng Cursor col or
You may want a different color display for the 3D Floating Cursor,
which is white by default. While viewing in quad-buffered stereo,
an optimum 3D Floating Cursor color is red. While viewing in
anaglyph, optimum 3D Floating Cursor colors are yellow and
white.

For example, the Stereo Analyst for ArcGIS 3D Floating Cursor is
also able, like the cursor you see in ArcMap, to activate hyperlinks
3D Floating Cursor Shape 3D Floating Cursor Name associated with features. You simply click the Hyperlink button on
the Tools menu, then click the feature to activate the hyperlink in
Dot which you’re interested.
Cross
Open Cross
Open Cross with Dot
Open X
Open X with Dot
Ap plyi ng the 3D Floa ting Cursor in ArcMap
The Stereo Analyst for ArcGIS 3D Floating Cursor returns X, Y,

and Z coordinate information to any active ArcMap tool. Note that
not all ArcMap tools make use of the Z coordinate, however.

Using the Terrain Following Mode
The Terrain Following Mode can be used to automatically place the Using a Raster or TIN surface
3D Floating Cursor on the feature of interest so that you don’t have
to manually adjust the elevation of the 3D Floating Cursor every One method used by the Terrain Following Mode is to specify an
time you collect a feature. You choose settings that control the elevation source such as a DEM or an ESRI-format TIN. In this
Terrain Following Mode on the Terrain Following Cursor tab of the case, Stereo Analyst for ArcGIS uses the current X, Y location of
Stereo Analyst Options dialog. the 3D Floating Cursor and references the elevation source at the
same X, Y location to determine the elevation value.
The Terrain Following Mode provides two methods of operation
that determine how elevation information is calculated for the 3D U s i n g a C o n s t a n t e le v a t i o n
Floating Cursor. The options are either to use an external elevation
source or to use image correlation. If a raster or TIN file is not available, you can select the Constant
elevation option, and then enter an average elevation for the scene.
U s i n g ext e r n a l e l eva t i o n i n fo r m a ti o n
Using imag e correlation
This method of determining 3D Floating Cursor elevation is useful
when a dense elevation source is available, such as LIDAR, or if the This method works well in areas with rolling to mountainous
quality of the Z coordinate is not of primary importance. terrain. This method is less effective in dense urban areas with
shadow, or forested areas.
In the setup above, the elevation source is a raster DEM file. Image correlation is set to 85 percent, which ensures acceptable accuracy.

Another method (and the default method) used by the Terrain Using Minimum correlation threshold
Following Mode is image correlation. In correlation, an image
patch on the left image is used as a reference to search for the During the image correlation process, two image patches (one from
corresponding image patch in the right image. Once Stereo Analyst the left image and the other from the right image) are compared,
for ArcGIS finds the matching area, correlation is achieved. Using and a correlation coefficient is computed ranging in value from 0 to
the correlated left and right image positions along with the sensor 100. The optimum setting for the correlation coefficient is 85.
model information, Stereo Analyst for ArcGIS calculates X, Y, and
Z coordinates for the 3D Floating Cursor. Since the correlation process finds multiple matches for a particular
point on the ground in hope of finding the best match, Stereo
For more information about image correlation, refer to appendix C Analyst for ArcGIS can be optimized to only consider statistically
“Applying photogrammetry” on page 209. valid correlations. A correlation threshold value can be specified
that weeds out possible false candidates while retaining good match
U s in g t e r r a in f o ll o w i n g w it h i m a g e c o r r e l a t i o n candidates.
With image correlation, Stereo Analyst for ArcGIS consults the Selecting a low Minimum correlation threshold value increases the
images themselves to derive 3D coordinate information. Using probability of a false match, whereas increasing the correlation
sensor model information and the correlated image positions of a threshold may yield no correlation at all. A high Minimum
point on the ground, 3D coordinate information is computed correlation threshold value is preferred in forested and urban areas
directly from imagery without requiring an external elevation (with shadows) where the probability of a false match is high. A
source. low value is preferred in grassy areas and other areas where a
specific land cover type is homogenous in the area of interest.
Using an external elevation source, like a DEM, the images
themselves are not consulted at all for elevation information. Using Terrain slope
Instead, elevation information comes strictly from the DEM, which
may be outdated due to construction, natural disaster, and so on In images with a large amount of slope, correlation can be more
since it was created. difficult since the relief displacement on the ground creates a
parallax effect that increases with terrain variation. Similarly, if
Using the Correlation Options each image of the image pair is collected at a radically different
angle, the matching can be more computationally stressful to
Three correlation options are provided for optimizing the process. Therefore, in both instances you can set the Terrain slope
performance of the Terrain Following Mode when image slider bar to Steep. This forces Stereo Analyst for ArcGIS to
correlation is used. These include correlation threshold, terrain perform more extensive computations to ensure that the match of
slope specification, and image contrast specification, and are all points between images is correct. If the area of interest is flat with
located on the Terrain Following Cursor tab of the Stereo Analyst very little variation in elevation, the Terrain slope slider bar should
Options dialog. be set to Flat.

Using Image contrast
In areas of low contrast, it is more difficult to locate matching

points in the left and right images of the image pair. Since the image
correlation process operates on the grey level values of the oriented
images, the image contrast plays a vital role in the success of image
correlation. Setting the Image contrast level to reflect the actual
condition of the imagery (that is, Low or High contrast) helps
Stereo Analyst for ArcGIS apply rigorous methods to improve the
correlation results.
Activa ting the Terrai n Fo llow in g Mode
To activate the Terrain Following Mode, you can do one of the

following:
• Click the Apply continuous terrain following check box on the

Terrain Following Cursor tab of the Stereo Analyst Options
dialog.
• Click the Terrain Following Mode button located on the Stereo
View toolbar.
• Press the “t” key on the keyboard.

Applying other Terrain Following Mode options
You can choose other settings that control the behavior of the 3D
Floating Cursor when it is in Terrain Following Mode in the Stereo
Window. To set these options, access the Stereo Analyst toolbar,
then click the Stereo Analyst dropdown list and choose Options.
Then, click on the Terrain Following Cursor tab. The Terrain Following Mode remains toggled on until you either
uncheck the check box on the Terrain Following Cursor tab, click
the recessed Terrain Following Mode button (shown below), or
press “t” on the keyboard to deactivate the mode.
See “Using keyboard shortcuts” on page 149 for more shortcut

information.
Apply ing e levatio n bi as
Elevation bias is used in conjunction with the Terrain Following

Mode. The Terrain Following Mode provides the base ground
elevation value to which the elevation bias is added.
An example of when this feature is useful is when you are

collecting telephone pole features. This is illustrated in the
following diagram.
This is the Terrain Following Cursor tab of the Stereo Analyst Options dialog.
Usi ng c ontinuou s terra in foll ow ing
By clicking the Apply continuous terrain following check box, you

specify that the 3D Floating Cursor is always in Terrain Following
Mode. This way, you don’t have to toggle the Terrain Following
Mode on and off via the Terrain Following Mode button on the
Stereo View toolbar.

Note that not all features, in this case telephone poles, are
necessarily at the same ground elevation—one may be at 450
meters, but the next is located on top of a small hill where the
ground elevation is 451 meters. This is why using the Terrain
Following Mode is important with elevation bias—the elevation
bias is added to the ground elevation determined by the Terrain
Following Mode.
8 meters
When elevation bias is not in use, no additional elevation is added

to features. The Z value you see in the status bar of the Stereo
Window is the elevation recorded for that feature or vertex, and the
bias is set to zero (0).
U s i n g e l e v a ti o n b i a s t o a f f e c t Y - p a r a l l a x
If, while you are viewing in stereo, you perceive Y-parallax, you’ll
This illustration shows application of an elevation bias, 8 meters, to derive notice that your perception of 3D may not be comfortable.
telephone pole feature height.
Y-parallax can be adjusted using the digitizing device, such as the
Regarding the diagram above, the steps to collect the telephone system mouse. Position the 3D Floating Cursor inside the Stereo
features are as follows: Window (you may have to press the F3 key to give the 3D Floating
Cursor focus), then press and hold the “y” key on the keyboard.
1. Begin by putting the 3D Floating Cursor in Terrain Following Then, click and hold the left mouse button and move the mouse up
Mode and position it at the base of the feature. The elevation and down to adjust the Y-parallax of the images. Release the mouse
displays in the status bar at the bottom of the Stereo Window. button and the “y” key when you have the Y-parallax set to a
For example, the base of the telephone pole feature may be at comfortable viewing level.
an elevation of 450 meters.
2. Adjust the elevation of the 3D Floating Cursor so that it is at If Allow elevation bias is turned on, once Y-parallax has been
the top of the same feature and collect it. That elevation may adjusted, Stereo Analyst for ArcGIS computes a correction that is
add 8 additional meters, for a total elevation of 458 meters. applied to the elevation associated with the 3D Floating Cursor at
3. Collect all remaining similar features at the top of the feature. the time of collecting a feature.
Each individual base height as determined by the Terrain
See “Correcting Y-parallax” on page 203 for more information.
Following Mode plus the elevation bias, 8 meters, yields a
total elevation for each separate feature.

Usi ng Snap To Gro und
Using Snap To Ground in other ways
An alternative to continuously operating in the Terrain Following
Mode is the Snap To Ground function. Snap To Ground Although the name implies that you can only use it to position
automatically snaps the 3D Floating Cursor to an X, Y, Z ground the 3D Floating Cursor on the terrain, you can also use Snap To
position. Snap To Ground consults the Z value at the X, Y Ground to position the 3D Floating Cursor on top of buildings
coordinate you place the 3D Floating Cursor upon to determine the and other features.
ground elevation.
The process is the same: position the 3D Floating Cursor over
In order for Snap To Ground to work, either an elevation source the feature of interest in the same approximate location in both
must be specified, or image correlation is used to drive the 3D the left and right image of the image pair, then press the “s” key
Floating Cursor to the ground position at a particular location. You on the keyboard.
can set these preferences on the Terrain Following Cursor tab of the
Stereo Analyst Options dialog.
Snap To Ground works in both Fixed Image Mode (wherein the 3D

Floating Cursor moves freely in the Stereo Window, but the images
are stationary) and Fixed Cursor Mode, as well as while you are
digitizing features. Note that the Snap To Ground functionality
does not work in conjunction with the Terrain Following Mode, as
the 3D Floating Cursor is already on the ground if you’re using that
utility.
While the 3D Floating Cursor is within the Stereo Window, press

the “s” key on the keyboard to snap the 3D Floating Cursor to the
ground. If you want to use the Snap To Ground feature while you
are collecting features, you must apply it using the “s” key on the
keyboard before you collect each vertex of the feature.
For more information about snapping in 3D, see “Using 3D Snap”

on page 162.

Ap plyi ng the Te rrain Following Mo de
Before you begin this exercise, you should already have

Stereo Analyst for ArcGIS installed, and both ArcMap and
Stereo Analyst for ArcGIS should be running on your
machine.
Using image correlation, the Terrain Following Mode checks

1
pixels from both images of the image pair to automatically
position the 3D Floating Cursor to rest on a feature of interest.
All you have to do is position the 3D Floating Cursor in the
Stereo Window in X and Y.

dropdown list and choose Options. 2
2. On the Stereo Analyst Options dialog, click the Terrain
Following Cursor tab.
3. Make sure that the Use image correlation option is active.
4. Click OK on the Stereo Analyst Options dialog. X
3 4

5. Click the Terrain Following Mode button on the Stereo
Analyst toolbar. 6 5
When it is selected, it appears recessed on the toolbar.
6. Click the Fixed Cursor button on the Stereo Analyst
Toolbar.
When it is selected, it appears recessed on the toolbar.
With the 3D Floating Cursor in a fixed location, you can
use the X and Y thumb wheels at the right of the Stereo 7
Window to adjust the displayed portion of the image pair.
You can also use the Roam Tool to move around the
image pair in the Stereo Window.
7. Move the X and Y thumb wheels up and/or down to
adjust the position of the image pair “under” the 3D
Floating Cursor to a desired position.
8. Note the elevation value displayed at the bottom of the
Stereo Window, which updates as you adjust the image
pair position.
As the 3D Floating Cursor moves to different positions,
new X, Y, and Z coordinates are automatically computed.
When image correlation succeeds, a green colorblock
displays in the lower-right portion of the Stereo Window.
When image correlation fails, a red colorblock displays in
the same area.
Reading LE90 and CE90
In cases where the Terrain Following Mode fails to reliably

position the 3D Floating Cursor on the ground or feature of
interest, a red colorblock is displayed in the lower-right portion
of the Stereo Window interface. See “Checking accuracy of 3D
information” on page 146 for an explanation of the CE90 and
LE90 computations. 8

Checking accuracy of 3D information
If you check the lower right-hand side of the Stereo Window when Using CE90 and LE90 while you wo rk
the 3D Floating Cursor is in Terrain Following Mode, you see
CE90 and LE90 with numerical values. These are accuracy indices As you work in Terrain Following Mode, CE90 and LE90 values
that are derived from the sensor model information associated with are reported in the lower-right corner of the Stereo Window. These
each oriented image in an image pair. values are theoretical error distribution values.
Both CE90 and LE90 are computed based on the sensor model If the correlation has failed, indicated by a red colorblock, the
information that is part of the metadata associated with the oriented numbers are not representative of anything. If the correlation has
images. This information is derived photogrammetrically when the succeeded, indicated by the green colorblock, the numbers indicate
position and attitude of the sensor as it existed as the time of capture the standard deviation of the point feature. This colorblock is only
is computed. active when the 3D Floating Cursor is in Terrain Following Mode.
CE90 and LE90 provide a quality index for the current position of If the colorblock is green, as shown below, then the 3D Floating
the 3D Floating Cursor. CE90 refers to circular error and LE90 Cursor is correlated and is located on the same feature in both the
refers to linear error. The 90 refers to the level of confidence in the left image and the right image of the image pair.
3D coordinates of the point. For example, an LE90 of 1.765 meters
means that the current position of the 3D Floating Cursor is reliable
to ± 1.765 meters.
The equation to compute CE90 is as follows: If the colorblock is red, as shown below, the 3D Floating Cursor is
not correlated and is not located on the same feature in both the left
image and the right image of the image pair.
CE90 = ( ΣX + ΣY )1.073
The equation to compute LE90 is as follows:
LE90 = ΣZ × 1.646
In these equations, sigma (Σ) represents the standard error of the

coordinate in question.

Using the 3D Floating Cursor
To ggli ng m a nual ly When the Manually Toggle 3D Floating Cursor Mode is toggled off
(as depicted below), the mouse controls a standard Windows
The Manually Toggle 3D Floating Cursor Mode button is located cursor, which allows you to make selections on toolbars and from
on the Stereo View toolbar. When the Manually Toggle 3D menus.
Floating Cursor Mode button is toggled on (as depicted below) and
you press the F3 key on the keyboard, you can freely move the 3D
Floating Cursor and update its position in the Stereo Window.
You’ll see the standard Windows cursor (an arrow) as you move it
into the Stereo Window. This is the best mode to use (if you don’t
have a special motion device like the Leica Geosystems
Any adjustment of the mouse’s scroll wheel adjusts the elevation of TopoMouse). Remember, to reenter the Manually Toggle 3D
Floating Cursor Mode, press the F3 key on the keyboard.
the 3D Floating Cursor. Use the status bar at the bottom of the
Stereo Window to see the current elevation. Press the F3 key again
to exit Manually Toggle 3D Floating Cursor Mode—you’ll see the Toggl ing a utoma tical ly
standard Windows cursor (an arrow) display in the Stereo Window.
When active, the Auto Toggle 3D Floating Cursor Mode eliminates
Of course, you might have the 3D Floating Cursor manually the need to press the F3 key in order to use the 3D Floating Cursor
toggled on in conjunction with Fixed Cursor Mode. The Fixed in the Stereo Window. The button associated with the toggled on
Cursor Mode button, toggled on, is shown below. Auto Toggle 3D Floating Cursor Mode is shown below.
As you move the 3D Floating Cursor inside the Stereo Window, it

In this case, you are moving the images “beneath” the 3D Floating
is already active, and the standard Windows cursor does not appear.
Cursor. Any adjustment of the mouse’s scroll wheel adjusts the
As you move the 3D Floating Cursor back outside of the Stereo
position of the left and right images of the image pair, which affects
Window, the standard cursor reappears, which enables you to select
parallax. Aligning the image pair so that the same features overlap
different target layers, editing modes, feature collecting and editing
yields accurate elevation. Use the status bar at the bottom of the
tools, and the like. This functionality is particularly helpful when
Stereo Window to see the current elevation of the 3D Floating
you use the ArcMap Editor to collect and/or edit features.
Cursor.
Some things to be aware of while using the Auto Toggle 3D
Floating Cursor Mode include:

• You cannot roam over the entire image pair unless it is zoomed
out to a large extent, but you can use the keyboard shortcuts
“x” and “z” to adjust the scale of the image pair displayed in
the Stereo Window.
• You can’t use Auto Toggle 3D Floating Cursor Mode in
conjunction with Fixed Cursor Mode, wherein the images can
be adjusted to improve the stereo view. The reason for this is
that the 3D Floating Cursor never exits the Stereo Window,
and therefore never is able to toggle off.
• You can’t keep the 3D Floating Cursor positioned on a specific
point if you need to use the mouse for normal system events
(like making a selection from a menu) since you need to
position the cursor close to a window border to exit.

Using keyboard shortcuts
Stereo Analyst for ArcGIS includes a number of keyboard shortcuts Using “c ”
that allow you to quickly access common functions. They can save
you time since it isn’t necessary to move the 3D Floating Cursor to Press the “c” key to toggle between Fixed Cursor and Fixed Image
execute the command specified by the keyboard shortcut. Mode. This can be useful if you prefer to roam about the image pair
displayed in the Stereo Window in Fixed Image Mode and collect
Usi ng F 3 features in the Stereo Window in Fixed Cursor Mode.
Press F3 to toggle the 3D Floating Cursor on and off in the Stereo Using “i ”
Window. This switches between the regular, Windows cursor and
the 3D Floating Cursor when the system mouse is positioned over Press the “i” key to toggle between Fixed Image Mode and Fixed
the Stereo Window and this shortcut is selected. You may have to Cursor Mode. See “Using “c””, above.
click inside the Stereo Window before pressing F3 to give the
cursor focus. Using “a ”
Usi ng F 4 Press the “a” key to activate the Arrow tool (the standard Windows
pointer), which can be used to select buttons and options.
Press F4 to resynchronize the ArcMap display with the display in
the Stereo Window. This shortcut modifies the ArcMap display so Using “z”
that it shows the same geographic area as the Stereo Window.
Press the “z” key to zoom in the area of display by 1.5 in the Stereo
Using “t” Window.
Press the “t” key to toggle the Terrain Following Mode. This Using “x ”
shortcut should be used when you want the 3D Floating Cursor to
follow the terrain’s elevation. See “Using the Terrain Following Press the “x” key to zoom out of the area of display by 1.5 in the
Mode” on page 138 for more information. Stereo Window.
Usi ng “s” Using “r”
Press the “s” key to apply Snap To Ground. This shortcut is good Press the “r” key to recenter the area of the image pair displayed so
when you’re doing feature extraction in an area where it is difficult that the 3D Floating Cursor is in the middle of the Stereo Window.
to accurately place the 3D Floating Cursor on the ground. The 3D This shortcut is useful when navigating near the edges of the Stereo
Floating Cursor’s elevation is automatically adjusted so that it is Window. See “Recentering the stereo cursor” on page 127 for more
placed on the ground or feature of interest. See “Using Snap To information.
Ground” on page 143 for more information.

U s in g “ y ”
Press the “y” key to adjust Y-parallax. The 3D Floating Cursor

must be toggled on in the Stereo Window. Hold down the “y” key,
then hold down the left mouse button and move up and down to
improve vertical separation. For more information, see “Using
elevation bias to affect Y-parallax” on page 142.

What’s next?
In the next section, you can learn about feature collecting and
editing in the Stereo Analyst for ArcGIS environment. You do so
using tools found in ArcMap and some new Stereo Analyst for
ArcGIS tools.

Working with features
Section 3
7 Capturing GIS data
7
IN THIS CHAPTER To collect features in Stereo Analyst for ArcGIS, you make use of the existing
ArcGIS tools that you’re probably already familiar with. These tools are located on
• Collecting features in different the Editor toolbar, and can be applied both in ArcMap and the Stereo Window.
modes Stereo Analyst for ArcGIS also provides you with some new tools to make your
feature collection and editing easy in the Stereo Window.
• Using 3D Snap
In this chapter, you’ll learn about how to determine the best mode for feature
• Using Squaring collection and whether or not you may be able to apply 3D Snap settings to collect
adjacent 3D features.
• Using the Monotonic Mode
You’ll also learn about applying Squaring settings to collect 3D features, and using
• Using digitizing devices the Monotonic Mode for special applications.
Finally, you’ll learn about the button mapping process for digitizing devices. If you
need more detailed information about digitizing devices, you can find it in the
Stereo Analyst for ArcGIS On-line Help.
155
Collecting features in different modes
Stereo Analyst for ArcGIS has different modes in which you can
digitize features in the Stereo Window. These different modes are
described in the following sections.
Usi ng F ixed Curso r Mo de Using Fixed Image Mode while collecting features is appropriate
when the feature you’re digitizing fits easily within the Stereo
When the Stereo Window is in Fixed Cursor Mode, the 3D Floating Window. Click inside the Stereo Window to give the cursor focus,
Cursor is fixed in the center of the Stereo Window. Adjustments then press F3 on the keyboard to apply the 3D Floating Cursor in
you make affect the position of the left image and right image of the the Stereo Window.
currently displayed image pair. When you are in Fixed Cursor
Mode, the Fixed Cursor Mode button on the Stereo View toolbar Using Terrain Fol lowin g Mode
appears to be recessed, as follows:
As you learned in “Using the Terrain Following Mode” on page
138, the Terrain Following Mode maintains the position of the 3D
Floating Cursor on the ground or a feature of interest without your
manual adjustment of the elevation of the 3D Floating Cursor.
When the Terrain Following Mode is active, the Terrain Following
Using Fixed Cursor Mode while collecting features is appropriate Mode button on the Stereo View toolbar appears to be recessed, as
when working in the Manually Toggle 3D Floating Cursor Mode follows:
and when you are using a TopoMouse. It is particularly useful when
the feature you’re digitizing extends beyond the Stereo Window
display.
You cannot use the Fixed Cursor Mode in conjunction with the
Auto Toggle 3D Floating Cursor Mode.
You can use the Terrain Following Mode while digitizing so that
the 3D Floating Cursor is on the feature. Make note of the CE90 and
Usi ng F ixed Imag e Mode
LE90 values and the red or green colorblock, which are located at
the bottom, right of the Stereo Window. These indicate whether or
When the Stereo Window is in Fixed Image Mode, the 3D Floating not the 3D Floating Cursor is correlated at that location to ensure
Cursor can move, but the images are fixed. Adjustments you make accuracy as you collect features. See “Checking accuracy of 3D
affect the separation and location of the 3D Floating Cursor. This information” on page 146 for more information about CE90 and
mode is appropriate when working with a system mouse, and works LE90.
best when the Auto Toggle 3D Floating Cursor Mode is in use.
When you are in Fixed Image Mode, the Fixed Cursor Mode button
on the Stereo View toolbar does not appear to be recessed, as
follows:

Usi ng Au to Toggle 3 D F loati ng Cursor
Mode
When you are in Auto Toggle 3D Floating Cursor Mode, you can
move your 3D Floating Cursor freely inside and outside the Stereo
Window without having to press the F3 key each time you want to
activate the 3D Floating Cursor for collecting or editing features.
When you are in Auto Toggle 3D Floating Cursor Mode, the Auto
Toggle 3D Floating Cursor Mode button appears recessed in the
Stereo View toolbar, as follows:
An advantage to using this mode is that you can freely change your
selections on the Editor toolbar, then move right back into the
Stereo Window to continue your work.
Usi ng the co ntext menu
As you collect and edit features in the Stereo Window, you have The options you’ll see on the menus change depending on the mode
access to shortcuts by clicking the right mouse button. These you’re in. The tools specific to Stereo Analyst for ArcGIS are
options are only available during feature collection and editing. explained in the rest of this chapter. All of the other tools are well
documented in the book Editing in ArcMap as well as the On-line
Help.
CAPTURING GIS DATA 157

Co llecting features in Fixed Imag e Mode
The next steps tell you how to collect features in Fixed Image
Mode in the Stereo Window. Fixed Image Mode is best used
when the feature you want to collect displays wholly in the
Stereo Window.
1. First, make sure that the editing toolbar is displayed by

clicking the View menu, then pointing to Toolbars. Then,
click Editor.
2. On the Stereo View toolbar, make sure that the Fixed
Cursor Mode is not active. (If it is active, it appears
recessed in the Stereo View toolbar.)
You cannot have the Fixed Cursor Mode active in 1
conjunction with the Auto Toggle 3D Floating Cursor
Mode. Click the button to deselect the Fixed Cursor
3 2
Mode button if necessary.
3. On the Stereo View toolbar, click the Auto Toggle 3D
Floating Cursor button.
4. On the Editor toolbar, click the Editor dropdown arrow
and choose Start Editing.
4
6. On the Editor toolbar, click the Target dropdown list and
choose the feature class into which you want the digitized
feature to be stored.
5 6
7. On the Editor toolbar, click the Sketch Tool button.
At this point, when you move the cursor back into the
Stereo Window, you’ll be able to digitize the feature of
interest. X 7

8. Click to collect the first vertex of the feature.
9. Continue digitizing around the perimeter of the feature
collecting corners.
10. Double-click to terminate collection of the feature.
11. On the Editor toolbar, click the Editor dropdown list and 8
choose Stop Editing.
12. Click Yes on the Save dialog to save the feature you just
collected, or No to discard the feature you just collected.
10
11
12

Co llecting features in Fixed Cu rs or Mode
Another way to digitize features is in the Fixed Cursor Mode.

In this mode, the feature’s position is adjusted by you
“beneath” the 3D Floating Cursor. This mode is best used
when the feature extends beyond the display of the Stereo
Window. 1
1. First, make sure your Stereo Window is open and that

the feature you want to digitize is clearly displayed with
minimal parallax.
D i g it i z i n g f e a t u r e s o u t s i d e t h e d is p l a y
You may encounter a feature that extends outside the Stereo

Window (depending on the scale at which you display the
image pair). In a case like this, you can set an option so that the
3D Floating Cursor is recentered as you approach the extent of 2
the Stereo Window. This way, you can continue to collect a
feature that was initially extending beyond the Stereo Window.
From the Stereo Analyst toolbar, click the Stereo Analyst

3
dropdown list, then click Options. Click the Stereo Display tab,
then click Automatic Recenter for Stereo Cursor. Click Apply,
then OK to activate the setting.
2. Make sure that the Editor toolbar is displayed. If it is not,

click the Editor Toolbar button, or click the View menu, 4
then point to Toolbars, then click Editor to display the
toolbar.
3. On the Stereo View toolbar, click the Manually Toggle 3D
Floating Cursor button and the Fixed Cursor Mode
button. Both appear recessed.
4. On the Editor toolbar, click the Editor dropdown list and
choose Start Editing. X

6. On the Editor toolbar, click the Target dropdown list and 5 6
choose the appropriate feature class.
7
7. On the Editor toolbar, click the Sketch Tool button.
8. Move the cursor into the Stereo Window, click, then press
the F3 button on the keyboard to toggle on the 3D
Floating Cursor.
You can tell that you are in Fixed Cursor Mode because
as you move your mouse the image pair changes
location in the Stereo Window, yet the 3D Floating Cursor
remains in the center of the Stereo Window.
9
9. Click to collect the first vertex of the feature, then click to
collect remaining vertices of the feature. When you are
finished, double-click to complete the feature, or press F2
on the keyboard.
10. Press the F3 button on the keyboard to toggle off
Manually Toggle 3D Floating Cursor Mode.
The Arrow Tool again appears in the Stereo Window, and
the image pair no longer changes position with your
mouse movement.
choose Stop Editing. 11
12. Click Yes on the Save dialog to save the feature you just
collected, or click No to discard the feature you just
collected.
12

Using 3D Snap
You can change the settings for 3D Snap by accessing the Editor
toolbar, then clicking the Editor dropdown list. Then click Options, Setting snapping in X and Y
then click the 3D Snap tab of the Editing Options dialog. These
options are specific to Stereo Analyst for ArcGIS. The 3D Snap options also work in conjunction with preferences
set on the General tab of the Editing Options dialog.
Using the se ttin gs on the 3D Sna p tab
There, you see a preference for Snapping tolerance (indicated
The settings on the 3D Snap tab only control snapping in the Z, or by the red box, below). You can set the snapping tolerance there
elevation, direction. as well as the units in which tolerance is measured. The
tolerance displayed in this window is for X and Y coordinates
only.
The 3D Snap tab is where you set tolerance values for coordinates in the Z,
elevation, direction.

S e t t i n g t h e sn a p p i n g t o l e r a n c e i n Z The following diagram illustrates snapping. The position of the 3D
Floating Cursor labeled 1 is within the tolerance of 1 map unit;
If the vertex you collect is not within the tolerance you set, the 3D therefore, clicking to select a vertex to begin the adjacent roof snaps
Snap tab on the Editing Options dialog has options for that case as to that vertex. However, the position of the 3D Floating Cursor
well. If you are very interested in the accuracy of the Z coordinate, labeled 2 is outside the 1 map unit tolerance, and would not be
set the preference so that no snapping occurs. If you are mostly snapped to the corner vertex.
concerned with the X and Y coordinates, click the 2D snap option.
S e t t in g c a c h e s iz e
The Cache size is used to store all features around the cursor
position as the 3D Floating Cursor moves around in the Stereo
Window. The default cache size of 10 means that the cache around 2
the 3D Floating Cursor covers a range 10 times the planar snapping
tolerance. The planar snapping tolerance is set on the General tab 1
of the Editor Options dialog.
Setting a small value causes the cache to be refreshed more

In the above illustration, 3D Floating Cursor 1 is inside the map unit tolerance
frequently, but reduces the time searching for the snapped feature.
and will be used for 3D Snap.
Increasing the cache causes the cache to be refreshed less
frequently, but increases the time searching for the snapped feature. In the case of the 3D Floating Cursor labeled 2 above, Stereo
Analyst for ArcGIS consults another setting on the 3D Snap tab: If
Ap plyi ng 3D Snap tools elevation out of tolerance. Had you clicked to select the vertex at
that location, either no snapping would occur, or the vertex would,
The 3D Snap functionality controls the 3D Floating Cursor so that indeed, snap to the existing vertex, but only in X and Y coordinates.
it must be within a certain map unit range in order to snap to a The Z coordinate (elevation) would not be used in snapping.
feature vertex (3D Vertex Snap) in X, Y, and Z; or part of a line
segment (3D Edge Snap) in Z. Some 3D Snap keyboard shortcuts include:
On the 3D Snap tab of the Editing Options dialog, you see a check • Endpoint—Ctrl + F5
box for Use elevation tolerance. The tolerance value, which is set
• Vertex—Ctrl + F6
to 1 by default, is measured in map units. That is, your 3D Floating
Cursor must be within one map unit, such as a meter, in Z in order • Midpoint—Ctrl + F7
to snap to the vertex. • Edge—Ctrl + F8

Ap plyi ng 3D sn appin g
When you use 3D Snap, you are snapping to existing vertices 2

in the X, Y, and Z direction.
1. You should already have Stereo Analyst for ArcGIS

running and raster data and feature data displayed in the
Stereo Window.
2. Click the Editor dropdown list, then choose Start Editing.
3. Click the Editor dropdown list again, then choose
Snapping.
A window opens displaying the snapping agents.
4. In the window, click the plus sign next to Miscellaneous.
5. Click the boxes to select either or both 3D Edge Snap
and 3D Vertex Snap. X

6. Navigate in the Stereo Window to the feature to which 8
you want to snap a new feature.
7. On the Editor toolbar, make sure that the Task and
Target settings are correct.
8. On the Editor toolbar, click the Sketch Tool.
9. Position the 3D Floating Cursor near the existing feature.
Notice that a second, smaller cursor appears alongside
the 3D Floating Cursor. This is to show you where the
snapping is to occur.
10. Click to collect the first vertex.
Notice that the vertex is automatically snapped to either
an edge or to a vertex, whichever is closest.
11. Continue to digitize your feature.
12. Double-click to digitize the last vertex, or press F2 on the
keyboard, so that it also snaps to the existing feature.
10
12

Cu s to m i zi n g 3 D Sn a p
3D Snap can be easily accessed from a toolbar by

customizing ArcMap.
1. In ArcMap, click the Tools menu, then click Customize.

This opens the Customize dialog.
2. On the Customize dialog, click the Command tab.
3. Click the Leica Feature Editing category.
4. One by one, click, hold, and drag Enable Snap 3D Edge
and Enable Snap 3D Vertex to an existing toolbar, such
1
as the Stereo View toolbar.
Once they are in place, selecting either of these buttons
activates their respective functions, which is the same as
checking the 3D snapping boxes in the Miscellaneous 2
section of the Snapping window.
5. Click Close on the Customize dialog.
3 4 5

Using Squaring
Squaring is intended to help you rapidly collect features with right Use of Squaring is most appropriate when you are digitizing
angles. Squaring is only for use in digitizing polylines and features with right angles. Squaring attempts to square a feature
polygons—it is not applicable to point features. based on the rotation method you select and the tolerance value you
specify.
You can change the settings for Squaring by accessing the Editor
toolbar, then clicking the Editor dropdown list. Then click Options,
then click the Square tab. To use Squaring during feature collection, Predicting results
click the check box labeled Enable squaring. The Squaring options
are specific to Stereo Analyst for ArcGIS. The results you get from Squaring are highly dependent upon
the tolerance setting, the rotation mode, and the order or
direction of digitizing.
Se ttin g th e to lera nce
In each of the rotation modes, the tolerance value used in squaring

is measured in map units. This tolerance value specifies the greatest
distance a vertex can be moved to square the feature.
If a vertex can be moved by a value that is less than or equal to the

tolerance to make the feature corner square, it is moved. If the
vertex would have to be moved farther than the tolerance to make
the corner square, it is not moved.
The tolerance value should be kept as small as possible. In the

following illustration, the red polygon represents the ideal
rectangle. One of the vertices can be moved because the distance is
within the specified tolerance. The other remains in its original
location.
You set Squaring tolerances on the Square tab.

This method is good because it averages out measurement
Outside tolerance inaccuracies at all points. The tolerance value in the following
example is 3.0. The red polygon represents the result of squaring.
d
rd
ra
c
Within tolerance a rc
Vertices within tolerance are moved. Those outside tolerance aren’t moved. b
rb
Setting rotation mode
You can choose from four methods to determine the alignment of The Weighted mean rotation mode calculates the average rotation based
the feature. The first choice, Weighted mean, uses the length- upon the length and angle of each segment.
weighted angle of all sides to determine the alignment. First line Using the First line rotation mode
uses the line formed by the first two digitized vertices of a feature
as alignment. Longest line uses the longest side of a feature as Using the First line rotation mode means that the first and second
alignment. Active view alignment makes the squared feature have vertices form the line which is used to square the feature.
sides either horizontal or vertical to the ArcMap data view.
The tolerance value in each of the following two examples is 10.0.
Using the Weighted mean rotation mode The red polygon represents the result of squaring.
Weighted mean is the default rotation mode used by Squaring.
Using the Weighted mean rotation mode means that the length- Figure A Figure B
weighted mean angle (R) of all sides is used to determine the 4
alignment. Once the alignment angle has been determined, the
vertices are adjusted within the tolerance to square corners where
possible.
3 1
The Weighted mean function is expressed in the following
equation:
2
( ra × a ) + ( rb × b ) + ( rc × c ) + ( rd × d ) If you digitize clockwise, the First line rotation mode uses the first line
R = ----------------------------------------------------------------------------------------------
a+b+c+d digitized as the basis for squaring. Figure A shows the original polygon;
Figure B shows the squared polygon.

The First line rotation method is sensitive to the order in which you
digitize the feature vertices. If you digitize the feature in a 1
clockwise direction, then the first line is the line formed between
the first two vertices. However, if you digitize the feature in a 2
counter-clockwise direction, then the first line is the line formed Figure A 4
between the last two vertices.
3
Figure A Figure B
2
Figure B
3 1
The Longest line rotation mode uses the longest line of the feature as the
basis for squaring. Figure A shows the original polygon; Figure B shows the
4 squared polygon in red. NOTE: segment 4 was not moved because it was
not within the tolerance value.
Digitizing the same line first but in the counter-clockwise direction can yield Using the Active view alignment rotation mode
vastly different results.
The Active view alignment rotation mode uses the borders of the
ArcMap data view to square the feature in either a horizontal or
D ig it i z in g f e a t u r e s vertical direction, or both if possible.
When using First line rotation, always digitize in a clockwise
direction.
U s i n g A c t i v e v i e w a li g n m e n t m o d e
Using the Longest line rotation mode When you are using this mode, it is best to have the Orient
ArcMap document to Image Pair when Image Pair changes
Using the Longest line rotation mode means that the line with the
option on. This option is located on the ArcMap Display tab of
greatest length is used to square the feature. In this mode, the order
the Stereo Analyst Options dialog.
in which you digitize vertices does not matter.
For more information about the Orient ArcMap document to
Image Pair when Image Pair changes option, see “Orienting
displays” on page 119.

When the Stereo Window and the ArcMap data view are oriented
in the same direction, the results from this rotation mode are more 1
consistent. That is, the final position of the feature is the same in Figure A
both. Otherwise, the feature may appear in a different rotation in the 2
Stereo Window and the ArcMap data view.
1
Figure B 2
1
4
Figure A 2
1
Figure C 2
Figure A shows the vertices outside tolerance. Figure B shows the squared
Sides 1 & 3 adjusted polyline. Figure C shows the straightened polyline. NOTE: Resultant line
to be parallel (red) is shown slightly offset for clarity.
Figure B
with the ArcMap
data view.
The Active view alignment uses the ArcMap data view boundaries as a
guide.
Squ ari ng po lyl ines
Squaring polylines also considers making them straight. If greater

movement of a vertex is required to make a right angle than to make
the line straight, the lesser movement is taken and the line is made
straight. As with squaring polygons, if movement of a vertex would
be greater than the tolerance value, the vertex is not moved. All
vertices are preserved, thus allowing you to edit the line after
creating it.

Co nfig uri ng th e Squaring tool
1
To set the proper options on the Square tab of the Editing
Options dialog, please read “Using Squaring” on page 167.
1. On the Editor toolbar, click the Editor dropdown menu.

2. Click Options to open the Editing Options dialog.
3. On the Editing Options dialog, click the Square tab.
4. Click the Enable squaring check box.
5. Select the preferred Rotation mode from the dropdown
list.
6. Set the Tolerance value.
7. Click Apply, then OK.
8. Collect features in the Stereo Window as usual.
2
4 3
5
6

Using the Monotonic Mode
The Monotonic Mode is useful when you are collecting features to
ensure that the elevations of all points composing a feature run
either uphill, downhill, or at the same elevation. This mode is 3
designed primarily for use in the collection of water drainage
features so that the water flows correctly, that is, not uphill.
The Monotonic Mode bases its upward (in the case that you start
digitizing at the water’s endpoint rather than starting point), same,
or downward flow on the elevation change between the first two
vertices you collect. The increment rate of increase or decrease is
determined by the 3D Floating Cursor elevation.
Ap plyi ng the Mono toni c Mode

choose Start Editing.
2. Click to select the first vertex of the feature.
3. Right-click and select Monotonic from the context menu.
You can also press the F10 key on the keyboard to enter and
exit Monotonic Mode.
4. Adjust the 3D Floating Cursor elevation to collect the next 6
vertex of the feature, and so on.
5. Double-click to complete the feature.
6. When you’ve finished, you can check the Sketch Properties
to see that the feature has been collected with increasing,
decreasing, or level elevation values, as appropriate.

Using digitizing devices
You can use devices other than the standard system mouse to
collect features in Stereo Analyst for ArcGIS. A list of the currently
supported digitizing devices for Stereo Analyst for ArcGIS is in the
On-line Help and on the Web site <http://support.erdas.com/specs/
specs.html>.
Adding a di giti zing d evic e
You’ll use the Devices dialog to add a digitizing device. First,

access the Stereo Analyst toolbar, then click the Stereo Analyst
dropdown list, then click Devices to open the dialog. The Add Device dialog gives you a list of the potential digitizing devices.
Mappi ng buttons
Each supported device comes with many of the buttons already

mapped to common digitizing functions. However, you may want
to change the default settings to suit your own, unique needs.
A detailed list of optimum button mappings for each supported

digitizing device can be found in the Stereo Analyst for ArcGIS
On-line Help.
The button mapping process is described in “Mapping buttons on

digitizing devices” on page 174.
The Devices dialog is your starting point for all device-related settings.
Next, you’ll specify the COM port to which the digitizing device is
attached in the Add Device dialog.

Mappin g buttons o n dig itizi ng devices
In general, the procedure for mapping buttons on digitizing

devices is as follows:

dropdown list and choose Devices. 1
2. Click in the Device Selection window and select the
digitizing device.
3. Click Button Mappings on the Devices dialog.
4. To check a button mapping, click the button on the
digitizing device.
The button number you pressed appears in the window
labeled Press/Select device button. 2
3
5. The currently assigned function (if there is one) appears in
the Currently assigned to window. X

6. To assign a new command to a button, select the button
on the digitizing device.
Remember, you can use a combination of keys on some
digitizing devices with the Shift button on the device. In
the case of the TopoMouse, for example, that is button 4. 7
8
7. Select a function category, namely Stereo Analyst, from
the Categories list.
Each category has its own list of commands. These
commands display in the Commands/Buttons list. 9
8. Select the command you want to map to the selected
button.
The current function displays in the Currently assigned to
11
window.
9. Click Assign.
10. Repeat steps 6 through 9 until you have mapped all of the
buttons on the device.
11. Click Close on the Digitizing Device Button Mapping
dialog.
12. Click Close on the Devices dialog.
For more information about digitizing devices and button
mapping, see the Stereo Analyst for ArcGIS On-line Help.
12

What’s next?
In the next section, you’ll find the appendices. The appendices tell
you about how data can be captured using imagery, how imagery is
used in stereo viewing, and how imagery is used in
photogrammetry. There is also a glossary of terms for your
reference.

Appendices
Section 4
A Capturing data using imagery
A
IN THIS APPENDIX This appendix gives you examples of how imagery is useful in the collection of
geographic data. This data is of primary importance for the creation and
• Collecting data for a GIS maintenance of a GIS. If the data and information contained within a GIS are
inaccurate or outdated, the resulting analyses performed on the data do not reflect
• Preparing imagery for a GIS true, real-world applications and scenarios.
• Using traditional approaches
• Applying geographic imaging
• Moving from imagery to a 3D GIS
• Identifying workflow
• Getting 3D GIS data from imagery
179
Collecting data for a GIS
Since its inception and introduction, GIS was designed to represent These approaches have been widely accepted within the GIS
the earth and its associated geography. Vector data has been industry as the primary techniques used to prepare, collect, and
accepted as the primary format for representing geographic maintain the data contained within a GIS; however, GIS
information. For example, a road is represented with a line, and a professionals throughout the world are beginning to face the
parcel of land is represented using a series of lines to form a following issues:
polygon.
• The original sources of information used to collect GIS data
Various approaches have been used to collect the vector data used are becoming obsolete and outdated. The same can be said for
as the fundamental building blocks of a GIS. These include: the GIS data collected from these sources. How can the data
and information in a GIS be updated?
• Using a digitizing tablet to digitize features from cartographic,
• The accuracy of the source data used to collect GIS data is
topographic, census, and survey maps. The resulting features
questionable. For example, how accurate is the 1960
are stored as vectors. Feature attribution occurs either during or
topographic map used to digitize contour lines?
after feature collection.
• The amount of time required to prepare and collect GIS data
• Scanning and georeferencing existing hardcopy maps. The
from existing sources of information is great.
resulting images are georeferenced and then used to digitize
and collect geographic information. For example, this includes • The cost required to prepare and collect GIS data is high. For
scanning United States Geological Survey (USGS) 1:24,000 example, georectifying 500 photographs to map an entire
quad sheets and using them as the primary source for a GIS. county may take up to three months (which does not include
collecting the GIS data). Similarly, digitizing hardcopy maps is
• Obtaining ground surveying geographic information. Ground
time-consuming and costly, not to mention inaccurate.
global positioning system (GPS), total stations, and theodolites
are commonly used for recording the 3D locations of features. • Most of the original sources of information used to collect GIS
The resulting information is commonly merged into a GIS and data provide only 2D information. For example, a building is
associated with existing vector datasets. represented with a polygon having only X and Y coordinate
information. To create a 3D GIS involves creating DTMs,
• Outsourcing photogrammetric feature collection to service
digitizing contour lines, or surveying the earth’s geography to
bureaus. Traditional stereo plotters and digital
obtain 3D coordinate information. Once collected, the 3D
photogrammetric workstations are used to collect highly
information is merged with the 2D GIS to create a 3D GIS.
accurate geographic information such as orthorectified
Each approach is ineffective in terms of the time, cost, and
imagery, DTMs, and 3D vector datasets.
accuracy associated with collecting the 3D information for a
• Applying remote sensing techniques, such as multispectral 2D GIS.
classification, which traditionally have been used for
• The cost associated with outsourcing core digital mapping to
extracting geographic information about the earth’s surface.
specialty shops is expensive in both dollars and time. Also,
performing regular GIS data updates requires additional
outsourcing.

With the advent of image processing and remote sensing systems,
the use of imagery for collecting geographic information has
become more frequent. Imagery was first used as a reference
backdrop for collecting and editing geographic information
(including vectors) for a GIS. This imagery included:
• Raw photography,
• Geocorrected imagery, and
• Orthorectified imagery.
Each type of imagery has its advantages and disadvantages,

although each is limited to the collection of geographic information
in 2D. To accurately represent the earth and its geography in a GIS,
the information must be obtained directly in 3D, regardless of the
application. Stereo Analyst for ArcGIS provides the solution for
directly collecting 3D information from stereo imagery.
Accurate 3D geographic information can be extracted from imagery.
CAPTURING DATA USING IMAGERY 181

Preparing imagery for a GIS
This section describes the various techniques used to prepare • Scan the photograph(s),
imagery for a GIS. By understanding the processes and techniques • Georeference the photograph using known GCPs,
associated with preparing and extracting geographic information
from imagery, problem issues can be identified and the complete • Digitize the features recorded in the photograph(s) using the
solution for collecting 3D geographic information can be provided. scanned photographs as a backdrop in a GIS, and
• Merge and geolink the recorded tabular data with the collected
Usi n g r aw p h o to gr a p hy features in a GIS.
The following examples describe the common practices used for This procedure is repeated for each photograph.
the collection of geographic information from raw photographs and
imagery. Raw imagery includes scanned hardcopy photography, E x a m p le 2 : C o l l e c t i n g g e o g r a p h i c i n f o r m a t i o n
digital camera imagery, videography, or satellite imagery that has from hardcopy photography using a transparency
not been processed to establish a geometric relationship between
the imagery and the earth. In this case, the images are not Rather than measure and mark on the photographs directly, a
referenced to a geographic projection or coordinate system. transparency is placed on top of the photographs during feature
collection. In this case, a stereoscope is placed over the
E x a m p le 1 : C o l l e c t i n g g e o g r a p h i c i n f o r m a t i o n photographs. Then, a transparency is placed over the photographs.
from hardcopy photography Features and information (spatial and nonspatial) are recorded
directly on the transparency. Once the information has been
Hardcopy photographs are widely used by professionals in several recorded, it is transferred to a GIS. The following steps are
industries as one of the primary sources of geographic information. commonly used to transfer the information to a GIS:
Foresters, geologists, soil scientists, engineers, environmentalists,
and urban planners routinely collect geographic information • Either digitally scan the entire transparency using a desktop
directly from hardcopy photographs. The hardcopy photographs scanner, or digitize only the collected features using a
are commonly used during fieldwork and research. As such, the digitizing tablet.
hardcopy photographs are a valuable source of information. • The resulting image or set of digitized features is then
georeferenced to the earth’s surface. The information is
For the interpretation of 3D and height information, an adjacent set georeferenced to an existing vector coverage, rectified map,
of photographs is used together with a stereoscope. While in the rectified image, or is georeferenced using GCPs. Once the
field, information and measurements collected on the ground are features have been georeferenced, geographic coordinates (X
recorded directly onto the hardcopy photographs. Using the and Y) are associated with each feature.
hardcopy photographs, information regarding the feature of interest
is recorded both spatially (geographic coordinates) and • In a GIS, the recorded tabular (attribution) data is entered and
nonspatially (text attribution). merged with the digital set of georeferenced features.
Transferring the geographic information associated with the This procedure is repeated for each transparency.
hardcopy photograph to a GIS involves the following steps:

E x a m p le 3 : C o l l e c t i n g g e o g r a p h i c i n f o r m a t i o n
from scanned photography
By scanning the raw photography, a digital record of the area of

interest becomes available and can be used to collect GIS
information. The following steps are commonly used to collect GIS
information from scanned photography:
• Georeference the photograph using known GCPs.

• In a GIS, using the scanned photographs as a backdrop, digitize
the features recorded on the photograph(s).
• In the GIS, merge and geolink the recorded tabular data with
the collected features.
This procedure is repeated for each photograph.
Ap plying g eo process ing techn iques
Raw aerial photography and satellite imagery contain large

geometric distortion caused by camera or sensor orientation error, Spatial information can be collected easily using Stereo Analyst for ArcGIS.
terrain relief, earth curvature, film and scanning distortion, and
measurement errors. Measurements made on data sources that have Applying geocorrection
not been rectified for the purpose of collecting geographic
information are not reliable. Conventional techniques of geometric correction (or
geocorrection) such as rubber sheeting are based on approaches
Geoprocessing techniques warp, stretch, and rectify imagery for that do not directly account for the specific distortion or error
use in the collection of 2D geographic information. These sources associated with the imagery. These techniques have been
techniques include geocorrection and orthorectification, which successful in the field of remote sensing and GIS applications,
establish a geometric relationship between the imagery and the especially when dealing with low resolution and narrow field of
ground. The resulting 2D image sources are primarily used as view satellite imagery such as Landsat and SPOT. General
reference backdrops or base image maps on which to digitize functions have the advantage of simplicity. They can provide a
geographic information. reasonable geometric modeling alternative when little is known
about the geometric nature of the image data.

Problems O r t h o r e c t i f i ca t i o n
Conventional techniques generally process the images one at a Geocorrected aerial photography and satellite imagery have large
time. They cannot provide an integrated solution for multiple geometric distortion that is caused by various systematic and
images or photographs simultaneously and efficiently. It is very nonsystematic factors. Photogrammetric techniques used in
difficult, if not impossible, for conventional techniques to achieve IMAGINE OrthoBASE eliminate these errors most efficiently, and
a reasonable accuracy without a great number of GCPs when create the most reliable and accurate imagery from the raw
dealing with high-resolution imagery, images with severe imagery. IMAGINE OrthoBASE is unique in terms of considering
systematic and/or nonsystematic errors, and images covering rough the image-forming geometry by using information between
terrain such as mountain areas. Image misalignment is more likely overlapping images and explicitly dealing with the third dimension,
to occur when mosaicking separately rectified images. This which is elevation.
misalignment could result in inaccurate geographic information
being collected from the rectified images. As a result, the GIS Orthorectified images, or orthoimages, serve as the ideal
suffers. information building blocks for collecting 2D geographic
information required for a GIS. They can be used as reference
Furthermore, it is impossible for geocorrection techniques to image backdrops to maintain or update an existing GIS. Using
extract 3D information from imagery. There is no way for digitizing tools in a GIS, features can be collected and then
conventional techniques to accurately derive geometric attributed to reflect their spatial and nonspatial characteristics.
information about the sensor that captured the imagery. Multiple orthoimages can be mosaicked to form seamless
orthoimage base maps.
Solution
Problems
Techniques used in Stereo Analyst for ArcGIS and IMAGINE
OrthoBASE overcome all of these problems by using sophisticated Orthorectified images are limited to containing only 2D geometric
techniques to account for the various types of error in the input data information. Thus, geographic information collected from
sources. This solution is integrated and accurate. IMAGINE orthorectified images is georeferenced to a 2D system. Collecting
OrthoBASE can process hundreds of images or photographs with 3D information directly from orthoimagery is impossible. The
very few GCPs, while at the same time eliminating the accuracy of orthorectified imagery is highly dependent on the
misalignment problem associated with creating image mosaics. In accuracy of the DTM used to model the terrain effects caused by the
short—less time, less money, less manual effort, and more earth’s surface. The DTM source is an additional source of input
geographic fidelity can be realized using the photogrammetric during orthorectification. Acquiring a reliable DTM is another
solution. Stereo Analyst for ArcGIS uses all of the information costly process. High-resolution DTMs can be purchased, but at a
processed in IMAGINE OrthoBASE and accounts for inaccuracies great expense.
during 3D feature collection, editing, and interpretation.

Solution
Stereo Analyst for ArcGIS allows for the collection of 3D

information—you are no longer limited to only 2D information.
Using sophisticated sensor modeling techniques, a DTM is not
required as an input source for collecting accurate 3D geographic
information. As a result, the accuracy of the geographic
information collected in Stereo Analyst for ArcGIS is higher. There
is no need to spend countless hours collecting DTMs and merging
them with your GIS.

Using traditional approaches
Unfortunately, 3D geographic information cannot be directly Can you easily edit and modify problem areas in the DTM? Many
measured or interpreted from geocorrected images, orthorectified times, the problem areas in the DTM cannot be edited, since the
images, raw photography, or scanned topographic or cartographic original imagery used to create the DTM is not available, or the
maps. The resulting geographic information collected from these accompanying software is not available.
sources is limited to 2D only, which consists of X and Y
georeferenced coordinates. In order to collect the additional Z Ex ample 3
(height) coordinate, additional processing is required. The
following examples explain how 3D information is normally This example involves using ground surveying techniques such as
collected for a GIS. ground GPS, total stations, levels, and theodolites to capture angles,
distances, slopes, and height information. You are then required to
Exa m ple 1 geolink and merge the land surveying information with the
geographic information contained in the GIS.
The first example involves digitizing hardcopy cartographic and
topographic maps and attributing the elevation of contour lines. Problem
Further interpolation of contour lines is required to create a DTM.
The digitization of these sources includes either scanning the entire Ground surveying techniques are accurate, but are labor intensive,
map or digitizing individual features from the maps. costly, and time-consuming—even with new GPS technology.
Also, additional work is required to merge and link the 3D
Problem information with the GIS. The process of geolinking and merging
the 3D information with the GIS may introduce additional errors to
The accuracy and reliability of the topographic or cartographic map your GIS.
cannot be guaranteed. As a result, any error in the map is introduced
into your GIS. Additionally, the magnitude of error is increased due Ex ample 4
to the questionable scanning or digitization process.
The next example involves automated DEM extraction. Using two
Exa m ple 2 overlapping images, a regular grid of elevation points or a dispersed
number of 3D mass points (that is, a TIN) can be automatically
The second example involves merging existing DTMs with extracted from imagery. You are then required to merge the
geographic information contained in a GIS. resulting DTM with the geographic information contained in the
GIS.
Problem
Where did the DTMs come from? How accurate are the DTMs? If
the original source of the DTM is unknown, then the quality of the
DTM is also unknown. As a result, any inaccuracies are translated
into your GIS.

Problem
You are restricted to the collection of point elevation information.

For example, using this approach, the slope of a line or the 3D
position of a road cannot be extracted. Similarly, a polygon of a
building cannot be directly collected. Many times, postediting is
required to ensure the accuracy and reliability of the elevation
sources. Automated DEM extraction consists of just one required
step to create the elevation or 3D information source. Additional
steps of DTM interpolation and editing are also required, not to
mention the additional process of merging the information with
your GIS.
Exa m ple 5
This example involves outsourcing photogrammetric feature

collection and data capture to photogrammetric service bureaus and
production shops. Using traditional stereoplotters and digital
photogrammetric workstations, 3D geographic information is
collected from stereo models. The 3D geographic information may
include DTMs, 3D features, and spatial and nonspatial attribution
ready for input in your GIS database.
Problem
Using these sophisticated and advanced tools, the procedures

required for collecting 3D geographic information become costly.
The use of such equipment is generally limited to highly skilled
photogrammetrists.

Applying geographic imaging
To preserve the investment made in a GIS, a new approach is
required for the collection and maintenance of geographic data and
information in a GIS. The approach must provide the ability to:
• Access and use readily available, up-to-date sources of

information for the collection of GIS data and information.
• Collect accurate 2D and 3D GIS data from a variety of sources.
• Minimize the time and cost associated with preparing,
collecting, and editing GIS data.
• Collect 3D GIS data directly from raw source data without
having to perform additional preparation tasks.
• Integrate new sources of imagery easily for the maintenance
and update of data and information in a GIS.
The only solution that can address all of those issues involves the
use of imagery. Imagery provides an up-to-date, highly accurate
representation of the earth and its associated geography. Various
types of imagery can be used, including aerial photography,
satellite imagery, digital camera imagery, videography, and 35 3D information can be used for GIS analysis.
millimeter photography. With the advent of high-resolution
satellite imagery, GIS data can be updated accurately and 3D geographic imaging is the process associated with transforming
immediately. imagery into GIS data or, more importantly, information. 3D
geographic imaging prevents the inclusion of inaccurate or
Synthesizing the concepts associated with photogrammetry, remote outdated information into a GIS. Sophisticated and automated
sensing, GIS, and 3D visualization introduces a new paradigm for techniques are used to ensure that highly accurate 3D GIS data can
the future of digital mapping—one that integrates the respective be collected and maintained using imagery. 3D geographic imaging
technologies into a single, comprehensive environment for the techniques use a direct approach to collecting accurate 3D
accurate preparation of imagery and the collection and extraction of geographic information, thereby eliminating the need to digitize
3D GIS data and geographic information. This paradigm is referred from a secondary data source like hardcopy or digital maps. These
to as 3D geographic imaging. 3D geographic imaging techniques new tools significantly improve the reliability of GIS data and
will be used for building the 3D GIS of the future. reduce the steps and time associated with populating a GIS with
accurate information.

The backbone of 3D geographic imaging is digital
photogrammetry. Photogrammetry has established itself as the
main technique for obtaining accurate 3D information from
photography and imagery. Traditional photogrammetry uses
specialized and expensive stereoscopic plotting equipment. Digital
photogrammetry uses computer-based systems to process digital
photography or imagery. With the advent of digital
photogrammetry, many of the processes associated with
photogrammetry have been automated.
Over the last several decades, the idea of integrating

photogrammetry and GIS has intimidated many people. The cost
and learning curve associated with incorporating the technology
into a GIS has created a chasm between photogrammetry and GIS
data collection, production, and maintenance.
As a result, many GIS professionals have resorted to outsourcing

their digital mapping projects to specialty photogrammetric
production shops. Advancements in softcopy photogrammetry, or
digital photogrammetry, have broken down these barriers. Digital
photogrammetric techniques bridge the gap between GIS data
collection and photogrammetry. This is made possible through the
automated processes associated with digital photogrammetry.
See appendix C, “Applying photogrammetry” on page 209 for

more information about photogrammetric applications.

Moving from imagery to a 3D GIS
Transforming imagery into 3D GIS data involves several processes
commonly associated with digital photogrammetry. The data and
information required for building and maintaining a 3D GIS
include orthorectified imagery, DTMs, 3D features, and the
nonspatial attribute information associated with the 3D features.
Through various processing steps, 3D GIS data can be
automatically collected and extracted from imagery.
Usi ng i m ag er y
Digital photogrammetric techniques are not restricted as to the type

of photography and imagery that can be used to collect accurate
GIS data. Traditional applications of photogrammetry use aerial
photography (commonly 9 × 9 inches in size). Technological
breakthroughs in photogrammetry now allow for the use of satellite
imagery, digital camera imagery, videography, and 35 millimeter
camera photography.
In order to use hardcopy photographs in a digital photogrammetric

system, the photographs must be scanned or digitized. Depending
on the digital mapping project, various scanners can be used to
digitize photography. For highly accurate mapping projects,
calibrated photogrammetric scanners must be used to scan the
photography to very high precisions. If high-end micron accuracy
is not required, more affordable desktop scanners can be used.
Conventional photogrammetric applications, such as topographic

mapping and contour line collection, use aerial photography. With
the advent of digital photogrammetric systems, applications have
been extended to include the processing of oblique and terrestrial
photography and imagery.
Given the use of computer hardware and software for

photogrammetric processing, various image file formats can be
used. These include TIF, JPEG, GIF, Raw, Generic Binary, and
compressed imagery, along with various software vendor-specific
file formats.

Identifying workflow
The workflow associated with creating 3D GIS data is linear. The Internal sensor model information describes the internal geometry
hierarchy of processes involved with creating highly accurate of the sensor as it exists when the imagery is captured. For aerial
geographic information can be broken down into several steps, photographs, this includes the focal length, lens distortion, fiducial
which include: mark coordinates, and so forth. This information is normally
provided to you in the form of a calibration report. For digital
• Define the sensor model, cameras, this includes focal length and the pixel size of the charge-
• Measure GCPs, coupled device (CCD) sensor. For satellites, this includes internal
satellite information such as the pixel size, the number of columns
• Collect tie points (automated),
in the sensor, and so forth. If some of the internal sensor model
• Perform bundle block adjustment (that is, aerial triangulation), information is not available (as in the case of historical
• Extract DTMs (automated), photography), sophisticated techniques can be used to determine
the internal sensor model information. This technique is normally
• Orthorectify, and
associated with performing a bundle block adjustment and is
• Collect and attribute 3D features. referred to as self-calibration.
This workflow is generic and does not necessarily need to be External sensor model information describes the exact position and
repeated for every GIS data collection and maintenance project. For orientation of each image as they existed when the imagery was
example, a bundle block adjustment does not need to be performed collected. The position is defined using 3D coordinates. The
every time a 3D feature is collected from imagery. orientation of an image at the time of capture is defined in terms of
rotation about three axes: omega (ω), phi (ϕ), and kappa (κ). Over
Definin g th e sen sor model the last several years, it has been common practice to collect
airborne GPS and inertial navigation system (INS) information at
A sensor model describes the properties and characteristics
the time of image collection. If this information is available, the
associated with the camera or sensor used to capture photography
external sensor model information can be directly input for use in
and imagery. Since digital photogrammetry allows for the accurate
photogrammetric processing. If external sensor model information
collection of 3D information from imagery, all of the characteristics is not available, most photogrammetric systems can determine the
associated with the camera/sensor, the image, and the ground must exact position and orientation of each image in a project using the
be known and determined. Photogrammetric sensor modeling bundle block adjustment approach.
techniques define the specific information associated with a
camera/sensor as it existed when the imagery was captured. This Measuring GCPs
information includes both internal and external sensor model
information. Unlike traditional georectification techniques, GCPs in digital
photogrammetry have three coordinates: X, Y, and Z. The image
locations of 3D GCPs are measured across multiple images. GCPs
can be collected from existing vector files, orthorectified images,
DTMs, and scanned topographic and cartographic maps.

GCPs serve a vital role in photogrammetry by establishing an Since it determines most of the necessary information that is
accurate geometric relationship between the images in a project, the required to create orthophotos, DTMs, DSMs, and 3D features,
sensor model, and the ground. This relationship is established using bundle block adjustment is an essential part of processing. The
the bundle block adjustment approach. Once established, 3D GIS components needed to perform a bundle block adjustment may
data can be accurately collected from imagery. The number of include the internal sensor model information, external sensor
GCPs varies from project to project. For example, if a strip of five model information, the 3D coordinates of points, and additional
photographs is being processed, a minimum of three GCPs can be parameters (AP) characterizing the sensor model. This output is
used. Optimally, five or six GCPs are distributed throughout the commonly provided with detailed statistical reports outlining the
overlap areas of the five photographs. accuracy and precision of the derived data. For example, if the
accuracy of the external sensor model information is known, then
Co llecting tie p oints the accuracy of 3D GIS data collected from this source data can be
determined.
To prevent misaligned orthophoto mosaics and to ensure accurate
DTMs and 3D features, tie points are commonly measured within Ex tra cting DT Ms
the overlap areas of multiple images. A tie point is a point whose
ground coordinates are not known; however, the tie point is visually Rather than manually collecting individual 3D point positions with
recognizable in the overlap area between multiple images. a GPS or using direct 3D measurements on imagery, automated
techniques extract 3D representations of the earth’s surface using
Tie point collection is the process of identifying and measuring tie the overlap area of two images. This is referred to as automated
points across multiple overlapping images. Tie points are used to DTM extraction. Digital image matching (auto-correlation)
join the images in a project so that they are positioned correctly techniques are used to automatically identify and measure the
relative to one another. Traditionally, tie points have been collected positions of common ground points appearing within the overlap
manually, two images at a time. With the advent of new, area of two adjacent images.
sophisticated, and automated techniques, tie points are now
collected automatically, saving you time and money in the Using sensor model information determined from bundle block
preparation of 3D GIS data. Digital image matching techniques are adjustment, the image positions of the ground points are
used to automatically identify and measure tie points across transformed into 3D point positions. Once the automated DTM
multiple overlapping images. extraction process has been completed, a series of evenly
distributed 3D mass points is located within the geographic area of
Ap plyi ng bundl e bl ock adju stmen t interest. The 3D mass points can then be interpolated to create a
TIN or a raster DEM. DTMs form the basis of many GIS
Once GCPs and tie points have been collected, the process of applications including watershed analysis, line of sight (LOS)
establishing an accurate relationship between the images in a analysis, road and highway design, and geological bedform
project, the camera/sensor, and the ground can be performed. This discrimination. DTMs are also vital for the creation of
process is referred to as bundle block adjustment. orthorectified images.

O r t h o re c t i f y i n g
Orthorectification is the process of removing geometric errors

inherent within photography and imagery. Using sensor model
information and a DTM, errors associated with sensor orientation,
topographic relief displacement, earth curvature, and other
systematic errors are removed to create accurate imagery for use in
a GIS. Measurements and geographic information collected from
an orthorectified image represent the corresponding measurements
as if they were taken on the earth’s surface. Orthorectified images
serve as the image backdrops for displaying and editing vector
layers.
Co llecting and attribu ting 3D fea tures
3D GIS data and information can be collected from what is referred

to as a digital stereo model (DSM). Based on sensor model
information, two overlapping images comprising a DSM can be
aligned, leveled, and scaled to produce a 3D stereo effect when Accurate 3D buildings can be extracted using Stereo Analyst for ArcGIS.
viewed with appropriate stereo viewing hardware. A DSM allows
for the interpretation, collection, and visualization of 3D Automated Terrain Following Mode capabilities can be used to
geographic information from imagery. The DSM is used as the automatically place the 3D Floating Cursor on the ground so that
primary data source for the collection of 3D GIS data. you do not have to manually adjust the height of the 3D Floating
Cursor every time a feature is collected. For example, the collection
A 3D GIS allows for the direct collection of 3D geographic of a feature in 3D is as simple as using the automated Terrain
information from a DSM using a 3D Floating Cursor. Thus, Following Mode with the Sketch Tool, then collecting vertices. The
additional elevation data is not required. True 3D information is resulting output is 3D GIS data.
collected directly from imagery.
For the update and maintenance of a GIS, existing vector layers are
During the collection of 3D GIS data, a 3D Floating Cursor is commonly superimposed on a DSM and then reshaped to their
displayed within the DSM while viewing the imagery in stereo. The accurate real-world positions. 2D vector layers can be transformed
3D Floating Cursor commonly floats above, below, or rests on the into 3D geographic information using most 3D geographic imaging
earth’s surface or object of interest. To ensure the accuracy of 3D systems. During the collection of 3D GIS data, the attribute
GIS data, the height of the 3D Floating Cursor is adjusted so that it information associated with a vector layer can be edited. Attribute
rests on the feature being collected. When the 3D Floating Cursor tables can be displayed with the DSM during the collection of 3D
rests on the ground or feature, it can be accurately collected. GIS data.

Interpreting the DSM during the capture of 3D GIS data allows for
the collection, maintenance, and input of nonspatial information
such as the type of tree and zoning designation in an urban area.
Automated attribution techniques simultaneously populate a GIS
during the collection of 3D features with such data as area,
perimeter, and elevation. Additional qualitative and quantitative
attribution information associated with a feature can be input
during the collection process.

Getting 3D GIS data from imagery
The products resulting from using 3D geographic imaging
techniques include orthorectified imagery, DTMs, DSMs, 3D
features, 3D measurements, and attribute information associated
with a feature. Using these primary sources of geographic
information, additional GIS data can be collected, updated, and
edited. An increasing trend in the geocommunity involves the use
of 3D data in GIS spatial modeling and analysis.
Find ing 3D GI S ap plica tion s
The 3D GIS data collected using 3D geographic imaging can be

used for spatial modeling, GIS analysis, and 3D visualization and
simulation applications. The following examples illustrate how 3D
geographic imaging techniques can be used for applications in
forestry, geology, local government, water resource management,
and telecommunications.
A p p ly i n g 3 D G I S t o fo r e s t r y
For forest inventory applications, an interpreter identifies different

tree stands from one another based on height, density (crown 3D geographic imaging techniques can be used in forestry applications.
cover), species composition, and various modifiers such as slope,
Based on the information collected from DSMs, forestry companies
type of topography, and soil characteristics. Using a DSM, a
use the 3D information in a GIS to determine the amount of
foreststand can be identified and measured as a 3D polygon. 3D
marketable timber located within a given plot of land, the amount
geographic imaging techniques are used to provide the GIS data
of timber lost due to fire or harvesting, and where problems may
required to determine the volume of a stand. This includes using a
arise due to harvesting in unsuitable geographic areas.
DSM to collect tree stand height, tree crown diameter, density, and
area.
Using 3D DSMs with high-resolution imagery, various tree species

can be identified based on height, color, texture, and crown shape.
Appropriate feature codes can be directly placed and georeferenced
to delineate foreststand polygons. The feature code information is
directly indexed to a GIS for subsequent analysis and modeling.

Ap plyi ng 3D GIS to g eolo gy • Land use/land cover mapping involves the identification and
categorization of urban and rural land use and land cover.
Prior to beginning expensive exploration projects, geologists take Using DSMs, 3D topographic information, slope, vegetation
an inventory of a geographic area using imagery as the primary type, soil characteristics, underlying geological information,
source of information. DSMs are frequently used to improve the and infrastructure information can be collected as 3D vectors.
quantity and quality of geologic information that can be interpreted
• Land use suitability evaluation usually requires soil mapping.
from imagery. Changes in topographic relief are often used in
DSMs allow for the accurate interpretation and collection of
lithological mapping applications since these changes, together
soil type, slope, soil suitability, soil moisture, soil texture, and
with the geomorphologic characteristics of the terrain, are
surface roughness. As a result, the suitability of a given
controlled by the underlying geology.
infrastructure development can be determined.
DSMs are utilized for lithologic discrimination and geologic • Population estimation requires accurate 3D high-resolution
structure identification. Dip angles can be recorded directly on a imagery for determining the number of units for various
DSM in order to assist in identifying underlying geologic household types. The height of buildings is important.
structures. By digitizing and collecting geologic information using • Housing quality studies require environmental information
a DSM, the resulting geologic map is in a form and projection that derived from DSMs including house size, lot size, building
can be immediately used in a GIS. Together with multispectral density, street width and condition, driveway presence or
information, high-resolution imagery produces a wealth of highly absence, vegetation quality, and proximity to other land use
accurate 3D information for the geologist. types.
A p p ly i n g 3 D G I S t o l o c a l g ov e r n m e n t • Site selection applications require the identification and
a c ti v iti e s inventory of various geographic information. Site selection
applications include transportation route selection, sanitary
In order to formulate social, economic, and cultural policies, GIS landfill site selection, power plant siting, and transmission line
sources must be timely, accurate, and cost-effective. High- location. Each application requires accurate 3D topographic
resolution imagery provides the primary data source for obtaining representations, geologic inventory, soils inventory, land use,
up-to-date geographic information for local government vegetation inventory, and so forth.
applications. Existing GIS vector layers are commonly • Urban change detection studies use photography collected
superimposed onto DSMs for immediate update and maintenance. from various time periods for analyzing the extent of urban
growth. Land use and land cover information is categorized for
DSMs created from high-resolution imagery are used for the each time period, and then compared to determine the extent
following applications: and nature of land use/land cover change.

Ap plyi ng 3D GIS to res ource m anag em ent
DSMs are a necessary asset for monitoring the quality, quantity,

and geographic distribution of water. The 3D information collected
from DSMs is used to provide descriptive and quantitative
watershed information for a GIS. Various watershed characteristics
can be derived from DSMs including terrain type and extent,
surficial geology, river or stream valley characteristics, river
channel extent, river bed topography, and terraces. Individual river
channel reaches can be delineated in 3D, providing an accurate
representation of a river.
Rather than manually survey 3D point information in the field,

highly accurate 3D information can be collected from DSMs to
estimate sediment storage, river channel width, and valley flat
width. Using historical photography, 3D measurements of a river
channel and bank can be used to estimate rates of bank erosion and
deposition, identify channel change, and describe channel
evolution and disturbance.
A p p ly i n g 3 D G I S t o t e l e c o m mu ni c a t i o n s
The growing telecommunications industry requires accurate 3D

information for various applications associated with wireless
telecommunications. 3D geographic representations of buildings
are required for radio engineering analysis and LOS between
building rooftops in urban and rural environments. Accurate 3D
building information is required to properly perform the analysis.
Once the 3D data has been collected, it can be used for radio
coverage planning, system propagation prediction, plotting and
analysis, network optimization, antenna siting, and point-to-point
inspection for signal validation.

B Understanding stereo viewing
B
IN THIS APPENDIX This appendix provides you with detailed, technical information about stereo
viewing and its effect on 3D stereoscopic viewing and feature collection.
• Learning principles of stereo
viewing
• Understanding stereo models and

parallax
• Understanding scaling,
translation, and rotation
• Understanding the epipolar line
199
Learning principles of stereo viewing
Definin g stereo scopic view ing Digital photogrammetric techniques used in Stereo Analyst for
ArcGIS extend the perception and interpretation of depth to include
On a daily basis, we unconsciously perceive and measure depth the measurement and collection of 3D information.
using our eyes. Persons using both eyes to view an object have
binocular vision. Persons using one eye to view an object have Understan ding how stereo wo rks
monocular vision. The perception of depth through binocular vision
is referred to as stereoscopic viewing. A true stereo effect is achieved when two overlapping images (an
image pair), or photographs of a common area captured from two
Using stereoscopic viewing, depth information can be perceived different vantage points, are rendered and viewed simultaneously.
with great detail and accuracy. Stereo viewing allows the human The stereo effect, or ability to view with measurable depth
brain to judge and perceive changes in depth and volume. In perception, is provided by a parallax effect generated from the two
photogrammetry, stereoscopic depth perception plays a vital role in different acquisition points.
creating and viewing 3D representations of the earth’s surface. As
a result, geographic information can be collected to a greater The stereo effect is analogous to the depth perception you achieve
accuracy in stereo as compared to traditional monoscopic by looking at a feature with your two eyes. The distance between
techniques. your eyes represents two vantage points like two independent
photos, as in the following pictures.
Stereo feature collection techniques provide greater GIS data
collection and update accuracy for the following reasons:
• Sensor model information derived from block triangulation

eliminates errors associated with the uncertainty of sensor
model position and orientation. Accurate image position and
orientation information is required for the highly accurate
determination of 3D information.
• Systematic errors associated with raw photography and
imagery are considered and minimized during the block
triangulation process.
• The collection of 3D coordinate information using stereo These two overlapping photos can be viewed together for 3D perception.
viewing techniques is not dependent on a DEM as an input
source. Changes and variations in depth perception can be The importance of using images is that by viewing the earth’s
perceived and automatically transformed using sensor model surface in stereo, you can interpret, measure, and delineate map
information and raw imagery. Therefore, DTMs containing features in 3D. The net benefit is that many map features are more
error are not introduced into the collected GIS data. interpretable and have a higher degree of accuracy in stereo than in
2D with a single image. The following picture shows a stereo view.

The 3D image formed by the brain is also referred to as a stereo
model. Once the stereo model is formed, you notice relief, or
vertical exaggeration, in the 3D model. A digital version of a stereo
model, a DSM, can be created when sensor model information is
associated with the left and right images comprising an image pair.
In Stereo Analyst for ArcGIS, a DSM is formed using an image pair
and accurate sensor model information.
Using the stereo viewing and 3D feature collection capabilities of

Stereo Analyst for ArcGIS, changes and variations in elevation
perceived by the brain can be translated to reflect real-world 3D
information. The following picture shows an example of a 3D
Using two images, a 3D stereo view is possible. feature created using Stereo Analyst for ArcGIS, which is displayed
in IMAGINE VirtualGIS.
When viewing the features from two perspectives, (the left photo
and the right photo), the brain automatically perceives the variation
in depth between different objects and features as a difference in
height. For example, while viewing a building in stereo, the brain
automatically compares the relative positions of the building and
the ground from the two different perspectives (that is, two
overlapping images). The brain also determines which is closer and
which is farther: the building or the ground. Thus, as the left eye
and the right eye view the overlap area of two images, depth
between the top and bottom of a building is perceived automatically
by the brain, and any changes in depth are due to changes in
elevation.
During the stereo viewing process, the left eye concentrates on the
object in the left image and the right eye concentrates on the object
in the right image. As a result, a single 3D image is formed within
the brain. The brain discerns height and variations in height by
visually comparing the depths of various features. While the eyes
move across the overlap area of the two photographs, a continuous This illustration shows a 3D model.
3D model of the earth is formulated within the brain since the eyes
continuously perceive the change in depth as a function of change
in elevation.
UNDERSTANDING STEREO VIEWING 201

Understanding stereo models and parallax
Stereo models provide a permanent record of 3D information
pertaining to the given geographic area covered within the L2
L1
overlapping area of two images. Viewing a stereo model in stereo
presents an abundant amount of 3D information to you. The a b a' b'
availability of 3D information in a stereo model is made possible by o o'
the presence of what is referred to as stereoscopic parallax. There
are two types of parallax: X-parallax and Y-parallax.
Co rrectin g X-paralla x
A
The following pictures show the image positions of two ground
B
points (A and B) appearing in the overlapping area of two images.
Ground point A is located at the top of a building, and ground point
B is located on the ground. This is a profile view of the image pair that illustrates the positions of point A
and point B.
Ground points A and B appear on the left photograph (L1) at image

positions a and b, respectively. Due to the forward motion of the
aircraft during photographic exposure, the same two ground points
appear on the right photograph (L2) at image positions a' and b'.
B
B Since ground point A is at a higher elevation, the movement of
image point a to position a' on the right image is larger than the
A
A image movement of point b. This can be attributed to X-parallax.
Principal Point 1 Principal Point 2 The following diagram illustrates that the parallax associated with
ground point A, depicted in the illustration of profile view above,
The left and right Images of an image pair have the same features, but at (Pa) is larger than the parallax associated with ground point B
different locations. depicted in the illustration of the profile view above (Pb).
The following diagram illustrates a profile view of the image pair

and the corresponding image positions of ground point A and
ground point B.

Y
X-parallax
Higher elevation
(~260 meters)
Pa Pb
a' a b' b
o
xa' xb
xa X-parallax
Lower elevation
X (~250 meters)
xb'
This diagram illustrates parallax comparison between points. Parallax changes with increases and decreases in elevation.
Thus, the amount of X-parallax is influenced by the elevation of a C o r r e c t i ng Y - pa r a ll ax

ground point. Since the degree of topographic relief varies across
an image pair, the amount of X-parallax also varies. In essence, the Under certain conditions, viewing a DSM may be difficult. The
brain perceives the variation in parallax between the ground and following factors may influence the quality of stereo viewing:
various features, and therefore judges the variations in elevation
• Unequal flying height between adjacent photographic
and height. The following picture illustrates the difference in
exposures. This effect causes a difference in scale between the
elevation as a function of X-parallax.
left and right images. As a result, the 3D stereo view becomes
Using 3D geographic imaging techniques, Stereo Analyst for distorted.
ArcGIS translates and transforms the X-parallax information • Flight line misalignment during photographic collection. This
associated with features recorded by an image pair into quantitative results in large differences in photographic orientation
height and elevation information. between two overlapping images. As a result, you experience
eyestrain and discomfort while viewing the DSM.
• Erroneous sensor model information. Inaccurate sensor model
information creates large differences in parallax between two
images comprising a DSM.

As a result of these factors, the DSMs contain an effect referred to To minimize Y-parallax, you are required to scale, translate, and
as Y-parallax, which introduces discomfort during stereo viewing. rotate the images until a clear and comfortable stereo view is
The following picture displays a stereo model with a considerable available.
amount of Y-parallax.
Scaling the stereo model involves adjusting the perceived scale of
each image comprising an image pair. This can be achieved by
Y adjusting the scale (that is, relative height) of each image as
required. Scaling the stereo model accounts for the differences in
altitude as they existed when the left and right photographs were
captured.
Translating the stereo model involves adjusting the relative X and

Y positions of the left and right images in order to minimize
X-parallax and Y-parallax. Translating the positions of the left and
right images accounts for misaligned images along a flight line.
X Rotating the left and right images adjusts for the large relative
variation in orientation (that is, omega, phi, kappa) for the left and
In this picture, Y-parallax exists.
right images.
The following picture displays the same stereo model without
Y-parallax.
In this picture, Y-parallax doesn’t exist.

Understanding scaling, translation, and rotation
When viewing a pair of tilted, overlapping photographs in stereo, The following picture displays the use of epipolar resampling
the left and right images must be continually scaled, translated, and techniques for viewing a DSM created with sensor model
rotated in order to maintain a clear, continuous stereo model. Thus, information.
it is your responsibility to adjust Y-parallax in order to create a clear
stereo view. Once properly oriented, you should notice that the
images are oriented parallel to the direction of flight, which was
originally used to capture the photography.
When using DSMs created from sensor model information, Stereo

Analyst for ArcGIS automatically rotates, scales, and translates the
imagery to continually provide an optimum stereo view throughout
the stereo model. Thus, the Y-parallax is automatically accounted
for. The process of automatically creating a clear stereo view is
referred to as epipolar resampling on the fly. As you roam
throughout a DSM, the software accounts and adjusts for Y-
parallax automatically. Using OpenGL software technology, Stereo
Analyst for ArcGIS automatically accounts for the tilt and rotation
of the two images as they existed when the images were captured. This DSM has sensor model information.
The following picture displays a DSM created without sensor As a result of using automatic epipolar resampling display
model information. techniques, 3D GIS data can be collected to a higher accuracy.
This DSM doesn’t have sensor model information.

Understanding the epipolar line
Geometric and radiometric characteristics (derived from sensor
model information and image grey values) associated with the
images comprising an image pair are used to constrain the image Epipolar plane
matching process in order to produce highly accurate and reliable
matching image point pairs. L1 L2
Exposure Exposure
station 1 station 2
The most common constraint, which is epipolar geometry
associated with an image pair, is used to constrain the search area
k k'
used to establish a pair of matching image points. The following
diagram illustrates an image point on a reference image being p p'
located along the epipolar line of an adjacent overlapping image.
z Epipolar line
P
Image point collected Corresponding image
from the left image of point located in the y
the image pair right image of the
Epipolar line image pair
x
Zp
Yp
Xp
Source: Keating et al 1975
Matching image points are located along the epipolar line.
The following diagram illustrates the image matching process The epipolar plane can be used as a geometric constraint to aid in the
identification of matching points.
using the epipolar plane as a geometric constraint. The figure
shows the epipolar plane which is the plane that is defined by the
Epipolar geometry is also commonly associated with the
two exposure stations ( L1 and L2 ) and the ground point, P. The
coplanarity condition. The coplanarity condition states that the two
lines pk and k′p′ are the epipolar lines and are defined by the sensor exposure stations of an image pair, any ground point, and the
intersection of the images and the epipolar plane. Using epipolar corresponding image position on the two images must all exist in a
constraint in the matching process transforms the matching common plane.
problem from a two-dimensional problem to a one-dimensional
problem, and is therefore beneficial since it reduces both the search
area and the computation time (Wolf 1983).

The common plane is also referred to as the epipolar plane. The
epipolar plane intersects the left and right images, and the lines of
intersection are referred to as epipolar lines. The image positions of
a ground point appearing on the left and right photos are located
along the epipolar line. The searching and matching process for
digital image matching occurs along a straight line (that is, the
epipolar line), thus simplifying the matching process. The epipolar
constraint can only be applied if the image orientation and position
of each sensor have been solved.

C Applying photogrammetry
C
IN THIS APPENDIX This appendix provides you with detailed, technical information about
photogrammetry, which is the foundation for stereo viewing.
• Learning principles of
photogrammetry
• Acquiring images and data
• Scanning aerial photography
• Understanding interior orientation
• Understanding exterior
orientation
• Using digital mapping solutions
209
Learning principles of photogrammetry
Photogrammetric principles are used to extract topographic The traditional, and largest, application of photogrammetry is to
information from aerial photographs and imagery. The following extract topographic and planimetric information (such as
picture illustrates rugged topography. This type of topography can topographic maps) from aerial images. However, photogrammetric
be viewed in 3D using Stereo Analyst for ArcGIS. techniques have also been applied to process satellite images and
close-range images to acquire topographic or nontopographic
information about photographed objects. Topographic information
includes spot height information, contour lines, and elevation data.
Planimetric information includes the geographic location of
buildings, roads, rivers, and so on.
Prior to the invention of the airplane, photographs taken on the

ground were used to extract the relationship between objects using
geometric principles. This was during the phase of plane table
photogrammetry.
In analog photogrammetry, starting with stereo measurement in

1901, optical or mechanical instruments, such as the analog plotter,
were used to reconstruct 3D geometry from two overlapping
photographs. The main product during this phase was topographic
maps.
This picture shows 3D topography.
Un derstan ding photogrammetr y
Photogrammetry is the “art, science and technology of obtaining

reliable information about physical objects and the environment
through the process of recording, measuring and interpreting
photographic images and patterns of electromagnetic radiant
imagery and other phenomena” (American Society of
Photogrammetry 1980).
Photogrammetry was invented in 1851 by Aimé Laussedat, and has

continued to develop since. Over time, the development of
photogrammetry has passed through the phases of plane table
photogrammetry, analog photogrammetry, analytical
photogrammetry, and has now entered the phase of digital
This is an analog stereo plotter.
photogrammetry (Konecny 1994).

In analytical photogrammetry, the computer replaced some
expensive optical and mechanical components. The resulting
devices were analog/digital hybrids. Analytical aerotriangulation,
analytical plotters, and orthophoto projectors were the main
developments during this phase. Outputs of analytical
photogrammetry can be topographic maps, but can also be digital
products, such as digital maps and DEMs.
Digital photogrammetry, sometimes called softcopy

photogrammetry, is photogrammetry applied to digital images that
are stored and processed on a computer. Digital images can be
scanned from photographs or directly captured by digital cameras.
Many photogrammetric tasks can be highly automated in digital
photogrammetry (such as automatic DEM extraction and digital
orthophoto generation).
The output products are in digital form, such as digital maps,

DEMs, and digital orthophotos saved on computer storage media.
Therefore, they can be easily stored, managed, and used by you.
With the development of digital photogrammetry, This is the IMAGINE OrthoBASE interface.
photogrammetric techniques are more closely integrated into
Photogrammetry can be used to measure and interpret information
remote sensing and GIS.
from hardcopy photographs or images. Sometimes the process of
Digital photogrammetric systems employ sophisticated software to measuring information from photography and satellite imagery is
automate the tasks associated with conventional photogrammetry, called metric photogrammetry. Interpreting information from
thereby minimizing the extent of manual interaction required to photography and imagery is considered interpretative
perform photogrammetric operations. One such application is photogrammetry, such as identifying and discriminating between
IMAGINE OrthoBASE, the interface of which is shown in the various tree types (Wolf 1983).
following illustration.
APPLYING PHOTOGRAMMETRY 211

Iden tify ing p hoto gra phs a nd im ag es Digital photogrammetric systems use digitized photographs or
digital images as the primary source of input. Digital imagery can
The types of photographs and images that can be processed include be obtained from various sources. These include:
aerial, terrestrial, close-range, and oblique. Aerial or vertical (near
vertical) photographs and images are taken from a high vantage • Digitizing existing hardcopy photographs,
point above the earth’s surface. The camera axis of aerial or vertical • Using digital cameras to record imagery,
photography is commonly directed vertically (or near vertically) • Using sensors onboard satellites such as Landsat, SPOT, and
down. Aerial photographs and images are commonly used for IRS to record imagery.
topographic and planimetric mapping projects and are commonly
captured from an aircraft or satellite. The following figure
illustrates a satellite. Satellites use onboard cameras to collect high-
Using terminology
resolution images of the earth’s surface.
This document uses the term imagery in reference to
photography and imagery obtained from various sources. This
includes aerial and terrestrial photography, digital and video
camera imagery, 35 millimeter photography, medium to large
format photography, scanned photography, and satellite
imagery.
Using photogra mmetr y
Raw aerial photography and satellite imagery have large geometric

distortion that is caused by various systematic and nonsystematic
This illustration shows a common satellite.
factors. Photogrammetric processes eliminate these errors most
efficiently and provide the most reliable solution for collecting
Terrestrial or ground-based photographs and images are taken with geographic information from raw imagery. Photogrammetry is
the camera stationed on or close to the earth’s surface. Terrestrial unique in terms of considering the image-forming geometry,
and close-range photographs and images are commonly used for utilizing information between overlapping images, and explicitly
applications involved with archeology, geomorphology, civil dealing with the third dimension: elevation.
engineering, architecture, industry, and so on.
Photogrammetric techniques allow for the collection of the
Oblique photographs and images are similar to aerial photographs following geographic data:
and images, except the camera axis is intentionally inclined at an
angle with the vertical. Oblique photographs and images are • 3D GIS vectors
commonly used for reconnaissance and corridor mapping • DTMs, which include TINs and DEMs
applications.

• Orthorectified images
• DSMs
• Topographic contours
In essence, photogrammetry produces accurate and precise

geographic information from a wide range of photographs and
images. Any measurement taken on a photogrammetrically
processed photograph or image reflects a measurement taken on the
ground. Rather than constantly go to the field to measure distances,
areas, angles, and point positions on the earth’s surface,
photogrammetric tools allow for the accurate collection of
information from imagery. Photogrammetric approaches for
collecting geographic information save time and money, and
maintain the highest accuracies.

Acquiring images and data
During photograph or image collection, overlapping images are Each photograph or image that is exposed has a corresponding
exposed along a direction of flight. Most photogrammetric image scale (SI) associated with it. The SI expresses the average
applications involve the use of overlapping images. By using more ratio between a distance in the image and the same distance on the
than one image, the geometry associated with the camera/sensor, ground. It is computed as focal length divided by the flying height
image, and ground can be defined to greater accuracies. above the mean ground elevation. For example, with a flying height
of 1000 meters and a focal length of 15 centimeters, the SI would
During the collection of imagery, each point in the flight path at be 1:6667.
which the camera exposes the film, or the sensor captures the
imagery, is called an exposure station.
D e term in in g S I
The flying height above ground is used to determine SI, versus

the altitude above sea level.
A strip of photographs consists of images captured along a flight

line, normally with an overlap of 60 percent. All photos in the strip
are assumed to be taken at approximately the same flying height
and with a constant distance between exposure stations. Camera tilt
relative to the vertical is assumed to be minimal.
The photographs from several flight paths can be combined to form

a block of photographs. A block of photographs consists of a
This illustration shows exposure stations in red over rough terrain. number of parallel strips, normally with a sidelap of 20-30 percent.
A regular block of photos is commonly a rectangular block in

Flight Line 3 Flight path which the number of photos in each strip is the same. The following
of airplane illustration shows a block of 3 × 2 photographs. In cases where a
nonlinear feature is being mapped (such as a river), photographic
Flight Line 2 blocks are frequently irregular.
Flight Line 1
Exposure station
This illustration shows exposure stations in blue along a flight path.

60% overlap
Strip 2
20-30%
sidelap
Flying
Strip 1 direction
This illustration shows a regular rectangular block of aerial photos.
The following illustration shows two overlapping images.
In these illustrations, the area of overlap is indicated by the curly brackets.

Scanning aerial photography
Usi ng p hoto gram m etric sc anners Desktop scanners are appropriate for less rigorous uses, such as
digital photogrammetry in support of GIS or remote sensing
Photogrammetric scanners are special devices capable of high applications. Calibrating these units improves geometric accuracy,
image quality and excellent positional accuracy. Use of this type of but the results are still inferior to photogrammetric units. The image
scanner results in geometric accuracies similar to traditional analog correlation techniques that are necessary for automatic tie point
and analytical photogrammetric instruments. These scanners are collection and elevation extraction are often sensitive to scan
necessary for digital photogrammetric applications that have high quality. Therefore, errors attributable to scanning errors can be
accuracy requirements. introduced into GIS data that is photogrammetrically derived.
These units usually scan only film because film is superior to paper, Choosing scanning resolutions
both in terms of image detail and geometry. These units usually
have a root mean square error (RMSE) positional accuracy of 4 One of the primary factors contributing to the overall accuracy of
microns or less, and are capable of scanning at a maximum 3D feature collection is the resolution of the imagery being used.
resolution of 5 to 10 microns (5 microns is equivalent to Image resolution is commonly determined by the scanning
approximately 5,000 pixels per inch). resolution (if film photography is being used), or by the pixel
resolution of the sensor.
The required pixel resolution varies depending on the application.
Aerial triangulation and feature collection applications often scan In order to optimize the attainable accuracy of GIS data collection,
in the 10- to 15-micron range. Orthophoto applications often use the scanning resolution must be considered. The appropriate
15- to 30-micron pixels. Color film is less sharp than panchromatic, scanning resolution is determined by balancing the accuracy
therefore, color ortho applications often use 20- to 40-micron requirements versus the size of the mapping project and the time
pixels. The optimum scanning resolution also depends on the required to process the project.
desired photogrammetric output accuracy. Scanning at higher
resolutions provides data with higher accuracy. The following table lists the scanning resolutions associated with
various scales of photography and image file size.
Using desktop scanners
Desktop scanners are general-purpose devices. They lack the image

detail and geometric accuracy of photogrammetric-quality units,
but they are much less expensive. When using a desktop scanner,
you should make sure that the active area is at least 9 × 9 inches,
which enables you to capture the entire photo frame.

12 microns 16 microns 25 microns 50 microns 85 microns
(2117 dots per inch) (1588 dots per inch) (1016 dots per inch) (508 dots per inch) (300 dots per inch)
Ground Ground Ground Ground Ground

Photo Scale
Coverage Coverage Coverage Coverage Coverage
1 to
(meters) (meters) (meters) (meters) (meters)
1800 0.0216 0.0288 0.045 0.09 0.153

2400 0.0288 0.0384 0.060 0.12 0.204
3000 0.0360 0.0480 0.075 0.15 0.255
3600 0.0432 0.0576 0.090 0.18 0.306
4200 0.0504 0.0672 0.105 0.21 0.357
4800 0.0576 0.0768 0.120 0.24 0.408
5400 0.0648 0.0864 0.135 0.27 0.459
6000 0.0720 0.0960 0.150 0.30 0.510
6600 0.0792 0.1056 0.165 0.33 0.561
7200 0.0864 0.1152 0.180 0.36 0.612
7800 0.0936 0.1248 0.195 0.39 0.663
8400 0.1008 0.1344 0.210 0.42 0.714
9000 0.1080 0.1440 0.225 0.45 0.765
9600 0.1152 0.1536 0.240 0.48 0.816
10800 0.1296 0.1728 0.270 0.54 0.918
12000 0.1440 0.1920 0.300 0.60 1.020
15000 0.1800 0.2400 0.375 0.75 1.275
18000 0.2160 0.2880 0.450 0.90 1.530
24000 0.2880 0.3840 0.600 1.20 2.040
30000 0.3600 0.4800 0.750 1.50 2.550

12 microns 16 microns 25 microns 50 microns 85 microns
(2117 dots per inch) (1588 dots per inch) (1016 dots per inch) (508 dots per inch) (300 dots per inch)
Ground Ground Ground Ground Ground

Photo Scale
Coverage Coverage Coverage Coverage Coverage
1 to
(meters) (meters) (meters) (meters) (meters)
40000 0.4800 0.6400 1.000 2.00 3.400

50000 0.6000 0.8000 1.250 2.50 4.250
60000 0.7200 0.9600 1.500 3.00 5.100
B/W File Size (MB) 363 204 84 21 7
Color File Size (MB) 1089 612 252 63 21
The Ground Coverage column refers to the ground coverage per pixel. Thus, a 1:40000 scale black and white photograph scanned at 25
microns (1016 dots per inch) has a ground coverage per pixel of 1 meter × 1 meter. The resulting file size is approximately 85 MB, assuming
a square 9 × 9 inch photograph.
Un derstan ding coordinate system s
Conceptually, photogrammetry involves establishing the relationship between the camera or sensor used to capture the imagery, the
imagery itself, and the ground. In order to understand and define this relationship, each of the three variables associated with the relationship
must be defined with respect to a coordinate space and coordinate system.
Applying a pixel coordinate system
The file coordinates of a digital image are defined in a pixel coordinate system. A pixel coordinate system is usually a coordinate system
with its origin in the upper-left corner of the image, the x-axis pointing to the right, the y-axis pointing downward, and the units in pixels,
as shown by axes c and r in the following illustration. These file coordinates (c, r) can also be thought of as the pixel column and row
numbers, respectively.

A p p l y i n g a n im a g e s p a c e c o o r d i n a t e s y s t e m
y
An image space coordinate system (see the following illustration)
c is identical to image coordinates, except that it adds a third axis (z).
The origin of the image space coordinate system is defined at the
perspective center S as shown in the following illustration.
x y
Image coordinate system
S x
r a
o
This illustration shows the origin of the image coordinate system (x, y) and
the origin of the pixel coordinate system (c, r).
Applying an image coordinate system Z

Height
An image coordinate system or an image plane coordinate system A
is usually defined as a 2D coordinate system occurring on the image Y
plane with its origin at the image center. The origin of the image
coordinate system is also referred to as the principal point. On
aerial photographs, the principal point is defined as the intersection Ground
of opposite fiducial marks as illustrated by axes x and y as in the coordinate
system X
diagram above. Image coordinates are used to describe positions on
the film plane. Image coordinate units are usually millimeters or
microns.
This illustration shows the image space and ground space coordinate
systems.

The perspective center is commonly the lens of the camera as it A topocentric coordinate system has its origin at the center of the
existed when the photograph was captured. Its x-axis and y-axis are image projected on the earth ellipsoid. The three perpendicular
parallel to the x-axis and y-axis in the image plane coordinate coordinate axes are defined on a tangential plane at this center
system. The z-axis is the optical axis; therefore, the z value of an point. The plane is called the reference plane or the local datum.
image point in the image space coordinate system is usually equal The X-axis is oriented eastward, the Y-axis northward, and the
to the focal length of the camera (f). Image space coordinates are Z-axis is vertical to the reference plane (up).
used to describe positions inside the camera, and usually use units
in millimeters or microns. This coordinate system is referenced as For simplicity of presentation, the remainder of this appendix does
image space coordinates (x, y, z) in this appendix. not explicitly reference geocentric or topocentric coordinates.
Basic photogrammetric principles can be presented without adding
A p p l y in g t h e g r o u n d c o o r d i n a t e s y s t e m this additional level of complexity.
A ground coordinate system is usually defined as a 3D coordinate
system that utilizes a known geographic map projection. Ground
coordinates (X, Y, Z) are usually expressed in feet or meters. The Z
value is elevation above mean sea level for a given vertical datum.
This coordinate system is referenced as ground coordinates (X, Y,
Z) in this appendix.
Applying the geocentric and topocentric

c o o r d in a t e s y s t e m s
Most photogrammetric applications account for the earth’s

curvature in their calculations. This is done by adding a correction
value or by computing geometry in a coordinate system that
includes curvature. Two such systems are the geocentric
coordinate system and the topocentric coordinate system.
A geocentric coordinate system has its origin at the center of the

earth ellipsoid. The Z-axis equals the rotational axis of the earth,
and the X-axis passes through the Greenwich meridian. The Y-axis
is perpendicular to both the Z-axis and X-axis, so as to create a
three-dimensional coordinate system that follows the right hand
rule.

Usi ng terrestrial pho tography
Photogrammetric applications associated with terrestrial or ground-based images utilize slightly different image and ground space
coordinate systems. The following figure illustrates the two coordinate systems associated with image space and ground space.
YG
ϕ Ground point A
Ground space ZA
ω YA
XG
κ
XA
ZG
xa'
Image space a'
ya'
x
z
Z
Y ZL
ϕ' Perspective Center
X
κ' L
YL
X
ω'
This illustration shows components associated with terrestrial photography.
The image and ground space coordinate systems are right-handed coordinate systems. Most terrestrial applications use a ground space
coordinate system defined using a localized Cartesian coordinate system.

The image space coordinate system directs the z-axis toward the
imaged object and the y-axis directed north up. The image x-axis is
similar to that used in aerial applications. The XL, YL, and ZL
coordinates define the position of the perspective center as it
existed at the time of image capture. The coordinates of ground
point A (XA, YA, and ZA) are defined within the ground space
coordinate system (XG, YG, and ZG).
With this definition, three rotation angles ω (omega), ϕ (phi), and

κ (kappa) define the orientation of the image. You can also use the
ground (X, Y, Z) coordinate system to directly define GCPs. Thus,
GCPs do not need to be transformed. Then the definition of rotation
angles ω', ϕ', and κ' is different, as shown in the figure on page 221.

Understanding interior orientation
Interior orientation defines the internal geometry of a camera or • Principal point
sensor as it existed at the time of image capture. The variables • Focal length
associated with image space are obtained during the process of
• Fiducial marks
defining interior orientation. Interior orientation is primarily used
to transform the image pixel coordinate system or other image • Lens distortion
coordinate measurement systems to the image space coordinate Defini ng p rin cipal poin t an d focal length
system.
The principal point is mathematically defined as the intersection of
The following figure illustrates the variables associated with the
internal geometry of an image captured from an aerial camera, the perpendicular line through the perspective center of the image
where O represents the principal point and a represents an image plane. The length from the principal point to the perspective center
point. is called the focal length (Wang 1990).
The image plane is commonly referred to as the focal plane. For

wide-angle aerial cameras, the focal length is approximately 152
z millimeters, or 6 inches. For some digital cameras, the focal length
Perspective Center is 28 millimeters. Prior to conducting photogrammetric projects,
y the focal length of a metric camera is accurately determined
(calibrated) in a laboratory environment.
The optical definition of principal point is the image position where

Focal length Fiducial mark the optical axis intersects the image plane. In the laboratory, this is
calibrated in two forms: principal point of autocollimation and
principal point of symmetry, which can be seen in the camera
calibration report. Most applications prefer to use the principal
point of symmetry since it can best compensate for any lens
yo x distortion.
ya'
Image plane xo O
Defining fiducial marks
xa' a
As stated previously, one of the steps associated with calculating
interior orientation involves determining the image position of the
This illustration shows components of internal geometry. principal point for each image in the project. Therefore, the image
positions of the fiducial marks are measured on the image, and then
The internal geometry of a camera is defined by specifying the compared to the calibrated coordinates of each fiducial mark.
following variables:

Since the image space coordinate system has not yet been defined
for each image, the measured image coordinates of the fiducial
marks are referenced to a pixel or file coordinate system. The pixel x = a1 + a2 X + a3 Y
coordinate system has an x coordinate (column) and a y coordinate
(row). The origin of the pixel coordinate system is the upper left y = b1 + b2 X + b3 Y
corner of the image having a row and column value of 0 and 0,
respectively. The following diagram illustrates the difference
between the pixel coordinate system and the image space The x and y image coordinates associated with the calibrated
coordinate system. fiducial marks and the X and Y pixel coordinates of the measured
fiducial marks are used to determine six affine transformation
coefficients. The resulting six coefficients can then be used to
transform each set of row (y) and column (x) pixel coordinates to
Ya-file Yo-file image coordinates.
The quality of the 2D affine transformation is represented using an

RMSE. The RMSE represents the degree of correspondence
xa between the calibrated fiducial mark coordinates and their
Θ
respective measured image coordinate values. Large RMSEs
Xa-file a indicate poor correspondence. This can be attributed to film
deformation, poor scanning quality, out-of-date calibration
Xo-file ya Fiducial mark information, or image mismeasurement.
The affine transformation also defines the translation between the

origin of the pixel coordinate system and the image coordinate
system (xo-file and yo-file). Additionally, the affine transformation
takes into consideration rotation of the image coordinate system by
considering angle Θ (theta). A scanned image of an aerial
This diagram shows the pixel coordinate system vs. the image space photograph is normally rotated due to the scanning procedure.
coordinate system.
The degree of variation between the x-axis and y-axis is referred to
Using a 2D affine transformation, the relationship between the as nonorthogonality. The 2D affine transformation also considers
pixel coordinate system and the image space coordinate system is the extent of nonorthogonality. The scale difference between the
defined. The following 2D affine transformation equations can be x-axis and the y-axis is also considered using the affine
used to determine the coefficients required to transform pixel transformation.
coordinate measurements to the corresponding image coordinate
values:

Definin g le ns di stor tion
Lens distortion deteriorates the positional accuracy of image points

located on the image plane. Two types of radial lens distortion
exist: radial lens distortion and tangential lens distortion. Lens
distortion occurs when light rays passing through the lens are bent,
thereby changing direction and intersecting the image plane at
positions deviant from the norm. The following diagram illustrates
the difference between radial and tangential lens distortion.
∆r ∆t
radial distance (r)
o x
This shows radial vs. tangential lens distortion.
Radial lens distortion causes imaged points to be distorted along

radial lines from the principal point o. The effect of radial lens
distortion is represented as ∆r. Radial lens distortion is also
commonly referred to as symmetric lens distortion.
Tangential lens distortion occurs at right angles to the radial lines

from the principal point. The effect of tangential lens distortion is
represented as ∆t. Because tangential lens distortion is much
smaller in magnitude than radial lens distortion, it is considered
negligible. The effects of lens distortion are commonly determined
in a laboratory during the camera calibration procedure.

Understanding exterior orientation
Exterior orientation defines the position and angular orientation of
the camera that captured an image. The variables defining the z´
position and orientation of an image are referred to as the elements
of exterior orientation. The elements of exterior orientation define z
y y´
the characteristics associated with an image at the time of exposure ϕ
or capture. κ ω
x
O x´
The positional elements of exterior orientation include Xo, Yo, and
Zo. They define the position of the perspective center (O) with f
respect to the ground space coordinate system (X, Y, and Z). Zo is
o p y
commonly referred to as the height of the camera above sea level, p
which is commonly defined by a datum. xp
The angular or rotational elements of exterior orientation describe

the relationship between the ground space coordinate system (X, Y,
and Z) and the image space coordinate system (x, y, and z). Three
rotation angles are commonly used to define angular orientation.
They are omega (ω), phi (ϕ), and kappa (κ). The following figures Zo
illustrate the elements of exterior orientation and the individual
angles (ω, ϕ, and κ) of exterior orientation. Ground point P
Z
Zp
Y
Xp
Xo
Yp
Yo
X
These are elements of exterior orientation.

Using the three rotation angles, the relationship between the image
space coordinate system (x, y, and z) and ground space coordinate
system (X, Y, and Z or x', y', and z') can be determined. A 3 × 3
z y z y matrix defining the relationship between the two systems is used.
This is referred to as the orientation or rotation matrix, M. The
rotation matrix can be defined as follows:
x x
ω ϕ m 11 m 12 m 13
omega phi M = m 21 m 22 m 23
z m 31 m 32 m 33
y
The rotation matrix is derived by applying a sequential rotation of

omega about the x-axis, phi about the y-axis, and kappa about the
x
z-axis.
κ
kappa Defini ng t he co llin eari ty eq uati on
The following section defines the relationship between the camera

The angles omega, phi, and kappa correspond to X, Y, and Z axes.
or sensor, the image, and the ground. Most photogrammetric tools
Omega is a rotation about the photographic x-axis, phi is a rotation utilize the following formulas in one form or another.
about the photographic y-axis, and kappa is a rotation about the
With reference to the figure on page 226, an image vector a can be
photographic z-axis, which are defined as being positive if they are
defined as the vector from the exposure station O to the image point
counterclockwise when viewed from the positive end of their
p. A ground space or object space vector A can be defined as the
respective axis. Different conventions are used to define the order
vector from the exposure station O to the ground point P. The
and direction of the three rotation angles (Wang 1990).
image vector and ground vector are collinear, inferring that a line
The International Society of Photogrammetry and Remote Sensing extending from the exposure station to the image point and to the
(ISPRS) recommends the use of the ω, ϕ, κ convention. The ground is linear.
photographic z-axis is equivalent to the optical axis (focal length).
The image vector and ground vector are only collinear if one is a
The x', y', and z' coordinates are parallel to the ground space
scalar multiple of the other. Therefore, the following statement can
coordinate system.
be made:

a = kA xp – xo Xp – Xo
y p – y o = kM Y p – Y o
where k is a scalar multiple. The image and ground vectors must be
within the same coordinate system. Therefore, image vector a is –f Zp – Zo
comprised of the following components:
The previous equation defines the relationship between the

perspective center of the camera/sensor exposure station and
xp – xo ground point P appearing on an image with an image point location
of p. This equation forms the basis of the collinearity condition that
a = y –y is used in most photogrammetric operations. The collinearity
p o
condition specifies that the exposure station of the image, ground
–f point, and its corresponding image point location must all fall along
a straight line, thereby being collinear. Two equations comprise the
where xo and yo represent the image coordinates of the principal collinearity condition:
point. Similarly, the ground vector can be formulated as follows:
Xp – Xo m 11 ( X p – X o ) + m 12 ( Y p – Y o ) + m 13 ( Z p – Z o )
x p – x o = – f ---------------------------------------------------------------------------------------------------------------------
1 1 1
-
m 31 ( X p – X o ) + m 32 ( Y p – Y o ) + m 33 ( Z p – Z o )
A = Yp – Yo 1 1 1
Zp – Zo
In order for the image and ground vectors to be within the same m 21 ( X p – X o ) + m 22 ( Y p – Y o ) + m 23 ( Z p – Z o )
y p – y o = – f ---------------------------------------------------------------------------------------------------------------------
1 1 1
-
coordinate system, the ground vector must be multiplied by the m 31 ( X p – X o ) + m 32 ( Y p – Y o ) + m 33 ( Z p – Z o )
1 1 1
rotation matrix M. The following equation can be formulated:
One set of equations can be formulated for each ground point

a = kMA appearing on an image. The collinearity condition is commonly
used to define the relationship between the camera/sensor, the
where image, and the ground.

Using digital mapping solutions
Digital photogrammetry is used for many applications including Understan ding space re section
orthorectification, automated elevation extraction, image pair
creation, stereo feature collection, highly accurate 3D point Space resection is a technique that is commonly used to determine
determination, and GCP extension. the exterior orientation parameters associated with one image or
many images based on known GCPs. Space resection uses the
For any of the aforementioned tasks to be undertaken, a relationship collinearity condition. Space resection using the collinearity
between the camera/sensor, the image(s) in a project, and the condition specifies that, for any image, the exposure station, the
ground must be defined. The following variables are used to define ground point, and its corresponding image point must be positioned
the relationship: along a straight line.
• Exterior orientation parameters If a minimum number of three GCPs is known in the X, Y, and Z
• Interior orientation parameters direction, space resection techniques can be used to determine the
six exterior orientation parameters associated with an image. Space
• Camera or sensor model information
resection assumes that camera information is available.
Well-known obstacles in photogrammetry include defining the
interior and exterior orientation parameters for each image in a Space resection is commonly used to perform single frame
project using a minimum number of GCPs. Due to the costs and orthorectification where one image is processed at a time. If
labor intensive procedures associated with collecting ground multiple images are being used, space resection techniques require
control, most photogrammetric applications do not have an a minimum of three GCPs on each image being processed.
abundant number of GCPs. Additionally, the exterior orientation
Using the collinearity condition, the positions of the exterior
parameters associated with an image are normally unknown.
orientation parameters are computed. Light rays originating from at
Depending on the input data provided, photogrammetric techniques least three GCPs intersect through the image plane through the
such as space resection, space forward intersection, and bundle image positions of the GCPs and resect at the perspective center of
block adjustment are used to define the variables required to the camera or sensor. Using least squares adjustment techniques,
perform orthorectification, automated DEM extraction, image pair the most probable positions of exterior orientation can be
creation, highly accurate point determination, and control point computed. Space resection techniques can be applied to one image
extension. or multiple images.

Un derstan ding space fo rward intersec tion
Space forward intersection is a technique that is commonly used to determine the ground coordinates X, Y, and Z of points that appear in
the overlapping areas of two or more images based on known interior orientation and known exterior orientation parameters. The
collinearity condition is enforced, which states that the corresponding light rays from the two exposure stations pass through the
corresponding image points on the two images and intersect at the same ground point. The following diagram illustrates the concept
associated with space forward intersection.
O1
O2
o1
p2 o2
p1
Zo1 Ground point P Zo2
Z
Zp
Y
Xo2
Xp
Xo1 Yo2
Yp
Yo1
X
This diagram illustrates space forward intersection.

Space forward intersection techniques assume that the exterior A bundle block adjustment is best defined by examining the
orientation parameters associated with the images are known. individual words in the term. A bundled solution is computed
Using the collinearity equations, the exterior orientation including the exterior orientation parameters of each image in a
parameters along with the image coordinate measurements of point block and the X, Y, and Z coordinates of tie points and adjusted
p1 on Image 1 and point p2 on Image 2 are input to compute the Xp, GCPs. A block of images contained in a project is simultaneously
Yp, and Zp coordinates of ground point P. processed in one solution. A statistical technique known as least
squares adjustment is used to estimate the bundled solution for the
Space forward intersection techniques can also be used for entire block while also minimizing and distributing error.
applications associated with collecting GCPs, cadastral mapping
using airborne surveying techniques, and highly accurate point Block triangulation is the process of defining the mathematical
determination. relationship between the images contained within a block, the
camera or sensor model, and the ground. Once the relationship has
Un derstan ding bun dle block ad justm ent been defined, accurate imagery and geographic information
concerning the earth’s surface can be created and collected in 3D.
For mapping projects having more than two images, the use of
space intersection and space resection techniques is limited. This When processing frame camera, digital camera, videography, and
can be attributed to the lack of information required to perform nonmetric camera imagery, block triangulation is commonly
these tasks. For example, it is fairly uncommon for the exterior referred to as aerial triangulation (AT). When processing imagery
orientation parameters to be highly accurate for each photograph or collected with a pushbroom sensor, block triangulation is
image in a project since these values are generated commonly referred to as triangulation.
photogrammetrically. Airborne GPS and INS techniques normally
There are several models for block triangulation. The common
provide initial approximations to exterior orientation, but the final
models used in photogrammetry are block triangulation with the
values for these parameters must be adjusted to attain higher
strip method, the independent model method, and the bundle
accuracies.
method. Among them, the bundle block adjustment is the most
Similarly, rarely are there enough accurate GCPs for a project of rigorous, considering the minimization and distribution of errors.
thirty or more images to perform space resection (that is, a Bundle block adjustment uses the collinearity condition as the basis
minimum of 90 is required). In the case that there are enough GCPs, for formulating the relationship between image space and ground
the time required to identify and measure all of the points would be space.
costly.
In order to understand the concepts associated with bundle block
The costs associated with block triangulation and orthorectification adjustment, the following picture illustrates ten images with
are largely dependent on the number of GCPs used. To minimize multiple GCPs whose X, Y, and Z coordinates are known.
the costs of a mapping project, fewer GCPs are collected and used. Additionally, six tie points are available. The IMAGINE
To ensure that high accuracies are attained, an approach known as OrthoBASE Graphic Status Display dialog illustrates the
bundle block adjustment is used. photogrammetric configuration.

The photogrammetric block configuration displays in the IMAGINE OrthoBASE Graphic Status Display dialog.

Glossary
Glossary This glossary defines terms commonly used in 3D GIS applications and photogrammetry.
Nu meri cs
2D
Images or photos in X and Y coordinates only. There is no vertical element (Z) to 2D images.
Viewed in mono, 2D images are good for qualitative analysis.
3D
Images or photos in X, Y, and Z (vertical) coordinates. Viewed in stereo, 3D images approximate
true earth features.
3D feature
A 3D feature is a feature that has vertex coordinates in X, Y, and Z. The Z component is the
elevation of a particular vertex.
3D Floating Cursor
The 3D Floating Cursor is apparent when you have a DSM (that is, two images of approximately
the same area) displayed. The 3D Floating Cursor’s position is determined by the amount of
X-parallax evident in the DSM and your positioning of it on the ground or feature of interest. You
adjust the position of the 3D Floating Cursor using the keyboard and the system mouse. See also
X-parallax.
3D model
A 3D model has vertex coordinates in X, Y, and Z, where the Z coordinate indicates elevation. A
3D model displays in 3D (that is, a volumetric object).
Sy mbols
*.blk
An IMAGINE OrthoBASE block file. A block file can contain only one image, but usually
contains two or more images with approximately 60 percent overlap. Block files can be viewed in
3D using Stereo Analyst for ArcGIS.
233
*.img aerial triangulation
An ERDAS IMAGINE image file. An .img file uses the (AT) The process of establishing a mathematical relationship
hierarchical file format (HFA) structure to store many types of between images, a camera or sensor model, and the ground. The
information in addition to the image data. For example, the .img information derived is necessary for orthorectification, DEM
format stores information about the file, sensor, layers, statistics, generation, and image pair creation. This term is used when
projection, and so on. processing frame camera, digital camera, videography, and
nonmetric camera imagery.
*.prj
affine transformation
A SOCET SET® project file, which contains sensor position and
projection information about images in the project. A 2D plane-to-plane transformation that uses six parameters to
account for rotation, translation, scale, and nonorthogonality in
*.sup between the planes. Defines the relationship between two
A SOCET SET® support file, which contains geometric coordinate systems such as a pixel and an image space coordinate
information about the image it supports. system.
κ airborne GPS
Kappa. The angle used to define angular orientation. Kappa is A technique used to provide initial approximations of exterior
rotation about the Z-axis. orientation, which defines the position and orientation associated
with an image as they existed during image capture. GPS provides
ω the X, Y, and Z coordinates of the exposure station. See also
Omega. An angle used to define angular orientation. Omega is global positioning system.
rotation about the X-axis. algorithm
ϕ “A procedure for solving a mathematical problem (as of finding the
Phi. An angle used to define angular rotation. Phi is rotation about greatest common divisor) in a finite number of steps that frequently
the Y-axis. involves repetition of an operation” (Merriam-Webster OnLine
Dictionary 2001).
American Standard Code for Information Interchange
Terms
(ASCII) A “basis of character sets...to convey some control codes,
additional parameter space, numbers, most basic punctuation, and unaccented letters
a–z and A–Z” (Free On-Line Dictionary of Computing 1999).
(AP) In block triangulation, additional parameters characterize
systematic error within the block of images and observations, such anaglyph
as lens distortion. A 3D image composed of two oriented or nonoriented image pairs.
aerial photographs To view an anaglyph, you require a pair of red/blue glasses. These
glasses isolate your vision into two distinct parts corresponding
Photographs taken from positions above the earth captured by with the left and right images of an image pair. This produces a 3D
aircraft. Photographs are used for planimetric mapping projects. effect with vertical information.

analog photogrammetry block file
A technique in which optical or mechanical instruments such as A term used to describe and characterize all of the information
analog plotters are used to reconstruct 3D geometry from two associated with a photogrammetric mapping project, such as:
overlapping photographs. projection, spheroid, and datum; imagery; camera or sensor model
information; GCPs; and geometric relationship between imagery
analytical photogrammetry
and the ground. A block file is a binary file.
A technique in which the computer replaces some expensive
block footprint
optical and mechanical components by substituting analog
measurement and calculation with mathematical computation. A graphical representation of the extent of images in a block file.
The images are not presented as raster images. Rather, they are
ASCII
displayed as vector outlines that depict the amount of overlap
See American Standard Code for Information between images in the block file.
Interchange.
block of photographs
AT
A series of photographs formed by the combined exposures of a
See aerial triangulation. flight. For example, a traditional frame camera block might consist
attribute of a number of parallel strips with a sidelap of 20–30 percent and
an overlap of 60 percent.
A piece of information about a feature, such as its length, location,
name, and so on. block triangulation
attribute table The process of establishing a mathematical relationship between

images, the camera or sensor model, and the ground. The
A collection of attributes in tabular format. information derived is necessary for orthorectification, DEM
attribution generation, and image pair creation.
Attribute data associated with a feature. bundle
auto-correlation The unit of photogrammetric triangulation after each point
measured in an image is connected with the perspective center by a
A technique used to identify and measure the image positions
straight light ray. There is one bundle of light rays for each image.
appearing in the overlap of two adjacent images in a block file.
bundle block adjustment
automated terrain following
A mathematical technique (triangulation) that determines the
Automatically places the 3D Floating Cursor on the ground so that
position and orientation of each image as they existed at the time of
you don’t have to manually edit the height of the 3D Floating
image capture, determines the ground coordinates measured on
Cursor. The X-parallax is adjusted using image correlation
overlap areas of multiple images, and minimizes the error
techniques to determine the image coordinate positions of a feature
associated with the imagery, image measurements, and GCPs. This
appearing on both the left and right image of an image pair.
is essentially a simultaneous triangulation performed on all
binocular vision observations.
Vision using two eyes. See also stereoscopic viewing.
GLOSSARY 235
calibration report collinearity condition
In aerial photography, the manufacturer of the camera specifies the The condition that specifies that the exposure station, ground point,
interior orientation of each camera in the form of a certificate or and its corresponding image point location must all be positioned
report. Information includes focal length, principal point offset, along a straight line.
radial lens distortion data, and fiducial mark coordinates.
contrast stretch
Cartesian coordinate system The process of reassigning a range of values to another range,
“A coordinate system consisting of intersecting straight lines called usually employing a linear function. Contrast stretching is often
axes, in which the lines intersect at a common origin. Usually it is used in displaying continuous raster layers since the range of data
a 2-dimensional surface in which a ‘x, y’ coordinate defines each file values is commonly much narrower than the range of
point location on the surface. The ‘x’ coordinate refers to the brightness values available to the display device.
horizontal distance and the ‘y’ to vertical distance. Coordinates can control point
be either positive or negative, depending on their relative position
from the origin. In a 3-dimensional space, the system can also A point with known coordinates in a coordinate system, expressed
include a ‘z’ coordinate, representing height or depth. The relative in the units (such as meters, feet, pixels, film units) of the specified
measurement of distance, direction and area are constant coordinate system.
throughout the surface of the system” (Natural Resources Canada control point extension
2001).
The process of converting tie points to control points. This
CCD technique requires the manual measurement of ground points on
See charge-coupled device. photos of overlapping areas. The ground coordinates associated
with GCPs are then determined using photogrammetric techniques.
centroid
coordinate system
The point whose coordinates are the averages of the corresponding
coordinates of the vertices of the polygon. “A system, based on mathematical rules, used to measure
horizontal and vertical distance on a surface, in order to identify the
charge-coupled device location of points by means of unique sets of numerical or angular
(CCD) A device in a digital camera that contains an array of cells values” (Natural Resources Canada 2001).
that record the intensity associated with a ground feature or object.
coplanarity condition
coefficient The coplanarity condition is used to calculate relative orientation.
One number in a matrix, or a constant in a polynomial expression. It uses an iterative least squares adjustment to estimate five
parameters (By, Bz, omega, phi, and kappa). The parameters
collinearity
explain the difference in position and rotation between two images
A nonlinear mathematical model that photogrammetric making up the image pair.
triangulation is based upon. Collinearity equations describe the
relationship among image coordinates, ground coordinates, and correlation
orientation parameters. Regions of separate images are matched for the purposes of tie
point or mass point collection.

correlation coefficient digital photogrammetry
Represents the measure of similarity between a set of image points Photogrammetry as applied to digital images that are stored and
appearing within the overlapping portions of an image pair. A large processed on a computer. Digital images can be scanned from
correlation coefficient (0.80-1.0) statistically indicates that the set photographs or can be directly captured by digital cameras.
of image points is more similar than a set of image points which has
digital stereo model
a low correlation coefficient value (less than 0.50).
(DSM) Stereo models that use imaging techniques of digital
correlation threshold photogrammetry that can be viewed on desktop applications.
A value used in image matching to determine whether to accept or digital terrain model
discard match points. The threshold is an absolute value threshold
ranging from 0.100 to 1.000. (DTM) A discrete expression of topography in a data array,
consisting of a group of planimetric coordinates (C, Y) and the
cross-strips
elevations of the ground points and breaklines.
Strips of image data that run perpendicular to strips collected along digitizing
the flight line.
Any process that converts nondigital data into numeric data,
datum usually to be stored on a computer. The creation of vector data from
“A datum is a system of reference for specifying the horizontal and hardcopy materials or raster images. The data are traced using a
vertical spatial positions of points” (Wolf and Dewitt 2000). See digitizer keypad on a digitizing tablet, or a mouse on a display
also reference plane. device.
DEM direction of flight
See digital elevation model. The direction in which the craft is moving (such as east to west).
Images in a strip are captured along the aircraft or satellite’s
digital elevation model
direction of flight. Images overlap in the same manner as the
(DEM) Continuous raster layers in which data file values represent direction of flight.
elevation.
draping
digital image matching
See feature draping.
The process of matching features common to two or more images
DSM
for the purpose of generating a 3D representation of the earth. Also
known as auto-correlation. See digital stereo model.
digital orthophoto DTM
An aerial photo or satellite scene that has been transformed by the See digital terrain model.
orthogonal projection, yielding a map that is free of most
elements of exterior orientation
significant geometric distortions.
Variables that define the position and orientation of a sensor as it
obtained an image. It is the position of the perspective center with
respect to the ground space coordinate system.
GLOSSARY 237
elevation source feature collection
Data, such as a DEM or TIN, that supplies the Z component of a The process of identifying, delineating, and labeling various types
feature or scene. An elevation source enables stereo viewing and of natural and human-made phenomena from remotely-sensed
3D feature extraction. images.
ellipsoid feature draping
“A surface all plane sections of which are ellipses or circles” A condition that the feature follows the subtle changes in elevation
(Merriam-Webster OnLine Dictionary 2000). of the terrain surface in the height dimension.
endlap feature extraction
The area common to two images in a strip of photos taken along the The process of studying and locating areas and objects on the
flight path. Another term for overlap. See also overlap. ground and deriving useful information from images.
epipolar line fiducial mark
The line traced on each image representing the intersection of the Four or eight reference markers fixed on the frame of an aerial
epipolar plane with the image plane. metric camera and visible in each exposure. Fiducials are used to
compute the transformation from pixel coordinates to image
epipolar plane
coordinates.
The plane, in space, containing a ground point and both exposure
Fixed Cursor Mode
stations.
A mode in which the 3D Floating Cursor remains at a constant
exposure station
position while the image pair can be repositioned in the display.
During image acquisition, each point in the flight path at which the
Fixed Image Mode
camera exposes the film. The exposure station has elements that
define its position and rotation: X, Y, Z, omega, phi, and kappa. A mode in which the image pair remains at a constant position
while the 3D Floating Cursor moves freely in the display.
exterior orientation
flight line
External sensor model information that describes the exact position
and orientation of each image as they existed when the imagery was One of, typically, consecutive lines flown by an airplane consisting
collected. The image’s position is defined as having 3D of exposure stations. A strip of photographs is captured along a
coordinates, and the orientation is defined as having three rotations flight line.
that include omega, phi, and kappa. flight path
exterior orientation parameters The path of an airplane including, typically, multiple flight lines
The perspective center’s ground coordinates in a specified map with multiple exposure stations where the camera exposes the film.
projection and three rotation angles around the coordinate axes. Photographs from several flight paths can be combined to form a
block of photographs.

focal length geolink
The distance between the optical center of the lens and where the A method of establishing a relationship between attribute data and
optical axis intersects the image plane. Focal length of a camera is the features to which they pertain.
determined in a laboratory environment.
GIS-ready image
focal plane Imagery that has information about the relationship between the
The plane of the film or scanner used in obtaining an aerial photo. image (as it existed when the image was recorded) and the earth’s
surface.
footprint
global positioning system
An outline corresponding to an image or image pair. Used to
visualize areas of overlap between image pairs. (GPS) “A surveying method that uses a set of 24 satellites in
geostationary position high above the Earth. Specially designed
GCP
GPS receivers, when positioned at a point on Earth, can measure
See ground control point. the distance from that point to three or more orbiting satellites. The
geocentric coordinates of the point are determined through the geometric
calculations of triangulation. GPS provides accurate geodetic data
A coordinate system with its origin at the center of the earth for any point on Earth” (Natural Resources Canada 2001).
ellipsoid. The Z-axis equals the rotational axis of the earth, the
X-axis passes through the Greenwich meridian, and the Y-axis is GPS
perpendicular to both the Z-axis and the X-axis so as to create a 3D See global positioning system.
coordinate system that follows the right-hand rule.
ground control point
geocorrect
(GCP) An easily identifiable point for which the ground
A method of establishing a geometric relationship between coordinates of the map coordinate system are known.
imagery and the ground. Geocorrection does not use many GCPs,
ground coordinate system
and is therefore not as accurate as orthocorrection or
orthorectification. See also orthorectification. A 3D coordinate system that utilizes a known map projection.
Ground coordinates (X, Y, and Z) are usually expressed in feet or
geographic information system
meters.
(GIS) A unique system designed for a particular application that
ground point
stores, enhances, combines, and analyzes layers of geographic data
to produce interpretable information. A GIS may include computer Another term for the 3D Floating Cursor.
images, hardcopy maps, statistical data, and any other data needed ground space
for a study, as well as computer software and human knowledge.
GISs are used for solving complex geographic planning and Events and variables associated with the objects being
management problems. A GIS consists of spatial data stored in a photographed or imaged, including the reference coordinate
relational database with associated ancillary information. system.
GLOSSARY 239
image INS
A picture or representation of an object or scene on paper or a See inertial navigation system.
display screen. Remotely sensed images are digital representations
interior orientation
of the earth.
Describes the internal geometry of a camera such as the focal
image center length, principal point, lens distortion, and fiducial mark
The center of an aerial photo or satellite scene. coordinates for aerial photographs.
image pair International Society of Photogrammetry and Remote
Sensing
Two overlapping oriented images. A set of two remotely-sensed
images that overlap, providing a 3D view of the terrain in the (ISPRS) An organization “devoted to the development of
overlap area. international cooperation for the advancement of photogrammetry
and remote sensing and their application” (ISPRS 2000). For more
image scale
information, visit the Web site <http://www.isprs.org>.
(SI) Expresses the ratio between a distance in the image and the
ISPRS
same distance on the ground.
See International Society of Photogrammetry and
image space
Remote Sensing.
Events and variables associated with the camera or sensor as it
kappa
acquired the images. The area between perspective center and the
image. In a rotation system, kappa is positive rotation around the Z-axis.
image space coordinate system least squares adjustment
A coordinate system composed of the image coordinate system A technique by which the most probable values are computed for a
with the addition of a Z axis defined along the focal axis. measured or indirectly determined quantity based upon a set of
observations. It is based on the mathematical laws of probability
image-to-earth association
and provides a systematic method for computing unique values of
The 3D mathematical relationship between an image and the coordinates and other elements in photogrammetry based on a large
earth’s surface. number of redundance measurements of different kinds and
inertial navigation system weights.
(INS) A technique that provides initial approximations to exterior lens distortion

orientation. This data is provided by a device or instrument. The Caused by the instability of the camera lens at the time of data
instrument collects data about the attitude of the airplane in which capture. Lens distortion makes the positional accuracy of the image
it is located. The information it collects includes pitch (tilting points less reliable.
forward and backward), roll (tilting sideways), and heading (the
line of sight
direction of flight) (National Oceanic and Atmospheric
Administration 2001). See also omega, phi, kappa. (LOS) The area that can be viewed along a straight line without
obstructions.

LOS mosaicking
See line of sight. The process of piecing together images, side by side, to create a
larger image.
map coordinate system
nadir
A map coordinate system that expresses location on the earth’s
surface using a particular map projection such as Universal The area on the ground directly beneath a scanner’s detectors.
Transverse Mercator, State Plane, or Polyconic. near vertical aerial photographs
mass points
Photographs taken from vertical or near vertical positions above
Points whose 3D coordinates are known (X, Y, and Z), and which the earth captured by aircraft. Photographs are used for planimetric
are used in creating a DEM or DTM. See also digital elevation mapping projects.
model and digital terrain model. node
metadata An element of a line or polygon, or the element of a point that has
A more highly organized or comprehensive level of data. Metadata specific coordinates in X, Y, and in the case of 3D data, Z.
files often contain lists of data files and auxiliary files such as
nonoriented image pair
header files, attribute files, and transform files. Metadata may be
thought of as data about data. An image pair made up of two overlapping photographs or images
that have not been photogrammetrically processed. Neither the
metric photogrammetry
interior nor the exterior orientation, defining the internal geometry
The process of measuring information from photography and of the camera or the sensor as well as its position during image
satellite imagery. capture, has been defined. You can collect measurements from a
mono nonoriented image pair; however, the measurements are in pixels
and 2D.
A view in which there is only one image. There are not two images
nonorthogonality
to create an image pair. You cannot see in 3D using a mono view.
monocular vision The deviation from perpendicularity between orthogonally defined
axes.
Vision using one eye.
oblique photographs
monotonic
Photographs captured by an aircraft or satellite deliberately offset
“Having the property either of never increasing or of never at an angle.
decreasing as the values of the independent variable or the
subscripts of the terms increase” (Merriam-Webster OnLine omega
Dictionary 2003). In a rotation system, omega is rotation around the X-axis.
GLOSSARY 241
omega, phi, kappa orthocalibration
A rotation system that defines the orientation of a camera/sensor as A form of calibration that corrects for terrain displacement and can
it acquired an image. Omega, phi, kappa is used most commonly, be used if a DEM of the study area is available. Unlike
where omega is positive rotation around the X-axis, phi is a orthorectification, this method depends upon a transformation
positive rotation around the Y-axis, and kappa is a positive rotation matrix to resample on the fly thus leaving the image file (data)
around the Z-axis. This rotation system follows the right-hand rule. unaffected.
optical axis orthocorrection
“The line joining the centers of curvature of the spherical surfaces A form of geometric correction that uses a DEM and sensor
of the lens” (Wolf and Dewitt 2000). position information to correct distortions resulting from earth
curvature and the like. See also orthorectification.
orientation
orthorectification
The position of the camera or satellite as it captured the image.
Usually represented by six coordinates: X, Y, Z, omega, phi, and The process of lessening geometric errors inherent within
kappa. photography and imagery caused by terrain displacement, lens
distortion, and the like. Then, the photography or imagery is
ORIENTATION MANAGEMENT
resampled to a specified resolution. Also called orthoresampling.
(ORIMA) Software designed to process and produce data detailing
overlap
orientation and triangulation in addition to bundle adjustment, etc.
Output files can be imported into Stereo Analyst for ArcGIS. In a traditional frame camera, when two images overlap, they share
a common area. For example, in a strip of photographs taken along
oriented image
the flight path, adjacent images typically overlap by 60 percent.
A first generation data product derived from imagery with a sensor This measurement is sometimes called endlap. See also sidelap.
model and spatial reference. Combining multiple oriented images
parallax
allows for the creation of DTMs and collection of 3D features.
“The apparent angular displacement of an object as seen in an aerial
oriented image pair
photograph with respect to a point of reference or coordinate
An image pair with known interior (camera or sensor internal system. Parallax is caused by a difference in altitude or point of
geometry) and exterior (camera or sensor position and orientation) observation” (Natural Resources Canada 2001).
orientation. The Y-parallax of an oriented image pair has been
perspective center
improved. Additionally, an oriented image pair has geometric and
geographic information concerning the earth’s surface and a (1) The optical center of a camera lens. (2) A point in the image
ground coordinate system. Features and measurements taken from coordinate system defined by the x and y coordinates of the
an oriented image pair have X, Y, and Z coordinates. principal point and the focal length of the sensor. (3) After
triangulation, a point in the ground coordinate system that defines
ORIMA
the sensor’s position relative to the ground.
See ORIENTATION MANAGEMENT.
phi
In a rotation system, phi is rotation around the Y-axis.

photogrammetric scanners principal point
Special devices capable of high image quality and excellent The point in the image plane onto which the perspective center is
positional accuracy. Use of this type of scanner results in geometric projected.
accuracy similar to traditional analog and analytical
principal point of autocollimation
photogrammetric instruments.
Part of the definition of principal point, the image position where
photogrammetry the optical axis intersects the image plane. The principal point of
The “art, science and technology of obtaining reliable information autocollimation is near the principal point (Wolf 1983).
about physical objects and the environment through the process of principal point of symmetry
recording, measuring, and interpreting photographic images and
patterns of electromagnetic radiant imagery and other phenomena” Part of the definition of principal point, the principal point of
(American Society of Photogrammetry 1980). symmetry can best compensate for lens distortion. “The point about
which [distortions] are symmetrical” (Wolf 1983).
pixel
project file
Abbreviated from picture element. The smallest part of a picture
(image). A SOCET SET® file containing the information required to restore
planar the current state of a work. All necessary files, settings, and
preferences are stored in the project file.
A constant elevation value (Z) is applied to each vertex of a feature.
projection
plane table photogrammetry
The manner in which the spherical surface of the earth is
Prior to the invention of the airplane, photographs taken on the represented on a flat (2D) surface.
ground were used to extract the geometric relationships between
objects. pushbroom
point A scanner in which all scanning parts are fixed and scanning is
accomplished by the forward motion of the scanner.
(1) A feature that has X, Y, and (sometimes) Z coordinates. A point
can represent a feature such as a telephone pole. You can also pyramid layer
collect multiple points to create a DEM or TIN. (2) In the case of An image layer that is successively reduced by a power of two and
defining the size of the 3D Floating Cursor used in the Stereo resampled. Pyramid layers enable large images to be displayed
Window, a point equals a pixel. faster at any resolution.
point spacing radial lens distortion
The distance between points sampled in terrain interpolation. Imaged points are distorted along radial lines from the principal
polygon point. Also referred to as symmetric lens distortion.
A set of closed line segments defining an area, composed of rational polynomial coefficients
multiple vertices. Polygons can be used to represent features such Coefficients, generally supplied by the data provider, that detail the
as buildings, and can contain elevation values. position of a satellite at the time of image capture.
GLOSSARY 243
raw image root mean square error
An image that does not have any projection associated with it. Raw (RMSE) Used to measure how well a specific, calculated solution
images serve as a record of features, relationships between fits the original data. For each observation of a phenomena, a
features, processes, and information. variation can be computed between the actual observation and a
calculated value. (The method of obtaining a calculated value is
reference coordinate system
application-specific.) Each variation is then squared. The sum of
A system that defines the geometric characteristics associated with these squared values is divided by the number of observations and
events occurring in object space. then the square root is taken. This is the RMSE value.
reference plane rotation matrix
In a topocentric coordinate system, the tangential plane at the A three-by-three matrix used in the aerial triangulation functional
center of the image on the earth ellipsoid, on which the three model. Determines the relationship between the image space
perpendicular coordinate axes are defined. coordinate system and the ground space coordinate system.
regular block of photos rubber sheeting
A rectangular block in which the number of photos in each strip is A 2D rectification technique (to correct nonlinear distortions) that
the same. This includes a single strip or a single image pair. involves the application of a nonlinear rectification (second order
rendering or higher).
Drawing an image in a view at the scale indicated by the zoom in screen dot pitch
or zoom out factor. Screen dot pitch is the size of the pixels on the screen—measured
resample horizontally in X and vertically in Y. The more accurate the screen
dot pitch values are, the more accurate scale representations are on
The process of extrapolating data file values for the pixels in a new the screen.
grid when the image is rescaled or rotated.
self-calibration
right-hand rule
A technique used in bundle block adjustment to determine internal
A convention in 3D coordinate systems (X, Y, Z) that determines sensor model information.
the location of the positive Z-axis. If you place your right hand
fingers on the positive X-axis and curl your fingers toward the sensor
positive Y-axis, the direction your thumb is pointing is the positive A device that gathers energy, converts it to a digital value, and
Z-axis direction. presents it in a form suitable for obtaining information about the
RMSE environment.
See root mean square error.

sensor model spatial reference
A model describing the 3D relationship between a sensor, raw A coordinate or other means by which a location can be specified.
image, and the earth’s surface. A sensor model is required in order
spot height
to create an oriented image, an image pair, a stereo model, and for
the collection of 3D features. A sensor model makes an image In feature collection, a point feature collected primarily for its Z, or
oriented and photogrammetrically aware. elevation, value. A spot height feature also contains X and Y
coordinate values.
SI
stereo
See image scale.
A mode of visualizing wherein two images are used to derive
sidelap
elevation information.
In a block of photographs consisting of a number of parallel strips, stereo model
the sidelap is measured between the strips and is usually 20–30
percent in traditional frame camera photos. Sidelap is measured The overlapping portion of an image pair. A 3D image formed by
perpendicular to flight path. the brain as a result of changes in depth perception and parallactic
angles. See also image pair.
single frame orthorectification
stereo pair
Orthorectification of one image at a time using the space resection
technique. A minimum of three GCPs is required for each image. A pair of images of the same area taken from slightly different
angles. See also oriented image pair.
softcopy photogrammetry
stereo scene
See digital photogrammetry.
Composed of two images of the same area acquired on different
space forward intersection
days from different orbits—one taken east of the vertical and the
A technique used to determine the ground coordinates X, Y, and Z other taken west of the nadir.
of points that appear in the overlapping areas of two or more stereoscopic parallax
images based on known interior orientation and exterior orientation
parameters. “The change in position of an image from one photograph to the
next caused by the aircraft’s motion” (Wolf 1983). Makes viewing
space intersection
of 3D data possible, composed of X-parallax and Y-parallax. See
A technique used to determine the ground coordinates X, Y, and Z also X-parallax, Y-parallax.
of points that appear in the overlapping areas of two images, based stereoscopic viewing
on the collinearity condition. See also collinearity condition.
Vision using two eyes. Also referred to as binocular vision.
space resection
A technique used to determine the exterior orientation parameters
associated with one image or many images, based on the
collinearity condition.
GLOSSARY 245
strip of images/photographs TIN
In traditional frame camera photography, consists of images See triangulated irregular network.
captured along a flight line, normally with an overlap of 60 percent
topocentric coordinate system
for stereo coverage. All photos in the strip are assumed to be taken
at approximately the same flying height and with a constant A coordinate system that has its origin at the center of the image on
distance between exposure stations. Camera tilt relative to the the earth ellipsoid. The three perpendicular coordinate axes are
vertical is assumed to be minimal. See also cross-strips. defined on a tangential plane at this center point. The X-axis is
oriented eastward, the Y-axis northward, and the Z-axis is vertical
support file to the reference plane (up).
A SOCET SET® file containing photogrammetric metadata transformation
associated with an image in a project file.
A series of coefficients describing the 3D mathematical
tangential lens distortion relationship between an image, the sensor that captured it, and the
Distortion that occurs at right angles to the radial lines from the ground it has recorded.
principal point. triangulated irregular network
Terrain Following Mode (TIN) A specific representation of DTM in which elevation points
A mode in which the 3D Floating Cursor follows the elevation of can occur at irregular intervals forming triangles.
the terrain displayed in the Stereo Window. This is accomplished triangulation
either by using an external elevation source, such as a DEM, or
image correlation techniques. Process of establishing the geometry of the camera or sensor
relative to objects on the earth’s surface. See also aerial
thinning tolerance triangulation.
A measure that prevents duplicate points within a certain distance vector
in terrain interpolation (such as 5 meters).
A point, line, or polygon. A vector is a one-dimensional matrix,
threshold having either one row (1 by j) or one column (i by 1). Vectors
Threshold is used during image correlation as a measure of typically represent objects such as road networks, buildings, and
probability that a points is the same in both the left image and the geographic features such as contour lines.
right image of an image pair. A high threshold value increases the vertex
probability of a correct match, but may take longer to process.
Setting a low threshold increases the probability of a false match. A component of a feature, typically made up of three axes: X, Y,
and (sometimes) Z. The Z component corresponds to the elevation
tie point of the vertex. A feature can be composed of only one vertex (such
A point. Its ground coordinates are not known, yet it can be as a point as in a TIN) or many vertices (such as a polyline or
recognized visually in the overlap or sidelap area between two polygon).
images.

vertical exaggeration
The effect perceived when a DSM is created and viewed. Vertical
exaggeration is also referred to as relief exaggeration, and is the
evidence of height differences in the stereo model.
vertices
More than one vertex, each with X, Y, and (sometimes) Z
components.
X-parallax
The difference in position of a common ground point appearing on
two overlapping images, which is a function of elevation.
X-parallax is measured horizontally.
Y-parallax
The difference in position of a common ground point appearing on
two overlapping images, which is caused by differences in camera
position and rotation between two images. Y-parallax is measured
vertically.
Z
The vertical (height) component of a vertex, 3D Floating Cursor, or
feature in a given coordinate system.
Z-axis
In the image space coordinate system, the Z-axis is the optical axis.
The image space coordinate system directs the Z-axis toward the
imaged object. In object space, the Z-axis is orthogonal to the X
and Y axes and is directed out of the earth’s surface.
GLOSSARY 247
References References
This appendix lists references mentioned in this book.
American Society of Photogrammetry. 1980. Photogrammetric Engineering and Remote

Sensing, XLVI:10:1249.
Asher & Adams. 1976. Asher & Adams’ Pictorial Album of American Industry: 1876. New
York: Rutledge Books.
Free On-Line Dictionary of Computing. “American Standard Code for Information

Interchange from FOLDOC: American Standard Code for Information Interchange.”
24 Oct. 1999 <http://foldoc.doc.ic.ac.uk/foldoc>.
International Society for Photogrammetry and Remote Sensing. “ISPRS—The Society.”

29 May 2000 <http://www.isprs.org/society.html>.
Keating, T. J., P. R. Wolf, and F. L. Scarpace. 1975. “An Improved Method of Digital Image
Correlation,” Photogrammetric Engineering and Remote Sensing 41, no. 8 (1975): 993.
Konecny, G. 1994. “New Trends in Technology, and their Application: Photogrammetry and
Remote Sensing—From Analog to Digital.” Paper presented at Thirteenth United
Nations Regional Cartographic Conference for Asia and the Pacific, Beijing, China, May
1994.
Merriam-Webster OnLine Dictionary. “algorithm.” 07 Feb. 2001 <http://www.m-w.com/>.
Merriam-Webster OnLine Dictionary. “ellipsoid.” 29 May 2000 <http://www.m-w.com/>.
Merriam-Webster OnLine Dictionary. “monotonic.” 28 Feb. 2003 <http://www.m-w.com/>.
National Oceanic and Atmospheric Administration. “Inertial Navigation System: Inertial

Navigation System (INS).” 29 Mar. 2001 <http://www.csc.noaa.gov/crs/tcm/ins.html>.
Natural Resources Canada. “Carto Corner - Glossary of Cartographic Terms: Cartesian

coordinate system.” 13 Jul. 2001 <http://www.atlas.gc.ca/english/carto/
cartglos.html#4>.
Natural Resources Canada. “Carto Corner - Glossary of Cartographic Terms: coordinate

system.” 13 Jul. 2001 <http://www.atlas.gc.ca/english/carto/cartglos.html#4>.
249
Natural Resources Canada. “Carto Corner - Glossary of Cartographic Terms: GPS, Global Positioning System.” 13 Jul. 2001
<http://www.atlas.gc.ca/english/carto/cartoglos.html#4>.
Natural Resources Canada. “Carto Corner - Glossary of Cartographic Terms: parallax.” 13 Jul. 2001 <http://www.atlas.gc.ca/english/
carto/cartoglos.html#4>.
Wang, Z. 1990. Principles of photogrammetry (with Remote Sensing). Beijing, China: Press of Wuhan Technical University of
Surveying and Mapping, and Publishing House of Surveying and Mapping.
Wolf, Paul R. 1983. Elements of Photogrammetry. New York: McGraw-Hill, Inc.
Wolf, Paul R., and Bon A. Dewitt. 2000. Elements of Photogrammetry with Applications in GIS. 3rd ed. New York: McGraw-Hill, Inc.

3D
Index
Index Symbols
*.blk file 79
defined 233
feature
defined 233 characteristics 88
*.img file collecting
defined 234 and attributing 193
*.mxd file 119 workflow 158, 160
*.prj file 82 defined 233
defined 234 Floating Cursor 132
format 82 accuracy of 133
*.rrd file 19 adjusting color 136
*.sde file 77 adjusting size 136
*.sup file 82 Auto Toggle Mode 147
defined 234 changing 46
format 83 custom commands 134
“a” keyboard shortcut 149 decrease elevation 134
“c” keyboard shortcut 149 defined 233
“i” keyboard shortcut 149 different shapes 136
“r” keyboard shortcut 149 how it works 132
“s” keyboard shortcut 54, 143, 149 how to position 133
“t” keyboard shortcut 55, 141, 149 increase elevation 135
“x” keyboard shortcut 149 keyboard shortcuts 149
“y” keyboard shortcut 150 line width 136
“z” keyboard shortcut 149 Manually Toggle Mode 147
recenter 135
Numerics use with Hyperlink tool 137
1-Pane View 26, 108 Floating Cursor tab 136
2D model
defined 233 characteristics 88
to 3D conversion 35, 93 defined 233
advanced options 95 Position Tool
feature draping 95 applying 48
invalid elevations 100 Snap
planar features 98 applying 163
point spacing 97 customizing 166
thinning 98 keyboard shortcuts 163
workflow 101 options 162
virtual 89 workflow 164
2-Pane View 25, 109 Snap tab 162
use in 3D Floating Cursor accuracy 133 to 2D conversion 31
251
to 2D exporter 103 Analytical photogrammetry defined 235
virtual 89 defined 235 Block
3D Floating Cursor AP (additional parameter) file 80
recenter 127 defined 234 characteristics 79
3-Pane View 25, 109 ArcMap defined 235
data view importing 79
A calculating threshold 120 footprint
Accuracy image pair display 119 defined 235
CE90 145, 146 orienting 21 of photographs 214
LE90 145, 146 orienting displays 119 defined 235
Active view alignment rotation mode Display tab 119 regular 244
169 ASCII (American Standard Code for triangulation
Add Information Interchange) defined 235
extension 14 defined 234 Brightness
image pair 18 AT (aerial triangulation) 231 adjusting 28
toolbars 15 defined 234 application in Stereo Window 115
Additional parameter (AP) At centroid 99 Bundle
defined 234 Attribute block adjustment 192, 231
Advanced options defined 235 defined 235
2D to 3D conversion 95 table defined 235
Aerial defined 235 Button mapping 45, 173
photographs Attribution workflow 174
defined 234 defined 235
triangulation (AT) 71, 231 Auto C
defined 234 -correlation Cache size 163
Affine transformation 223 defined 235 Calibration certificate/report
defined 234 Roam Mode defined 236
Airborne GPS activating 27 Cartesian coordinate system
defined 234 Toggle 3D Floating Cursor Mode defined 236
Algorithm 50, 147, 157 CCD (charge-coupled device)
defined 234 limitations 147 defined 236
American Standard Code for Information Automated terrain following CE90 145, 146
Interchange (ASCII) defined 235 applying 55
defined 234 Automatic recenter 127 Centroid
Anaglyph 24, 27, 108, 122 Average interpolated 99 defined 236
3D Floating Cursor color with 136 Axis-To-Ground setting 43 Charge-coupled device (CCD)
Analog photogrammetry B Coefficient
defined 235 Binocular vision 106 defined 236

Collinearity Cartesian 221 image matching
condition 228, 230, 236 defined 236 defined 237
defined 236 geocentric 220 orthophoto
defined 236 ground 220 defined 237
equation 227 image 219 photogrammetry
Colorblock 55, 133, 145, 156 image space 219 defined 237
green 146 pixel 218 stereo model (DSM) 107
red 146 topocentric 220 defined 237
Commands Coplanarity condition 206 terrain model (DTM)
customizing 134 defined 236 defined 237
Leica Feature Editing 134 Correlation 133 Digitizing
Stereo Analyst 134 coefficient defined 237
Configuring defined 237 devices 173
system mouse 43 defined 236 adding 173
Constant elevation elevation bias 142 choosing COM port 173
with Virtual 2D To 3D 89 image contrast 140 mapping buttons 173
Context menu 157 terrain slope 139 supported 43
Continuous threshold 139, 237 outside Stereo Window 160
Roam Mode Cross Direction of flight 214
applying 115 (3D Floating Cursor) 137 defined 237
Zoom Mode -strips 237 Display
applying 40, 117 Customizing tools 134 entire image pair 124
Contrast overlap region 124
adjusting 28 D polygon outlines 127
application in Stereo Window 115 Datum Docking Stereo Window 114
effect on correlation 140 defined 237 Dot (3D Floating Cursor) 137
stretch Default Zoom Draping 89
defined 236 applying 39 DSM (digital stereo model) 107
types of 125 DEM (digital elevation model) defined 237
Control point defined 237 DTM (digital terrain model)
defined 236 with Virtual 2D To 3D 89 defined 237
extension Device 43, 173 extraction 192
defined 236 mapping buttons 45
Convert properties 43 E
2D to 3D 34, 93 settings Edge
workflow 94 accessing 42 keyboard shortcut 163
3D to 2D 31, 103 Digital Elements of exterior orientation
Features to 2D dialog 103 elevation model (DEM) defined 237
Coordinate system 218 defined 237 Elevation 100
INDEX 253
bias 141, 142 F2 keyboard shortcut 51 Image Mode 156
invalid F3 keyboard shortcut 50, 149 defined 238
default value 100 F4 keyboard shortcut 149 feature collection workflow
keep original 100 Feature 158
minimum value 100 collection Flight
source 3D Snap options 162 line 214
defined 238 3D snapping defined 238
ensuring accuracy 37 workflow 164 path 214
for 2D to 3D conversion 36 defined 238 defined 238
in IMAGINE OrthoBASE 76 digitizing devices 173 Focal
Raster surface 36 Monotonic Mode 172 length 73, 223
Virtual 2D To 3D 90 workflow 172 defined 239
Ellipsoid 220 point feature 56 plane
defined 238 polygon feature 49 defined 239
Endlap polyline feature 54 Footprint
defined 238 squaring changing color 119
Endpoint workflow 171 defined 239
keyboard shortcut 163 Squaring options 167
Epipolar with elevation bias 142 G
correction 124 workflow 158 GCP (ground control point)
line 206 draping defined 239
defined 238 defined 238 Geocentric
plane 206 editing coordinate system 220
defined 238 adjust location 64 defined 239
resampling 205 adjust vertex 61 Geocorrect 183
Exporter complete 135 defined 239
3D to 2D 103 extraction Geographic
Exposure station 214 defined 238 imaging 188
defined 238 to 3D Options dialog 95 information system (GIS)
Exterior orientation 73, 226 Fiducial defined 239
defined 238 mark 223 Geolink
parameters 238 defined 238 defined 239
External elevation source First line rotation mode 168 Geoprocessing techniques 183
DEM 89 Fixed GIS (geographic information system)
TIN 89 Cursor Mode 156 3D GIS applications 195
with Terrain Following Mode 138 applying 25 application 74, 180
definition 238 building blocks 180
F feature collection workflow defined 239
F10 keyboard shortcut 172 160 extracting 3D information 181

-ready image 18, 71 nonoriented 241 K
defined 239 Pair dropdown list Kappa
Global positioning system (GPS) applying 23 defined 234, 240
defined 239 Pair Selection Tool Keyboard shortcuts 149
GPS (global positioning system) applying 23 3D Floating Cursor 149
defined 239 scale 214 3D Snap 163
Graphics card scale (SI)
information 122, 125 defined 240 L
specs 125 space LE90 145, 146
supported with Stereo Analyst for coordinate system applying 55
ArcGIS 24 defined 240 Least squares
Ground defined 240 adjustment 229
control point (GCP) 73, 191 space coordinate system 219 defined 240
defined 239 -to-earth association 71 Left image
coordinate system 220 defined 240 applying tools to 115
defined 239 types 190, 212 Leica Feature Editing 134
point IMAGINE OrthoBASE 80 Lens distortion 225
defined 239 calibration 76 defined 240
space using to create oriented images 76 Line of sight (LOS)
defined 239 Import defined 240
IMAGINE OrthoBASE *.blk 80 Linear contrast stretch 127
I process 81 Longest line rotation mode 169
Image SOCET SET® *.prj file 82 LOS (line of sight)
Analysis process 84 defined 240
using to create oriented images Inertial navigation system (INS)
78 defined 240 M
center INS (inertial navigation system) Manually Toggle
defined 240 defined 240 3D Floating Cursor 147
coordinate system 219 Intelligent image 71 Map coordinate system
correlation Interior orientation 73, 223 defined 241
options 139 defined 240 Mass points
with Terrain Following Mode International Society of Photogrammetry defined 241
138 and Remote Sensing (ISPRS) Maximum
defined 240 defined 240 interpolated 99
pair Invert stereo model 110 threshold 120
changing 23 ISPRS (International Society of Metadata
defined 240 Photogrammetry and Remote Sensing) defined 241
display 124 defined 240 Metric photogrammetry
invert 110 defined 241
INDEX 255
Midpoint phi, kappa 222, 226 Orthorectify 193
keyboard shortcut 163 defined 242 Overlap
Min/max contrast stretch 126 Open changing color 119
Minimum Cross (3D Floating Cursor) 137 defined 242
interpolated 99 Cross with Dot (3D Floating Cursor) display only 124
threshold 120 137 percentage 120, 214
Mode X (3D Floating Cursor) 137 Overlapping images
Auto Toggle 3D Floating Cursor X with Dot (3D Floating Cursor) threshold 120
157 137
Fixed Cursor 156 Optical axis P
Fixed Image 156 defined 242 Parallax
Terrain Following 156 Orientation defined 242
Mono changing 119 Perspective center 219
defined 241 defined 242 defined 242
Monocular vision 106 ORIENTATION MANAGEMENT Phi
defined 241 (ORIMA) defined 234, 242
Monotonic defined 242 Photogrammetric quality scanners
defined 241 Oriented defined 243
Mode 172 image 72 Photogrammetry 107
Mosaicking defined 242 defined 243
defined 241 process 70 digital 237
using Image Analysis for ArcGIS history 210
N 78 metric 241
Nadir using IMAGINE OrthoBASE plane table 243
defined 241 76 types of 188, 210
Near vertical aerial photographs using SOCET SET® 82 uses 212
defined 241 image pair Photograph types 212
Node defined 242 Photography
defined 241 Orienting ArcMap display 21, 49 terrestrial 221
Nonoriented image pair ORIMA (ORIENTATION Pixel
defined 241 MANAGEMENT) coordinate system 218
Nonorthogonality defined 242 defined 243
defined 241 Orthocalibration 76 Planar
O Orthocorrection feature 89, 98
Oblique photographs defined 242 At centroid 99
defined 241 Orthorectification 184 Average interpolated 99
Omega defined 242 Maximum interpolated 99
defined 234, 241 single frame 229, 245 Minimum interpolated 99

Plane table photogrammetry Recenter S
defined 243 3D Floating Cursor 127, 160 Scale
Point Reference changing 47
defined 243 coordinate system Scaling 205
spacing 97 defined 244 stereo model 204
defined 243 plane Scanners 216
Polygon defined 244 Scanning resolution 216
defined 243 Regular block of photos Screen dot pitch 125
outlines 127 defined 244 defined 244
Principal point 219, 223 Rendering SDE 77
defined 243 defined 244 Self-calibration
of autocollimation Resample 76 defined 244
defined 243 defined 244 Sensor
of symmetry Resolution defined 244
defined 243 scanners 216 model 72, 191
Project file 82 Right defined 245
defined 243 -hand rule 220 SI (image scale) 214
Projection defined 244 defined 240
defined 243 image Sidelap
Pushbroom applying tools to 115 defined 245
defined 243 RMSE (root mean square error) percentage 214
Pyramid layer defined 244 Single frame orthorectification 229
creating 19 Roam Mode defined 245
defined 243 applying 39 Slope 139
Root mean square error (RMSE) Snap To Ground 143
Q defined 244 applying 54
Quad-buffered stereo 24, 27, 108, Rotating stereo model 204 use on buildings 143
122 Rotation 205 use on terrain 143
3D Floating Cursor color with 136 matrix 227 Snapping tolerance 163
defined 244 SOCET SET®
R mode 168 importing 82
Radial lens distortion 225 Active view alignment 169 Space
defined 243 First line 168 forward intersection 230
Rational polynomial coefficient 73 Longest line 169 defined 245
defined 243 Weighted mean 168 intersection
Raw RPC (rational polynomial coefficient) defined 245
image 70 73 resection 229
defined 244 Rubber sheeting defined 245
photography 182 defined 244 Spatial reference 72
INDEX 257
defined 245 visualization 107 options 141
Spot height Window preferences 143
defined 245 applying tools in Snap To Ground 143
Squaring workflow 115 using image correlation 139
options 167 context menu 157 using with elevation bias 141
polyline 170 opening interpolation
rotation mode 168 workflow 24, 114 point spacing 97
tab 167 using with data view 119 thinning tolerance 98
tolerance 167 views 24 slope 139
Standard deviation of unit weight 1-Pane View 108 Theta 224
defined 244 2-Pane View 109 Thinning tolerance 98
Stereo 3-Pane View 109 defined 246
Analyst toolbar 16, 111 Stereoscopic Threshold 120
defined 245 parallax 202 defined 246
display defined 245 Tie point 192
contrast stretch 125 viewing 106, 200 defined 246
linear 127 defined 245 TIN (triangulated irregular network)
min/max 126 how it works 200 defined 246
none 127 Strip with Virtual 2D To 3D 89
two standard deviations of images Tolerance
126 defined 246 use with Squaring 167
displaying polygon outlines of photographs Toolbar
127 defined 246 adding 15
epipolar correction 124 Support file 82 Stereo Analyst 111
recentering the stereo cursor defined 246 Stereo Enhancement 16, 113
127 Synchronize Geographic Displays Stereo View 16, 112
screen dot pitch 125 applying 49 StereoAnalyst 16
Display tab 124 Topocentric coordinate system 220
Enhancement toolbar 16, 113 T defined 246
model 202 Tangential lens distortion 225 Transformation 73
rotating 204 Terrain Translating stereo model 204
scaling 204 Following Cursor tab 53, 141 Translation 205
translating 204 Following Mode 156, 193 Transparency 182
pair accuracy 146 Triangulated irregular network (TIN)
defined 245 applying 53, 55, 144 defined 246
scene continuous 141 Triangulation
View toolbar 16, 112 methods of operation 138 Two standard deviations contrast stretch

126 defined 247
screen dot pitch 125
V snapping tolerance 163
Vector thumb wheel
defined 246 applying 145
Vertex
defined 246 Z
keyboard shortcut 163 Z
Vertical exaggeration 201 -axis
Vertices Axis-To-Ground setting 43
Views scroll wheel control 43, 44,
1-Pane View 108 133, 147
2-Pane View 109 snapping tolerance 163
3-Pane View 109 thumb wheel
Stereo Window 108 applying 25
Virtual 2D To 3D 89 values
applying 92 updating 93
options 90 Zoom
process 90 adjusting 26
In/Out By 2
W applying 26
Weighted mean rotation mode 168 To Data Extent 122
X
X
(3D Floating Cursor) 137
-parallax 202
defined 247
screen dot pitch 125
snapping tolerance 163
thumb wheel
applying 145
Y
Y
-parallax 203
adjusting 142
INDEX 259

Using Stereo Analyst For Arcgis: Geographic Imaging by Leica Geosystems Gis & Mapping

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Using Stereo Analyst for ArcGIS

Geographic Imaging by Leica Geosystems GIS & Mapping

Copyright © 2003 Leica Geosystems GIS & Mapping, LLC

The information contained in this document is subject to change without notice.

U.S. GOVERNMENT RESTRICTED/LIMITED RIGHTS

SOCET SET is a registered trademark of BAE Systems Mission Solutions.

Contents Contents iii

4 Working with 3D data 87

5 Visualizing in stereo 105

6 Applying the 3D Floating Cursor 131

IV USING STEREO ANALYST FOR ARCGIS

B Understanding stereo viewing 199

C Applying photogrammetry 209

VI USING STEREO ANALYST FOR ARCGIS

An image of the earth’s surface is a wealth of information. Images capture a

The new extensions by Leica Geosystems are technological

On behalf of the Image Analysis for ArcGIS and Stereo

VIII USING STEREO ANALYST FOR ARCGIS

By adding feature datasets to ArcMap, the features are

During the collection of accurate GIS feature data using Stereo

New feature datasets can be created using ArcCatalog. In addition

You can easily update feature vertices to greater accuracy.

INTRODUCING STEREO ANALYST FOR ARCGIS 5

6 USING STEREO ANALYST FOR ARCGIS

INTRODUCING STEREO ANALYST FOR ARCGIS 7

8 USING STEREO ANALYST FOR ARCGIS

INTRODUCING STEREO ANALYST FOR ARCGIS 9

Stereo Analyst for ArcGIS adds additional functionality to

As you know, ArcCatalog is an application with which you can

10 USING STEREO ANALYST FOR ARCGIS

INTRODUCING STEREO ANALYST FOR ARCGIS 11

14 USING STEREO ANALYST FOR ARCGIS

3. On the Extensions dialog, click the check box for Stereo

Once the Stereo Analyst check box has been selected,

With the Stereo Analyst toolbar, you can choose image

2. Click the View menu, then point to Toolbars, then click

With the Stereo Enhancement toolbar, you can change

16 USING STEREO ANALYST FOR ARCGIS

4. Arrange the toolbars in the ArcMap window so that you

In order to view or update existing features or collect new 2

18 USING STEREO ANALYST FOR ARCGIS

2. Click OK on the next three Create pyramids dialogs to

Viewing overlapping areas

Two adjacent rasters that overlap are referred to as an image

Because the images are diagonal, but their bounding

20 USING STEREO ANALYST FOR ARCGIS

2. On the Symbology tab of the Layer Properties dialog,

2. Click the ArcMap Display tab of the Stereo Analyst

4. Click OK to apply the orientation setting and close the

22 USING STEREO ANALYST FOR ARCGIS

The yellow overlap graphic changes position to indicate

Ch angin g th e imag e pair

See the Web site <http://support.erdas.com/specs/specs.html>

1. On the Stereo Analyst toolbar, click the Stereo Window

The ArcMap window contents adjust to include the

24 USING STEREO ANALYST FOR ARCGIS

2. On the Stereo Enhancement toolbar, click, hold, and

28 USING STEREO ANALYST FOR ARCGIS

The following picture shows the image pair with