2.introduction of Surveying
2.introduction of Surveying
2.introduction of Surveying
SURVEYING
Objects Types Classification Principles Scale
Surveying
Surveying
is defined as the process of measuring horizontal distances and included angles to determine the location of points on, above or below the earth surfaces. OR
The The
is the art and science of determining of the relative positions of various points or stations on the surface of the earth by measuring the horizontal distances, angles and taking the details of these points and by preparing a map or plan to any suitable scale. term surveying is the representation of surface features in a horizontal plane. process of determining the relative heights in the vertical plane is referred as levelling.
Objectives of Surveying
The
Setting
data obtained by surveying are used to prepare the plan or map showing the ground features. out of any engineering work like buildings, roads, railway tracks, bridges and dams involves surveying.
Uses of Surveying
To To To To To
Cadastral Map
Contour Map
Since
the shape of the earth is spheroidal, the line connecting any two points on the earth surface is not a straight line, but a curve. When the surveys extend over a large areas or when the accuracy required is great, the curvature of earth has also to be taken into account.
Plane Surveying
The The
surveying where the effect of curvature of earth is neglected and earths surface is treated as plane, is called plane surveying. degree of accuracy in this type of surveying is comparatively low. when the surveying is conducted over the area less than 250 Sq.Km., they are treated as plane surveying. surveying is conducted for the purpose of engineering projects and tackle by local authorities.
Generally Plane
Geodetic Surveying
The It It
effect of curvature is taken into account and it generally extends over large area. is a special branch of surveying in which measurements are taken with high precision instruments. trigonometry. are also made with help of spherical is also known as Trigonometrical Surveying.
Calculations It
Classification of surveying
Based Based Based Based
Theodolite
Survey for measurement of horizontal angles survey for measuring ver. & hori. angles survey for measuring ver. & hori. Dist.
& Aerial survey Photographs taken from higher altitude for collecting details of earths features sensing Data collected from satelites for determining the positions of earths features
Remote
Chain Compass
Theodolite
Remote Sensing
Classification
based on Methods
Triangulation
Traversing
Classification
based on Purposes
Engineering survey for collecting data for designing civil engineering projects like road, bridges, railways, etc. Mine survey for exploring mineral wealth.
Geological survey for determining the different strata in the earths crust. Archaeological survey for unearthing relics of antiquity.
Military survey for military purpose & working out plans of strategic importance.
survey conducted on water bodies like ocean, rivers, etc. survey conducted to study the position & movement of celestial bodies.
Principles of Surveying
Principle 1:
number of control points are fixed in the area concerned by adopting very accurate and precise methods. lines joining these control points will be control lines. measurements are made to locate points inside these control lines. main triangles and traverses are formed first.
The
Other Thus,
The By If
main triangles and traverses are divided into smaller ones by using less rigorous methods. doing so, accumulation of errors is avoided and any local error can be easily identified. survey work is started from a part (smaller triangle or traverse) and proceeded to whole there are chances of errors getting multiplied at every stage. any survey work should be from whole to part and not from part to whole.
Hence
Principle 2:
points should be fixed by at least two independent measurements.
R R l1 1 P Figure 1 Q P Figure 2 2 Q P 1 Figure 3 Q R
New
l1
l2
As per the Principle 2, the location of a new point involves one of the following.
(a)
(b) (c)
R l
1
R l
2
R l
P Figure 1
1 Figure 3
Figure 2
Fig 1: It shows the method of locating R with reference to known length PQ by using the known distances of PR (l1) and QR (l2) Fig 2: It shows the method of locating R with reference to the length PQ by using the known angles QPR (1) and PQR (2) Fig 3: It shows the method of locating R with reference to known length PQ by using the known distance of PR (l1) and known angle QPR (1)
Plan
A plan is a graphical representation, to some scale, of the features on, near or below the surface of the earth as projected on a horizontal plane.
In plan, the areas involved are small, and is drawn on a relatively large scale. In plan, the earth surface may be considered as plane, so that plan is constructed by orthographic projections and is drawn on a relatively large scale.
Map
If the scale of the graphical projection on a horizontal plane is small, the plan is called map.
Thus, graphical representation is called plan if the scale is large while it is called a map if the scale is small. On a plan, only horizontal distances and directions or may be angles are shown, while on a topographic map, the vertical distances are also represented by contour lines.
Scale
The ratio by which the actual length of the object is reduced or increased in the drawing is known as the Scale. Its used to represent large distance on paper.
Representative
It If
Fraction (RF)
is the ratio of the distance of object on drawing to the corresponding actual distance of object on ground. a line 1 cm long on the drawing sheet represents 50 m on ground, this scale can be expressed as
1 cm = 50 m
The For
Example : 1 cm = 50 m RF = dist. Of object on drawing sheet corresponding actual dist. Of object on ground = 1 cm/(50)(100) cm = 1/5000 RF = 1 : 5000
Example
1. 5 cm = 1 m
a)
Plain scale
Plain
scale is used to represent two successive units such as meters and decimeters.
Units of measurement
A
1 mile = 1.609 km
1 hectare = 10000 m2