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    Overlay Operation: - Raster Overlay - Vector Overlay

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    NP Neupane
    This document discusses different types of overlay operations in GIS. There are two main types: raster overlay and vector overlay. Raster overlay combines the pixel values in raster maps using logical operators like OR, AND and NOT to produce a new output map. Vector overlay integrates feature attributes by applying logical rules when combining different map layers, such as polygon-on-polygon, line-in-polygon, or point-in-polygon overlays. Proximity operations can also be performed by creating buffer zones around features to analyze surrounding areas.

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    Overlay Operation: - Raster Overlay - Vector Overlay

    Uploaded by

    NP Neupane
    174 views12 pages
    This document discusses different types of overlay operations in GIS. There are two main types: raster overlay and vector overlay. Raster overlay combines the pixel values in raster maps using logical operators like OR, AND and NOT to produce a new output map. Vector overlay integrates feature attributes by applying logical rules when combining different map layers, such as polygon-on-polygon, line-in-polygon, or point-in-polygon overlays. Proximity operations can also be performed by creating buffer zones around features to analyze surrounding areas.

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    This document discusses different types of overlay operations in GIS. There are two main types: raster overlay and vector overlay. Raster overlay combines the pixel values in raster maps using logical operators like OR, AND and NOT to produce a new output map. Vector overlay integrates feature attributes by applying logical rules when combining different map layers, such as polygon-on-polygon, line-in-polygon, or point-in-polygon overlays. Proximity operations can also be performed by creating buffer zones around features to analyze surrounding areas.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    174 views12 pages

    Overlay Operation: - Raster Overlay - Vector Overlay

    Uploaded by

    NP Neupane
    This document discusses different types of overlay operations in GIS. There are two main types: raster overlay and vector overlay. Raster overlay combines the pixel values in raster maps using logical operators like OR, AND and NOT to produce a new output map. Vector overlay integrates feature attributes by applying logical rules when combining different map layers, such as polygon-on-polygon, line-in-polygon, or point-in-polygon overlays. Proximity operations can also be performed by creating buffer zones around features to analyze surrounding areas.

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    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 12

    Overlay Operation

    • This operation allows us to overlay multiple feature


    classes to combine, erase, modify, or update spatial
    features, resulting in a new feature class.
    • New information is created when overlaying one set of
    features with another.
    • There are basically two different types of overlay:
    (depending on the data structures)
    – Raster Overlay
    – Vector Overlay
    • The basic of overlay operation is logical operators: OR,
    AND, NOT, XOR
    Vector Overlay
    • More Difficult and Complex Processing
    • During vector overlay map features and associated attributes are
    integrated to produce new composite map. Logical rules can be applied to
    how the maps are combined.
    • It can be performed on different types of map features: { Polygon-on-
    Polygon, Line-in-Polygon, Point-in-Polygon}
    Raster Overlay
    • Less Difficult and Less Complex
    • During raster overlay, the pixel or grid cell values in each map
    are combined using arithmetic and Boolean operators to
    produce a new value in the composite map.
    Vector and Raster Overlay
    Operators
    • Logical:
    OR
    AND
    NOT
    • Conditional:
    == EQ
    <> NE
    <= LTE
    >= GTE
    < LT
    > GT
    • Arithmetic:
    +
    -
    *
    /
    ‸
    A Small Practice:
    • Develop resulting attribute table when the following district road network
    is topologically overlaid on the district area map:
    Solution:
    Raster Overlay: HighValue-LowValue
    • Comparison of values in frame#1 and frame#2
    • The highest value is picked for high value approach
    • The lowest value is picked for low value approach
    • The comparison is carried out on a grid cell by grid
    cell basis
    • Note:
    – High Value approach is for progressive activities
    – Low Value approach is for alternative activities
    Raster Overlay: HighValue-LowValue
    Raster Overlay: TopMap-BottomMap
    • For top map, assign a value in frame#3T to indicate
    where the highest value was found.
    • For bottom map, assign a value in fram#3B to
    indicate where the lowest value was found.
    • [If the highest value is found in frame#1, a 1 will be
    assigned; if the highest value is found in frame#2, a 2
    will be assigned] in top map
    • [If the lowest value is found in frame#1, a 1 will be
    assigned; if the lowest value is found in frame#2, a 2
    will be assigned] in bottom map
    • If the values are equal a 9 will be assigned.
    Raster Overlay: TopMap-BottomMap
    Proximity Operations (Buffer Zones)
    • It is used to create zones around selected geographic
    object in order to perform proximity analysis.
    • Area surrounding a specific object is evaluated
    • Types of Buffer:
    – Point Buffer
    – Line Buffer
    – Area Buffer

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