Geometric Transformation: Map-To-Map Transformation and Image-To-Map Transformation (Especially for GATE-Geospatial 2022)

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Definition

Convert the raster dataset from one projection to another, or change the cell size, you are performing a geometric transformation.

Geometric transformation is the process of changing the geometry of a raster dataset from one coordinate space to another.

The process of geometric transformation requires a set of control points and transformation equations to register a digitized map, a satellite image, or an aerial photograph onto a projected coordinate system.

It is commonly used in GIS to transform maps between coordinate systems.

This Image Shows Geometric Transformation

In GIS, geometric transformation includes map-to-map transformation and image-to-map transformation.

This Diagram Shows Two Geometric Transformation

Map-To-Map Transformation

  • Geometric transformation converts a newly digitized map into projected coordinates
  • A manually-digitized map has the same measurement as its source map: measured in inches
  • A converted scanned image of the map is measured in dots per inch (dpi)
  • To make the digitized map usable in GIS – it must be converted into a projected coordinate system to align with other layers

Geometric transformation also applies to satellite imagery.

Image-To-Map Transformation

  • Remotely sensed data transformation involves changing row and columns
  • Can spatially register a georeferenced image in a GIS database
  • Must have same coordinate system

The rows and columns can be transformed into a projected coordinate system.

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