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Orthorectification

Orthorectification is the process of removing the distortion within an image caused by terrain relief and the camera. This is done by modeling the nature and magnitude of geometric distortions in the imagery. Camera or satellite models in conjunction with limited ground control, allow construction of correction formulae that produce accurate, geometrically correct, map-oriented imagery. SATPALDA uses Leica Photogrammetric Suite to produce ortho images.

SATPALDA offers various options of terrain datasets for orthorectification. The choice of DTM used for this process depends upon customers accuracy requirements. SATPALDA offers orthorectification using following terrain sources:

  1. GE-1 DTM
  2. ALOS PRISM DTM
  3. ASTER DTM
  4. SRTM (Cheapest and most coarse option)
  5. Customer provided DTM

To learn more about DTM’s please click here

Orthorectification is also usually required if several images or scenes need to be mosaicked in order to ensure that the joins are seamless. For both rectification and orthorectification, accurate ground control is essential to produce geometrically accurate imagery. SATPALDA also provides options of Seamless mosaicking of large detests for a visually appealing image. 

                                   Figure 1: Schematic of Orthorectification process

An animation showing change in shape of ground features before and after Orthorectification. Note how mountain tops appear shifted between the images. This underlines the need for Orthorectification of imagery, especially in high relief areas.