Qualitative Assessment of Linear and Quadratic Transformations in Georeferencing of Satellite Imagery

In continuous georeferencing any point can be located using a set of addresses while in indirect one only some selected points of an imagery can be georeferenced and therefore intermediate points can be located using indirect method. Continuous georeferencing is used for more accuracy. Two methodologies used for the estimation of intermediate points are linear transformation method and quadratic transformation method. 20 Ground Control Points (GCP) are chosen for the imagery of New Delhi taken by Probe HRC (ESA) and the lat-long coordinates are also calculated for the same points using Global Positioning System (GPS). Idrisi Kilimanjaro is used for georeferencing. The coordinates of the points that represent the same places in both the old and the new coordinate system have been calculated. Resampling where the coordinates of the old image are designated to the points of the new image falling exactly above it has been done. Softwares used for georeferencing uses equations to construct a relationship between the new and the old coordinate systems. By looking the above tests it can be concluded that georeferencing occurs much more accurately when done by quadratic transformations as compare to linear transformation.