The purpose of georeferencing is to transform the image coordinate system (u,v), which may be distorted due to the factors discussed above, to a specific map projection (x,y) as shown in Figure 4.8. The imaging process involves the transformation of a real 3-D scene geometry to a 2-D image
Figure 4.8. Georeferencing is a transformation between the image space to the geographical coordinate space
Terms such as geometric rectification or image rectification, image-to-image registration, image-to-map registration have the following meanings:
1) Geometric rectification and image rectification recovers the imaging geometry
2) Image-to-image registration refers to transforming one image coordinate system into another image coordinating system
3) Image-to-map registration refers to transformation of one image coordinate system to a map coordinate system resulted from a particular map projection.
Georeferencing generally covers 1) and 3).