Numerical error analysis of CSL georeferencing process implementation

We present the specific georeferencing and geoprojection process we have implemented into the CSL interferometric SAR processor. The paper addresses the geometric aspects for georeferencing a point in a SAR image given in azimuth-slant range coordinates, and describes the implementation. Conversely, we present geometrical aspects of back projection, i.e. from a georeferenced position toward azimuth-slant range coordinate system, and the way it is implemented. In order to evaluate numerical errors of both implementations, we performed back-and-forth projections of a given point to determine shifts between initial and final coordinates. Numerical errors are estimated with respect to slant range position, Doppler centroïd, altitude and latitude of the point. This procedure does not give information on the accuracy of the georeferencing but well on the reliability and precision of the implementation. Finally, we present the resampling technique we have implemented to geoproject SAR and InSAR products with respect to the achieved georeferencing. An example is given to estimate georeferencing accuracy. This work was performed under financing of the Belgian Scientific Policy in the frame of the ORFEO program.