Implementation

The algorithm described in Annex D is used for the conversion between (line,pixel) coordinates to the corresponding point P on an ellipsoid. (The Doppler, range and ellipsoid equation.) This step consists of three steps basically.

1. For the center (line,pixel) of the master image, compute the position (x,y,z in system of the orbits) of the point P on an ellipsoid.
2. Based on the Doppler equation, compute the position of the slave satellite, corresponding to the point P on an ellipsoid, and compute the (line,pixel) coordinates in the slave system.
3. The difference (slave-master) between the (line,pixel) coordinates is defined as the offset.