I have a dual pol TanDEM-X imagery with a bi-static acquisition mode. To calculate the vertical wavenumber, I need a local incidence angle map of the Master and Slave image. As a first step I co-registered both images and then I proceed a Multilooking. The next step was a terrain correction (with SNAP) or the geocoding and radiometric calibration procedures with SarSCAPE to get the local incidence angle maps. After I check both results (retrieved from SNAP and SarSCAPE) I found that both local incidence angle maps from the Master and Slave imagery are identical what surprised me very much. Do you have an Idea what could be the reason for this result? What should I do?