How to get a local incidence angle map from SAR-Imagery?

I have a dual pol TanDEM-X imagery with a bistatic 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) to get the local incidence angle maps. After I check the results 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?

Thank you very much in advance for your answer.

After coregistration, the terrain correction only knows the incidence angle of the master geometry.
If you want both local incidence angles of master and slave then terrain correct both individually.


Hello lveci,

at first thank you for your valuable answer. So to calculate the vertical wavenumber I have to calculate the difference from the incidence angle between the master and slave file as you described. Is the interferometer configuration and acquisition geometry the terrain corrected interferometer file?

Once again thank you very much!

Hello everyone!
I am working with Sentinel-1 data. I do pre-processing on it which includes the (radiometric calibration< Speckle filtering <Geodoing <db coversion)
I need two bands
1- backscattering coefficient(sigma_not)
2- Local incidence angle (theta)
As far my understanding the pre-processed Sentinel-1 data, every pixel’s value is backscattering coefficient(sigma_not). as it or not?
Now how can I get local incidence angle?

You get it after applying Range Doppler Terrain Correction, there is a checkbox to include the local incidence angle as a separate band.

ok i got this Thanks