InSAR DEM generation

Hello everyone! need help:slightly_smiling_face:
I have created a DEM using sentinel 1 data using InSAR analysis and finally did the phase to elevation and terrain corrected using range dopler terrain correction. The result was fine but i need to clarify these three questions.

1).What is the purpose of using SRTM DEM in the process of DEM making using inteferometry.
2).The elevation made from Insar DEM, based on geoid height or ellisoidal height??
3).when finally doing the terrain correction for the Insar dem, it is projected to WGS84. is it affecting to the height model.(will it change to ellisoidal to geoid or geoid to ellipsoidal) ???


Not sure about other questions, I guess the experts will reply. But, you should not use SRTM or any other DEM on the DInSAR (but yes on the BackGeocoding), just remove the FlatEarth (reference phase). If you apply TopoPhaseRemoval you will never get close to a DEM as you would be unwrapping only deformation+atmosphere+noise.

I hope this helps