DEM that supports image processing?

Hello everyone,

I am generating DEMs with two IW images with the use of SNAP 3.0, in this process a SRTM downloaded by the software is used in some steps, my question is the following one:
If the SRTM altitude values are quite good and very similar to the reality why the altitude values I have obtained in my interferometric DEM differ in an average of 120 meters from the reality? How is this SRTM DEM used in the process if the altitude values are so far??

Thank you very much for your time!!! :slight_smile: