Let’s discuss the matter one by one,
First point I mentioned in here the selecting SAR pairs conditions for DEM creation
In case we try up to apply all the aforementioned conditions to your case, or Sentinel -1 case, we could find that, more than one of S1 characteristics don’t meet the DEM creation, and example of that is, the temporal baseline, as you know, there’s no tandem pass in S1, also the perpendicular baseline is important to take in account as it is mentioned,
Here our colleague @ABraun has mentioned the properties and increasing the quality of DEM
In our colleague post you could find out the lack of S1 for DEM creation, and the solution of increasing the DEM quality by multi-looking to 20 m, and goldstein filtering,
Other way to increase the quality of DEM creation is to by Interferogram averaging for DEM generation
Coming back to your results, concerning the SRTM DEM, I think it is incomparable with the S-1 in most cases (personal opinion) for example following are some reasons,
Other reason,
BUT BUT BUT, That doesn’t mean to stop our research to creating DEM from S-1, especially in the real need when SRTM or other DEM missions don’t cover the AOI,
I think your results are good, think about the Unwrapping method we use, Unfortunately there is no other approach of unwrapping is available could be used to compare the results or at least to be more affable to one case rather than the other,
Technically I found you passed all the steps successfully, you got very good results so far, Now, my advice to you is, to start change the parameters, in each step starting from the ESD, reaching the last step of processing,
The difference between S1 DEM yours,
And SRTM
I think they are reasonable, according to what are mentioned above,
Your mission now is , to follow the approach I gave to you within this post to decrease this differences as much as possible.