Problems in coregistration of S1 GRD IW data

Hey everyone!
I am working with the coregistration of images from same orbits. The processing I have done is as follows: Apply Precise Orbit File > Thermal Noise Removal > Calibration> Slice Assembly>Speckle Filtering > range doppler terrain correction . Now I tried to coregister images from different time with coregistration tool and I set the parameter of initial offset method with Orbit and Geolocation respectively, other parameters are default. The results with parameter Geolocation provides some offsets ,but which with parameter Orbit are totally zero values. I also tried to use the DEM assisted coregistration. this still provides zero values. What am I doing wrong and what is recommended workflow to coregister the Sentinel 1 GRD data?
I used the next images:
Thanks for help !

I’m not quite sure if I got you right:

Did you try to co-register after all these steps?

Precise Orbit File > Thermal Noise Removal > Calibration> Slice Assembly>Speckle Filtering > range doppler terrain correction

yeah, after these steps, I coregister the images.

In this case I’d suggest to co-register before the terrain correction.
It is especially meant for data in Slant Range geometry or also Ground Range where slight shifts due to incidence angles or image acquisitions occur.

thank you very much for your help!
given that my study area is in plain , maybe slope normalization isn’t necessary. I find that the coregistration tool is aimed at INSAR data in SNAP and the DEM assisted-coregistration is used to process GRDH data. I’ m confussed that whether I can use the coregistration tool to coregister the Sentinel GRDH data.
best wishes!

yes, if you don’t expect much topography, calibrating to Sigma0 is enough.

Coregistering also works on GRDH data and makes totally sense because there can still be shifts within your rasters which are adjusted by the GCP-generation.
But if you don’t have topography the DEM assisted-coregistration won’t make much sense so I’ll suggest the normal one.

I really appreciate your help!
As mentioned in previous question, I process the images with corgistration tool. what’s the difference between Orbits and Geolocation parameter about initial offset method ? Especially when I choose the default parameter Orbit, result s of some images are fine but there are totally zero values in some images.

I’m not sure about the implementation in SNAP so maybe someone other can explain this better.

For InSAR on SLC images, using the orbits to calculate the initial offset should be more precise especially for missions like ERS or ENVISAT. For S1 and GRD it probably doesn’t make as much difference.

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