we have so many topics on this - the short answer is: It’s currently not implemented in StaMPS or SNAP, but different approaches exist to do it manually.
- Vertical Velocity Displacement along Ascending and Descending tracks
- How can I get the real deformation of the surface with interferograms using Sentinel 1 images?
- Phase Unwrapping to Vertical Displacement
- Horizontal and vertical displacement
- LOS and Vertical Displacement / Sentinel-1
- Phase to Displacement Units? - #29 by mengdahl
Also, we hope to cover this in future versions: https://senbox.atlassian.net/browse/SITBX-730