Back-Geocoding does not have an option to apply EGM to an external DEM. Is Back-Geocoding insensitive to the vertical reference? I’m assuming not, so EGM vertical adjustment of external MSL DEMs needs to be performed by another tool prior to Back-Geocoding.
I believe that the externalDEMApplyEGM option has been added for most other modules using external DEMs. Please add this option to Back-Geocoding, if as I suspect, ellipsoidal DEMs are required.
Unlike Terrain Flattening and Range Doppler Terrain Correction, the spatial resolution and vertical accuracy of the DEM have a smaller impact for DEM-based coregistration.
So while external DEMs make sense in many applications, the actual coregistration accuracy for Sentinel-1 SLC data is achieved by the ESD operator
Thank you Andreas. I measured only the tiniest (<3rd decimal place) difference in coherence computed from use of either MSL or ellipsoidal DEM for Back-Geocoding. My results at least partially confirm what Marcus and Andreas have posted.