Offset Tracking with TerraSAR-X Data

Hi ABraun,
Just two quick questions. I have generated some offsets that I am happy with and have exported the raster as a TIF. Is there a way I can export the vectors of the offset too? I can visualse them in SNAP but when I try use “geometry as shapefile” I get an error message saying “current fid index is null, next must be called before write”

Secondly, I understand most of the process, but I am a bit confused by the DEM assisted co-registration and how it works. Since the ice is flowing, is it not advisable/possible to mask out the glacier and only co-register the “stable” parts of the image?

Thanks,

Ben