Hello everyone!
I am working with GRD products from Sentinel-1 to calculate glaciers velocity in Greenland. So far I have used ACE30 DEM for DEM-assisted coregistration step and everything worked fine. Recently I’ve changed DEM to new Copernicus 30m DEM. Now I receive totally different results (previous velocities were comparable with MEaSUREs data) and I am not sure what is the reason.
Moreover, I’ve another pair of GRD images: from different satellite mission (same area, same dates) and in this case Copernicus DEM gives the best results - and they agree with results from S1 data with ACE30 DEM. Applying ACE30 gives far to high velocities (over 120 m/day - quite impossible).
Some ideas what is the reason of such differences? Why one DEM gives great results, when the other one is totally wrong? And why 1 DEM works great with S1 data and for different satellite another one is much better (area and timspan are the same so that’s not the problem)?