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bopen / sarsen

Algorithms and utilities for Synthetic Aperture Radar (SAR) sensors
Apache License 2.0
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Documentation of vertical reference required for DEM #11

Open S0sh0rt opened 2 years ago

S0sh0rt commented 2 years ago

What is the vertical reference for the DEMs? Most DEMs are MSL, but the SAR computations require WGS84. Are you applying EGM 96 or 2008 to the DEM?

alexamici commented 2 years ago

This is entirely left to GDAL/Proj, if the metadata on the DEM files is correct and Proj handles the translation to geocent / ECEF, then you are fine.

You can see in the download script for the notebooks that I add the explicit vertical reference EPSG:5773 to the command line in the pre-process step, as the DEM uses EGM96 heights but doesn't declare it: gdalwarp -r bilinear -s_srs EPSG:4326+5773 ... Then GDAL converts the DEM to WGS84 ellipsoid heights and add correct metadata.

alexamici commented 2 years ago

@S0sh0rt but you are right, I need to document this. [I was quite sure I mentioned it in the README, but it's not in the there]