SRTM ZIP-files are corrupted or not found

snap Problem Reports
46

The SRTM 3 Sec data are no longer located at the cgiar-csi server, so SNAP can no longer access them. This affects

  • Range Doppler Terrain Correction
  • S1 BackGeocoding
  • Topographic Phase Removal
  • Orthorectification
    as long as SRTM 3Sec (AutoDownload) is selected.

A new location has already been implemented, but the latest update does not yet cover all cases.
To go sure, please test one of the suggestions below unil this is covered by the next update.

Solution

Please update SNAP (Help > Check for updates), the latest update (8.0.3) fixes the error.

Work around

Select SRTM 1Sec HGT (AutoDownload) as DEM instead.

Manual solution (no longer required)

  1. Go to your SNAP installation directory (e.g. C:\Program Files\snap) and go inside the ect folder where you find the file snap.auxdata.properties
  2. Open it with a text editor (maybe needs administrator privilleges) and go to line 27 which defines the location of SRTM 3Sec data. Change it from
    DEM.srtm3GeoTiffDEM_HTTP = http://cgiar-csi-srtm.openterrain.org.s3.amazonaws.com/source/
    to
    DEM.srtm3GeoTiffDEM_HTTP = http://skywatch-auxdata.s3-us-west-2.amazonaws.com/dem/SRTM90/tiff/
  3. Save the file and restart SNAP.

It has also been reported that deleting old DEMs downloaded into the user directory helped after changing the data source. This means to remove all files inside:
user\.snap\aux\dem\SRTM 3Sec
especially the ones which are only 1 KB. Otherwise, SNAP tries to re-use them in the future, but they are empty.

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