I get this error when computing interferogram using SRTM 1Sec HGT:
SEVERE: org.esa.snap.core.dataop.dem.ElevationFile: error in opening zip file
INFO: org.esa.snap.core.dataop.dem.ElevationFile: http retrieving http://step.esa.int/auxdata/dem/SRTMGL1/N37W010.SRTMGL1.hgt.zip
I’m processing interferograms with SLC products from sentinel 1 A, referring ≈ 1 year (7/26/2019 - 6/26/2020).
I’m using SRTM 1Sec HGT in Back-Geocoding and TopoPhaseRemoval.
WARNING: org.esa.s1tbx.sar.gpf.orbits.ApplyOrbitFileOp: error in opening zip file
WARNING: org.esa.s1tbx.sar.gpf.orbits.ApplyOrbitFileOp: ApplyOrbit ignoring error and continuing: java.util.zip.ZipException: error in opening zip file
Apparently, everything in snap that downloads a zip fails (it creates a corrupt zip file).
Hello,
I would like to know if these issues are related with downloads made on 3 or 4 December nights, when STEP server was upgraded and restarted or if this still happens with downloads made today.
Thank you for this clarification.
FYI: It seems things have been fixed now. Preprocessing (including apply orbit file and download of EGM96 zip) works ok again here. Did not test the srtm tiles, as we’ve cached those ourselves to not hammer esa’s servers too much. Thanks for the fix!
2´ ago I was processing Sentinel-1 GRD products using SRTM 1sec HGT and running!, but when I use SRTM 3sec GHT it doesn´t run. I am not sure if my results are good
Hallo @ABraun, I am facing the same problem. I am doing an urban footprint with SLC-Product so I am creating the Terrain Corrected image to use for computing the coherence. I am using the ESA Tutorial with the steps: split-orb-cal-deb-ML and finally the TC. I was trying with SRTM 1sec and also as default SRTM 3sec and all the process stops by writing ~20% and doesn’t want to finish the processing at all. Last time it worked was Monday or Tuesday. Then suddenly this bug.
I was using SNAP v8 and v7 for Windows because I thought going to the previous version would be a temporal solution… but no. And also today I switched on my another laptop with the versions for Linux and same story.
Is it possible the issue comes from some SNAP update by ESA? Can’t be it worked fine with same data with same settings and after Monday/Tuesday it suddenly isn’t.
Would be really nice to find out the solution for this problem as soon as possible. Thanks in advance. Greetings.
This happened after the release of SNAP 8, but something has changed - maybe the access to the SRTM data. @mengdahl@lveci
We are currently looking into this.
This issue occurred because the location of SRTM 3Sec (AutoDownload) has changed, so SNAP is no longer able to retrieve it during Terrain Correction, Back Geocoding, Topographic Phase Removal ect.
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)
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
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/
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.