SNAP Land-sea SRTM mask problem


please have a look about the Land Sea mask with SRTM because there is a problem that should be fixed.
If you run this command on some AoI it could be return a wrong mask.
e.g.: I ran it on Bosphorus area but the land mask wasn’t really well executed.

So I examined the SRTM tile looking for data corruption…
The investigation showed that the SRTM data have an anomaly on the sea:

  • some areas show height set to no data
  • other areas show height set to 0 (zero)

e.g.: Please have a look at the tile Z_42_4.tif

  • On the Black sea, the sea level is set to 0 everywhere
  • On the Aegean sea, the sea level is set to no data everywhere

Seems that this is the problem. Pheraps the correct one should be no data value.
Could you fix it?
If you add a new selection (SRTM from local path) the user can avoid it. Harmonising the SRTM data value on the sea, inside the local files, could be a possible solution.

Thank you in advance.
Claudio Di Paola


you are referring to the blocks in the black see which are shown in the image below, right?
I’ve informed the guys responsible for the Land-Sea-Mask. Let’s wait what they have to say about this.

Hi @marpet .
I am currently working on the black sea and when I am using the land sea mask in the oil spill detection function, I have what seems to be the same issue with the SRTM.
Has there been any news on the subject ?
Thank you


Sorry, but I have no news on this.
But I check with the developers again.

This is just how the SRTM has it’s data. For most shallow in land water bodies there is data. In this case the SRTM can’t be used for a land/sea mask. In this case you could use the Fractional Land/Water Mask operator.

I tried to use the Fractional Land/Water Mask but I can’t seem to mask out the land… I don’t understand how to use this mask to remove Land in my product…

Is this sorted?

Elevation Model has links to NASADEM, which NASA says is an improved version so might do better than the
original SRTM for the Black Sea. You will likely need a NASA EarthData login.

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