Unable to create Gamma0 with terrain correction routine


#1

I am getting inconsistent results when using the Geometric --> Range Doppler Terrain Correction to obtain Gamma0 images. The input is S1A IW GRD products. Sometimes the routine works with no issues. Sometimes Gamma0 generation fails and I only get a Sigma0. No errors are reported in this case.

My internet connection is pretty good but I wonder if there is a way to check where the SRTM DEM from auto-download is stored? Is SNAP perhaps looking for a DEM file and failing once it finds that it doesn’t cover the whole scene?

Any inputs would be highly appreciated.

Best,

Naiara.


#2

if you have areas outside 60° no SRTM is found. Could this be an explanation?


#3

In this case I do have SRTM coverage. Thanks for the suggestion.


#4

are these scenes at the same location in terms of track and frame?


#5

Yes, same location. The routine doesn’t show any errors but the gamma naught band is never produced. It’s making a local incidence angle for me so it’s reading the DEM. I’m currently using that band to calculate gamma naught.


#6

have you tried Calibrating to Beta0 and applying Radiometric Terrain Flattening instead? This produces radiometrically corrected Gamma0.


#7

Hi,

that’s an OK solution, but the radiometric terrain flattering routine doesn’t use the same method (facet) as the Range Doppler Terrain Correction. I may be misunderstanding the outputs of the Range Doppler Terrain Correction. A Gamma Naught image is produced, but it’s a “virtual band”. How can I export it to geotiff?


#8

To export virtual bands right-click and select convert band, then save your product.
Then you van select it under File > Export


#9

Hello, I was able to export the images, thank you.