Sentinel-1 Radiometric Terrain Flattening in GEE


I’m need apply the Radiometric Terrain Flattening in a lot of Sentinel-1 images within Google Earth Engine.

But in GEE the Sentinel-1 GRD data are currently with Orbit File applied, Terrain Corrected and converted to dB. After this processing is possible write ab algorithm to apply RTF with efficiency?

My bests regards.

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No, it would have to be added at their input stage. I proposed that they add flattening during input already years ago, but so far AFAIK they have preferred to stay with the GTC products you’re familiar with.

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A recent publication on Angular-Based Radiometric Slope Correction for Sentinel-1 by Andreas Vollrath et al, 2020

Check out the complementary material on github here:

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The Vollrath et al solution is not the same as terrain flattening. Rather it is some empirical angle correction factor depending on 2 assumed terrain types.

For terrain flattening, the correction is (also) based on the normalization for pixel area. One would expect pixel area to be a constant depending only on SAR viewing configuration and local DEM derived slope angles. That suggests you would need to derive that only once and provide it as a reference layer (ignoring small difference in SAR viewing config between orbit passes).


Thank by explanation @glemoine!