Soil Moisture with Sentinel 1+ Understanding


I have a few questions as I’m new to this topic/ new to work with Sentinel 1
a) I’m a bit confused of which value to use for Soil Moisture: is it Sigma Value ?
b) I understand that the best channel to use for estimation would be the VV polarization ?
c) I would like to work in RStudio ( like here: Soil Moisture Estimation - Practical: Use in situ data to estimate soil moisture from Sentinel-1 - YouTube): is there a API to SNAP for R / a library like snappy for Python ?
d) when looking at the values for soil moisture , I found a script (Soil Moisture Estimation Script | Sentinel-Hub custom scripts) that uses obviously decibel values and masks out urban areas or water bodies, but why does it cut off soil moisture values above 60 % ? I understand that values above are rather backscatter from urban “things” …is this correct ?
e) when looking in the EO Browser, I see a lot of preprocessed possibilities for download: for instanne a “linear_gamma0_-_radiometric_terrain_corrected.tiff”. Would it be recommended to work directly with these pictures for instance on a 8-bit-Level and then directly using the greyscale values for soil moisture estimation ? And why do they put it in Gamma-Mode ?

I know, there may be a few really dumb questions but I’ve read so much about it now and you get lots of different answers…so maybe anyone can help, I would be very happy.


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