there is no method in xsarsea to match with sigma0 denoised values provided by ESA in Level-2 products

[agrouaze]

Currently there is no specific methods in xsarsea to get a NRCS (aka sigma0 denoised) value from a Sentinel-1 product as a Level-2 like. For instance, WV products computing the average value of xsar sigma0 values lead to values up to 3 dB below compare to the value provided in official ESA Level-2 product (oswNrcsNezCorr variable).
Looking at the ESA processor it seems that some steps are potentially* missing in xsarsea.
Typically what ESA processor do to compute the sigma0 is:

1. read digital number
2. apply calibration (dividing by the sigma0_lut²)
3. low pass filter the image
4. keep intensity multiplying by <abs(image)²>
5. remove platform (I suppose it is related to https://en.wikipedia.org/wiki/Apodization technics.
6. final average sigma0 value is mean((image* np.conj(image)).real)

• I don't know if we need to be able to reproduce the sigma0 given by ESA