Sigma0 calculation

Hi everyone,

I’m trying to calculate sigma0 from S-1 raw data.
How can I get the same result as the output of ‘Radar-Radiometric-Calibrate-sigma0’ using MATLAB?
This document could be helpful, but I have some questions.
In CADS(calibration annotation data set), calibrationVector-pixel count is only 5-600 counts.
(i.e. 0 40 80 120 160 …)
but real pixel number is much bigger than it…
So, I wonder how I can use the CADS, and how to calculate sigma0 from L1 image directly.

Hi, it is true that the calibration vector pixel count is a few hundred values but they span the whole of the product width, e.g. for a SM GRD product:

0 40 80 120 160 … 8080 8120 8160 8190

Since the calibration vector is slowly changing across the swath, linear interpolation can be used for values inbetween. For example for a range pixel coordinate of 30, the values at 20 and 40 can be used via linear interpolation.

The calibration LUT provides calibration factors for some pixels (a coarser grid) in the image. For pixel not on the grid, its corresponding calibration factor is computed by interpolation.