Hi
In SNAP, when I tried to open the Capella data with the “Capella Product Format” option (here I used Strip GEO data), it’s directly adding Sigma0 calibrated data.
Is this a Sigma0 calibrated data or any algorithm is being applied to calibrate the data while reading it?
As per the Capella products guide, the GEO products contains amplitude information only.
Thanks in advance!
I noticed that the following algorithm is being applied to calibrate the Capella Strip GEO product while reading it.
Line 153, in github code here
I’m wondering why sqrt, when input is amplitude?
Old question, but the problem is still relevant (I used S1TBX Version 9.0.4):
The sqrt seems to be a bug. I realized that when calculating statistics for Spotlight GEC images.
For the Equivalent number of looks (ENL) we expect approx. 9 for homogenous areas in Capella Spotlight
GEC images. Calculating statistics with SNAP using the imported Sigma0-Band produced much higher values for the ENL parameter. Using the original Tif-Data resulted in the expected values.
From the Capella SAR PRODUCTS FORMAT SPECIFICATION:
In general:
A JIRA ticket ([SNAP-3628] - JIRA) has been created to track the issue. We will look into it, thank you.
The problem has been fixed. The fix should be available in the next release. Thank you for reporting the issue.
I have seen your changes:
However, I think there is still a problem. The imported Band is “Sigma0_HH”, i.e. we expect sigma0, the calibrated backscatter coefficient (Intenstity). According to the Capella documentation, just skipping the “Math.sqrt” operation results in the square root of sigma0 (Amplitude).
I think square of (srcArray[i] * scaleFactor) is the correct value. To me it is a little bit uncommon that we have to square the given calibration-scale-factor to calculate sigma0-values, but it is confirmed by statistics-calculation within Capella-GEC Spotlight images I think.
Fixed, thank you
