Pixel values ruin with Calibration and/or Spekle filter

mohammad.imangholilo · September 29, 2016, 7:17pm

In processing chain, Calibration>Multilook> Train Correction, or Calibration>ML>Spk filt>TC, and saving in bigtiff geotiff for further analysis, I see that pixel values got to be between 0-0.3 while it is float 32. But excluding calibration and/or speckle filter, pixel values became nicely between zero to couple of hundreds.

Wondering why “Calibration” and or “Speckle Filter” ruin the pixel values unexpectedly?
normal? any advice?

junlu · September 30, 2016, 4:12pm

Calibration produces sigma0 whose value is generally in range of [0, 1].

ABraun · September 30, 2016, 5:45pm

I agree with @junlu - the values are not ruined, just transformed.

You can check if everything is fine by logarithmising (right-click > linear to db) the values. If they result in a range between -35 and+5 db everything is fine.

Sigma0 image:

Sigma0 histogram:

Sigma0db image:

0db

Sigma0db histogram:

mohammad.imangholilo · October 10, 2016, 8:21am

Thank you so much. It solved the problem.