Terrain flattering, Sigma0, Beta0 and Gamma0

Dear all,
I have IW data and I want to get backscattering image from it. I do not know what are the best steps for it but I did like this:

  1. S_1 Tops split
    2- Apply orbit file
    3- Callibration—I chose Beta0
    4-S_1 Tops deburst
    5- Multilooking
    6- Terrain flattering
    7- Terrain correction
    8- speckle filtering
    9- re-projection
    11- Raster—Data conversion—Linear to/from db

A. Are these steps good and enough for backscattering?
B. As I know for backscattering we should use Sigma0 in calibration processing but when I use Sigma0, then I can not do terrain faltering. What can I do now?
C. What is the difference between Sigma0, Gamma0 and Beta0? Why does Sigma0 use for backscattering?
D. When I do terrain flattering, it coverts Beta0 to Gamma0. Why?
D. Frankly speaking, I just heard people do terrain flattering but I do not know why? Would you please explain for me?


Why not start from GRD data instead of SLC? Saves you a factor 4 in download size and you would only need to do step 2, 3, 5, 6, 7, 8 , 11. Speckle filtering should be after 5. Not sure what resampling does and reprojection is part of 7. Terrain flattening is a radiometric correction/normalization for non-flat terrain, but check the Small et al, TGARSS paper for details. I understand that it should work now in a similar way as in the paper (previous SNAP versions deviated from that).

Thanks my friend. As I am working on ice, I understood now, I do not need train flattering.:slight_smile:

You’re welcome. If you’re working on ice, you should be more worried about climate change :smile:

A nice comparison between Beta0, Sigma0 and Gamma0 can be found here:
http://sss.terrasar-x.dlr.de/papers_sci_meet_3/tricks/TSX-products_tips_and_tricks-1.pdf (slide 34-36)

Yessss my friend:grin:

Please check the paper from 2012-TGRS-Improving PolSAR Land Cover Classification With Radiometric Correction of the Coherency Matrix, “The reference areas used within the , and backscatter conventions are illustrated in Fig. 2. Each convention employs its own definition of the backscatter reference area, placing it in: 1) the slant range plane itself ( with area ) the ground as modeled by an ellipsoidal Earth ( with area ); or 3) the plane perpendicular to the local look direction ( with area ) [26].”

and 2009-TGRS-A Revised Radiometric Normalisation Standard For SAR, the figure above shows SAR image before and after terrain-flatten which removes the stereoscopic sensation.

after the ideal radiometric correction, your radiometric variable no matter sigma/beta or gamma-naught, should not be a function of local incidence angle.

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The link is break. Someone know where I can find it?

I noticed that as well, someone must have taken it down. :frowning:


If someone is still interested in the linked document, I’m assuming it’s this one:

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