Radiometric & Geometric Correction Workflow

are you sure you are using SLC data? In this case you would need to perform TOPSAR Deburst after Calibration in order to remove the black stripes.

Coregistration is only needed when you work with multiple datasets at once.

You could also make a subset earlier in order to save computing time .

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I try to obtain the backscatter coefficient of Sentinel-1A using SNAP. Is the radiometric calibration the first step?

depends on the level of your product. Have you downloaded SLC or GRD data?

SLC, IW mode, VV and VH polarization

If I perform TOPSAR Deburst, Filtering and radiometric calibration, the results of VH polarization is Ok, but the values of VV polarization are zeros.

for SLC data I would suggest

  1. Calibration to Beta0
  2. TOPSAR Deburst
  3. Apply Orbit file
  4. Radiometric terrain flattening
  5. (Speckle filtering)
  6. Range Doppler Terrain Correction

If you don’t need the phase information you can also download it as a GRD product and only apply the following:

  1. Thermal noise removal
  2. Apply Orbit file
  3. Calibration to Beta0
  4. Radiometric terrain flattening
  5. (Speckle filtering)
  6. Range Doppler Terrain Correction

or (if you don’t have much topography):

  1. Thermal noise removal
  2. Apply Orbit file
  3. Calibration to Sigma0
  4. (Speckle filtering)
  5. Range Doppler Terrain Correction
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Thank your very much for your suggestions. Does the Thermal noise removal and Apply Orbit file are the necessary steps?

I performed the SLC data using SNAP
1 TOPSAR Deburst
2 Calibration to Sigma0
3 Speckle filtering
4 Range Doppler Terrain Correction
For the radiometric calibration results, the VV is right, but the VH is incorrect.

Thermal noise is not present in every product. In case you don’t rely on highly accurate radiometric values you can also skip it.
The orbit file adds information about the geometric location of your product. If you want to combine it with other data it can improve the position accuracy.

Your suggested workflow is sufficient for most applications.

Why do you think calibrated VH is not correct?

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Thanks for your reply, I follow your suggestion to perform the Sentinel-1A data using SNAP. In the previous results, when the radiometric calibration was performed, the results of VV polarization are zeros, only the VH polarization is correct. Can you supply an email for me, thus I can transform the results to you.

sorry, I can’t help you outside this forum.

But indeed, zeroes as an output are obviously wrong. Was the data correct/complete before radiometric correction?

Sorry, the results of VH is correct, but the calibrated VV are zeros.

Yes, before the radiometric calibration both of the intensity of VV and VH are correct. When the radiometric calibration was implemented, the calibrated VV are zeros, and the calibrated VH is correct.

I can’t think of a reason why this could happen.
Is it zero or no data /nan?

What order should I take steps in ?I’ve seen one of the above threads says that it should be good after orbit to apply thermal noise removal in order to decrease radiometric variation between subswath.
Best regards!

could be a good idea :slight_smile:

Thanks for your reply .Do you mean orbit before thermal noise removal is better ?What are the differences between the various epolynomial degrees and which is recommended?
Thank you for help

I really don’t know, sorry. Try it out and compare the outcomes.

Thank you very much !

Hello,
I understand the theoritical difference between beta0 and sigma0, if I want to do intensity correlation analyisis between 2 images, or in this case 3 images. I was usggested to use sigma0, however the area I am working is very hilly and has some mountains. The values of sigma0 and beta0 are ofcouse different from pxel to pixel, but only beta0 allows me to do terrain flatering.

What do you suggest I can do for my application in this case?
Thank you