Radiometric & Geometric Correction Workflow

[ABraun]

After which step do the NaN values occur?
Is there extreme topography in your image?

[Industrial_Freak]

After GLCM, at Gamma0 VV Contrast band. I dont have extreme topography (Study area Lesvos island, Greece)

[ABraun]

if the NaN occurs after GLCM it means that the texture is 0 at those locations. You can disable the NaN display in the band properties by unckecking “No Data Value Used”

[dtnguyen]

Do you find out what the problems and how to resolve? Thanks advantage.

[ABraun]

I have no idea, sorry

[dtnguyen]

Somebody already mention about 2 years ago

Preserving complex S1 data (SLC) in Calibration and ThermalNoiseRemoval operators

When applying the Calibration or ThermalNoiseRemoval Operators to a S1 SLC dataset (complex data), the result obtained is no longer complex valued. However, for our application we need to have the complex nature of the data preserved. Are there perhaps undocumented settings, or a recommended workaround to achieve this?

[dtnguyen]

Problem I believe about save from ThermalNoiseRemoval, if s/w continue with complex they can able to save
complex and the lines on images will be solve too.

[PiriReis]

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

I have topography in the subset image but there is no topography in my ROI. Should I do terrain flattening you think?

[ABraun]

flattening only changes the radiometric properties of areas, so if you make sure that they are correctly georeferenced (Range Doppler Terrain Correction), you can skip Terrain Flattening and directly calibrate to Sigma0.

[racha_laishram]

hi, i would to know a simple software to do the calibration of sentinel 1 image except SNAP toolbox, as it is not working in my p.c. (with windows 10, 4 gb ram ) despite my repeated attempts. Also i’d like to know how to access the metadata of sentinel1 data.

[ZHAOMINGLE]

Excuse me. There is one question during my process of “Radiometric Terrain Flattening”. Should I check the “Re-grid method” checkbox? Thanks.

[ABraun]

if everything works fine, don’t select it.

[Industrial_Freak]

I have to do post-classification comparison between ERS 2 and Sentinel 1.
Could I use the same workflow for ERS1/2?
If not, could someone suggest me one tested workflow?

[ABraun]

Radiometric Calibration, Terrain Correction, Classification.
However, ERS has only one polarization. Classification is not easy then.

[Industrial_Freak]

At first, thanks for your fast response and your help!!

Could you explain me the reason that the ERS needs only Radiometric Claibration and Terrain Correction for classification and S1 needs all these steps from your suggested workflow? Do you have some reference for that?

So, are you suggesting me to use only the 1 polarization (same as the ERS polarization) of Sentinel-1?

[ABraun]

Could you explain me the reason that the ERS needs only Radiometric Claibration and Terrain Correction for classification and S1 needs all these steps from your suggested workflow? Do you have some reference for that?

ERS (and most other SAR sensors) are primarily acquired in StripMap mode. It is generated line by line.
Sentinel-1 is acquired in TOPS mode (illustrated as ScanSAR principle below). Neighboring pixels are of different acquisition phases. That is why Sentinel-1 data needs some more calibration and corretion steps.

Source: https://eijournal.com/print/articles/discover-the-benefits-of-radar-imaging

[ABraun]

So, are you suggesting me to use only the 1 polarization (same as the ERS polarization) of Sentinel-1?

ERS, ENVISAT and Sentinel-1 are C-band satellites at quite similar spatial resolution. This makes them potentially comparable and usable within the same scope.

• https://www.sciencedirect.com/science/article/abs/pii/S0034425712000612
• https://www.tandfonline.com/doi/abs/10.1080/15481603.2016.1269404
• https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JC011149

However, most classification approches need a multi-dimensional feature space. Optical satellites acquire information at multiple wavelengths (visible, infrared, thermal), but SAR data is restricted to one wavelength. Its potential for classification purposes is therefore limited.
Have a look at the possibilities to increase feature space for SAR data:

Classification of GRD product

If you only have VV polarization classification is difficult. Typical supervised classification is based on samples which help to divide your feature space. But even if you have VV and VH, your feature space is only n=2 so your classes won’t be much distinctive. To increase your feature space you have the following options: add image textures (GLCM module), but this should be done before speckle filtering. Speckle filtering destroys most of the image texture. add images of different dates (dry…

[Industrial_Freak]

For ERS i must calibrate the bands, and create Beta band? Am I right?

For terrain correction i must do SAR Simulation or SAR-Simulation Terrain Correction? (I think Range-Doppler TC you must do only for Sentinel SAR… Am I right?)

[ABraun]

Both sensors need to be calibrated, but it is better to select no band in the calibration tab.

Range Doppler Terrain Correction and SAR Simulation Terrain Correction do the same task and can be applied to both sensors. It’s just different methods to place the pixels at the correct location.

[Industrial_Freak]

I have GRD S1 product. I follow all the workflow.
If I write “30” at pixel spacing(m)( at Range Doppler Terrain Correction), I resampling my product to 30X30 meters pixel size?
I need after this to do registration between S1 and L8. And ERS with L5, so I need all the final products at the same resolution (30 m).