S1 Pre-processing chain and parameter setting

[WenjiaYan]

Hello everyone!
I am a new user with SAR data and I’m working with Sentinel-1 data with the goal of classification.
I found that the tool SAR processing > Apply Precise Orbit File > Removal of border > Thermal Noise Removal > Calibration > Multilooking > Speckle Filtering > range doppler terrain correction > Slope Normalisation, is necessary to carry out all the above steps or other steps that are lack (or am I wrong?).
I used the next images:
S1A_IW_GRDH_1SDV_20160116T095421_20160116T095446_009518_00DD1D_3A0D.SAFE
What I’m also confused is about the step of Apply Precise Orbit File. Which number about polynomial Degree should I set and what is the difference among various numbers?
Thanks for help!
Wendy

[ABraun]

The border removal is only needed if you work with multiple scenes and when you have problems making a mosaic.
Multi-looking and speckle filtering are just for image enhancement. You don’t need to apply them necessarily.

Basically the following steps remain:

Radiometric & Geometric Correction Workflow

for SLC data I would suggest Thermal noise removal Calibration to Beta0 TOPSAR Deburst Apply Orbit file (Speckle filtering) Radiometric terrain flattening 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: Thermal noise removal Apply Orbit file Calibration to Beta0 (Speckle filtering) Radiometric terrain flattening Range Doppler Terrain Correction or (if you don't have much topography): The…

[WenjiaYan]

Thanks for your reply, I follow your suggestion to perform the Sentinel-1A data. In the left image, when the terrain flattening was performed, the result of VH polarization is not better than the result when only the calibration is implemented.

The part in the red rectangle is gone when the terrain flattening was performed.8
Best regards.

[ABraun]

is this not just a matter of color adjustment?

[WenjiaYan]

The VH in the red rectangle is zero in the left image.
Thanks a lot .

[ABraun]

I see. This could be because of a missing elevation information. Did you use the auto download DEM or an own one?

[WenjiaYan]

Yeah, I used the auto download DEM.

[ABraun]

I experienced a similar thing when a small part at the edge of the image was missing. Try to download the DEM from USGS (http://earthexplorer.usgs.gov/) by yourself, make sure it covers your whole SAR image (maybe you need to make a mosaic out of more tiles, leave it in WGS84) and select it in the Flattening module.
For a first try you could test if the other Auto Download DEM delivers better results. In flat areas the resolution of the dem is of minor importance.

[WenjiaYan]

Thank you for inputs.And how to adjustment the color of image?
Best

[ABraun]

this is just a visual enhancement, it won’t change the values.

You find it in the color manipulation tab

[WenjiaYan]

Thank you for your help:slight_smile:

[mengdahl]

It usually makes sense to convert from linear to dB for visual purposes.

[WenjiaYan]

Thanks a lot.I’m new with SAR data.What 're the meaning of dB?
Best.

[ABraun]

What 're the meaning of dB?

please have a look at some topics in here. You will find most of the answers to your questions:

Sigma0_VH vs. Sigma0_VHdb

As this is a very basic question: If you're new to SAR I recommend the SAR EDU page which provides lots of information about the SAR principles and theories as well as tutorials and talks: https://saredu.dlr.de/ The visual amount of information is related to the distribution of backscatter information over the given color range: While the VH intensities have an extensive range and only very light objects appear sharp, the db data is logarithmised, meaning that the values are now distributed mo…

[WenjiaYan]

Thank you very much！

[WenjiaYan]

Hi,@ABraun
There is the initial Sentinel-1 GRDH product in figure1.After performing Apply orbit file tool,a gap appeared as shown follow.What’s wrong ?

Regards,
Wendy

[ABraun]

I don’t know, sorry.

[WenjiaYan]

Thanks a lot for your reply!

[lveci]

How did you get that? Could you provide the product name? Thanks

[WenjiaYan]

Hi,@Levic
I used the next images:
S1A_IW_GRDH_1SDV_20160116T095421_20160116T095446_009518_00DD1D_3A0D.SAFE
S1A_IW_GRDH_1SDV_20160116T095446_20160116T095511_009518_00DD1D_14D7.SAFE
Thank you very much!