Sentinel1 TOPSAR split & calibration

Good morning everyone,

I am beginning my PHD here in Germany and I will have a lot to do with S1 TOPSAR data. As a beginner user of SNAP I am trying various operations and a lot of questions are coming out. I have seen a lot of threads about this topic but it is really hard to find what can be the right one for me. My first question here is about the creation of a stack of two sub-swaths from two S1 SLC IW data products. After applying for each data product the TOPSAR-SPLIT and ‘Apply orbit-file’ , I should use the BACK-GEOCODING processor using the two selected subswaths as input.
If I wanted to obtain calibrated stack of S1 data, should I insert the CALIBRATION processor for both the input before the back geocoding block or after that for its output? I have tried the first option but I got an error from the back geocoding saying that its inputs should be SLC products. I hope I have been clear enough and I can have some help. I saw that especially @ABraun is quite active on that but also other contributes will be so much appreciated.

To stack two S1 images you can directly use Radar > Coregistration > S1 TOPS Coregistration > S1 TOPS Coregistration. It includes all steps required to have them correctly aligned, including the selection of sub-swaths in order to save memory. You need to perform Debursting afterwards because it still has stripes.

You can calibrate the data before this, but you should check the box “complex calibration”. Then, your data remains in intensity values.

Yes, thanks, theS1 TOPS Coregistration is something I know and also the S1 TOPS Deburst block to “fix” the stripes. The point was really if it is possible to insert the calibration before the back geocoding. So with “complex calibration” you mean to tick the “save as complex output” option? Really thanks for your support here

yes. exactly.

1 Like

Thanks!! that was clear finally. I also have another question, How is it possible to implement an amplitude calibration such as sqrt(linear sigma0)? you are definitely the most reliable source here, thanks so much

I am not sure what you mean. If you perform the calibration and select “complex” you can consider your amplitude as calibrated.