it does make sense 
I’ll update my suggestion above.
I would also say the Orbit file goes before the Thermal Noise Removal or may be it doesn’t matter but that is how it has been suggested most of the times.
well, the orbit information does not change the pixel values so I think the order is not crucially important here. Do you have a reference for that?
You are right. It doesn’t matter. Just thought I should bring into the notice.
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Hello Mr. @ABraun ! In SNAP help file, it is written that “GRD products have thermal noise removed” then may I know why is it necessary to remove thermal noise in GRD products again according to your workflow ?
maybe the help is wrong here. I was referring to
If I want to stack calibrated, speckle filtered and terrain corrected RADARSAT-2 products should I co-register them or should I just stack them?
if you want to use interferometry, you skip the calibration to Sigma0 and directly start with the co-registration.
If you simply want to create a stack of backscatter time-series, you calibrate, geocode and then stack them (Create stack). If you want to go sure, you can coregister the geocoded products (Coregistration). This takes more time but especially if you use images of ascending and descending orbits the quality of the alignment of the images is better. Just to go sure you select “geolocation” as initial offset method.
Once you have a stack of multiple images, you can decide if you want to apply a multi-temporal filter. But especially if you are aiming for subtle changes, you need to check that these changes are not elimited by the filter. They are adaptive but there are also reports where they caused the loss of relevant informaiton.
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Hi @ABraun,
I need to find some trihedral corner reflectors by Sentinel SLC imagery.
So, to do this, is it correct to follow your procedure for SLC data?
Thanks in advance.
yes, the terrain correction is the most important part because it produces geolocated pixels. You can also try the SAR simulation terrain correction which is often even more exact, but you can compare both.
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Okay, I try the SAR-Simulation Terrain Correction and then I will compare both.
In your opinion, for find a corner reflector, could be it useful to convert linear to db? If yes, at which step is it okay to do it?
Thanks again @ABraun.
The conversion to dB should always be the last step.
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Hi everyone,
to find my corner reflectors by S1 SLC, I have tried to do this workflow:
- TOPSAR-Split (VV polarisation)
- Apply-Orbit-File
- Calibration (output beta0 band)
- TOPSAR-Deburst
- Terrain-Flattening (default parameters)
- Speckle-Filter (default parameters)
- Terrain Correction (default parameters)
Then I covert the gamma0 linear to dB.
But I have some questions about this workflow.
I see some papers that use sigma0 band instead gamma0 band to find the corner reflectors, so to do this I need to select as output the sigma0 band in the step 3 and to delete the step 5 (because it converts sigma0 band to dummy); first quesiton: which is the difference between gamma0 and sigma0 and which is better for my goal?
Second question: @ABraun I’ve tried to use SAR simulation terrain correction instead terrain correction, but the graph builder show the following error message: “Source product should include a simulated intensity band.”. Do you know why?
Every suggestion is welcome, thanks in advance.
please have a look here: Difference Sigma, Gamma and Beta nought?
are you sure you used this tool?
Because actually, simulation of an intensity band is part of the operator.
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Technically speckle-filtering should take place before TF so you should swap 5. and 6.
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I wouldn’t consider it mandatory, only if you have this kind of noise and want to get rid of it.
Hello.
I tired doing the SLC steps for generating gamma0 bands for VV and VH. However, the resulting bands are empty. Do you know any further step I need to do for this?
Thanks!
after which step is the product empty?
