Sentinel-1, Multi-temporal speckle filter

Hi all,

It takes the SNAP 3 days to do multi-temporal speckle filtering on my 70 images and now what I got is all black images (0). The parameters I used was Gamma Map, with 3x3 filter size. Any idea what the problem is and how can I do speckle filtering on my data?

Thanks for your help in advance

Did you visually check if all your layers are valid?
The processing time doesn’t surprise me, 70 images is quite much for this operation, but it should surely provide better results.
Maybe you first test it on a subset of your stack. Did you convert to db before filtering?

All layers were valid, I did check it. And I didn’t convert it to db before filtering, Should I?
How can I get a subset from the stack can I use a vector file to clip an area?

you can just zoom in and right-click > Create subset from view and then save your product. You can also use a shapefile for the subset, just import the vector and use the land/sea mask module. You’ll find many descriptions on this issue by using the search function.

So, is this Speckle filter, systematic, or all of them are just something close to mean filter? I am asking because if it is not sensor-specific I might better to skip it, because my features are so small.

the differences to a mean filter:

  1. Every image gets filtered instead of one average output
  2. The filter decides, based on the temporal variation, if an area is more likely to be speckle or a real edge.