SAR specialists from CNES and Cesbio have developed a nice tool named S1Tiling, to calibrate, ortho-rectify Sentinel1 data onto Sentinel2 MGRS2 grid, and to filter speckle with a spatio-temporal filter.
S1Tiling is an open source python code (developed by Thierry Koleck) available on github, that uses the radar ortho-rectification application from OrfeoToolbox (developed by J.Michel). It is quite efficient and fast.
S1Tiling is also available as an on-demand software on PEPS collaborative ground segment (without filtering)
You will find more info from Thierry Koleck’s post in CESBIO multitemp blog.
I used the online PEPS software for ortho-rectification. Everything is working fine and I downloaded all the S1 images I needed.
However, looking at the S1 images it seems that there are some negative values for some pixels. Do you know if I missed something ? If I understand well the images from PEPS are in linear scale so they should have only positive values.
Thanks a lot for your time;
what steps did you perform on the S1 data and in which order?
I just followed the “utilisation dans PEPS” steps (as explained here : http://www.cesbio.ups-tlse.fr/multitemp/?p=14844 ) in order to download ortho-rectified images directly.
I didn’t perform any other steps after that. Should I ? For now, the downloaded images have negative values for a really small amount of pixels (also the negative values are really small like -0.01), maybe these are artefacts. In that case I can simply ignore them but I wanted to be sure that I didn’t miss some important step.
I’m part of the team who developed the processing chain.
Small values nearby zero are artefacts caused by accuracy issue, future version should overcome this problem. To solve this, you could just threashold the images at zero to get away with the negative values.
Sorry for the inconvenience and thanks a lot for your contribution.
Thanks a lot for your response ! A treshold should be ok then