Issue with gradient looking displacement result

Hello all,

I posted smilar question about an month ago having gradient looking displacement and still having the exact same issue:Something is not right with my result :( - #7 by ArkLade

Some of you commented it may be because of long time interval (few years) so I re-did everything with fresh data (12 day interval):


I am trying to see how well can InSAR pick up tornado damage. Many buildings were severly damaged and it was at Rolling Rork, MS, March 26, 2023. Below is updated workflow I did and some figures. Please help me what I might have done wrong.

I followed “TOPS Interferometry Tutorial” by Braun and Veci (2021) @ABraun to generate a surface displacement from a single image pair of SLC radar data.

Basic steps goes as follows:

  1. Download SLC pair
  2. Coregistration
  • S1 TOPS Split
  • Apply Orbit File
  • S-1 Back Geocoding
  1. Interferogram Formation
  2. S-1 TOPS Deburst
  3. Goldstein Phase Filtering
  4. Subset
  5. Phase Unwrapping
  • Export
  • Unwarrping
  • Import
  1. Phase to Displacement
  2. Range Doppler Terrain Correction
  3. Export as KMZ

I tried VV and VH on slighly different area.
I used default setting for Snaphu Export

Everything worked out well without an error, but the end result is just not right.







Unwrapped Phase

At the end, the both VV and VH displacement shows gradient pattern, which is just not right.



I was expecting to pick up some changes along the tornado path (vegitation and building damage ), but gradient looking displacement just don’t seem right.

Please help :frowning:

If there was no significant coherent ground movement and you removed the DEM-contribution, you are basically left with atmospheric/ionospheric artifacts that are always present to a degree. So this is a dead-end.

I would drop the Goldstein filter and experiment with different coherence window sizes. I would be a bit surprised if nothing shows up. Another thing to experiment with is different intensity-changes between pre- and post-event intensities, plus VV/VH ratios etc. Keep trying!

1 Like

My 5 cent - try changing DEFO to SMOOTH in unwrapping step. In some cases it works better.