Issue with gradient looking displacement result

Microwave Toolbox
1

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):

S1A_IW_SLC__1SDV_20230316T000319_20230316T000346_047662_05B986_1A83.SAFE
S1A_IW_SLC__1SDV_20230328T000320_20230328T000347_047837_05BF6A_C649.SAFE

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

image
image1020Ă—427 39.9 KB

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

Intensity_VV

image
image1920Ă—459 160 KB

Phase_VV

image
image1920Ă—462 221 KB

Coherence_VV

image
image1920Ă—458 251 KB

Intensity_VH

image
image1920Ă—459 200 KB

Phase_VH

image
image1920Ă—466 271 KB

Coherence_VH

image
image1920Ă—461 266 KB

Unwrapped Phase

image
image1920Ă—461 24.3 KB

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

KMZ_VV

image
image1920Ă—1461 425 KB

KMZ_VH

image
image1920Ă—1392 288 KB

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:

2

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
3

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