Interferogram Interpretation in Urban Areas

I’ve been using Sentinel-1 images to generate interferograms to monitor deformation (subsidence). I’ve noticed that the urban areas tend to show a few “color blobs”, rather than fringes that I’m seeing south of the area. I know that the cross-like artifacts are a Goldstein filtering issue, but I wanted to know how these “color blobs” differ from fringes and how they should be interpreted?

To generate the interferogram, I followed the recipe below.

  1. S-1 Tops Co-registeration (Default Settings)
  2. Interferogram Formation (Default settings)
  3. S-1 Tops Deburst (Default settings)
  4. Topographic Phase Removal (Default settings)
  5. Multi-looking ( changed the range looks to 6)
  6. Goldstein Filtering ( Default settings)
  7. Range Doppler TC (Default)

could you somehow mark the “color blobs” in the image? :slight_smile: I’m not quite sure what you mean.

This attached picture is south of the original I posted but I believe it better demonstrates the “color blob”

I guess what I’m asking is how to interpret the colors in the highlighted areas compared to the fringes I’m seeing elsewhere

technically, each color cycle represents surface displacement between both images at the scale of the wavelength. But there is always the risk of atmospheric contributions to the phase.

Maybe this topic also help you: Some explanations about concepts of fringes of interferogram and coherence

Or do you mean something different?

so what would it mean if an area is just showing up as a solid color, like the purple over the hourma area?

is this due to higher coherence in an urban area? What does it mean if it’s not a complete color cycle?

Areas without phase noise indicate high coherence. Areas with litte color variation indicate little change between both images
If you want to draw conclusions about subsidence, you should run the Phase to Displacement operator on the unwrapped phase. It converts the radian phase cycle into metric units.

Solid colour would mean that the coherence level is good and:

  • The DEM and orbits you used are very good.
  • There is no displacement.
  • The atmosphere is quiet at that scale.

Thanks for the feedback!

Hello, sir @ABraun and other scholars here, Please, what do you think of this messy interferogram? How can I interpret it? The study area covers the recent Turkey-Syria quakes. Thank you.