Problem with the final steps of interferometry

s1tbx Interferometry
#1

Hello everyone, Im working recently with interferometry, but I don’t understand something in the results, Could anyone help me? Thanks in advance

I chose two images from Mocoa Colombia (there was a landslide and it left 300 dead people on march 31)

My two images are 12 days apart and are 36.95m apart.

3.png1253×89 5.14 KB

I chose the polarisations VV

And this is my interferogram

5.png586×886 558 KB

And this is Mocoa (The white square) and the landslide’s zone… at North East from there (blue part)

6.png1210×845 2.22 MB

Apparently all is fine, so in my next step I unwrapped the Phase and create the displacement layer.

7.png1920×1040 423 KB

My problem with this image (the displacement) is: that is different from the interferograma and I see a degradation of colors, a scale not a patron, I assumed that mocoa should be seen or highlighted over the other parts, but it’s no clear for me.

And this is Mocoa:

8.png1063×848 1.12 MB

This is fine?? All the displacement is positive, yes I know the vegetation is too dense as well the rain (The images are 20 march and 1 april, the landslide occurred on March 31)

I try a new pair, again, the images are from the 20 march and the new image April 25
Here is the interferogram.

9.png1012×860 1.83 MB

Again in the displacement I see a color scale not a patron (I chose a bad gradient to remark this)

10.png744×868 795 KB

And this is the displacement of mocoa

11.png991×792 493 KB

So, I try again but with another orbit, a descent orbit. My images are from March 27 and April 08.

And this is the displacement

13.png1078×839 755 KB

Tell me what do you think? Is fine, there was a problem with the final step? Or maybe the color scale?

Thanks for your help.

Difference between vertical and LOS displacement
Phase unwrapping and low coherence
#2

If the displacement has such as strong ramping I believe that the orbit files are not exact enough so an overall trend is misguidingly superimposing the displacement patterns.

#3

Thanks Andreas for your answer.

So:

  • When I choose the orbits, I choose the same orbit and, in the overview The modeled coherence, the distance between the orbits It’s the recommended in the tutorials, guides and some comments that I read
  • When I see my interferogram, It’s apparently good. Im wrong?
  • All my interferograms have the same behavior, The interferogram is clear, but the displacement is different.

What do you recomend me? I should try with another zone?, maybe more distance between dates?

#4

hard to tell actually. What is the perpendicular baseline between your images?

#5

According to overview: -36.95

#6

that leaves quite litte space for errors in the orbit state vectors. Would be worth a try with a larger baseline but I can’t promise that the results will be better, as atmosphere and other factors still play a role. I had similar problems here: The Order of DEM Creating Steps

#7

Thanks again, I’ll Ckeck your post, maybe I get some hint