Displacement miscalculation

Microwave Toolbox Interferometry
#1

Hi!!!

I have generated an interferogram according to the TOPSAR tutorial. The images that I’ve used are these:
S1A_IW_SLC__1SDV_20150901T162225_20150901T162253_007524_00A64C_FC74
S1A_IW_SLC__1SDV_20150913T162226_20150913T162254_007699_00AB02_ABD8
I have unwrapped the images using SNAPHU and then calculated the vertical displacement and applied range doppler terrain correction. The problem is that the displacement values at the colour bar don’t agree with the stage data that I have. Furthermore, I notice that there is a displacement value for every pixel in the image, which doesn’t make sense to me. I am working in a small subset that covers an area of 8 km^2.

What could there be wrong? Is there any extra filter that I should apply or any setting that I should change?

pic1.png1920×997 461 KB

I would really appreciate any kind ideas!

#2

the vertical displacement usually is just a relative measure. So you should then level it to your ground by identifying a pixel where you expect no change and subtract this value from your image.

You could also consider to mask out areas with low coherence.

Both was described in this topic:

Different results in the study of land subsidence using the Sentinel-1 satellite image
#3

I haven’t seen this so far, thank you very very much! :slight_smile:

#4

Even if your processing is “perfect” the InSAR-phase still contains the atmospheric contribution on top of the deformation-related signal.