Collocation fails for mountain region

snap
#1

I am trying to collocate a coherence image with a sentinel-2 image, the region that I am trying to collocate is in the High mountain Asia. For some reason, there is a major noticeable shift in the final result. My steps were as follows :

  1. Create a coregistered stack
  2. Calculate coherence using the Coregistration tool
  3. Subtract flat-earth phase and subtract the topographic phase by using external DEM (ALOS world 3D)
  4. Perform collocation using the collocation tool.

Result :-

RGB of the sentinel data

image
image1028×900 157 KB

collocation for the coherence image
image
image1028×900 267 KB

#2

The Collocation tool will work only if your two images cover the same area, that is your AOI must appear complete in the two images to be collocated,

#3

In this case it is covered, yet there is an issue.

#4

Could you show the SAR image?

#5

The SAR image is

image
image896×834 239 KB

The Optical image is

image
image1173×759 144 KB

#6

Well, it is difficult to say. I understand your master is the OLCI scene. Check the accuracy of the geocoding in OLCI and S1. In SNAP S3TBX preferences check the box use “per-pixel geocoding instead of tie-points”. I am not sure how your coherence band is accurate, you could also check that,