Interpretation of displacement map along a coastal area

Hello everyone,

I have produced a displacement map along a coastal area (looking for detecting coastal erosion) in Scotland and try to understand if the displacement map make sense to me. It is estimated that this specific location undergoes an erosion of 4-6cm per year. Looking at the image below, we see some subsidence occurred along the coast (- sign) and also some uplift (+ sign). The color in blue that shows an uplift, I am trying to understand, does this uplift make sense along the coast? What might have caused this uplift? Can that be rocks movements or maybe ground water re-charge due to heavy rainfall?

One more thing, I have read a few posts and on-line tutorials about the + and - signs in the displacement map. According to my understanding, - sing denotes subsidence (away from satellite) and +sign denotes uplift (towards the satellite).
According to the website below, it sates the opposite. It confused me a bit
I would appreciate any help on this matter.

Thank you

you should also consider including the coherence. Only areas with coherence > 0.4 can be used. Maybe the blue ones are of low coherence and therefore invalid.
You can define a valid pixel expression as suggested here:

Besides that, there can still be atmospheric disturbances left which could affect your fringes.
If you want to go sure, analyze more image pairs and compare if the patterns of subsidence are always more or less the same. If not, chances are high that some of them are just random noise.

thanks for your quick answer.
Do you know by any chance is there is any open source tool that can remove the atmospheric component from InSAR?

I don’t know any.

removing the atmospheric component in SAR is the tricky part unfortunately.

the only solution I can think of would be using multiple images to level out temporal variations.

Yes, I agree
thanks for your help


I think PS analysis could help you to answer more precisely.

Yes, that’s the way to go