Extensive areas in interferogram with unexpectedly high interferometric phase - the result of atmospheric artefacts?

Hi all. I have been creating interferograms to look at the activity of various large landslides in the southern French Alps. In many of these interferograms there are wide areas with unexpectedly high interferometric phase, for example this interferogram created for the 12-day period 08.07.16 - 20.07.16:

The processing was done with batch processing using the graph below:

My question is, could these likely erroneous phase differences across wide areas be the result of an error in my batch processing chain or are they more likely the result of the atmospheric phase screen? If the latter, can such an image be used (following interferogram averaging, for instance) or should it be discarded?

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Would you please to take at this

Also what about the Unwrapping step?

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Hi smithalas

I have a question: Which is the value of coherence for this pair?

Hi falahfakri, thanks for your reply and for redirecting me to your previous comment. Are you suggesting that I should during the back-geocoding tick the box that says “Output deramp and demod phase”? Also, I had originally included the S1 range and azimuth shifts but I was told that these operations are not intended for TOPS data. I did not do the export the SNAPHU step yet.

Hi Gabriela, sorry I am quite new to this so I don’t know how to check what the coherence is. Where can I find this?


Well, if you is working with SNAP you can to get the coherence band of two forms:

1.- Interferometric… Products… Interferogram Formation (selecting Include Coherence Estimation in Processing Parameters)
2.- Interferometric… Products… Coherence Estimation

Oh I see what you mean. Here are the coherence and interferometric phase bands for 08.07.16 - 20.07.16:

This look good, please do you can to calculate the mean for coherence band???

Sure, is this done through the “Band maths” operator?

Yes, is one way, and through of Analysis…Statistics

Ok, the mean coherence is 0.404

I think that you can works with this value of coherence, but is necessary document you, in the link, you can to get information about coherence and atmospheric artifacts

Please if I am wrong, someone that correct me!!! :flushed:

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This looks fantastic, thank you - I will have a look.

Yes, indeed I’d suggest that for the reason you could find out here


This step it is already exist within ESD,

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Assuming the topo-removal step has worked correctly the remaining phase still contains phase-terms related to atmospheric artefacts, errors in the DEM, and terrain movement. It would be instructive to see the InSAR-phase before the topo-removal step.


Also, what is the meaning of “unexpected high interferometric phase”? What is your expectation, and on what is it based? I can understand that you may find “unexpected difference in terrain height”, i.e. comparing to an existing DEM, after phase unwrapping. Is there any particular area where the i-phase is unexpectedly high?


By that I just meant that I doubt that there has been as much ground
displacement in the 12-day period as shown in this image’s interferometric
phase, which is why I asked if maybe this was due to atmospheric artefacts.

Thank you for your suggestions and clarification falahfakhri!

An interferogram generated from 2 SLC scenes relates to terrain height (i.e. the DEM), not to changes in terrain height. For that you need to combine more than 2 scenes (i.e. perform differential interferometry).

I am doing differential interferometry using 2 SLC scenes to create the interferogram and then using an external DEM to remove the topographic phase contribution, as instructed in the S1 TOPS tutorial. Does this make sense?