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

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?

Yes, but that tutorial is not about DIFFERENTIAL interferometry. DInSAR is used to find surface movement that is in the order of the wavelength (~5.5 cm for S1), typically over a longer time series. Your residual phase is likely related to both the quality of your reference DEM and the usual issues that influence interferometric phase plus the possible changes that you are interested in.

As I understand it from the resources I have read (e.g. ESA’s InSAR
Principles: Guideline for Interferometry and Interpretation) they explain
the differential interferogram as being the result of a subtraction of the
DEM’s contribution to the interferometric phase. I may be wrong but from
what i have read I think the that work I’ve done meets the definition of
differential interfrometry as there is no specification of requisite time
interval length, just that there is some time interval.

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An interferogram relates to both the DEM and terrain movement if latter is present. More than 2 scenes are needed to separate the two.

Hi mengdahl sorry I misread what you said. I understand that the interferogram on its own has phase contributions from both the topography and the surface displacement (if the latter is present). However, I also understand that you can remove topographic phase from a single interferogram by subtracting the synthetic interferogram generated from an independent DEM, and you only need one pair of SAR images to do this. Then I understand there is the three-pass method whereby a “topography only” interferogram is created and this is subtracted from the other two passes.

Your understanding is correct.

which is why 3- or more pass is called differential…

Differential mathematically is generally the common relation between many parameters, in this case more than two passes,

It would seem that different papers use “differential” to refer to different things then, because I have heard the term ‘differential’ being used as a blanket term to refer to interferometry in which the topographic phase has been removed (by either the two-pass or three-pass method.)

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I am working on differential interferometry for identifying ground subsidence. The trickiest part in the removal of the atmospheric noise. Many authors suggest to investigate the interferogram for finding any atmospheric-delay anomalies and potentially discard the severely affected interferograms

Hence, my question is how can we identify interferograms affected by atmospheric noise?
is there any specific pattern we try to identify?
is there any book or papers that shows examples of interferogmras that are affected by atmospheric noise?

thanks you