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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Hello,
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