Sorry for bothering you again.
I have tried to use different Initial method and Tile cost threshold in SNAPHU export, the unwrapping results still seem have the same problem.
The result I obtained is as follow:
hm, seems that nothing changed. I saw that these patchy areas are not covered in the interferogram at first. So theoretically you can just go on and have them removed in the Range Doppler Terrain Correction as a last step.
The left one is the DInSAR result and the right one is the result after apply phase to displacement and Range Doppler Terrain Correction as the last step.
I don’t understand why interferometric rings mainly appear in the red block area but we got a large displacement in the yellow block area in the right-hand side figure.
Is there anything I misunderstanding? Thank you for your help!!
Did your interferogram look alright after Topographic Phase Removal? It could be that a DEM of bad quality introduced the errors and they are already present before the unwrapping step. In this case, choose a different DEM for the topographic phase removal.
As it can be seen in one of your screenshots above, coherence is low in some areas. In this regions the DInSAR result is not valdid, especially at the edges of your image where unwrapping errors potentially add up. So try to apply a mask on your image: Right click on your Phase band > Properties and add ‘coh_IW1_VV... > 0.3’ in the field for valid pixel expression. This removes all areas with low coherence from your interferogram. Of course you need the full name of the coherence band. If the result looks better, you can add the coherence band in the band maths operator to your displacement band as well and use it there for masking.
But first you will have to get a proper interferogram. I agree that with this lines it cannot be used. How many bursts did you use by the way? could these lines be potential borders between the bursts which are merged at the TOPS Deburst step?
actually debursting after making the interferogram is the right step. But that also means that topographic phase removal is not the error but rather debursting the interferogram causes these stripes.
Have you tried a different image pair? Can’t think of a reason why there are stripes after debursting.
You can’t really mask out areas with low coherence but you can define them as invalid so you can concentrate on the areas which provide valid interferometric information.
I am using snaphu in order to unwrap some interferograms and see the deformation due to a seism. It is working but as you can see some fringes are not unwrapped, I tried to modify the different parameters (DEFO or SMOOTH, MST or MCF) but no differencies. Someone has an idea how to unwrapped these interferograms ?
I have tried other image pair for analysis (different time and area). I didn’t get the discontinuous lines after deburst step. But the unwrapping result still looks strange.
This is another case, I want to detect the creep motion of landslide in mountain area.
The left one is the DInSAR result after filtering, and the right one is the unwrapping result.
I have tried the following thing, but nothing changed of the unwrapping result:
Changed the DEM used for topographic phase removed with SRTM(3sec) and ASTER (1sec)
Changed the initial method - MCF and MST
Changed the tiles row and column from10 to 30 and the tile cost threshold to 1000
Chose different time and area image pair to test
And I also tried to masking by coherence > 0.4. But it seems no help?!
Actually, I will analysis slow-move landslide with PSInSAR method.
I found some interference information of settlements in mountain areas by DInSAR with sentinel images. So, I want to check the move motion by interferograms in different time. I’m not sure will it work or not, because we couldn’t get good interferogram in mountain areas with other C-band data. In addition to that, I also tried to process the co-seismic surface deformation and land subsidence by DInSAR method.
Could you tell me how to check the topographic phase removed correctly or not? If there exist some problem in this step, how to solve it?
I have followed the steps in “Sentinel-1 TOPSAR Interferometry” tutorial from ESA website. And I have tried many times with different SAR images and parameters, but I couldn’t find the key to solve this error …