ERS-Topographic Phase removal-SNAP

why are the sea areas masked out in your images? Did you alread apply Range Doppler Terrain correction?

I used DEM Assisted Coregistration and I checked the option
Mask out areas with no elevation.

ah, I see…

I followed your steps (except for the masking of the water areas) and can reproduce the error:
I don’t know if its the data. I remember making interferometry with ERS data as well.

So I will try processing a different ERS dataset of another area and see if
I have the same error. What parameters did you use here, in cross correlation
(number of GCPs, window sizes, coherence threshold) and in interferogram
formation did you use independent window sizes ?

Hi All, thank you for reporting the problem. We have looked into the problem and indeed it is a bug that affects ERS and ENVISAT products. Now the problem has been fixed. Hopefully the fix can be in the new release.

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I look forward for the new release. Thank you for the information!

PS InSAR Analysis Possible with SNAP?
Plz Inform me immidiately.
ASVirk

Hello drosoula,
thank you for reporting your problem. I have been going through the same problem. I have closely followed your discussion in this forum. Do you have any idea about when we would possibly receive the new release?

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The release is now planned for the end of the month, maybe early August.

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Dear Marco Peters,
I am very much obliged to you for your quick and considerate reply.
Thank you so much.
Regards,
Prashant

You can pre-process your InSAR stack with SNAP and then export in into PSI-processing with the StaMPS-software.

Hi @junlu, @marpet,
I am working with ERS2 and ENVISAT images.
With ERS, I report the same error as the mentioned above during the “Topo Phase Removal” process. Now, i know that I would have to wait until the new release… ok!
On the other hand, I do not get any error messages when I apply the Topo Phase Removal to interferograms that derive from ENVISAT pairs… I would have to remake the “Topo Phase Removal” process to those ENVISAT interferograms due to the bug that you have looked?
Thank you very much!

Can you try adding the polarisation to band names (e.g. i_ to i_VV_) for both master and slave? This can be done by right clicking on the band name and selecting Properties. After making this change, then you can apply the Topo Phase Removal and see if you still have the problem.

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Hi @junlu,
I have renamed the bands as you said, and the problem has desapeared.
Thank you very much.

I also tried this solution and it works!Thank you!

Hi ABraun,
I am facing a problem with the topographic phase removal. In one pair, there is no difference when I am removing the topographic phase, and without removing it. In the second pair, there is a small difference and in the third pair, the difference is very prominent. I did not understand why it is so. I have also used different DEMS with these three pairs, but all are giving the same result. Will it be a problem if I want to generate a deformation map?

topographic phase.pdf (229.7 KB)

It depends on the baseline - with zero baseline the topography has no effect at all.

Thank you for your reply. The perpendicular baseline of these 3 pairs are -19.35, -66.85, and -122.62 respectively and are of the same area. Can I reduce the baseline errors and how to do that? Can I do that in SNAP? I have taken flooded images and need to find changes in water level. Only one image in the pair 1 was before flood.

how please ??

A new tutorial was published - maybe interesting to anyone who stumbles upon this topic: InSAR Displacement mapping with ERS data