Error unwrapping with the snaphu plugin

[eleeeel]

Hi all

I’m trying to follow the steps of the Sentinel-1 Toolbox TOPS Interferometry Tutorial:

S1TBX%20TOPSAR%20Interferometry%20with%20Sentinel-1%20Tutorial_v2.pdf

My problem is that it doesn’t seem to be working properly the generation of the unwrapped phase…

I have read the following posts:

Snaphu import problem

I think copy all these results you have to other drive and repeat the process of exporting and unwrapping and then import again,

SNAPHU Unwrapping

Hello all, I have followed these steps of the ESA tutorial to extract an interferogram for my area of interest. It’s my goal now to unwrap it, so that I can calculate the water level of a lake. I have never worked with satellite imagery before, so I would like to find a simple way to do that. I already have Matlab in my computer installed, but I still can’t understand how can I import there my unwrapped data in order to use the algorithm below: Should I carry on trying to get results with …

But the problem is that I have no .img file generated when I’m going to import the unwrapped phase.

I show my the steps, one by one:

I think that unwrapping was “too fast”, according to the Figure 23 (“Progress of the unwrapping”) of the tutorial.

Thanks in advance!!

[ABraun]

can you please check in the snaphu folder if the img file of the unwrapped phase was created?
To import the unwrapped phase into SNAP, you need both

• UnwPHase_ifg_VV_04AUg2020_23Jul2020.snaphu.hdr
• UnwPHase_ifg_VV_04AUg2020_23Jul2020.snaphu.img

The second is produced by SNAPHU. If it was not created, try executing snaphu from the command line instead from inside SNAP.

[eleeeel]

Hi Andreas

I checked and img file of the unwrapped phase was not created… only the hdr file.
These are the steps I’m following:

[ABraun]

Exporting alone is not enough. You have to run snaphu as well, as it is described in the tutorial, either from the command line or within SNAP
This will create the img file.

[eleeeel]

Thank you for your patience Andreas:

I managed to unwrapp and then, import the unwrapped phase, but now the problem is that:

The Phase to Desplacement tool doesn’t work.
This is the log file:
messages.log (163.2 KB)

It would seem that the error concerns to the projection, but I don´t know how to do:

[ABraun]

“Source product should not be map projected” already says it.

Terrain correction should be the very last step. Please follow the steps in the order as they are presented in the tutorial.

[eleeeel]

The problem (I think) is that I was checking the option “save Wrapped interferogram in the target product”. I solved it but now I have this message:

[Mohitvermaji51]

thank you for sharing with us

[eleeeel]

Maybe it needs to be the metadata from the original product and not the subset product because its size would be different. Given that I don’t know how to set the metadata, I will try to do the unwrapping process with original the image (without subset).

[ABraun]

@eleeeel

Maybe it needs to be the metadata from the original product and not the subset product because its size would be different.

exactly this is done with the SNAPHU import. You select the reference product (interferogram) in SNAP, also the unwrapped interferogram in the second.
The product should therefore no longer be named “UnwPhase”, but again starting with “subset_S1A…”. Please stick to the order of the tutorial.

[Mohitvermaji51]

I discovered that sometime snaphu can stop to unwrap, and seems to be linked with a bad coregistration or low coherence product