Snaphu unwrapping not working

Microwave Toolbox Problem Reports
1

Dear all,

the SNAPHU plugin does not work properly and gives a wrong unwrapped phase output.
I am trying to create a DEM from Sentinel 1 Data, following the ESA tutorial at: https://step.esa.int/docs/tutorials/S1TBX%20DEM%20generation%20with%20Sentinel-1%20IW%20Tutorial.pdf.
I am using the same 2 SAR images.

I can run the Snaphu Export, Snaphu Unwrapping and Snaphu Import, however the final unwrapped output is absolutely wrong. Here the comparison between the interferogram (which worked well), the unwrapped (wrong) and the phase to elevation output (wrong again):

wrapped+unwrapped+elevation
wrapped+unwrapped+elevation1920Ă—1039 223 KB

In the following the histograms for the phase to elevation and unwrapped outputs:

Histogram_elevation
Histogram_elevation955Ă—561 34.5 KB

Histogram_unwrapped
Histogram_unwrapped955Ă—561 25.3 KB

I have just installed the latest version of SNAP (10.0.0) and of SNAPHU (v2.0.4) and I am using Windows 11. In the following the snaphu-unwrapping configuration:

snaphu_bundlebinaries
snaphu_variables

image
image516Ă—538 10.1 KB

My data is not located in the same directory but in:
D:….….….….….….….….…\Results
each … represents a folder. I have also been trying to use the data inside the same folder where the snaphu is installed but nothing changes.

I had the same issue reprocessing data that I processed a couple of years ago, to obtain deformation maps following a strong earthquake in Croatia.

Someone has any idea or knows how to solve this issue?

2

@lveci or @jun_lu could you have a look at this?

3

A JIRA ticket ([SNAP-3879] - JIRA) has been created to track the issue. We will look into it. Thank you.

4

We have tried the procedure given in the tutorial with SNAP 11 and got the correct Snaphu unwrapping result. One thing you can pay attention to is the “USERPROFILE” setting in the snaphu-unwrapping configuration (see image below). It should be the folder which is generated by Snaphu Export. Another thing is that you should select the .hdr file (not .img file) in “Read-Unwrapped-Phase” in Snaphu Import UI. If you still have trouble with SNAP 10, try download SNAP 11 which should work for you.

image
image825Ă—523 19.8 KB

1 Like
5

Dear Jun_lu,
thank you very much for the support. I will try again on Monday in the hope it is going to work.

6

Dear Jun Lu,
thank you very much for your valuable help. I did as you suggested and everything works fine.
The only issue now is that, after changing the USEPROFILE folder, the SNAPHU status turns orange. I am still able to run the unwrapping, but when it is finished I have to cancel the process. However, following this, I can import the unwrapped file with no problems.
I hope it will not be a problem, wich does not seem to be.