SNAPHU Unwrapping

more information is required: What data are you using? Which steps did you apply?
Where is the snaphu export stored? What is the command you called?

Thanks ABraun.

I used SLC products of Sentinel-1 Interferometric Wide swath and the processing software is SNAP. After filtering the differential interferogram by using Goldstein phase filter, I unwrapped the filtered interferogram using snaphu code in linux (virtual machine). In SNAP, I applied “Snaphu Export” and the output files were stored in “shared folder” between windows and virtual machine.
Command line used in linux terminal is from “snaphu.conf” file.

When processing snaphu export, I used default parameters from SNAP.

That sounds right at first.
I wonder a bit about the file name. Is this how it occurs in the snaphu command?

I just copied the snaphu command from “snaphu_conf” file generated by “Snaphu Export” command in SNAP software and I pasted the copied snaphu command in snaphu processing.

All parameters for unwrapping phase in snaphu were generated when the snaphu export process in SNAP.

However, I am so sorry that all files from my processing were already deleted. So, I am difficult to recheck the history of the processing.

For the processing, I followed the tutorial of Sentinel-1 Stripmap interferometry as in this link

Dear Andreas Braun,

A attached file in this email is a screenshot of my snaphu process,
including snaphu command, result list and error messages. I hope this
picture giving clearer the problem.

Hopefully, I will have solution from you.


Best Regards,

your file is quite large with 24529 lines.
snaphu divides into smaller tiles which are processesd seperately. The tiles are stored in temporary files (which we could see above). They are mosaiced to a final result and then deleted. At some point, this tile processing failed.

So you can try to export a smaller subset so you won’t have too much tiles. If it works, increase the size of the subsed gradually.
You can also define the number of tiles in the snaphu config file.

The data is already subset SLC data (subswath IW2 only). Actually, in IW2 there are some bursts which may be able to make smaller data. Unfortunately, I don’t know to do it using SNAP.

you can open your Interferogram (after the Goldstein phase filter), zoom to a smaller location, right-click > “Spatial Subset from View”
Then, perform the snaphu export again.

I update this topic in order to ask if there is is description of the parameters in the Snahpu export dialog box and more specifically what is the meaning of initial method MCF/MST. The rest of the parameters are not clear too.
Please advise.
I’ve read the above posts and mentioned tutorials, but I’m still unable to find reasonable explanation.

there is a snaphu manual:

1 Like

Hello, I tried to unwrap the Fogo volcano data of the tutorial ( after having followed the tutorial, I unwrapped the phase using snaphu in vmware, and then phase to displacement) and I exported the image in Google Earth (also as done by @gabrielaquintana77 and posted in this topic time ago) . I got the same disposition of of the colors, but the scale results different. So is like, where expected blue is positive, my blue is negative. any idea?

Hi,@gabrielaquintana77,I have the same problem: Unexpected or abnormal exit of child process… for unwrapping terrasar-x images.How do you deal with it?Thanks

thanks,I will try ,Do you have meet the same questions?

Hi, yes, mine is working now.

Oh,I meet this problem for some time,but I don’t solve this problem with some ways.:joy:

Hi tangyin

Sorry for my late response, I did an subset for unwrapping and used tile of 20x20 for ALOS PALSAR 1 images…

Hi Cecilia

Sorry for my late response, I saw an step that is for after, don’t apply the terrain correct before the export for unwrapping…

It doesn’t matter,I only to ask you some solved ways about problems.

Dear all,
I’m new in SNAP, and I tried to process the co-seismic surface deformation of an earthquake in Taiwan on 2016/02/06 by sentinel-1A IW ascending images (20160202 and 20160214).
I have got the interferogram and the coherence map, but there is something wrong after unwrapping by SNAPHU.
I don’t know why there appeared value in the sea area. And the unwrapping result seems wrong. Could anyone help me to deal with this problem or give me some hints? Thank you!

The parameters I used for snaphu export is as follow:

Statistical-cost mode: DEFO
Initial method: MCF
Number of tile rows: 10
Number of tile columns: 10
Number of processors: 4
Row overlap: 0
Column overlap: 0
Tile cost threshold: 500