SNAPHU Unwrapping

Yes, sir. Is this the option in the red circle below

yes, but it has to be properly installed and executed (explained by @oana_hogoiu here: Snaphu Unwrapping Plugin)

Yes, sir, I have successfully installed the tool. But when I open the “UnwPhase *. hdr” file, it gives the following error message

Another thing,I got the "snaphu export"files according to the following figure1/2/3

Is there anything wrong?

for the unwrapping, you have to select the Phase_ifg_VV (the UnwPhase does not exist yet).

The pre-processing of the exported interferogram looks alright, also the file structure from your screenshot above.

Yes, you are right. I should enter Phase_ifg_VV file. In fact, what I input yesterday is also this file, only the output folder and the source product folder are the same. As a result, there is no change in the contents of the folder. Is this a software bug?

It should work actually. Alternatively, you can run snaphu from the command line as described here: Snaphu Export

I am currently preparing a revision of the TOPS InSAR tutorial, but this will still take a bit of time until it is finished.

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That’s great, I look forward to your completion soon.

You can download the tutorial now from here:

The other InSAR tutorials will also be revised in the next weeks:

I saw in the tutorial how to improve the extracted displacement results. Thank you again, Abraun, you are a very patient and serious person.

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Hi ABraun,

When I tried to use snaphu unwrapping, I am getting following error:

“Unexpected or abnormal exit of child process

Attached a screenshot. Can you please tell me what might be a problem and how to solve it?

Thank you!

I’m not sure - please try to increase the number of tiles in the config file and run again.


When I increase the number of tiles, I get error saying

“Tiles too small or overlap too large”.

Any suggestions?

Reduce the tile overlap to 50, it depends on the extents of the entire scene.

I am using number of rows and columns as 50. Tile overlap is now set to 100 (It wasn’t working when I had set the overlap to 50). Anyway, I believe I have figured out what was the problem. I will let you know the results.

50 rows and columns is too much, each individual tile should be considerably larger than the defined overlap:

the overlap must be selected in relation to the size of a single tile (can be calculated based on the total image size and the numbers of colums and rows):

If the overlap is the same size as a tile (or larger), snaphu will give this error message.



Thank you for all your help!

Another and older question that is arising still: I am getting weird lines in between the image (Image attached). I have tried everything I know, but the lines still appear. Our last discussion was to increase the tile numbers, but that does not help either, since I get the other error. What can I try now? Or can I just ignore those lines? Is it possible those lines appear due to presence of vegetation?

Yes, if the interferogram is of bad quality before the unwrapping, the tile will produce bad results which do not fit to the neighboring tiles.
Last you could try is to select SMOOTH instead of TOPO or DISP.

In your case, it doesn’t seem so bad, you could ignore it otherwise.

Alright. I will try all combinations and share the results here so everyone can see them. Thank you so much for your help!

Continuing the discussion from SNAPHU Unwrapping:


snaphu v1.4.2
usage: snaphu [options] infile linelength [options]
most common options:
-t use topography mode costs (default)
-d use deformation mode costs
-s use smooth-solution mode costs
-f read configuration parameters from file
-o write output to file
-a read amplitude data from file
-c read correlation data from file
-b perpendicular baseline (meters)
-i do initialization and exit
-l log runtime parameters to file
-v give verbose output
–mst use MST algorithm for initialization (default)
–mcf use MCF algorithm for initialization

type snaphu -h for a complete list of options

E:\SNAPHU\snaphu-v1.4.2_win64\bin>snaphu -f snaphu.conf Phase_ifg_VV_18Oct2014_01Jan2019.snaphu.img 17618

snaphu v1.4.2
27 parameters input from file snaphu.conf (84 lines total)
only one tile–disregarding multiprocessor option
Logging run-time parameters to file snaphu.log
Reading wrapped phase from file Phase_ifg_VV_18Oct2014_01Jan2019.snaphu.img
No weight file specified. Assuming uniform weights
Reading correlation data from file coh_IW2_VV_18Oct2014_01Jan2019.snaphu.img
Calculating deformation-mode cost parameters
Building range cost arrays
Building azimuth cost arrays
Initializing flows with MCF algorithm
Setting up data structures for cs2 MCF solver

it stucks at here for 1 day. im using i5 8400, 8gb ram running on windows 10. where did i get wrong?