Hi ABraun,
When I tried to use snaphu unwrapping, I am getting following error:
“Unexpected or abnormal exit of child process
Abort”
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.
Hi!
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.
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Hi!
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:
E:\SNAPHU\snaphu-v1.4.2_win64\bin>snaphu
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?
the MCF solver takes the longest time for the last step. One day is pretty much though.
Hello,
I am new in Sentinel 1 processing. I am trying to determine land subsidence.
After phase unwrapping, I tired to convert the phase values into height but the results look strange to me.
I tried different snaphu export parameters, but the results are similar.
Difference between images is 24 days.
Can You tell me what I am making wrong? How can I improve my results?
if the quality of the interferogram is bad (as in your example) due to phase decorrelation, the unwrapping can introduce weird random patterns, because there are no fringes which can accurately be integrated. The larger the noisy areas in your product, the less accurate is the output of the unwrapping because neighboring pixels do not contain real phase gradients.
Is there a chance to select a more suitable image pair?
Hi, I have the same problem: Unexpected or abnormal exit of child process for unwrapping Sentinel-1. I did it with 20 also but it didn’t work for me. How did you overcome that problem? As you mentioned above that you tried it with 30 40 and so on but nothing works.
How may I calculate the overlap in this case? the size of a single tile if I the image was segmented into 10 tiles, would be 2595 columns and 419 rows.
Are you processing an entire Sentinel-1 image? The water in the middle will surely interrupt the unwrapping, so could it make sense to process each part of both sides separately.
Maybe you first show an image of the interferogram before unwrapping.
This is only three bursts of IW3 subswath, I believe the interferogram quality is diminished, no visible fringes but I Thought I could see if there’s any minimal deformation of this area through phase to displacement, based on the earthquake locations I received.
oh, sorry, then it’s allright. The interferogram looks alright regarding temporal decorrelation but the patterns probably have some atmospheric effects. So it would be good to compute some more pairs to check if the same patterns persist.
How does the unwrapped interferogram look like? If there are no sharp borders between the tiles, you shouldn’t worry too much about the tile size.
I can’t figure out any information form this unwrapped ifg, does it look like that because the tile size? or LOS displacement isn’t pronounced relative to the wavelength used. That color grade is only caused by the water body. I am sorry If I were asking a lot, my supervisor isn’t particularly specialized in interferometric processing so my results aren’t validated.
