SNAPHU Unwrapping

Microwave Toolbox Interferometry
141

Iveci,
There is a training session (SAR interferometry) scheduled soon?

1 Like
143

Hello all,

I have followed these steps of the ESA tutorial to extract an interferogram for my area of interest. Itā€™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 canā€™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 Matlab or is it maybe simpler to dual boot Linux in my Windows PC and work with SNAPHU?
I am sorry if my question is silly, but Iā€™ve been reading loads of things for days and I canā€™t get to a conclusionā€¦:frowning:

144

Hi,

Some hints you could find in SAR-EDU_Tutorial_Focussing_Matlab.pdf from https://saredu.dlr.de/

145

But you could implement the unwrapping step by using snaphu under linux or unix machine,

146

thank you for replying. I have worked so far with a pair of slc images in SNAP and I have an interferogram as a result. I want to unwrap it through matlab but I canā€™t figure out how to import the SNAP data in to Matlab.

147

Hi,
I donā€™t think it is done before, but Iā€™m keen to know how as well if you have any results

148

ok, good to know! thanks

149

Hi,
An other way to speedup the unwrapping is to increase the number of processors in the configuration file for snaphu, In my case it was set to 4 by default but when i tried to unwrapped on a 24 core work station using Snaphu/CygWin I increased the number of processors to 20 in the config file and it worked like a dream. You can set it to a higher number in SNAP while exporting to snaphu. You would only be restricted by the physical number of cores on you machine

Regards

150

Hi Alex,

Were you able to address your problem with the incorrect unwrapped phase output (using IW)? I am facing a similar problem and am curious if you were able to troubleshoot this. Any info would be appreciated!

151

@katjensen @Alex
The SM mode is used by the sentinel 1 satellite in exceptional cases of emergency and the data in this mode is rarely available. Where IW mode is available for interferometry at global scale

On the previous question of wrong unwrapped phase, you have to use the correct wrapped phase (the one you used as a source for snaphu export) in combination of the unwrapped phase during your Snaphu import step.

Hope this help you

Thanks

152

Hi,

I have set vmware configuration as follows, but it is taking 4 hours to execute phase unwraping.

could some one let me know how to configure to get complete snaphu unwrapping quickly within one hour.

I am confused to set ā€œNo. Of processors and No.of cores per processorā€ in vmware

My system configuration is

Processor: Core i7-6700 CPU @ 3.4 GHZ
RAM : 8 GB

vmware.jpg1915Ɨ1003 305 KB

153
1 Like
154

Hi ABraun, Thanks for your review.

looking further for your support to get clear many issues with open source softwareā€™s.

after unwrapping, while snaphu import iā€™am getting error in

SNAP as "NodeId: 3-SnaphuImportOp requires at least one product with InSAR metadata. "

and in

NEST 5.1 as ā€œJava.lang.NullPointer exceptionā€.

could you let know the solution if you come across this issueā€¦

NEST.jpg609Ɨ511 41.4 KB
SNAP.jpg831Ɨ641 54.7 KB

155

what is your input for
1-Read-Phase
2-Read-Unwrapped-Phase
3-SnaphuImport?

Did you successfully run snaphu?

Have a look at the help menu of this module. It is explained what is needed at which step.

156

I have successfully run the snaphu.

  1. Read-1: Phase HDR
  2. Read-2: Unwrapped Phase HDR

after entering these values then error is coming.

  1. Snaphu Import: I havenā€™t checked the checkbox.

even if the checkbox checked there is no change in error messageā€¦

How to add Insar metadataā€¦here in with SNAP.

157

For read-1, use the whole last interferogram product before exporting for snaphu. This will probably be a dimap product which you applied topo phase removal or Goldstein phase filtering.

1 Like
158

Hi Luis Veci,

Thanks for your valuable reviewā€¦

I have given inputs as you said. but I am getting the following error ā€œcan not construct data bufferā€.

import.jpg818Ɨ630 53.5 KB

I tried again it is storing the both input files in the result folder, without showing any progress.

could you let me know for furtherā€¦

159

Hello all,

I am trying to reproduce the InSAR scene of 2016 Kumamoto Earthquake as the one shown in http://insarap.org/. Iā€™ve used the same product sources (Ascending track 156: 2016-04-08 / 2016-04-20, Perp. baseline -67.3m), only change Iā€™ve made is cropping them to some parts of subswath that covers the earthquake.

askforumf_ss.jpg1920Ɨ1030 613 KB

The resulted wrapped product I got is quite similar to theirs. However, after doing unwrapping and using phase-to-displacement function, the result is quite strange. The blue blob above the fault (black line, approximately) should be other color as it is a right-lateral earthquake. Thus, I guess I might do something wrong with the unwrapping process.

Iā€™ve used all the default values when processing in S1TBX and snaphu image provided in the tutorial.
Is there any suggestion to improve the unwrapped result?

Regards,

160

Hello, I got this error using snaphu: ā€œtiles too small or overlap for given inputā€. Donā€™t you know what it means? I did diferrent region yesterday and it was OK. Could my interferogram be too small? That is nonsence right? :smiley:

161

Hi,

I tried to unwrap phase using snaphu, and I got the following error messages:

Assembling tiles
Canā€™t open file snaphu_tiles_10980/tmptile_UnwPhase_ifg_VV_26Nov2016_20Dec2016.snaphu.img_0_0.2453_regions
Abort

How to solve this problem?
Thanks.