Problem in Snaphu Import section


Hi all

I done the added of the metadata and, its DEM!


Left, DEM from Sentinel 1. Right, DEM SRTM.


I have generated unwrapped phase data using Sentinel1 Tool Box and Snaphu, but i have problem for importing data (merging unwrapped data with phase data) using sanphu import tool. I appreciated if you let me know how did you solve this problem.


In the snaphu import you specify the original wrapped phase product that you used to export to snaphu and then you also include the unwrapped phase band (Unw… .hdr) output from snaphu.


Yes, I did. But I get following error:

First I have imported unwrapped phase (UnwPhase_ifg_srp_IW1_VV_31Dec2015_17Feb2016.snaphu.img) file and converted to Unwrapped_phase.dim file. Then I used my filtered wrapped phase file (srp_ifgs_W1.dim) for snaup importing. This file I have used SNAPHU Export step. Thanks


Why convert to dimap? in the Snaphu import graph, use the Unw .hdr file


Thanks. It works now !! when I use *.hrd file for importing. Here is unwrapped phase of one burst.

I am trying to generate DEM of he coastal area of Bangladesh. Area almost flat and some area below see level. I have a DEM of this area (50 m x 50 m) generated from topographic survey. I would like to use this DEM as an external DEM. I appreciate if you give me some idea to create a high resolution DEM from this unwrapped_phase and my existing DEM. Thanks again.


Use the unwrapped phase with the phase to elevation operator and use
your dem as an external dem. This should tie the relative heights to
some points on your dem.


Thanks. I will do this. I have a question: When I have to mask out the sea - before or after phase to elevation step?


Masking can help before unwrapping.


before unwrapping with SANPHU?


Yes, there is no point to unwrap in the sea.


Thanks. I appreciate.


I’ve tried to follow the help of snaphu import, which says:

Specifically the import graph performs the following:
Reads the “phase-only” interferometric product constructed during Snaphu Data Export step.
Reads the “unwrapped-phase-only” product ingested in the Toolbox using Generic Binary Readers. Note that due to restrictions of the framework currently it is not possible to chain the generic binary reader in the graph, and hence it is not possible to ingest unwrapped data directly into the Toolbox. This has to be done outside Snaphu Import graph.
Arranges the metadata and merges the bands of the source product into a unwrapped phase product. In this step metadata and bands are arranged in a compatible form for further InSAR processing.
Writes “unwrapped phase product” in the standard DIMAP format.

So I’ve put the Phase.hdr file for the “Read-Phase” operator, and the UnwPhase.hdr file for the “Read-Unwrapper-Phase” operator. With this setting the following error message is returned:
Error: [NodeId: SnaphuImport] SnaphuImportOp requires at least one product with InSAR metadata.

So I tried also to follow your suggestion, providing as input of Read-Phase operator the wrapped phase product that I used to export to snaphu, but it still doesn’t work :cry:
The error that is returned this time is:
org.esa.snap.core.gpf.OperatorException at org.esa.snap.core.gpf.graph.GraphProcessor$GPFImagingListener.errorOccurred( at at at at at com.bc.ceres.glevel.MultiLevelImage.getData( at org.esa.snap.core.gpf.internal.OperatorContext.getSourceTile( at org.esa.snap.core.gpf.internal.OperatorContext.getSourceTile( at org.esa.snap.core.gpf.internal.OperatorImage.computeRect( at at at at at

Could you please help me on this?

P.S.: I’ve perfomed such tests with gpt tool on both SNAP 3 and SNAP 4, and my OS is CentOS release 6.5 (Final)


In the first Read, put the product you used just before doing the snaphu export. This has the metadata needed.


Dear Luis,

thank you for the reply.

If I’ve correctly understood your last suggestion, it is the same operation that I’ve already described in the second part of my previous post, i.e. I’ve used in the first read operator the wrapped phase product which I used as input on snaphu export operator, and I get an error (listed in the bottom of the previous post).

Please let me know if I’m wrong and If I’ve to use the import operator in a different way

Thank you very much in advance


I am unable to get unwrapedphase out put img image;I got corresponding hdr file. because of this I am not able to import snapu for meta data matching. would you any body have same problem in Sentinel1A interferometry processing?


Dear gabrielaquintana77,

Can you please help?? How u added metadata because i am getting error

Thank You


Hi Prashant

In 2- Read-Unwrapped-Phase.

The SNAPHU Import have the goal to construct Interferometric product that will contain unwrapped phase band, and the metadata of the source interferometric product.


Thank you :slight_smile: @gabrielaquintana77


Thanks for responses.And Mehdi I’ll try that!