Coregistration hangs at 1%

Again I am working with a group of students, who are supposed to examine (D)InSAR using SNAP and Sentinel-1 IW data. Now, when some of them are trying to coregister the original products downloaded from the ESA Copernicus SciHub, the coregistration hangs at 1% and will not proceed. Is that a known error? I have not yet been able to reproduce it myself.

I tried to disentangle the individual steps by not using S1 TOPS Coregistration but the individual modules (Apply Orbit, TOPS Split, Coregistration) one after the other instead. This also failed, unfortunately, as SNAP only issues an error that for S1 TOPS data the S1 TOPS Coregistration module MUST be used. This is really uncomfortable…

This is probably a misunderstanding: You can process the different steps one after another (and I recommend this over the TOPS Coregistration graph), but for Sentinel-1 you need BackGeocoding instead of the “classic” Coregistration module, followed by Enhanced Spectral Diversity (in case of several bursts).

Have you seen this tutorial? Sentinel-1 TOPS interferometry

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Awesome hint. But now, applying TOPS split hangs. :see_no_evil:

EDIT: Restarting made it work. I sometimes really don’t understand SNAP…

these processes are quite memory-consuming so restarting to release some RAM makes sense.

My PC has quite some RAM - still I am facing problems. After having disentangeld the coregistration steps, I feel:

  • the auto-download of the 3sec SRTM DEM seems to be some kind of bottleneck
  • since I got Java Heap Space and related errors, it seems that there are JAVA-related memory problems.

Only solutions for now: Use less Bursts in the Sub-Swath of interest to reduce data load, and use other DEM. It’s a pity that this is not handled in a more robust way.

Have you increased the jxmx parameter accordingly?

I always recommend SRTM 1Sec, the tiles are smaller and less prone to download errors

What is the jxmx parameter?

please have a look at this FAQ answer: I’m getting the error “Cannot construct DataBuffer”, “GC overhead limit exceeded” or “Java Heap Space”. What can I do?

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