TOPSAR-Split subswath resets to IW1 in Graph Builder on Validate/Run (SNAP 13)

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1

Hi all,

I’m having a strange issue with a Sentinel-1 DInSAR workflow in SNAP and would appreciate some help.

Environment

  • SNAP Desktop: 13.0.0 (fresh reinstall)

  • OS: Windows 11 Pro (25H2), 64-bit (OS build 26200.7462)

  • Data: Sentinel-1 IW SLC (dual-pol VV/VH)

  • Goal: DInSAR over a small AOI using IW3 only (master and slave both IW3)

Issue

In Graph Builder I have a typical DInSAR chain with two TOPSAR-Split nodes (one for master, one for slave).

In the graph XML, both TOPSAR-Split nodes are explicitly set to IW3, e.g.:

<node id="TOPSAR-Split">
  <operator>TOPSAR-Split</operator>
  <parameters>
    <subswath>IW3</subswath>
    <selectedPolarisations>VV</selectedPolarisations>
    <firstBurstIndex>4</firstBurstIndex>
    <lastBurstIndex>7</lastBurstIndex>
  </parameters>
</node>

<node id="TOPSAR-Split(2)">
  <operator>TOPSAR-Split</operator>
  <parameters>
    <subswath>IW3</subswath>
    <selectedPolarisations>VV</selectedPolarisations>
    <firstBurstIndex>4</firstBurstIndex>
    <lastBurstIndex>7</lastBurstIndex>
  </parameters>
</node>

When I load this graph in SNAP and open Graph Builder:

  • Both TOPSAR-Split nodes initially show IW3 in the GUI, as expected.

  • As soon as I press Validate, the subswath dropdown(s) switch back to IW1.

  • If I manually change them back to IW3 and press Run, they flip back to IW1 again.

So it looks like the UI is overriding the subswath parameter back to a default (IW1), despite the XML being correct.

What I’ve already tried

  • Completely reinstalled SNAP 13.0.0

  • Downloaded a fresh pair of S1A IW SLC products (IW1–IW3 present)

  • Edited the XML by hand to ensure both <subswath> entries are IW3 (no IW1 anywhere)

  • Confirmed I’m loading exactly this XML file (no duplicate graphs)

  • I don’t think I’m hitting a GC/memory issue (no obvious “GC overhead exceeded” warning), but I can check logs if you tell me where best to look

Has anyone seen Validate/Run forcing TOPSAR-Split back to IW1 like this (especially in SNAP 13)? Any ideas what could be causing it, or a recommended workaround?

Thanks,
Nick

2

The issue has also been reported in another topic, and Jira ticket SNAP-4109 has been created to track it.

3

It’s a bit clunky, but for now, if you just execute each step separatedly, it works. Fist Split, then Apply Orbit File.

Outside of a graph, just tool by tool individually per image.

1 Like
4

I’ll give that a go. Any idea on when there’ll be a patch?

5

The fix is included in the 13.0.2 module update. Please update SNAP to apply it.

1 Like
6

Excellent news. Thank you @diana_harosa

7

When 13.0.2 is expected to be published to the SNAP Plugin Manager? Currently it isn’t ther although I can see it on Github.

8

Microwave 13.0.2 is already available. To update SNAP, go to Help → Check for Updates :

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9

Thats great @diana_harosa. Thank you to you and the team for fixing the bug.

Nick Kinsella