When using QGIS 2.x I have used Topology checker to find gaps between polygons, crossing lines and duplicated points/vertex. I also liked that it shoved a list of errors where I could zoom into each error to fix it.

In version 3.0.3 I see that topology checker is running automatically and tells me at once when I put two point on top of each other.

How can I make it check for gaps? Is there somewhere to set the topology rules?

1 Answer 1


The answer maybe late, but for QGIS 3.4.1, which I expect it was available in QGIS 3.0.3, you can define topological rule to check for gaps using the following steps:

  • Go to Vector -> Topology Checker
  • A panel will be opened

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  • Click on the Configure in the red box above to define a rule
  • Select the layer you want to check its topology -> Under Rule select Must not have gaps -> Click on Add Rule -> Click OK:

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  • The Configuration window will be like this:

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  • Click on Validate all to to check if there is a gap in the layer

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  • Click on the row and it will highlight the gap location

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  • 3
    I noticed in QGIS 3.6, the topology plugin is installed but not loaded by default, you need to go into installed plugins and tick it.
    – Damien
    Jun 14, 2019 at 1:29
  • For some reason, this plugin does not find gaps. I created a trial polygon layer with bad geometry, overlaps, and gaps. It only found bad geometry and overlaps. Does not flag gaps. Is there a tolerance I have to set? Using QGIS 3.8.2
    – Sharad
    Aug 30, 2019 at 13:15

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