error message "There are invalid geometries in layer parcels."

QGIS QGIS US
1

I’m going through Kurt Menke’s Discover QGIS 3.x by Kurt Menke, 2019 edition.

I’m on Exercise 3, Creating Geospatial Data, and I can’t complete step 16 on page 68.

I’ve begun digitizing a map of Albuquerque, New Mexico. When I select “Fill all rings in selected polygons with new features” (pulled down from the Fill All Rings with New Features tool). When I click on figure SU-1, I get the error message “There are invalid geometries in layer parcels.”

What does this error message mean, and how can I fix the problem, and proceed with the “entering the attributes for the new O-1 polygon (id=2, zonecode=O-1)”?

I’d like to complete this, otherwise, I won’t be able to complete the next two pages of this exercise.

Thanks for your help, sincerely, J.C. (John Clifford) Armbruster, jcarmbruster@earthlink.net

2

It sounds like there are topology errors In your copy of the parcels data set. Run the check geometry tool.

On Fri, Aug 1, 2025, 4:21 PM jcarmbruster via OSGeo Discourse <noreply@discourse.osgeo.org> wrote:

jcarmbruster
August 1

I’m going through Kurt Menke’s Discover QGIS 3.x by Kurt Menke, 2019 edition.

I’m on Exercise 3, Creating Geospatial Data, and I can’t complete step 16 on page 68.

I’ve begun digitizing a map of Albuquerque, New Mexico. When I select “Fill all rings in selected polygons with new features” (pulled down from the Fill All Rings with New Features tool). When I click on figure SU-1, I get the error message “There are invalid geometries in layer parcels.”

What does this error message mean, and how can I fix the problem, and proceed with the “entering the attributes for the new O-1 polygon (id=2, zonecode=O-1)”?

I’d like to complete this, otherwise, I won’t be able to complete the next two pages of this exercise.

Thanks for your help, sincerely, J.C. (John Clifford) Armbruster, jcarmbruster@earthlink.net

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3

This is most likely a case of a polygon boundary crossing itself, which may happen at a corner where two vertices were added very close to each other. Or if you were using snapping, two points were added at the exact same location.

In the QGIS processing toolbox, there are two tools that will help:

  • Check validity – this will analyze a layer and output three temporary layers (valid polygons, invalid polygons, and points showing exactly where the errors occur)
  • Fix geometries – this will automatically fix any invalid geometries (this usually does exactly what you want, although it might not work in some situations where the error is more complicated)

You can just run the 2nd tool to fix the geometries, but checking the validity first will help you to understand what the issues are, so you can get better at creating valid polygons when digitizing.

Good luck!

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