The upper image shows the "single" feature selected and two nodes moved to the left to show a gap between its separate polygons (0 and 1). All I want to do is make this a single polygon, without that diagonal line where the gap is. The one suggestion did not help, or I just did not understand how to proceed. Diagonal line across dark poly in edit mode In QGIS, one polygon feature resulted from merger of several adjacent polygons. This one new polygon feature has a single line through it that I would like to eliminate. When hovering over individual nodes in edit mode a balloon displays polygon number, ring number, and vertex number and in this case the adjacent parts of the new polygon have polygon numbers 0 or 1. How do I combine the polygon parts of this new single polygon feature?

  • I should have mentioned I am doing this in QGIS. Jan 17, 2016 at 19:03
  • Could you add an image of your polygon to your post? It seems to be an issue that the "Digitizing Tool" plugin may be able to fix.
    – ArMoraer
    Jan 17, 2016 at 19:15

1 Answer 1


So, I suggest my cartographic approach to solving your problem and its name sounds like “wedge” or “insertion” (I'm not sure that Google will translate it correctly, though ...)

Initial data: two broken adjacent polygons.

1) Polygon into points, for which run the tool: Vector-> Geometry Processing-> Extract vertices;

2) Edit the points, as shown in my screenshot below, i.e. leave the adjacent points unchanged (4 - two each next to numbers 1 and 2);

enter image description here

3) Run the Vector-> Geometry-processing tool on points-> Delaunay Triangulation ...

see screenshot below;

enter image description here

4) Select the "wedge", copy it and paste in edit mode into your working layer;

see screenshot below; enter image description here

5) Combine the three parts of your polygons into one by running the Vector-> Geoprocessing-> Merge by Basis ... tool, replace it in the original layer

and everything seems to be ...

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