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This question already has an answer here:

I work with QGIS 2.10.1 on Windows 7 (x64). I have dissolved polygons from an attribute value and the polygons geometries being not perfectly joined together, I get some 'garbage' nodes I need to delete. I have tried to edit the layer and using nodes tool, selecting and deleting the nodes, but it seems impossible to do (nodes are not deleted at all!). Any idea on how to process this kind of clean-up?

EDIT : you can download the shapefile here for testing.

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marked as duplicate by nmtoken, whyzar, Oto Kaláb, PolyGeo Jul 23 '17 at 22:00

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  • 2
    Those are called sliver polygons, this might help you find more information. – bugmenot123 Sep 1 '15 at 8:41
  • Thanks! This helps. But my problem remains: I can't select the sliver polygons in order to merge them with the bigger ones (using new tool Vector > Geoprocessing tools > Eliminate sliver polygons). – wiltomap Sep 1 '15 at 9:07
  • Try to use the Node Tool and remove the vertices of the sliver polygons. – wittich Sep 1 '15 at 9:50
  • I wrote in my post that this tool did not work... – wiltomap Sep 1 '15 at 11:21
  • Perhaps you could upload and share your shapefile so that others could test it? – Joseph Nov 10 '15 at 16:34
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+50

I tested your shapefile and used GRASS algorithm v.clean from the Processing Toolbox. I applied snap as the cleaning tool and used a threshold of 5 which seemed to have cleaned up your shapefile a fair bit.

This is your original shapefile loaded:

Original shapefile

This is it cleaned using GRASS (notice the little yellow polygon that was dissolved originally but is now separate):

Cleaned shapefile

Just to show the difference in nodes, here was the original:

Original nodes

And here it is after being cleaned:

Cleaned nodes

Hope this helps!

  • 1
    Many thanks @Joseph! This worked perfectly... I'm not used to GRASS functions, I should deep in those in the coming times. – wiltomap Nov 12 '15 at 7:56
  • @wiltomap - Awesome buddy, glad it worked for you too and it wasn't just a fluke for me! Yup, GRASS has some pretty powerful tools so check them out :) – Joseph Nov 12 '15 at 10:43

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