I am using QGIS 2.14.0 and I need to fix some topology errors. Problem is that when I move polygon node to the another node they seem to snap correctly. However, when I move that node again, in too many cases snapped nodes don't move together, and of course topology testing will fail. Is there any way around this problem?

I attached few images below. I've tried to turn off and on "Enable snapping on intersection" and "Avoid intersections". I've also experimented with different snapping tolerances with no success.

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1 Answer 1


Well I just figured it out by myself a few minutes after posting this question. The solution is to set 'on-the-fly' transformation CRS so that it matches CRS of the shapefile. I assume it has something to do with transformation and floating point inaccuracy.

  • try using 10 pixels instead of map units in the snapping dialog box Commented Apr 4, 2016 at 13:40
  • @Gerardo Jimenez That was my initial setting, but it didn't work either. Commented Apr 5, 2016 at 7:08

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