I am trying to simplify a polygon layer of parliamentary constituencies in Kenya using SimplyPy in QGIS and appear to be getting an erroneous result.

The method is working for most of the polygons but there are 10 or so which are disappearing in the final result. Interestingly, the polygons which are disappearing all have similar object IDs (from 280-290 - there are 290 altogether) and so it could be due to SimpliPy having a limit of only 280 polygons at once... (I hope not!). Before and after below:

enter image description here

I have included a link to my shapefile here.

My question is: Why are my polygons disappearing in the final output?

  • Have you tried running this on the same shapefile with only 280 polygons? Are you encountering the issue with other shapefiles with more than 280 polygons?
    – juturna
    Commented Aug 17, 2017 at 15:31
  • Hi - thanks for the reply. I do not have any other shapefiles with >280 polygons nor have I tried to reduce the number of polygons in this one. I will try not and edit this post on the outcome.
    – tda
    Commented Aug 18, 2017 at 8:44
  • @TaylorDay - Could you provide a screenshot of the options you used for the plugin please?
    – Joseph
    Commented Aug 18, 2017 at 11:08
  • Hi - I could provide a screenshot... but I tried numerous tolerance parameters and snap precisions to no avail. Options I selected were: Douglas-Peucker; first to last (any tolerance gave the same output); prevent shape removal ticked; use topology ticked (any snap precision gave the same output). Latest version 0.52.
    – tda
    Commented Aug 18, 2017 at 12:55


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