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I know there is a lot of previous posts to this subject, but I simply cannot find the solution I am after in the other posts.

I have to following problem: I have two very extensive polygone layers, one contains the planning zones of a region and one contains the actual allotments. Now one allotment can be in two differen planning zones, which is where I would like to split the allotment-polygons in to separet allotment-splitters per planning zone.

In theory, this sounds like a very basic thing, but I just dont seem to find anything in QGIS that enables it. I have thousands of polygons in both layers, so logically the Editing Tools where you have to select each pair of polygons/polygon-line is not an option. I wouldn't mind turning the planning zones into a multi-line-object and working from there but also that way I couldnt find a solution. Am I overlooking the obvious?

In ArcGIS this would be rather easy if one had the necessary licences, which I don't plus I am not a python-programmer.

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    Wouldn't the Intersect tool in QGIS split your allotment polygons into their respective planning zones? – Joseph Nov 6 '15 at 10:58
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    @Joseph Yes it would, but what does one do when both the polygon layers are very large (such as the example above), and one or both of them has many errors/invalid geometries in it? The intersect function doesn't seem to handle these. I am also yet to find a tool/function to resolve hundreds of invalid geometries in a very large layer without crashing QGIS? – guestagain Nov 30 '16 at 5:52
  • @guestagain - You can use the Geometry Checker plugin or the GRASS tool v.clean to fix various types of invalid geometries. If the layers are indeed very large then I would suggest importing them to PostGIS and use the ST_Intersects function ;) – Joseph Nov 30 '16 at 10:33

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