I have two polygon layers, A and B, both in the same projection. I am trying to create a new layer, C, which is all polygons in A less the areas where polygons in A and polygons in B intersect.
I am using v2.14.1 - Essen.
I have checked the geometries are valid in both layers, removed duplicate notes and dealt with crossovers. Running the validity query in QGIS shows that there are no errors.
I ran the 'difference' geoprocessing tool, and, for the most part, this works. C is created, which includes all A polygons, less those areas that overlapped with B polygons.
However, there is one polygon in A which, for some reason, does not seem to work as part of the process. When I create C, the entirety of this polygon has disappeared, despite there only being a small overlap with several polygons in B.
Can anyone point me towards a reason why this might be?
(Apologies for A, B and C, but thought I would generalise the question)