Bug report #15962

Updated by Giovanni Manghi about 3 years ago

I found some strange issues when running Intersect & Union from the Vector>>GeoProcessing Menu. I've reproduced this on QGIS 2.14.4 as well as 2.18.0 on Windows 8

I observed, that for some datasets, the results of Overlay analysis are strange, and not at all what you expect. I've attached two sample datasets which show this.

1)Sample 1 consists of 2 shapefiles and the results of Union & Intersection. As you can see from the Image, this is not the results one should be getting.!Intersect1!

2)Sample 2 consists of the data where I saw the issue for the first time. When you Union 'dissolved.shp' & 'wards.shp' you expect to get an layer with unioned shapes of all features , but you get some kind of data which is closer to a 'Difference'; But if you closely look, there are more artifacts present in the data.

This might be related to Bugs #14846 & #8456 ,bu I'm not sure.

It should also be noted that the input shapefiles were created in QGIS itself, so if there is any issue with incorrect Geometries, there might be a bug in the module which created these shapefiles as well.