Null values in polygon intersection results

Question

I am using 2.8.3-Wien to analyse two polygon layers, one with many more polygons (layer A) than the second. (layer B)

I need to know which of the polygons in A overlap with each of the polygons in B, as a new layer, with every overlap as a new polygon.

I've tried using Intersect, but I get a great big table with only half the data in it. It has all the polygons, labelled with data from B, but the fields which should say which polygon from A has overlapped is all null.

I had managed to get Intersect working with layers with less polygons, so is this just a processing power problem, or is there some other tool within QGIS that I can use?

I've not been using QGIS for long, so it's entirely possible I'm missing something really basic but vital.

Possible duplicate of Selecting features within polygon from another layer using QGIS? — Oto Kaláb, May 10 '17 at 14:10
Not a duplicate, as either I'm using Intersect incorrectly, or it isn't working. — Poi, May 10 '17 at 15:03
Sorry, you are right, I misunderstand it. I thought that you want select overlapping polygons (select by location), now I get it that you want create layer with overlaps (intersect). — Oto Kaláb, May 11 '17 at 08:05

score 3 · Answer 1 · answered May 10 '17 at 18:29

3

I have diagnosed the problem. Shared field names!

Once I had created unique field names across both layers, the intersect worked perfectly.

answered May 10 '17 at 18:29

Poi

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Null values in polygon intersection results

1 Answers1