topic Re: overlapping polygons in State & Local Government Questions

overlapping polygons

KenDonald — Mon, 19 Aug 2019 12:52:39 GMT

I have a polygon shapefile in desktop 10.7 in which some of the polygons overlap partly or totally. Is there a simple way to create records of these 'shared' areas which retain the attributes of both?

The best I have been able to come up with is a Union geoproccess using the same layer twice. The problem with this is that is created 4 records for the shared area. If the overlapping polygons were called A and B the 4 shared areas would include records with fields A+A, B+B, A+B and B+A. By adding a field, calculating the area of each polygon, and identifying the polygons with the same area I can identify the duplicate records and delete 3 of the 4, but hope to find a simpler solution.

The attachment show what I hope to achieve. If I start with 2 polygons called A and B I want to end up with 3, the unshared part of A, the unshared part of B, and the shared area.

Re: overlapping polygons

JoeBorgione — Mon, 19 Aug 2019 13:57:59 GMT

Is it a shapefile or a feature class? If the latter, I suggest creating a topology with a 'must not overlap' rule and look for violations

Re: overlapping polygons

KenDonald — Tue, 20 Aug 2019 14:26:43 GMT

Thanks Joe, but I only have a basic license and from what I can see I can't create topologies. I found some interesting new stuff trying though.

Re: overlapping polygons

JoeBorgione — Tue, 20 Aug 2019 14:53:00 GMT

Yes, that makes it tough. If two polygons overlap, would you consider merging one into the other? Or would you want to keep them separate and create a third polygon of just the intersection of the two?

Re: overlapping polygons

JoshuaBixby — Tue, 20 Aug 2019 15:36:33 GMT

Do you want the original polygons to remain intact, or do you want the overlap area to be removed from the original polygons and a new polygon created from just the overlap?

Re: overlapping polygons

KenDonald — Wed, 21 Aug 2019 07:40:52 GMT

The latter - if I start with 2 polygons which overlap I want to end up with 3 polygons which don't, but retain the data of the original polygons.

Re: overlapping polygons

AshokVanam1 — Wed, 30 Oct 2019 00:24:01 GMT

Hi Ken,

have you tried to find the intersection of two polygons? This should result in a single polygon of overlapping part of A and B polygons.

Regards

Ashok

Esri Australia