topic Re: Inexact Buffers in ArcGIS Pro Questions

Inexact Buffers

m3 — Wed, 24 May 2023 18:00:48 GMT

I'm using the buffer tool, on polygons, using 2.9.6, with the option to Exclude the input polygon from the buffer, with a dissolve by attribute, and nearly every buffer is inexact. It's leaving slivers inside the polygon. I tried setting a low tolerance, I tried geodesic and planar all same result.

Excuse my gaudy symbology.

How to I get this to work properly? There are only 90 polygons and I'm most of the way through editing them but this seems like kind of a big deal if buffers are being drawn incorrectly.

Re: Inexact Buffers

Robert_LeClair — Wed, 24 May 2023 20:25:29 GMT

I wonder if you do not have a geographic transformation applied? Right-click on your Map name in the Contents pane, click Properties, followed by Transformation. In the Transformation pane, is there a geographic transformation applied?

Re: Inexact Buffers

m3 — Wed, 24 May 2023 20:46:55 GMT

I do but removing it makes no difference.

I was also just testing in ArcMap without a transformation and get similar results, it seems to be related to the size of the buffer which in this case is 2 miles. Bringing down to 200 feet works but then I have to do a series of buffers to merge to get my 2 mile result. It's a specific use case (cartographic overlay in map series) but nonetheless, not an expected result.

Still it seems kind of a weird bug to have run up against after all these years.

Re: Inexact Buffers

m3 — Wed, 24 May 2023 21:11:25 GMT

Workaround 1, build Multiple Ring Buffers one small and one as big as you need, the larger buffer respects the polygon you're starting with. Query out the smaller buffer and you have your result.

Re: Inexact Buffers

MrRamonG — Thu, 25 May 2023 14:48:24 GMT

Have you tried running Check / Repair Geometry geoprocessing tools before buffering?

Re: Inexact Buffers

m3 — Thu, 25 May 2023 15:26:35 GMT

Well it's fine today, I rebooted 😐