topic Re: Merge polygons without creating multipart feature in ArcGIS Pro Questions

Merge polygons without creating multipart feature

AmyDunn — Tue, 06 Dec 2022 18:12:48 GMT

I am trying to merge polygons that share a boundary in ArcPro and end up with a multipart feature that I can then explode back into its separate polys. If I pull the polygons into ArcMap and merge them, it creates a single-part feature. When I try to explode in ArcMap, it doesn't warn me that there are no multipart features to explode, but it also doesn't separate the polygons either. It just recreates the same single-part poly with a new object ID. If I add that back into ArcPro, it will not let me explode because there's nothing to separate.

Any ideas about what is going on here? I would just like to merge polys into a single-part feature in ArcPro.

Re: Merge polygons without creating multipart feature

Robert_LeClair — Tue, 06 Dec 2022 18:32:36 GMT

What workflow/GP tool are you using? On the Edit core tab in ArcGIS Pro is the Modify Features command that opens up a pane of modification tools. In the Modify Features pane is the Merge command. You can read more about it here as well as it's options. I don't believe it creates multipart polygons.

Re: Merge polygons without creating multipart feature

AmyDunn — Tue, 06 Dec 2022 18:42:54 GMT

I am using the Merge tool on the Edit tab. It should create multipart polygons if my polygons didn't share a boundary, but they do and I'm still getting multipart features. I've run topology, and I don't have any gaps in my polygons and their boundaries are covered by the linework used to create them, so the vertices should match.

Re: Merge polygons without creating multipart feature

Scott_Harris — Tue, 06 Dec 2022 18:56:38 GMT

@AmyDunn Merge (Modify tool Edit tab) will create multipart polygons, even if they share a boundary when they have at least 1 Z value that doesn't match between them. The reasoning behind this was to prevent creating non-planar polygons, which are problematic for analysis. However, we are reconsidering this approach for a future release of the software.

Suggestions:

Set the Z values to match using Edit Vertices
Set them all to 0 using Edit Vertices
- See attached image
Or if Z values are not important to you, run Feature Class To Feature Class but set the 'Output has Z Values' to Disabled in the tool's environment setting. https://pro.arcgis.com/en/pro-app/latest/tool-reference/environment-settings/output-has-z-values.htm

Re: Merge polygons without creating multipart feature

DanLee — Tue, 06 Dec 2022 21:09:44 GMT

You can try Dissolve tool with "Create multipart features" option unchecked.

https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/dissolve.htm

Re: Merge polygons without creating multipart feature

AmyDunn — Tue, 06 Dec 2022 21:42:23 GMT

Z values aren't necessarily important to us right now, but they might be in the future. We are in the infancy of 3D mapping. I think the Z values the vertices had were the same anyway, but I also tried setting them to 0 and using Update Feature Z with a DTM, and it still wouldn't let me merge polys into a single-part feature. Merge only seems to work properly if I disable the z values entirely. I then enabled them again, and it merged correctly. As soon as I use Update Feature Z again, it does multipart so it doesn't seem like we can have Z values at all.

Re: Merge polygons without creating multipart feature

AmyDunn — Tue, 06 Dec 2022 22:03:56 GMT

This is a workaround where I would have to dissolve the polys using every attribute field, delete the old polys, and import the new dissolved poly. I should be able to merge polys with Z values, this used to work. Maybe a bug in 3.0.3? It's just another thing I have to go back to ArcMap for.