I've been having issues with polygons getting deleted and re-created in this layer, and also with polygons not merging the way I would expect. I thought I had everything fixed-- my topology check comes back clean (no gaps or overlaps) and when I fill the layer with a solid color there are no gaps-- but now my layers are behaving very strangely, and I'm worried I might not have fixed everything and I don't know what sanity check to use aside from my topology.

For instance, this polygon was originally split in two along a vertical line: enter image description here

I merged it:

enter image description here

but sometimes when I zoom out, it looks like it is still in 2 pieces.

When I export it to a KML file and open it in Google Earth, it still seems to be in 2 pieces:

enter image description here

I feel like I'm pretty experienced with ArcMap but I have no idea where to start with trying to fix this!

I am using ArcGIS 10.6.1 on Windows 7.

  • How exactly are you splitting and merging this polygon?
    – Hornbydd
    Commented Nov 26, 2018 at 23:14
  • Do you mind to upload that polygon somewhere.
    – FelixIP
    Commented Nov 27, 2018 at 2:53
  • What happens if you try to select one half of the "split" polygon?
    – Andy
    Commented Nov 27, 2018 at 3:33
  • I assume you also ran a Repair Geometry on your layer. If you add the layer into a new project from wherever it is stored does it still act strangely? Over the years I've found every once in awhile an ArcMap project acts weirdly, as if it is caching information somewhere for its display.
    – John
    Commented Nov 27, 2018 at 13:35
  • @Hornbydd I'm using the cut tool in the Editor, and then merging them with the merge tool from the editor as well. It's worked fine with all the other shapefiles that I've used it.
    – ale19
    Commented Nov 28, 2018 at 16:37

1 Answer 1


The zoom effect is strange, but the merge tool only combines datasets, you will get an edge between them. To remove that edge you need the dissolve tool http://pro.arcgis.com/en/pro-app/tool-reference/data-management/dissolve.htm

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