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I have a shapefile consisting of many polygons, and I would like to merge them when they touch each other (see red lines below).

enter image description here

I've been trying quite a few tools in ArcMap 10.7 such as Dissolve, but they don't seem to do what I want exactly. The Aggregate Polygons in the coverage toolbox pops up in my search, but I can't actually click the toolbox, perhaps I don't have access to this in ArcMap.

Alternatively, I'd be content if I could merge all polygons separated by <1000m (in the example picture, all 'cells' are 1 square kilometers, so in this case I would end up with one large polygon except for the two blocks in the top-left), which I tried to do with the Aggregate Polygon tool in the Cartography toolbox, but the output shapefile is identical to the input.

PolyGeo
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Beardedant
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  • there's no field by which to dissolve, so then it'd just dissolve everything into one massive polygon, regardless of the distance between them, if I'm not mistaken? – Beardedant Oct 18 '21 at 11:25
  • If you are also looking for an R solution then please ask about that in a separate question so that this one stays focused on ArcMap. – PolyGeo Oct 18 '21 at 11:34
  • Ok, thank you polygeo. Furthermore, BERA, thanks but I don't think dissolve is the way to go, as I am not dissolving based on anything in the attribute table, so when multi_part is false, the dissolve function does not actually do anything. – Beardedant Oct 18 '21 at 11:44

1 Answers1

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  1. Intersect the grid with itself, output type POINT
  2. Buffer the points with a small distance, I use 10 m for a 100 km grid
  3. Merge input grid with buffers
  4. Now the adjacent polygons are connected where the corners meet. Dissolve without multipart

enter image description here

BERA
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  • This works BERA, thanks a lot! What is the rationale behind this solution? Is it that Arcmap doesn't recognize polygons as adjacent when they share a single node so there is need for a somewhat larger buffer, or is there something else to it? – Beardedant Oct 18 '21 at 13:54
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    I dont know why, but ArcMap doesnt dissolve polygons only touching at one corner. – BERA Oct 20 '21 at 08:42