Finding Contiguous Counties?

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10-14-2014 07:57 PM
MatthewThomas3
New Contributor

I was given a list of over 200 US Counties ("home counties") that I need to produce a list of contiguous counties to each "home county."

 

Any suggestions how to produce such a list?

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3 Replies
DarrenWiens2
MVP Honored Contributor

The main tool you're looking for is Select Layer By Location, where overlap_type = (ideally) BOUNDARY_TOUCHES or (more realistically) WITHIN_A_DISTANCE (search_distance = 1m or so).

You can cycle through individual geometries using a Search or Update Cursor.

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curtvprice
MVP Esteemed Contributor

I suggest trying the Polygon To Line tool and using the LEFT_FID and RIGHT_FID fields to find your neighborhoods, for example, for the county with FID = 23, you can get a list of neighbors by listing all lines that have LEFT_FID and RIGHT_FID value of 23.

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SepheFox
Frequent Contributor

Hi Matthew, another option is to use the Get Adjacent Polygons from the ET Geowizards add-in (ET GeoWizards UserGuide ). The free version limits the number of features you can process at once, but you could always do them in batches, There are a ton of other useful functions of this add-in, so it's worth getting regardless.

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