calculate distance to the coast

6301
6
07-24-2012 10:27 AM
MiguelGomez
New Contributor
Hi all,

I have a shapefile with the regions boundary. I need to have a unique polygon that englobes all the regions and then I need to calculate the distance of the centroid of each region to this external boundary.

Does anyone knows how could I get this external boundary? I tried union, dissolve, aggregate but I have not been able to obtain it?

Once I have this external boundary I will just need to use the MNEAR function I guess.

Thanks
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6 Replies
LT
by
Occasional Contributor
Hi Miguel,

it sounds like you're looking for the concave hull of a set of polygons. 

I think you can trick the Buffer analysis tool into doing this for you (though there may be a more elegant way). 

Set the buffer distance to zero (or tiny if it won't accept a zero value) and then set the dissolve option as "ALL". 

I could be wrong about this, but I think it should work.  Try it out and let me know!

Cheers!
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ROMANFILOZOF
New Contributor III
You can also select all regions and use Union tool from Editor toolbar (not from toolbox). It can be useful if you are going to obtain the external boundary manually, not inside the model.
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
If your region polygons are connected (with common boundaries), Dissolve tool and Aggregate Polygons tool should work. If your region polygons are apart from each other, Aggregate Polygons tool should work with a distance. Could you describe in detail why they didn't work for your data or post a sample data?
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LT
by
Occasional Contributor
It seems like the Min bounding geometry tool might be relevant.

http://resources.arcgis.com/en/help/main/10.1/index.html#//00170000003q000000
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
My guess is that Miguel needs the enclosing polygons to follow the existing boundaries/coast. If that's the case, Minimum Bounding Geometry tool wouldn't be suitable.
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BruceNielsen
Regular Contributor
Try this workflow (untested):
-Feature to Point to create a point layer of the regions' centroids
-Dissolve to reduce the regions to a single polygon
-Polygon to Polyline to convert the single polygon from the previous step to a line representing the coast
-Near to determine the shortest distance from the centroids to the coast
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