topic Re: calculate distance to the coast in Geoprocessing Questions

calculate distance to the coast

MiguelGomez — Tue, 24 Jul 2012 17:27:49 GMT

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

Re: calculate distance to the coast

LT — Wed, 25 Jul 2012 00:02:29 GMT

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!

Re: calculate distance to the coast

ROMANFILOZOF — Wed, 25 Jul 2012 12:23:17 GMT

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.

Re: calculate distance to the coast

DanLee — Mon, 30 Jul 2012 20:27:18 GMT

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?

Re: calculate distance to the coast

LT — Wed, 01 Aug 2012 16:36:45 GMT

It seems like the Min bounding geometry tool might be relevant.

http://resources.arcgis.com/en/help/main/10.1/index.html#//00170000003q000000

Re: calculate distance to the coast

DanLee — Wed, 01 Aug 2012 16:56:55 GMT

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.

Re: calculate distance to the coast

BruceNielsen — Wed, 01 Aug 2012 17:50:08 GMT

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