topic Re: Finer Scale Convex Hull in Geoprocessing Questions

Finer Scale Convex Hull

DarrenWiens2 — Mon, 16 May 2011 18:25:06 GMT

Is there a way to shorten the search distance for creating a minimum convex hull polygon from line features? Basically, I want a polygon surrounding the line features in picture 1, but the best I can do so far is what's in picture 2. It would be nice if I could say, "only look this far ahead and make a polygon edge from those lines it has encountered".

Re: Finer Scale Convex Hull

DanPatterson_Retired — Mon, 16 May 2011 19:13:44 GMT

What you are describing is a variant of the concave hull. There is one implementation here:
http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=AA23C5C6-1422-2418-8811-1365253A756A
There are other ways of generating concave hulls, but this may be a start.

Re: Finer Scale Convex Hull

Anonymous User — Mon, 16 May 2011 19:13:47 GMT

Original User: jscheirer

Like a concave hull?

Re: Finer Scale Convex Hull

DarrenWiens2 — Mon, 16 May 2011 19:41:31 GMT

Yes, thank you. I ran the tool, and it looks like that would be a good starting point (it would need some work to clean up). I ended up finding a boundary polygon afterall, but it's nice to know this exists.

Re: Finer Scale Convex Hull

Anonymous User — Tue, 17 May 2011 19:12:51 GMT

Original User: bruce_harold

Darren

Please also see the attached tool, with thanks to the University of Minho in Portugal for the idea.
It requires point input data (use Feature Vertices to Point GP tool to make this) and is not as fast as the other referenced tool, but may be closer to what you need.

Regards

Re: Finer Scale Convex Hull

DanLee — Wed, 18 May 2011 15:10:20 GMT

If you are using ArcGIS 10, you can do the following:
- Run the Feature Vertices To Points with the ALL option to convert your lines into points.
- Run the Aggregate Points Tool to combine the points into a polygon with an aggregation distance you specify.
- If you get undesired holes in the polygon, run Eliminate Polygon Part tool to remove them.

Hope this is a good alternative for you.

Thanks.

Re: Finer Scale Convex Hull

Anonymous User — Wed, 18 May 2011 15:23:11 GMT

Original User: dkwiens

Thanks all. That's exactly what I was looking for Dan. I should probably explore the cartography toolbox a bit more.

Re: Finer Scale Convex Hull

DanLee — Wed, 18 May 2011 15:37:38 GMT

Really glad to hear! 🙂

Re: Finer Scale Convex Hull

DanPatterson_Retired — Wed, 18 May 2011 16:37:21 GMT

I am sure all of the ArcInfo license holders are ecstatic...but don't get too excited for the ArcView of ArcEditor holders...(please ESRI...qualify license levels)