Concave Hull and/or Alpha Shapes geoprocessing tool

08-26-2010 03:44 PM
Status: Closed
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New Contributor III

While I know that there are places to find concave hull and/or alpha shape algorithms, it seems like the biggest/best/most pervasive GIS company in the world would have this tool or a set of tools to do this kind of operation.  My suggestion is to add a concave hull tool as well as an alpha shapes tool for creating a bounding polygon around a set of features.


If you have ArcInfo, try the Aggregate Points/Polygons tools in the cartography>generalization toolset.

Also, please keep a watch on the geoprocessing gallery in September 🙂

 Hey Bruce,
Thanks for the tip, that looks useful but I think you need to spruce up the doc a little bit.  What methodology is used?  The second usage tip implies that there are some limitations.  A bit more discussion would be helpful.
So what should I expect in the geoprocessing gallery?  Cool script tool that works at 9.3??  🙂
Hi Nathan

Thanks for the feedback on the GP tools.

The item we hope to put on the GP gallery is an arcpy script tool, easily backported to use arcgisscripting.  We're just going through the permissions process.


so long.... so little movement....

at least an interim solution until basic algorithms are implemented... I know... low market share.

Concave Hulls ... for arcgis Pro 


Still dreaming of an out-of-the box tool from ESRI.


I think it'd be great to see this tool get added.


In the Minimum Boundary Geometric tool, there are 5 different options for geometry type. It would be really useful for me if I could choose "Concave Hull" as an option. 

I am working with Lidar data that are points, showing the area of a mussel bank. In order to be able to work further with the data, eg. calculate the area, calculate area of different depth strata, I need to be able to delimit the area closer than what is possible with the convex hull option or others. It is possible to do so with python or add-on products or other GIS software. I think it should be possible to do so in the standard ArcGIS Pro interface. 

In the attached map, you can see the points in different blue color groups, it is the black line, that delimits the area polygon, I would like to have e tool for. 

by Esri Regular Contributor

Concave hull is different from the geometry types produced by Minimum Bounding Geometry (MBG).  Each geometry type from MBG is uniquely defined. But a concave hull is not unique and depends on a tolerance that controls how much the shape concaves.

What you need may be done by Aggregate Points tool. The larger the aggregation distance is, the more generalized shape you get.

This tool may produce polygons with holes. If you don't want the holes, you can use Eliminate Polygon Part to get rid of them.



Thank you so much for your reply, DanLee. The Aggregate Points tool was just what I needed. I only searched for concave hull in the tools, I never would have guessed to search for this name. It produces (largely) the same results as ET Geowizards for ArcGIS and QGIS Concave tools, when the same threshold values are used. Plus ArcGIS Pro handles the huge amount of points (+300,000) way better and faster. 

by Esri Regular Contributor

Hi  KerstinGeitner,

Sorry for my delayed reply; I was on vacation last week.  🙂

I am glad Aggregate Points tool worked for you. There are various terms people use to describe this functionality, including concave hull, alpha-shape, etc. You can actually search by concave hull in the Geoprocessing pane to find the tool down a bit in the list.  We can still improve the search keywords so people can find it more easily.

Thanks for your feedback.  I really appreciate your comments about the good  performance of the tool.  Cheers!