Concave Hull and/or Alpha Shapes geoprocessing tool

[NathanWarmerdam]

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.

[DrewFlater]

A dedicated Concave Hull or Alpha Shape geoprocessing tool has not been developed and is not planned at this time. 

The Aggregate Points tool can often be used to accomplish the generation of similar enclosing shapes. 

[KerstinGeitner]

Hi DanLee, 

thanks for your reply. I have an additional question. Is there a way to make a lot of concave hull areas from one point file based on an attribute? I can not find an option to use an attribute to group points in the Aggregate points tool. 

I have a file with a lot of sampling stations that are being sampled every year. Since they are taken by boat it is not possible to do it at the exact same point, so we would like to calculate the area that is covered but each of the stations. I can convert the point file to a polygon file, but the picture I get is a bit blurred since I just want a outline around the stations and the stations are not necessarily in the order to make that possible, even though I could sort them by the year they are sampled. 

Thanks in advance.

[DanLee]

Hi KerstinGeitner,

I am not clear about your description "I can convert the point file to a polygon file, but the picture I get is a bit blurred ..." Can you show a screenshot?

Currently Aggregate Points doesn't have the Aggregate Field parameter as Aggregate Polygons tool does.  You can create a very small polygon around each point using Buffer tool, which carries over input attributes. Then use Aggregate Polygons tool with a desired Aggregation Distance and your station ID/attribute as Aggregate Field to obtain the needed polygons.

Would that work for you?

[KerstinGeitner]

Hi @DanLee, 

Thank you so much. I made a very small buffer around my stations and then used the aggregate polygon tool. The resulting polygons are just what I needed to get to the next step in the research. 

Again, thank you very much for your help, I really appreciate it. 

Cheers

Kerstin

[Jennifer_Andrews]

Has anyone found a simple and accurate way to produce concave hull/alpha shape polygons?  I've spent a couple years trying to do this and in the wee hours of the morning, I finally got it. I ran it on my 100,000 points and the script accurately created concave hulls around these points that I told it to group by a particular attribute. If anyone else has a working method for this, I'd like to see it and compare!  

FYI, I have zero training/education/experience in programming or code writing so I was very excited to see it run.

Jenn