[OSGeo-Discuss] open source polygon cluster aggregation algorithm?

[G. Allegri]

Thanks Andrea for the links. Yes, I think the problem is similar, in
fact I was also looking for concave hull and alpha shapes algoithms,
but the only open solution I've found is from CGAL [1] and... it's too
complex to extract and reimplement in my context (database procedural
programming).

IWe have implemented something very "rude":

1 - logically aggregate polyongs in clusters (given a certain distance)
2 - buffer each polygon mantaining the shape (not the usual buffer,
which make rounded artifacts)
3 - geometrical union
4 - shrink the result (unbuffer)

But I have the time for a long holiday waiting the end of the process :)

[1] http://www.cgal.org/Manual/last/doc_html/cgal_manual/Alpha_shapes_2/Chapter_main.html

2010/5/6 Andrea Aime <aaime at opengeo.org>:
> G. Allegri ha scritto:
>>
>> I'm looking for an algorithm to do polygon cluster aggregation,
>> similar to the ArcInfo "Aggregate Polygon" [1].
>> I know about GEOS "Cascaded Union", but I need two more features:
>>
>> 1 - clustering of polygons that fall within a a certain threshold
>> distance from each other
>> 2 - mantain orthogonality, i.e. the original angles/shapes
>
> I don't know of any such implementation, but it looks somewhat
> similar to the computation of a concave hull:
>
> http://ubicomp.algoritmi.uminho.pt/local/concavehull.html
> http://stackoverflow.com/questions/83593/is-there-an-efficient-algorithm-to-generate-a-2d-concave-hull
>
> Cheers
> Andrea
>
> --
> Andrea Aime
> OpenGeo - http://opengeo.org
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