[Qgis-user] concave hull/alpha shapes in QGIS

[Andreas Neumann]

 Hi,

 Postgis SVN (2.0) has a function called ST_ConcaveHull 
 (http://www.postgis.org/documentation/manual-svn/ST_ConcaveHull.html) - 
 it says it builds upon GEOS - (but probably only in geos-svn) - so there 
 should be some way to expose it in a future QGIS version.

 See also this thread:
 http://www.mail-archive.com/postgis-users@postgis.refractions.net/msg10785.html

 and Regina's examples:
 http://www.bostongis.com/postgis_concavehull.snippet

 I currently can't find the GEOS class/method that calculates it, but 
 since Postgis makes a reference to GEOS it has to be somewhere in GEOS.

 If you want to speed up the process, you can perhaps pay a developer to 
 include it.

 Andreas

 On Tue, 3 Jan 2012 11:36:28 +0800, maning sambale wrote:
> We have a nifty convex hull in ftools/vector plugin. I'm looking for
> ways to create concave hulls.  I have a set of csv points as a source
> to generate the polygon.  This is updated regularly by non-geo field
> workers.  Any workaround to generate concave hull in QGIS?
>
> Mappy new year to all!
>
> PS. I've seen old discussions in the qgis-dev list.

-- 
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 Andreas Neumann
 Böschacherstrasse 10A
 8624 Grüt (Gossau ZH)
 Switzerland