[Qgis-user] concave hull/alpha shapes in QGIS
Andreas Neumann
a.neumann at carto.net
Tue Jan 3 01:50:59 PST 2012
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.
--
--
Andreas Neumann
Böschacherstrasse 10A
8624 Grüt (Gossau ZH)
Switzerland
More information about the Qgis-user
mailing list