Thanks for the tips Alex, Andreas and Giovanni. Unfortunately, I need to "turnover" the maintenance of the data to a non-geo user, hence I need a workflow that can avoid R or postgis for now.
On Tue, Jan 3, 2012 at 6:13 PM, G. Allegri <[email protected]> wrote: > AFAICS ST_ConcaveHull is written in PL/PgSQL, and doesn't use GEOS methods > [1]. > I suppose it is based on the common "alpha shapes" [1] approach. > Martin has written something for JTS, but I think he hasn't release it > yet... > > giovanni > > [1] http://trac.osgeo.org/postgis/browser/trunk/postgis/postgis.sql.in.c#L4419 > [2] http://www.mpi-inf.mpg.de/~jgiesen/tch/sem06/Celikik.pdf > > > > 2012/1/3 Andreas Neumann <[email protected]> >> >> 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/[email protected]/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 >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/qgis-user > > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > -- cheers, maning ------------------------------------------------------ "Freedom is still the most radical idea of all" -N.Branden wiki: http://esambale.wikispaces.com/ blog: http://epsg4253.wordpress.com/ ------------------------------------------------------ _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
