Astrid, I had the same need for topological functions too. And I also did end up using ST_OrderingEquals/ST_ForceRHR. Having an ST_IsRHR or an ST_IsCCW (for single rings) or an ST_WindingFactor/ST_CrossProduct (for portions of a ring) would help performance. The last one would probably be the fastest for topological oriented code a ticket exists about it: http://trac.osgeo.org/postgis/ticket/1498
--strk; On Thu, Feb 23, 2012 at 09:07:53AM -0000, Astrid Emde wrote: > > On Thu, February 23, 2012 8:46 am, Astrid Emde wrote: > > Hello, > > > > > > I want to check whether my polygons follow the Right-Hand-Rule. Is there > > a function to do this? > > > > I found the function ST_ForceRHR [1] that will modify my polygons to > > follow the rule. But it would be nice to check first which polygons will be > > effected. > > > > Astrid > > > > > > [1] http://www.postgis.org/documentation/manual-1.5/ST_ForceRHR.html > > Hello, > > I used the following SQL to find out which polygons do not follow the RHR: > > Select gid, st_orderingEquals(the_geom, st_forceRHR(the_geom)) > from mytable > where st_orderingEquals(the_geom, st_forceRHR(the_geom)) = false; > > Astrid > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users -- ,------o-. | __/ | Delivering high quality PostGIS 2.0 ! | / 2.0 | http://strk.keybit.net - http://vizzuality.com `-o------' _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
