On 31 March 2010 17:20, James Le Cuirot <ch...@aura-online.co.uk> wrote:
> Hello, > > I'm trying to turn the English (ceremonial) county boundaries from > OSM into MultiPolygons for use with PostGIS. The last step of the > process is... > > ST_Multi(ST_BuildArea(multi-line string)) > > ST_BuildArea returns NULL if the given lines do not form a Polygon or > MultiPolygon. This has worked fine for the majority of counties, even > MultiPolygons like Cumbria and Polygons with holes like Greater London. > However, some simple ones such as Kent and County Durham return NULL > here and I cannot figure out why. > > Here's the relation for Kent. > > http://api.openstreetmap.org/api/0.6/relation/88071/full > > The relationship analyzer says that the segment for Kent is closed. > > > http://betaplace.emaitie.de/webapps.relation-analyzer/analyze.jsp?relationId=88071 > > Am I misunderstanding what it means by closed? Looking at the map, it > appears to be closed. I have called the PostGIS functions ST_IsRing and > ST_IsClosed on the MultiLineString and they return false. Am I making a > bad assumption here? > > I'll be in a lot of trouble if I don't figure this out soon so some > help would be greatly appreciated. :) > You can use http://analyser.openstreetmap.fr By entering the relation, you can see that there are 3 self intersections on the coast. Emilie Laffray
_______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
