On Wed, Apr 16, 2008 at 11:28:32PM +0200, Martijn van Exel wrote: > Hi all, > > The only exceptions apparently being that self-intersecting polygons > are allowed in OSM. He found a couple hundred in the Netherlands' OSM > data. > > Is this something that is being considered? I guess it would be easy > to check for self-intersection upon adding / changing a polygon.
"Easy"? I don't think that this is true... determining self-intersection is hard. Also, note that many many 'GIS' implementations also allow self-intersecting polygons. Shapefiles, GML, etc. etc. and the tools around them all 'allow' this insofar as there is typically no technological limitation preventing it. It seems likely that the netherlands 'self intersecting polygons' are simply the result of poorly curated coastline imports or something similar: in general, self-intersecting polygons aren't useful for anything I can think of in OSM, but preventing it is hard, and not really within the spirit of *most* simple geographic data tools. Regards, -- Christopher Schmidt MetaCarta _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
