> Drawing this as one outer ring touching itself in one point seems to > be invalid for JTS (self-intersection) while drawing an inner ring > touching outer ring at one point is OK for JTS.
I don't know JTS, but as you describe it, it implements validity as define by the OGC for this case. See here, the "banana polygon" : http://workshops.opengeo.org/postgis-intro/validity.html But it shouldn't be forgotten that multipolygons in OSM are not OGC multipolygons. The sentence used on the wiki since the beginning was : "multipolygon relation can be used to build multipolygons in compliance with the OGC" In the case http://wiki.openstreetmap.org/wiki/Relation:multipolygon/validity#F_- _Polygon_self_touching_on_one_node A valid OGC can still be constructed as you described it (one outer and one inner touching on one point) -- sly (sylvain letuffe) _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
