On Wed, Oct 17, 2012 at 08:15:55AM +0200, Igor Brejc wrote: > Here's another complex multipolygon that I'm not sure the Wiki properly > addresses: http://www.openstreetmap.org/browse/relation/11104 > > Situation: there are several holes within holes ( > http://www.openstreetmap.org/browse/way/143604319 is one). The geometric > situation is clear (and wiki covers that in > http://wiki.openstreetmap.org/wiki/Relation:multipolygon#Island_within_a_hole > ). > > But the problem is in how to handle tagging in this case. The existing wiki > "rules" describe only the tagging of top outer rings, but they don't > mention how to handle various cases/combinations of tagging holes within > holes.
Why would there a difference between "top outer rings" and "holes within holes"? There is no difference between multiple outer rings next to each other and multiple outer rings that are inside each other in some way. There is no "hole in hole" hierarchy. You can think about it this way: Make a forest thats as big as the whole planet. Make a small hole in it with a lake. Make an island in the lake with a forest. Now grow the lake and the island with it. Make it bigger and bigger. You'll end up again with a forest on an island in a lake in a forest. But the original huge forest is now on the small island. There is no difference between outer rings. Another way to think about multipolygons: A multipolygon divides all points on the planet into two classes. This inside and those outside. Thats it. There isn't more than this. Jochen -- Jochen Topf joc...@remote.org http://www.remote.org/jochen/ +49-721-388298 _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
