On Sun, Aug 14, 2011 at 10:13:36PM +0200, Wolfgang Hammel wrote:
Im not sure wether tile splitter did some processing in order to close the multipolygon along the bounding box, but probably this ist not the case.
It does not. This is a known problem in the tile splitter. mkgmap does try to work it around to the extent possible. For what it is worth, the splitter in Osmosis implements an option not to break relations (such as multipolygons). It costs much more processing time. I do not know how much additional effort it would take to clip multi-polygons (and polygons, for that matter) along tile borders in splitter.
As I already mentioned, this large multipolygon is no more present in the actual osm database.
There are some large multipolygons elsewhere on the planet. One example is Lake Päijänne in Finland. The largest lake, Saimaa, is in several multipolygons, and every now and then someone adds an island to the wrong multipolygon relation. Best regards, Marko