[mkgmap-dev] Multipolygon problem

Sat Feb 26 09:38:06 GMT 2011

On Fri, Feb 25, 2011 at 11:36:39PM +0100, WanMil wrote:
>But I also found out that some polygons that crosses the tile border 
>which are closed in the OSM data are not neccessarily closed in the 
>tiles. This has to be investigated.
>Does the splitter ensure that all closed ways in the OSM dump are also 
>closed in the splitted tiles?

Could mkgmap be aware of the tile borders when closing polygons? When 
the open endpoints are within the current tile, do not close the 
polygon, and possibly emit a complaint to the error log. When the 
endpoints are outside the current tile borders, close by adding lines 
along the tile borders?

On a somewhat related note, there is some natural=coastline problem in 
Finland that JOSM cannot find in the natural=coastline extract of 
finland.osm.pbf. The error message only mentions generated relation and 
way IDs:

63240006: 2916352,960000 to 3014656,1474560
#       : 62.578125,20.599365 to 64.687500,31.640625

2011/02/26 11:13:04 WARNING (MultiPolygonRelation): 63240006.osm.gz: 
Multipolygon 
http://www.openstreetmap.org/browse/relation/4611686018427480001 
contains errors.
2011/02/26 11:13:04 WARNING (MultiPolygonRelation): 63240006.osm.gz: 
Polygon 4611686018427486852(8P)(4611686018427483429[8P]) carries role 
inner but lies inside an inner polygon. Potentially its role should be 
outer.

It would be helpful to see a coordinate of one of the ways. I guess that 
this is being caused by two islands being on top of each other.  
Apparently, JOSM could only catch that if the coastlines intersected.

	Marko