[mkgmap-dev] Multipolygon problem

Sat Feb 26 10:43:53 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?

That should be no problem.

>
> 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.

Ok, sounds good as a first solution. I'll post a patch.

>
> 	Marko