[mkgmap-dev] Wrong multipolygon warnings

Fri Feb 12 18:18:38 GMT 2010

> Compiling Spain I get several warnings similar to the one below, that
> point to data that are correct (or it seems to me).
>
> |2010/02/12 09:26:39 ADVERTENCIA (MultiPolygonRelation):
> 63240004.osm.gz: Multipolygon
> http://www.openstreetmap.org/browse/relation/319017 contains errors.
> 2010/02/12 09:26:39 ADVERTENCIA (MultiPolygonRelation): 63240004.osm.gz:
> Polygon 4611686018427391078[5P : (44132028[5P]) carries role inner but
> is not inside any outer polygon. Potentially it does not belong to this
> multipolygon.
>
> |Reported way (hole in the building) lacks in the resulting map.
> Is it a know bug?
> Another question, why are polygons so deformed in MapSource compared to
> Mapnik?
>
Carlos,

the way http://www.openstreetmap.org/browse/way/44132028 overlaps the 
outer way of multipolygon 
http://www.openstreetmap.org/browse/relation/319017. If we look keenly 
on the definition of the multipolygon relation 
(http://wiki.openstreetmap.org/wiki/Relation:multipolygon) this is not 
allowed. The current implementation of mkgmap does not support this.

But it is widely used. There is a patch 
(http://www.mkgmap.org.uk/pipermail/mkgmap-dev/2010q1/007086.html) which 
is not yet committed and which fixes the problem. I think it will be 
committed within the next days.

The deformations do not look good. I think the problem is that mkgmap 
rounds the exact OSM coordinates to lower resolution garmin coordinates.

WanMil