[mkgmap-dev] Incorrect multipolygon warnings?

Sun Mar 28 19:44:54 BST 2010

Am 28.03.2010 17:24, schrieb Carlos Dávila:
> WanMil escribió:
>>> Hi,
>>>
>>> Whilst processing Italy, I've been getting a lot of mp warnings like:
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz:
>>> Polygon 4611686018427439638 intersects itself. It is splitted into 2
>>> polygons.
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz: The
>>> polygon is composed of
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz: -
>>> http://www.openstreetmap.org/browse/way/36433060
>>>
>>> I can't see anything wrong with this mp and the JOSM validator does not
>>> pick up on anything.  Is this an error with mkgmap's MP code or am I
>>> missing something?
>>>
>>
>> Yes and no. While reading in the data from osm files mkgmap converts all
>> coordinates to the garmin internal format. This reduces the resolution
>> of the coordinates. So the multipolygon code works with other
>> coordinates than OSM. Due to this a polygon might intersect itself
>> although it does not in the original OSM data.
>>
>>
>>> Here's another:
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz:
>>> Polygon 4611686018427439886 intersects itself. It is splitted into 2
>>> polygons.
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz: The
>>> polygon is composed of
>>> 2010/03/27 13:57:27 WARNING (MultiPolygonRelation): 63242013.osm.gz: -
>>> http://www.openstreetmap.org/browse/way/36434237
>
> I also have a mp warning in which I can't see any error:
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> Cannot join the following ways to closed polygons. Multipolygon
> http://www.openstreetmap.org/browse/relation/2909
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52489521
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889739
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/11276547
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/11276563
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52288870
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52288868
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/51442603
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/11276562
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52489071
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52489520
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/52489515
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889860
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889776
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889848
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889700
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/51334155
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> - way: http://www.openstreetmap.org/browse/way/4889699
> 2010/03/28 14:32:08 ADVERTENCIA (MultiPolygonRelation): 63240002.osm.gz:
> Multipolygon http://www.openstreetmap.org/browse/relation/2909 does not
> contain any way tagged with role=outer or empty role
>
> If I check relation 2909 in JOSM it does have lots of ways tagged with
> role outer and they are connected in a closed polygon, apparently in the
> right order. Do you have any clue? May it be a
> clockwise/counterclockwise issue?

Clockwise/Counterclockwise does not make any difference.
Probably this is a tile splitter problem and therefore the multipolygon 
is not completely cotainted in the tile.