[mkgmap-dev] Bogus warnings about intersected ways in multipolygons

Mon Jan 25 21:45:53 GMT 2010

Hi Adrian,

> I don't think these warnings are bogus. Mkgmap definitely has problems
> with multipolygons. The Languedoc-Roussillon extract (southern France)
> from Geofabrik provokes about a hundred of these warnings. But I believe
> that the intersected ways are being generated by mkgmap and that the OSM
> data is OK. Mkgmap-r1475 did not have this problem but r1502 and r1507
> both do. I am unable to pinpoint more accurately when the behaviour
> changed because I do not have copies of the relevant releases. Perhaps
> r1494 could be put back on the web site, in the hope that we might have
> the benefit of the fixes to generate-sea without the multipolygon
> problems.
> 
> Exactly where the problems show up can depend on where the tiles are
> split. One example is at
> http://www.openstreetmap.org/?lat=43.4047&lon=3.5107&zoom=13&layers=
> B000FTF
> as seen on Lambertus' site. Take a look at his tile 63240406.img dated
> 20-01-2010. If you look at the vineyards (land-use polygons) in the
> vicinity of Pinet, you will see an obvious straight edge which is
> spurious, and areas where the inside and outside of the polygon have
> swapped over.

The new MP code has a problem with inner polygons that touch the outer. 

What you say makes me think that whenever the splitter splits an inner
polygon it's going to cause trouble because it splits outers/inners
along the same line so they will always intersect then.

Whaddyathink WanMil?

Mark