[mkgmap-dev] Sensible resolutions - (or patch 5)

Wed Mar 2 12:56:25 GMT 2011

On 02.03.2011 13:45, Minko wrote:
> In the Netherlands most of the landuse has been imported, it consists of many very small polygons.
> The drop small polygons method seems to work very well in drawing the map much faster on the GPS!
> Negative consequence is that on Mapsource most of the forest disappears too soon, when zooming out.
> At 5km, with medium details, most of the forests are gone on my map.
> Can this be controlled in the style file? Like, dont drop small polygons of forests until a certain zoomlevel?
No, and this is a principal OSM problem. OSM is basically the only 
existing map database, that has no different detail for different 
resolutions. This works well when zoomed close in, or for raster maps it 
just increases computing time (at some point the hole is smaller than 1 
pixel). However any normal database would have a different approach that 
has a detailed forest for high resolutions, and the lower the 
resolutions the more detail gets dropped in the data itself. So holes of 
a forest would dispappear.

The solution would be to have forest relations for lower zoom levels. So 
like from mkgmap resolution 21 and down - only show relation polygons or 
very big polygons.

In the end this change just shows how crappy dutch data imports actually 
are for a vector map database. In most places even a setting of 15 
(forest would disappear one resolution earlier - which would be 3km) 
works fine.