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

Wed Mar 2 12:20:43 GMT 2011

Even though the drop small polygons patch does improve mkgmap created 
maps, there are still really bogus resolutions.

take kindergarten polygon (or actually most amenity) which shows up 
before! primary roads. Light rails (17) that in theory show up before 
primary roads (only in theory because garmin does not display the 
railway type before resolution 23, so cutting clutter, but still this is 
a lot of crap and unused data that the default style puts into the map). 
There loads of other examples.

Certainly landuse like forest is more important on a map like a 
kindergarten, grave_yard or college and so on.
It really seams like, everyone just wanted to see his favourite stuff 
really early, and by continuing this approach the maps get really 
overloaded without providing any real information on top. Of course a 
lot of this has been written when OSM had relatively few information, 
and showing stuff stupidly early made the map look nice and gave the 
impression of OSM having lots of data which it had not. Nowadays at 
least in Western and Central Europe - and especially there where people 
use mkgmap created maps, there is actually lots of information in OSM 
and the goal has to be to declutter. That's what this patch does. Adding 
so many polygons early in a raster map would be somehow okay because it 
is barely noticeable, and there is no penaly in the time to show it on 
screen, but on a vector map it is simply not good.

On top of the resolutions changes I introduced resolutions 21 and 19 for 
rendering to have smoother addition of information when zooming. Most of 
the data is in resolutions 24-22 anyhow (each resolution even if showing 
the same detail, halves the space needed for including it). Overall I 
think maps should work out the same size as without this patch (even 
though there are two resolutions added), but draw much faster on 
GPS/Mapsource/Qlandkarte GT and give a much better tool for orientation. 
I don't think adding resolution=23 is good, because it increases map 
size by more or less 25% (whereas 21 only increases total map size by 
~5%, 19 by ~1%)

I still left most resolutions 1 step of where I would personally put 
them, so that in countries with less information the style is still 
working well. Nevertheless in big cities the map is showing much 
information too early.
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