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

Fri Mar 25 07:42:18 GMT 2011

Hi Felix,

Finally I got time for this patch. The gmapsupp.img for Finland has 
grown a lot, and much of it is probably due to Corine landuse imports.  
I hope that this patch will scratch that itch too. :-) Now Finland is 
finally liberated from unclosed polygons, too. I even got address search 
working again on the Edge (without --index), by replacing 
--charset=latin1 with --code-page=1252.

>Nope, motorways stay (at least if the default resolutions are used. By 
>default no resolution 14 is created. But compiling Europe at 14 with 
>motorways looks crap. Been there, done that.

Right, there should be some method of simplifying and merging polygons 
in the lowest resolution levels. Until we are there, it is probably best 
to drop the polygons from the widest zooms. A good use case of merging 
polygons would be the huge lake areas in Finland. If you look close, the 
lakes are small and scattered. From bigger distance, it could be 
approximated with one huge lake. But, currently the map does not show 
any lakes when zooming out.

One thing that I do not understand in your patch is this:

< --- styles/default/options	(revision 1902)
< +++ styles/default/options	(working copy)
< @@ -17,7 +17,7 @@
<  <  # The levels specification for this style
<  # < -levels = 0:24, 1:22, 2:20, 3:18, 4:16
< +levels = 0:24, 1:22, 2:21, 3:20, 4:19, 5:18, 6:16

Is the "resolution" a mkgmap-only entity, which is mapped to zoom layers 
known as "levels" in the IMG file? If that is the case, wouldn't this 
change introduce two more zoom layers to the map, potentially growing 
the file size?

Regarding railways, you are lowering them to resolution 22, with one 
exception: railway=subway&!(tunnel=yes) is resolution 21. I guess that 
it is a typo and you meant 22. I think that this lowering is OK, because 
Garmin would not show railways when zooming out from 500m, even in the 
highest map detail level. They must really hate railways, I guess.

Best regards,

	Marko