[mkgmap-dev] Maximum map resolutions people use

Tue Sep 1 13:04:41 BST 2009

I've just chatted to Steve about this and it turns out my description below 
is incorrect. What really matters is the resolution of the overview map, 
NOT the resolution of the lowest zoom level you're using.

Given that mkgmap is currently hard-coded to use a resolution of 14 for the 
overview map, there's no need for anyone to be changing the --resolution 
parameter in the splitter just yet. This is also good news for the density 
map code I'm working on, it means I don't have to worry too much about the 
amount of memory it will require.

Chris

L>> I never used the --resolution parameter as I don't know what it
L>> means and does to the output/maps. Maybe I missed a discussion about
L>> it earlier, but can you explain again?
L>> 
CM> Oh... I was about to point you to the documentation on the website
CM> but you've just made me realise that there isn't any documentation
CM> for that parameter yet! Whoops, I'll add it...
CM> 
CM> I think (but am not 100% sure - SteveR, can you please comment?) it
CM> should be described something like this:
CM> 
CM> --resolution=13
CM> Rounds the split areas off so they are suitably aligned to use with
CM> mkgmap
CM> at the specified resolution. The resolution value you supply should
CM> be less
CM> than or equal to the lowest resolution value you plan to use in
CM> mkgmap. For
CM> example, if you are using --levels=0:24,1:22,2:20 in mkgmap, the
CM> resolution
CM> you supply here must be 20 or less.
L>> As you probably know, I split two files that to be able to cover the
L>> whole world: A North/South America file and one that contains the
L>> rest (I call it Eurasia).  The max-nodes is set to 1.200.000 and
L>> problem areas are divided further by hand. Hope this info helps.
L>> 
CM> Thanks. If you're splitting even the whole planet using the default
CM> resolution of 13 then there won't be a problem with the density map
CM> at all.
CM> 
CM> Chris