[mkgmap-dev] Maximum map resolutions people use

Tue Sep 1 13:30:36 BST 2009


Chris Miller wrote:
> 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.
>   
overview map is at 15 AFAIK, are you sure it's 16?

Anyhow we would really need not an empty overview map but overview map 
with say all objects inside of the last map level. Say you specify down 
to 16, then everything at 16 should be put into the overview map (say 
huge cities/capitals, national boardes, motorways) and the map 
themselves start at 17 or 18. This would give a good performance 
improvement when panning far out on GPS. Currently even having only very 
basic info in say level 16 will be quite slow.
If I were creating maps for myself only I would only go down to 18, and 
use basemap on GPS from 17 down as it is more suitable at those 
resolutions, however then in Mapsource orientation gets more difficult 
(as our overviewmap is empty).
> 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
>
>
>
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