[mkgmap-dev] Rounding bug in splitter?

Wed Aug 12 23:49:44 BST 2009

Hi Valentijn,

> Chris Miller schreef:
> 
>> but my impression is that the conclusion was that the splitter should
>> be rounding areas off to boundaries in multiples of 4096 rather than
>> 2048?
>> 
> As far as I've seen - thanks to Steve Ratcliffe's findings - divisible
> by 2048 is enough, if you make sure that the difference is a multiple
> of 4096. (i.e. if your bounds are 0x123800 and 0x456800, that is OK;
> but 0x123800 and 0x456000 is not OK).
> 
> Anyway, dividing by 4096 is a good method of achieving this.

I've checked in what is hopefully a fix for this to the splitter. There's 
a new parameter called --resolution, which represents the lowest zoom level 
specified in your style file and dictates what boundaries to align the split 
tiles on. By default it's 13 which equates to tiles on boundaries of 2048 
map units, and tiles with width/height in multiples of 4096 units.

I've tested this with the netherlands.osm map and can't see any obvious problems 
(including around the tile borders and when routing across tiles), but as 
this is the first time I've used mkgmap to load osm files into MapSource 
I'm not 100% sure what I'm supposed to be looking for and your testing and 
comments would be appreciated.

Have a play and let me know if you think it's an improvement.

Cheers,
Chris