[mkgmap-dev] New locator branch

Sun Mar 20 12:05:07 GMT 2011

> On 03/18/2011 02:55 PM, Ralf Kleineisel wrote:
>> On 18.03.2011 14:45, WanMil wrote:
>>> Yes, we provide the same option for coastlines. So it's possible
>>> although there is the size restriction.
>>> Boundaries take around 3% of the complete OSM data (3% as osm.gz
>>> compared to osm.pbf). So think about creating a europe map from the 4.5
>>> GB dump. The boundary data file would be around 3%*4.5GB(osm.pbf) =
>>> 135MB(osm.gz). So in the end your computer additionally needs as much
>>> main memory as you need to compile a 135MB big tile.
>
> Wouldn't it be enough to keep that part of the boundaries in memory which
> lie in the area of the map tile mkgmap is processing?
>

Yes. For this we need:
* A preprocessing that converts the (complete) boundary file to a file 
format that allows to load parts only. This may be one file for each 
1°x1° part.
* mkgmap would have to load the relevant parts during tile processing. 
Each boundary area gets and unambigious id so we could merge them easily 
when a tile overlaps more than one 1°x1° boundary part.
* The boundary information might be ignored while loading the tiles.

The same algorithm can be reused for coastline processing.

WanMil