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[mkgmap-dev] Size Limits

From Andrew Ayre andy at britishideas.com on Wed Dec 10 20:03:31 GMT 2008


Thanks for the info. I'm trying to understand your process. So you take 
a large OSM file and using style files generate multiple IMG files (one 
contains roads, etc.). Then you use the --gmapsupp option to merge the 
IMG files together into a single IMG file?

thanks, Andy

f.hartmann wrote:
> No, I too don't know. The resulting .img can be around 11-16MB big 
> maximum right now. It mainly depends on your style-files. I noticed 
> however that options like --net do increase the .img size, without 
> however inflicting upon whether that error incurs when generating or not 
> (--net produces about 20% bigger tiles).
> Instead of using osmosis (I wouldn't use osmcut, as it's too buggy for 
> me - maybe others are more succesfull), you can also split up your 
> maptiles by using several style-files. So you create one layer with all 
> motorways, one layer with all residential roads, one layer for all 
> polygons, one layer for all POI, etc... Just give them the same PID and 
> FID and it works nicely. Garmin doesn't do such a seperation, so I don't 
> know wheter it can break something. I do use this a lot however. I can 
> easily get OSM files of 3-4 GB parsed without osmosis/osmcut by 
> following this procedure. In Mapsource or on the gps you don't see a 
> difference. When selecting maps for exporting to your gps you can't 
> click on the maptiles in Mapsource however, but you have to capture them 
> by drawing a rectangle while holding the left mouse button on selection. 
> On click only one layer will be chosen, and not all. This is the only 
> limitation I have found.
> I noticed however that the Garmin Topo Adria 2.11 map has maptiles of up 
> to 29MB in size. The tiles themselves do not support autorouting, but do 
> have a built-in DEM (which is in seperate subfiles if you decompile the 
> .img). So I don't know where the real limit is of how big tiles you 
> could theoretically produce. I do think that the Topo Adria 2.11 tiles 
> are in NT format too. I think mkgmap writes non NT format tiles so the 
> limitations are different.
> Felix
> Andrew Ayre wrote:
>> I have an OSM file which is 836Mb in size. When I try to convert it to
>> an IMG file I get:
>> "There is not enough room in a single garmin map for all the input data
>> The .osm file should be split into smaller pieces first."
>> I understand how to solve this problem (osmosis, osmcut, etc.) but I'm
>> wondering what the size limit is and whether it is imposed by the IMG
>> file format or mkgmap. Does anyone know?
>> thanks, Andy

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