[mkgmap-dev] Maps crashing Mapsource in big cities

Fri Feb 12 14:26:37 GMT 2010

On 12.02.2010 15:15, Mark Burton wrote:
> Hello Lambertus,
>
>    
>> The same problem about crashing MapSource and RoadTrip has also been
>> reported for my maps (e.g. eastern Australia, north and south of
>> Brisbane). The mapbuilding script tries to make those maps as large as
>> possible. Perhaps related is that I  upped the max-nodes from 1.400.000
>> to 1.600.000 for the current map version.
>>
>> I'll reduce the max-nodes for the next update but, ideally, Mkgmap
>> should complain and quit if there is too much information in the source
>> data (This is certainly no complaint, ofcourse I know this all depends
>> on the understanding of the Garmin format).
>>      
> OK - you tell us what the limit is and we'll make sure that mkgmap
> gripes if you bust the limit.
>
> Seriously, if you can provide any info as what works and what doesn't
> in terms of maps sizes, numbers of lines, polys, nodes, etc. that would
> be useful and we can code accordingly.
>
>
>    
The problem seems to me, that if a tile has more max-nodes, then a very 
dense city (like Athens, Melbourne, ...) in an otherwise rather empty 
area (huge tile) will crash. For Athens I had to go as low as 600.000, 
for Melbourne 800.000 was fine.
1.600.000 is definitely not only crashing a few tiles, but in my eyes 
around 10% of European tiles.

A solution to use bigger max-nodes would be if resolution=23 were 
usable. Currently the rounding goes havoc if you use 23 as lowest 
resolution (and drop 24). In my eyes 23 would be easily enough for OSM 
data (which is largely less accurate anyhow).