[mkgmap-dev] Inter-tile routing failures - not all our fault?

Fri Aug 14 09:33:07 BST 2009

MB> There is a particular failure of inter-tile routing that we have
MB> seen quite often which is that it fails to find a route when the
MB> source and destination are in the same tile and the only (sensible)
MB> route is via another tile. (If a sub-optimal route that only uses
MB> the source tile is available that will get used.)
MB> 
MB> Well, I naturally assumed that this was caused by mkgmap doing
MB> something wrong but I'm not so sure now because I have been looking
MB> at the free nz mapset that is generated using cgpsmapper and that
MB> exhibits exactly the same behaviour as our maps do in this respect.
MB> 
MB> So, either the bug is in mapsource (and all Garmin GPS units?) or
MB> mkgmap and cgpsmapper are both getting it wrong in the same way.

When I get a chance in the next couple of days, I'll have a play around with 
some of the official Garmin maps and see if they can be made to exhibit the 
same problem. If so then the limitation is most likely in the routing algorithm 
in MapSource and/or on the device. If that's the case then we should probably 
start thinking of it as a 'feature' rather than a bug...

Chris