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

From Valentijn Sessink valentyn at blub.net on Fri Aug 14 08:10:10 BST 2009

Mark Burton schreef:
> There is a particular failure of inter-tile routing that we have seen
> quite often which is that it fails to find a route when the source and
> destination are in the same tile and the only (sensible) route is via
> another tile. (If a sub-optimal route that only uses the source tile is
> available that will get used.)

Maybe we should investigate one such problem really thoroughly? I've
also been thinking that a map with all of these problems would be a good
idea, but I don't know if that would be feasible.

Pro: have all problems in one, easily compilable, easily editable map;
this map being small and exchangeable (by e-mail or svn).
Con: the need to maintain this map; in fact, many of the corner cases
will only be transferrable to this testmap once you know what to
transfer, which is probably 90% of the investigation. What do you think?

> Well, I naturally assumed that this was caused by mkgmap doing
> something wrong but I'm not so sure now because I have been looking at
> the free nz mapset that is generated using cgpsmapper and that exhibits
> exactly the same behaviour as our maps do in this respect.

They're built on the same reverse engineered information, aren't they?

> So, either the bug is in mapsource (and all Garmin GPS units?) or mkgmap
> and cgpsmapper are both getting it wrong in the same way.

As said before (in the first A, B, C routing problem), my Garmin Nuvi
will take routes that Mapsource won't. Also, the first problem had to do
with three tiles, MapSource unwilling to route from tile A to tile C
through tile B on a specific road. So we're not sure if it's Mapsource,
mkgmap & cpsmapper, or some subtle interaction between all three.

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