[Talk-ca] Mapping intersections properly - the impact on routing and illegal routing maneuvres

[Marc Provencher]

I did look at turn restrictions.

But would the Garmin auto-routing algorithms even consider those
restrictions?

Not without pain to implement either. The editors would need to make this a
one or two click solution.

Not complaining, just thinking aloud.

Marc.


On Thu, Apr 8, 2010 at 3:36 PM, Richard Weait <richard at weait.com> wrote:

> On Thu, Apr 8, 2010 at 4:33 PM, Marc Provencher <marc at marcprovencher.com>
> wrote:
> > I recently posted with an open question asking how others map junction
> nodes
> > at complex intersections.
> >
> > Today I was trying to reproduce certain routing errors which I observed
> > while driving, and was able to cause Mapsource to route me through an
> > illegal U-turn, because of a misplaced junction node where there
> shouldn't
> > be one.
> >
> > This picture shows the U-turn:
> >
> http://provencher.smugmug.com/Other/Misc/IllegalUturn/831296827_sYc5e-X3.jpg
> >
> > The problem lies with the access ramp,which has a junction node on both
> ways
> > of the divided residential road.  And for some reason the routing
> algorithm
> > doesn' t consider this a U-turn, even thought the "avoid U-turns"
> setting
> > is enabled.
> >
> > Actually, the real problem is that the routing algorithm is using these
> > "connecting ways"  between the two sides of a divided road, to make a
> > U-turn. I'm not sure if this problem can be resolved easily.
> >
> > In my attached picture, removing the junction node which I thought was
> the
> > problem simply moved the problem to another intersection.
>
> I see this fault from navigation systems too.  I'm not sure that the
> commercial vendors worry about this error.  Their systems seem to
> suggest those illegal turns often enough.
>
> We can do better, and eliminate these routing errors with turn
> restriction relations.
> http://wiki.openstreetmap.org/wiki/Turn_restrictions
>
> See what you think.
>



-- 
Marc Provencher
marc at marcprovencher.com
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