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

[Michael Barabanov]

This should have been "reply all".

On Thu, Apr 8, 2010 at 3:46 PM, Michael Barabanov <
michael.barabanov at gmail.com> wrote:

> AFAIK, the garmin maps produced with osm2mp/cgpsmapper do respect turn
> restrictions.
>
> On Thu, Apr 8, 2010 at 3:01 PM, Marc Provencher <marc at marcprovencher.com>wrote:
>
>> 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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>>
>
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