[mkgmap-dev] [PATCH] turn restrictions - alpha code for testing

Mon Feb 23 17:14:06 GMT 2009

First off, superb work on mkgmap and routing - my Vista HCx regularly
gets new maps as new features are added!  Thanks very much.

At http://www.openstreetmap.org/browse/relation/79516, there is an
offset crossroads where it is acceptable to approach Boroughgate from
Beech Hill, but not from Manor Square.  (On a "normal" crossroads, it
would be acceptable to go straight on to Boroughgate, but not to turn
left or right into it).  The crossroad is sufficiently offset that the
centre point has been added as a way rather than a node.  The via part
of the turn restriction is on a way, rather than a node.

Either this is a reasonable example of having a way as the via part,
or there is a better way for me to have added the turn restriction.
Does anyone have any alternative suggestions?

Alan

2009/2/23 Mark Burton <markb at ordern.com>:
>
> Folks,
>
> The attached patch implements the OSM turn restriction relation as described in
>
>  http://wiki.openstreetmap.org/wiki/Relation:restriction
>
> Here's an example that shows multiple relations being used at a junction
>
>  http://www.openstreetmap.org/?lat=50.26386&lon=10.96498&zoom=17
>
> JOSM shows little restriction signs but I think a lot of renderers won't
> show anything.
>
> Only "well formed" turn restrictions are handled - i.e. the 'from' and 'to'
> ways must terminate at the 'via' node.
>
> Badly formed turn restrictions will yield a (hopefully) useful error
> message that includes the OSM id so that you can go find the relation
> using JOSM, etc and fix it.
>
> Multiple 'via' members or the 'via' member being a way rather than a node are
> not handled. Those variants are not forbidden by the above description but
> not encouraged either and I don't, at this time, think there's good reason
> to handle them - if you believe otherwise and can present a compelling case
> for their inclusion, I will add support for them.
>
> The "except", "day_on/off", "hour_on/off" tags are ignored. I don't
> know how to express those constraints in garmin-speak.
>
> The --ignore-turn-restrictions option can be used to disable the feature.
>
> Please test and report success/failure, etc.
>
> Cheers,
>
> Mark
>
>
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