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

Mon Feb 23 20:02:41 GMT 2009

That's not an offset crossroads that's 2 T junctions!!!. I'll bow to
your local knowledge if you say that you can go down Boroughgate from
Beech Hill but that just seems wrong to me but who are we to argue with
the gods of town planning ;)

Incidentally you were missing a tag in your relations. Along with the
restriction, no_left_turn you also need a type,restriction tag. I've
added these for you and you'll notice that in the latest versions of
JOSM this now shows an icon for a turn restriction on the southern of
the 2 nodes. As the northern junction is "incorrect" this does not show
an icon and instead has an * next to the relation in the list of relations.

Cheers

Paul

Alan Bowman wrote:
> 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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>>
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