[OSM-talk] Turn restrictions ambiguity

Teemu Koskinen teemu.koskinen at mbnet.fi
Thu Apr 23 20:32:32 BST 2009


On Thu, 23 Apr 2009 22:25:36 +0300, SteveC <steve at asklater.com> wrote:

>
> On 23 Apr 2009, at 12:17, Teemu Koskinen wrote:
>
>> On Thu, 23 Apr 2009 21:34:05 +0300, SteveC <steve at asklater.com> wrote:
>>
>>> I don't see a clear explanation as to why there is ambiguity if you
>>> don't do turn restrictions at the end of ways on the wiki. There is
>>> some stuff in the talk page
>>>
>>> 	http://wiki.openstreetmap.org/wiki/Talk:Relation:restriction
>>>
>>> Anyone care to provide an explanation?
>>>
>>> The reason I ask is that I've come across some roads where there is a
>>> restriction every  other turn in both directions... and splitting a
>>> mile long road in to 30 pieces seems nuts. As a follow up, I can
>>> guess, but what will the renderer do in that situation? I'm guessing
>>> mapnik will give up trying to put 30 names on a one mile road and
>>> won't notice they're the same name?
>>
>>
>> If both from and to ways continue after the via point and neither is  
>> one-way, there's two possible ways to interpret it: the restriction  
>> could apply when coming from either of the ends of the from-way. This  
>> of course doesn't matter if there is similar restriction coming from  
>> both directions, but that's not nearly always the case. And even if  
>> there is symmetry in the real life restrictions, it's not appropriate  
>> in my opinion to map those with just one restriction.
>
> eh? don't you assign direction by saying 'from' and 'to' ?
>

Yes in the sense of which of the two ways you are coming from, but if the  
way is not one-way and it doesn't end at the via-node, there's two  
possible directions from where you can come to the via-node using the way.


Regards Teemu Koskinen




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