[OSM-talk] Turn restrictions
karouf at gmail.com
Thu Aug 16 13:03:09 BST 2007
On 16 Aug 2007, at 11:58, Steve Coast wrote:
> On 16 Aug 2007, at 10:29, David Earl wrote:
>> On 15/08/2007 22:48, Steve Coast wrote:
>>> So I'm on a train otherwise I'd link to Andys wiki page he pointed
>>> to today, but I want to try out a turn restrictions scheme,
>>> Given a road direction, and roads 'Baker Street' and 'Marylebone
>>> Road' you tag the way 'Baker Street' with
>>> no_turn_left:'Marylebone Road'
>>> If you can't turn right then it's 'no_turn_right'. If you can't
>>> turn at all it's 'no_turn'. And thats it. There are three major
>>> problems with this
>>> First, as far as I know JOSM doesn't let you use keys more than
>>> once but the API does. So you can't have more than one
>>> no_turn_left. So fix JOSM.
>>> Second, what if it's no turn for car but ok for bikes, or
>>> whatever. Well, then shouldn't we look at triple tags?
>>> car:no_turn_left:Marylebone Road ? That is, keyvals now have
>>> third string along with key and val? We'd add a third keyval
>>> property, call it what you will, and all the current keyvals will
>>> have that third proprty set to 'general'. So general:name:Foo
>>> Street and so on. Then, this third column can be specialised
>>> along the lines of Map Features as the keys and vals are.
>>> Third, what if someone misspells 'Marylebone Road' or the road
>>> isn't joined, or it doesn't exist or something. Well, people will
>>> enter bad data ON PURPOSE and our map data will never be perfect
>>> ANYWAY. And, it's a wiki so you can fix it. And, it's incredibly
>>> simple compared with any competing scheme I've seen. Also, JOSM
>>> (or potlatch) can prompt you and say 'ah-ha Mr. Mapper, that
>>> looks wrong!' And you can read it, but you can't read
>> Frederick's prototype for relationships addresses this properly, by
>> grouping the Ways affected by reference rather than name.
>> See http://openstreetmap.gryph.de/entities/
> Yes but my way is about a billion times simpler, human readable and
> works today. :-)
> have fun,
> SteveC | steve at asklater.com | http://www.asklater.com/steve/
Entities are not that complex for anybody who uses JOSM on a regular
basis. It keeps the data consistent, it is human readable and it
works since Frederick made an implementation of it. It provides a
solution to a lot of things we want and will want to do.
For once that somebody is going through the trouble of proposing
something and actually implementing it, I think we should give it
some credit. We'll need to move toward this kind of relationships and
objects one day or another anyway...
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