[OSM-talk-be] busroutes

[Ivo De Broeck]

2010/8/10 Ben Laenen <benlaenen at gmail.com>

> Maarten Deen wrote:
> > Have a look at http://wiki.openstreetmap.org/wiki/VRS , for a lot of
> > relations, there are two routes. Often also tagged with a from and to in
> > the relation, although I don't know if that really helps in a program.
>
> "a lot of relations": I count 12 on that page with two relations, given the
> number of routes on it I wouldn't really call that "a lot" :-)
>
>
> Anyway, I personally don't see why splitting the relation in two would be
> so
> much better. Basically the only reason why you'd do it because it tags a
> little bit easier since you don't have to add 'forward' and 'backward'
> roles.
> It doesn't solve anything else: the ambiguous possibilities to follow a
> route
> when a bus makes loops are all still there for example.
>

With 2 relations you can put the stops at the right relation. If you work
with one relation you have a way in both directions, a stop 'forward' and a
stop 'backward' .

>
> IMHO, the best option would be to stick with just one relation, but map it
> differently: take a starting point on the bus route and then just add the
> ways
> in the order the bus follows them to get to the other end, and then add the
> ways in order as the bus goes back to the start point (so usually adding
> the
> same ways to this relation again). In principle, you don't need
> forward/backward tags with that either.
>
> Alas, we have problems with this since one of the main editors can't handle
> ways that belong multiple times to the same (so if someone else e.g. splits
> up
> a way in that editor the relation is broken), and it doesn't keep the order
> of
> the members in the relation.
>
>
> I have the impression that making two relations of them is trying to patch
> this: avoid ways that belong multiple times to the same relation by putting
> them in two different ones. This doesn't work properly btw, since I know
> bus
> routes that go up and down the same road in both directions between the
> termini. One could suggest the topology of the ways belonging the unordered
> relation would always make it possible to get the exact way order the bus
> follows, but I'm not really convinced of that yet. Certainly if you drop
> the
> forward/backward roles: then you really cannot know anymore in which
> direction
> the bus rides a loop in its route. And for now I can see only one thing two
> relations without forward/backward can represent more that one with
> forward/backward: if the bus follows a loop in one direction, but doesn't
> follow it in the other. But if that's worth it to start tagging something
> differently? Better to wait for when Potlatch can finally handle relations
> nicely and map the bus routes properly instead of going to this
> intermediate
> method that doesn't bring much advantages and brings its own problems.


I agree. That s why intermediate it seems a good idea to work with 2
relations. It will be easy to merge (if necessary) the two relations.

>


> Greetings
> Ben
>
>
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-- 
Ivo De Broeck
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3360  Korbeek-lo
Tel (0)16 43 84 93
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