[Tagging] rail routes: how are platforms and stops associated (rail question 2)

[Bjoern Hassler]

Hi Michael,

that's very helpful, thanks. I'll implement the ref as well as the
ordering. I'll also add this to the English wiki pages where needed. I'll
have a look at the DE page as well.

Examples for nodes as requested. Stop_position at:
- End of platform (middle of line) node 13328915
- End of platform (end of line) node 20955753
- Middle of platform node 1620401529

(Disclaimer: I was just adding tags for 13328915, but I'll fix this shortly
to be in the center of the platform. IMHO that is the convention that does
make sense from a passengers perspective, but yes, it doesn't address
Colin's comments about physical stop train positions from the drivers
perspective.)

Many thanks,
Bjoern


On 12 May 2017 at 15:48, Michael Reichert <nakaner at gmx.net> wrote:

> Hi Bjoern,
>
> Am 2017-05-10 um 18:59 schrieb Bjoern Hassler:
> > In an  osm:relation:route
> > <https://wiki.openstreetmap.org/wiki/relation:route> (type=route,
> > route=train/...), you have both platforms and stop positions. How is a
> > particular platform associated with a stop that serves it?
> >
> > E.g. for public transport routing, you'd walk (highway=footway) to a
> > platform (public_transport=platform), at which point you'd change to a
> > train stopping at a stop (public_transport=stop_position). How would the
> > routing algorithm know that the platform is associated with the stop?
> >
> > Is there an existing mechanism or convention, e.g. a tag on the platform
> > that indicates the stop, or both tagged with the same name or similar?
>
> Stop positions can have a tag ref=* or local_ref=* giving the track
> number which is signed on the platform. The platform has ref=*, too. The
> ref tag of the platform often contains multiple numbers because many
> platforms have to edges, i.e. ref=2;3 or even worse: ref=2a;2b;2;3a;3b;3
> (if the track can be occupied by two trains behind each other at the
> same time – very common at busy stations).
>
> If you don't want to parse ref=*/local_ref=* and route relations are
> properly mapped, you can check which route relations reference a
> platform. If a route relation contains both platforms and stop
> positions, the next member of a relation after a stop position node is
> should be the platform.
>
> I think that both variants provide better results than simple snapping
> on the next edge in your pedestrian routing graph (if platforms are in
> your routing graph). There are cases in reality where a railway track
> has platforms on both sides but you can or must leave the train only to
> one direction.
>
> > PS I've noticed that sometimes the stop position is at the far end of a
> > platform (i.e. the two stop positions are at opposite ends of the
> station).
> > Maybe that's so that an association can be made?
>
> From my point of view this is wrong mapping. (In Germany mainly done by
> user rayquaza) To give a correct answer, you should give some examples
> (node IDs).
>
> Best regards
>
> Michael
>
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