[Tagging] Railway=station + area=yes questions:

[Martin Koppenhoefer]

2016-10-04 21:36 GMT+02:00 Michael Reichert <nakaner at gmx.net>:

> I agree with you that the extend of the area orthogonal to the direction
> of the tracks is well defined. But the extend along the tracks is
> different depending on the definition.
>


there is no problem. Either we offer different tags to map the situation
according to different definitions, or we decide on one of the definitions
and decide to not map the other. Either way, a node is not a solution to
these problems.




>
>
> https://wiki.openstreetmap.org/wiki/File:Station-asymmetric.svg
>
> (1) A passenger might define the station as the area around the
> platforms, the station building, and – that's another dispute – maybe in
> addition the bus stop and car parking. This is shown as the purple thick
> line.
>



if I understood your sketch "simple station" correctly, you see
public_transport=station as a way of representing this, right? Anyway, with
an extensively mapped station, a passenger could find out "his version of
the station" by looking at all accessible footways/highways and platforms
inside the station area.




>
> (2) Train staff and other people interested in railway operations have a
> much larger definition of the station. It includes the whole siding and
> yard tracks which belong to the station. Depending on the country, a
> station begins either at the entry signal (left outermost signal in
> the image) or at the first point a train passes when it enters the
> station. The station ends either at the entry signal of the opposite
> direction (right outermost signal in the image) or the last point a
> train passes which leaves the station towards the right edge of the
> image. This is shown as the thin rose line.
>


this is what I would use for railway=station. I guess "point" was meant to
be "switch point"? I would prefer "switch point" for the limit along the
tracks, because this is easy to spot on aerial imagery, easy to map,
logical because outside of the first switch you are likely on a track meant
to go somewhere, rather than a less important track inside the station. I
wouldn't oppose "entry signal" neither, and I guess there is not so a big
difference between the 2 variants. It wouldn't actually matter for my
mapping and to get an idea how big the station is (I think, feel free to
tell me more).




>
> If we used (1), we would exclude yard (freight) tracks near the
> platforms. But I think that many passengers include them into their
> definition of a station if they are located next to the platforms.
>


this seems like a contradiction: you describe in (1) what you think
"passengers might define", and here you write you think passengers would
include more than what you had thought they would in (1). Rather than
speculating about what someone would think, we should give a clear
definition (also countryspecific, if it is necessary) and you'll see that
mappers (maybe opposed to ordinary passengers) will be able to follow it.





>
>
> https://umap.openstreetmap.fr/de/map/unbenannte-karte_
> 105414#17/48.94774/9.13638
> shows you definition (1) and (2) at the example of Bietigheim-Bissingen.
> All tracks in Bietigheim-Bissingen which do not have a platform, are
> freight tracks. Definition 1 is shown in blue, definition 2 in red.
>


there's a bug in this scheme, because you forgot to include the access
tunnel in the blue version, the station building and the tracks would
usually be connected (1 polygon), and not 2 separate areas like it is now,
even if you thought about it like "an ordinary passenger".




>
> I think that we should use the established tag railway=station for nodes
> only because the node will located where everyone agrees that there is a
> station. If we tag (2) with railway=station, the centroid of the area
> will be at a position where users would not expect it – neither
> passenger nor railway staff.
>


If you think you will need an extra node or more, call it
station_access_point or something similar (btw. there is a suggestion in
the wiki to call all these railway=subway_entrance, not my favorite term
actually, because of the word "subway"). This simple idea of putting
floating nodes has serious limitations anyway in all cases where the
station is more complex (e.g. access from both ends). From a logical point
of view, it makes not sense that "railway=station" represents something
different than a railway station, and railway stations do have significant
spatial extent.

Cheers,
Martin
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