[Tagging] Feature Proposal - RFC - More Consistency in Railway Tagging
mart at degeneration.co.uk
Sat Apr 13 18:11:32 UTC 2013
On 04/13/2013 10:18 AM, Rovastar wrote:
> The example you gave for tunnels and bridges are the same for roads as well.
> If you have a bridge or tunnel with 2 roads (one for each one-way) and a
> train line(s) and footpath each will be a tagged with a separate bridge. So
> in that regard rail is actually are consistent with the road network.
Point taken: it is a general problem with bridge tagging, not one with
railway tagging. I found some discussions on the wiki about modelling
bridges as areas that would address this, but I don't really have any
interest in mapping bridges in particular, so example retracted for the
purpose of this discussion.
> Also you say you want it better for simple mapping and other can do more
> detailed mapping if they want to. I see no part of your proposal to add
> additional tracks like is now yet you imply in the posts here that it is. If
> you do think this then it doesn't not help the crossing example you gave as
> we will have the same problem again.
I have not described a way to describe the actual routes of tracks; I
lack the expertise (or interest, frankly) to describe that next level of
detail, I just propose that we separate that next level of detail from
this simpler level of detail, rather than using the same tags for both.
I've seen the area:highway proposal for mapping the detailed shape of
streets, sidewalks and footways. My assumption was that this proposal
could be extrapolated to include a similar model for railways, modeling
the precise shapes of the trackbed the rails run along, the positions of
the individual tracks within that trackbed, etc.
If I were trying to define such a thing my first thought would be to
define a new way tag to mean "the exact path of a track" and use
separate ways from the simple route network. e.g. railway:track=rail .
I've not spent nearly as much time pulling that idea apart as I have my
simple route-oriented proposal, so I'm sure someone who knows more about
railways than I do could find examples where that doesn't apply, but
it's a strawman to start with.
I could also compromise on making the schematic network be the thing
that gets new tags, but I think it's tough to say whether it's better to
suggest re-tagging detail work in dense areas where there are evidently
lots of avid mappers at work (and the re-tagging could thus happen
relatively quickly), or to suggest re-tagging the basic network in areas
where there is less detail and there are fewer (or no) active mappers.
> Do you propose that we change *all* the currently mapped multi track rails
> to conform to your new standard?
> e.g. here there are hundreds of tracks/railways which IMHO accurately
> reflects what is on the ground.
Under my proposal it wouldn't do any harm to leave existing detailed
tagging in place where the railway doesn't cross the highway, since a
railway way represents "one or more tracks", and that holds for the
example you showed. Optionally one could add tracks=1 to the existing
ways to make it very clear.
The converse is not true: if you define that a railway way represents
exactly one track, then there's lots of work to do to turn miles of
existing one-way-per-railway tagging into one-way-per-track.
When it comes to tramways and level crossings, whichever approach we
take there are many counter-examples to be corrected, of course.
I would note that if we *did* adopt a separate tagging scheme for
detailed mapping of tracks then at least one could simply re-tag the
existing railway=rail as (e.g.) railway:track=rail and not destroy the
existing detailed geometry. Of course, someone would have to draw in the
basic route network too; I bet the data for that is somewhere buried in
the OSM historical record, since a schematic view of the UK railway
network was imported into OSM as a starting point many years ago and is
still the basis of simple mapping in many rural areas, but admittedly I
have no idea how or whether it could easily be recovered for situations
like your Battersea example.
> However what I do agree with you is that the rail guidelines should be more
> detailed but I would go the other way with saying that all tracks should be
> mapped not less for complete mapping. That is a common way of doing things
> and going forward especially as we get more detailed mapping (it's slowly
> coming to the US ;))
I'd be fine with that as long as the result includes details about how
to connect the road and rail networks in a clear, unambiguous way at all
levels of detail. It is the lack of definition around these interactions
that causes the most difficulty, I think.
London isn't a great example of the problem since it has many, many
railways but very few situations where railways connect with highways at
Croydon Tramlink is one counter-example, and I'd concede that someone
has done great work in accurately mapping the path of it that I wouldn't
want to destroy, but it is sadly completely disconnected from the
highway network, and that is what I'd like to address.
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