On 04/13/2013 10:18 AM, Rovastar wrote:
Martin,
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.
http://www.openstreetmap.org/?lat=51.47119&lon=-0.14847&zoom=15&layers=M
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
grade.
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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