Changeset: 35582900
rail tagging Derby to Chesterfield (passenger_lines, usage, proposed:frequency, plus missing tags)
Closed by lcmortensen
Tags
build | 2.4-12-g7158c69 |
---|---|
created_by | Potlatch 2 |
version | 2.4 |
Discussion
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Comment from SomeoneElse
Hi,
You've added "passenger_lines=2" to at https://www.openstreetmap.org/way/212750580#map=19/53.18452/-1.40075
What exactly is it supposed to indicate? -
Comment from lcmortensen
passenger_lines indicates the number of tracks a line has, e.g. passenger_lines=2 indicates a double track line. It replaces the deprecated tracks key. See http://wiki.openstreetmap.org/wiki/Key:passenger_lines
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Comment from SomeoneElse
But at https://www.openstreetmap.org/way/212750580#map=19/53.18452/-1.40075 there are 4 (of 5) lines that could be considered "main lines", not 2.
What is the point of tagging something that can be obtained simply by looking at other nearby data? I wouldn't map a house, and then add a tag "houses_nearby=26"?
Also in what way is "tracks" deprecated? It's not useful here, because all lines are individually mapped, but it's useful in plenty of other places around the world.
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Comment from lcmortensen
There are only two parallel lines at that point (the third appears to be a loop). Once the Midland Main Line and Erewash Valley Line physically join closer to Grassmoor, it goes up to passenger_lines=4.
OSM can't detect multiple parallel tracks and when you're looking at zoom 12 or lower, you can't see individual tracks. Passenger_lines bridges this gap. -
Comment from SomeoneElse
No, there really are 4 parallel main lines at https://www.openstreetmap.org/way/212750580#map=19/53.18452/-1.40075 . Have a look from the bridge at the south end of Ankerbold Road (the side of the bridge isn't too high to see over the top of).
I'm not sure what you mean by "OSM can't detect multiple parallel tracks". "OSM" is just a big pile of data - are you talking about a particular rendering here?
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Comment from lcmortensen
There are four parallel tracks geographically, but two sets of two parallel tracks topographically until you reach the junction north of Bridge Street/Hagg Hill. Another example would be the Underground District and Piccadilly lines between Acton Town and Earls Court - they run parallel geographically but topographically they never connect and therefore are separate lines.
And did you even read the wiki article? It specifies renderings where passenger_lines shows. -
Comment from SomeoneElse
Sorry, but that's rubbish. At https://www.openstreetmap.org/way/212750580#map=19/53.18452/-1.40075 there are no joins between the four parallel tracks. In what way is that "two sets of two parallel tracks topographically"?
Adding "nonsense" tags makes OSM data harder for data consumers to understand and harder for them to use.
OSM data is supposed to be verifiable - a local mapper (like me) is supposed to be able to go to a place and say "yes, I can see that". Here the "passenger_lines" is not just superfluous (i.e. something that ought to be derivable from the data) the value that you have used is actually wrong.
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Comment from chillly
What does the wiki have to do with sensible, logical tagging?
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Comment from lcmortensen
So if a two-lane road merges with another two-lane road to form a four-lane road, I should stat tagging them lanes=4 as soon as they are parallel, not when they merge?
Standing on the Station Road bridge looking south you can see the two sets of lines diverging while looking north you can see there are no points or crossovers connecting them, meaning they're separate parallel lines at that point.
"a local mapper (like me) is supposed to be able to go to a place and say "yes, I can see that"." How do you know that the track gauge is 1435mm - have you actually risked life and limb to measure that? Or that the electrification is definitely 25,000 volts?
Nobody else has complained about the usage of the passenger_lines tag in the whole time I was tagging west of the Pennines - it's when I venture east of them that hostile mappers bite everyone and anyone. -
Comment from SomeoneElse
Re "How do you know that the track gauge is 1435mm" I've seen trains with that track gauge go down it and they haven't fallen off :)
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Comment from SomeoneElse
The "two-lane road" analogy isn't a good one because there's no "passenger_lanes=8" tag/value on e.g. http://www.openstreetmap.org/way/30175700 - there's "lanes=4", and also "lanes=4" on the other carriageway http://www.openstreetmap.org/way/40895418 . In my opinion the same would work here - just use the implicit tracks=1 on each of the four lines and leave it at that. However, if you must tag "there are some lines quite close together here" at least use a value that corresponds to "the number of lines that are quite close together".
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Comment from lcmortensen
Here is the rendering of passenger_lines: http://product.itoworld.com/map/231?lon=-1.65321&lat=53.42826&zoom=8.
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Comment from chillly
Ah, so you're tagging for the renderer!
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Comment from lcmortensen
One closer to home (for me) are https://www.openstreetmap.org/way/106857413 and https://www.openstreetmap.org/way/106857420.They are labeled passenger_lines=2 despite there being four parallel tracks because the two central tracks belong to a separate rail route and are super-elevated relative to the outer lines. They do not physically join together until Wellington Distant Junction to the south near Aotea Quay. (https://www.openstreetmap.org/node/3235330766)
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Comment from lcmortensen
"Ah, so you're tagging for the renderer!"
You did read the section entitled "clarification"? You're allowed to enter tags for a specific renderer to understand, as long as they're not completely misleading (e.g. tagging flowerbeds as industrial areas). -
Comment from chillly
And doubling the number of tracks for no reason is not misleading?
I've heard enough. Life is too short to argue about this.
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Comment from lcmortensen
You have to tag at least one way passenger_lines=2 for the renderer. Tagging the other way is just for redundancy (and I'm a bit OCD on ways matching).
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Comment from SomeoneElse
Perhaps a bit of background about the layout here will help. Historically, there were 4 tracks down towards Nottingham, not 2. at https://www.openstreetmap.org/node/2202969410 Someone's added a pair of abandoned railways, and they did used to join the MML at about that location. Handily, wikipedia has a photo from 1983:
https://en.wikipedia.org/wiki/File:Clay_Cross_station_site_geograph-3110788-by-Ben-Brooksbank.jpg
Around 10-15 years ago the 2nd pair of tracks towards Nottingham were removed, and the trackbed on the other pair was changed, which resulted in them being resited slightly.
The reason there's more of a gap between the pairs of tracks at the bridge because that's where the station was (island platform). The station's gone but there's now a bridge pillar there, which is why the two pairs of 4 lines are fairly close at the site of Clay Cross Junction, separate a bit to go under the bridge, and then get closer together again. You can get a bit more of an idea from http://claycross.org.uk/History/railways.htm .
It's also perhaps worth mentioning that at around https://www.openstreetmap.org/node/2203012981 there's some new-build work taking place (looks like a new passing loop located where some of the old trackbed was), so that bit in OSM is incomplete or soon to be so.
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Comment from lcmortensen
I stand corrected - it should be passenger_lines=4 as far south as the old Clay Cross South Junction. I've even double checked against the sectional appendix and there appears to be a break in mileage and a change in engineers line reference at that point too. I'll correct it shortly.
- Midland Main Line (205652787), v3
- Midland Main Line (61951529), v6
- Midland Main Line (61951530), v4
- Midland Main Line (212750580), v5
- Midland Main Line (212750584), v4
- Midland Main Line (102896822), v4
- Midland Main Line (171491376), v5
- Midland Main Line (171491377), v3
- Midland Main Line (171491381), v2
- Midland Main Line (171491383), v2
- Midland Main Line (29426615), v10
- Midland Main Line (29426616), v8
- Midland Main Line (202671665), v2
- Midland Main Line (202671666), v2
- Midland Main Line (202671667), v2
- Midland Main Line (202671668), v2
- Midland Main Line (202671670), v2
- Midland Main Line (103434097), v5
- Midland Main Line (103434098), v4
- Midland Main Line (86608811), v6
Nodes (2)
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