On Roger's point about sidings - I'd map those as a separate track group, since they are the sorts of things people would expect to disappear at lower zooms. So north of Oxford station, I'd have the 4 down carriage sidings as one group, the four running lines as one group and the 4 up carriage sidings as a third group. Within each of those three groups, you could either do the individual tracks (as 1of4), or the tracks as a group (tracks=4).
On loops, I'd probably exclude them from the running lines group, and use other tags (perhaps has_loops=yes) to tell me that there are extra tracks for a short-distance. You might also do has_loops:left and has_loops:right, but one-sided rendering is on the tricky side. So just south of Oxford at Kennington, you'd have the two running lines as tracks=2 (or 2xtracks=1of2) with has_loops=yes. If I had done the two tracks separately, the renderer would be entitled to expect me to have done the freight loops separately as well, so they can ignore has_loops=yes at high zooms, and just render the ways that have been drawn. Richard On Mon, Jun 22, 2009 at 10:45 AM, Roger Slevin <ro...@slevin.plus.com>wrote: > As someone who doesn't have the experience of mapping that you all do, but > I > do know something about public transport, I can see how the various > concepts > for single track and double track etc work along straightforward corridors > (note these must be "tracks" (or maybe some other term) and not "lines" - > as > a "line" in public transport is something completely separate from the > infrastructure) ... but what happens when operational details get more > complicated ... at stations, or near and in depots and sidings? What > happens for passing bays? Does a track have a directionality associated > with it (even if it is only implied by a national convention of "driving on > the left/right"... though that will give some issues on the German border > where operations switch sides) - and what happens when multiple tracks are > signalled for bi-directional working? > > I sense that there is a potential issue here between describing the > physical > infrastructure and describing its functional performance ... and I am not > sure the boundary has been drawn correctly between the two. > > Roger > > -----Original Message----- > From: talk-transit-boun...@openstreetmap.org > [mailto:talk-transit-boun...@openstreetmap.org] On Behalf Of Peter Miller > Sent: 22 June 2009 10:31 > To: Jochen Topf > Cc: osm > Subject: Re: [Talk-transit] Multiple tracks > > > On 22 Jun 2009, at 07:51, Jochen Topf wrote: > > > On Sun, Jun 21, 2009 at 05:09:35PM +0100, Richard Mann wrote: > >> No, simpler than that: > >> > >> tracks=1 => render a single line at all zooms > >> tracks=2 => render a double line at all zooms > >> tracks=X => render a multiple line with X tracks at all zooms > >> tracks=1ofX => render a single line at high zooms, but render as if > >> tracks=X > >> at medium/low zooms > > > > But then you'd still draw several lines nearly on top of each other > > in medium > > zoom levels which doesn't look good, which was the problem we were > > trying to > > fix? > > > > Anyway, this is a rather specialized trick about rendering the > > number of tracks > > properly. But what if you want to render other attributes. Say one > > of your two > > tracks is an industrial railway, the other a normal passenger > > railway and you > > want to distinguish those types. On medium zoom levels, is this a > > two track > > thing and we loose the type distinction, or do we keep it? > > The dual_carriageway and Junction relations would appear to the a good > way of doing such things. I realise that the 'dual carriageway' term > is not right and that other work would be required on the > specifications, however it would seem a better starting point. > > http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions > http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways > > A group of parallel tracks would be combined using 'dual carriageway' > and then a group short sections of track and nodes can be combined as > a 'Junction'. The render would then have a choice of drawing modes, > either a single line and single point, or multiple lines/points. > > > > Regards, > > > > Peter > > > > > > > > Jochen > > -- > > Jochen Topf joc...@remote.org http://www.remote.org/jochen/ > > +49-721-388298 > > > > > > _______________________________________________ > > Talk-transit mailing list > > Talk-transit@openstreetmap.org > > http://lists.openstreetmap.org/listinfo/talk-transit > > > _______________________________________________ > Talk-transit mailing list > Talk-transit@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk-transit > > > _______________________________________________ > Talk-transit mailing list > Talk-transit@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk-transit >
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