[Talk-transit] Multiple tracks

Richard Mann richard.mann.westoxford at googlemail.com
Mon Jun 22 12:53:40 BST 2009


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 <roger at 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-bounces at openstreetmap.org
> [mailto:talk-transit-bounces at 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  jochen at remote.org  http://www.remote.org/jochen/
> > +49-721-388298
> >
> >
> > _______________________________________________
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> > Talk-transit at openstreetmap.org
> > http://lists.openstreetmap.org/listinfo/talk-transit
>
>
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