<div>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).</div>
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<div>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.</div>
<div><br>Richard</div>
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<div class="gmail_quote">On Mon, Jun 22, 2009 at 10:45 AM, Roger Slevin <span dir="ltr"><<a href="mailto:roger@slevin.plus.com">roger@slevin.plus.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">As someone who doesn't have the experience of mapping that you all do, but I<br>do know something about public transport, I can see how the various concepts<br>
for single track and double track etc work along straightforward corridors<br>(note these must be "tracks" (or maybe some other term) and not "lines" - as<br>a "line" in public transport is something completely separate from the<br>
infrastructure) ... but what happens when operational details get more<br>complicated ... at stations, or near and in depots and sidings? What<br>happens for passing bays? Does a track have a directionality associated<br>
with it (even if it is only implied by a national convention of "driving on<br>the left/right"... though that will give some issues on the German border<br>where operations switch sides) - and what happens when multiple tracks are<br>
signalled for bi-directional working?<br><br>I sense that there is a potential issue here between describing the physical<br>infrastructure and describing its functional performance ... and I am not<br>sure the boundary has been drawn correctly between the two.<br>
<font color="#888888"><br>Roger<br></font>
<div class="im"><br>-----Original Message-----<br>From: <a href="mailto:talk-transit-bounces@openstreetmap.org">talk-transit-bounces@openstreetmap.org</a><br></div>
<div class="im">[mailto:<a href="mailto:talk-transit-bounces@openstreetmap.org">talk-transit-bounces@openstreetmap.org</a>] On Behalf Of Peter Miller<br>Sent: 22 June 2009 10:31<br>To: Jochen Topf<br>Cc: osm<br>Subject: Re: [Talk-transit] Multiple tracks<br>
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<div class="h5">On 22 Jun 2009, at 07:51, Jochen Topf wrote:<br><br>> On Sun, Jun 21, 2009 at 05:09:35PM +0100, Richard Mann wrote:<br>>> No, simpler than that:<br>>><br>>> tracks=1 => render a single line at all zooms<br>
>> tracks=2 => render a double line at all zooms<br>>> tracks=X => render a multiple line with X tracks at all zooms<br>>> tracks=1ofX => render a single line at high zooms, but render as if<br>
>> tracks=X<br>>> at medium/low zooms<br>><br>> But then you'd still draw several lines nearly on top of each other<br>> in medium<br>> zoom levels which doesn't look good, which was the problem we were<br>
> trying to<br>> fix?<br>><br>> Anyway, this is a rather specialized trick about rendering the<br>> number of tracks<br>> properly. But what if you want to render other attributes. Say one<br>> of your two<br>
> tracks is an industrial railway, the other a normal passenger<br>> railway and you<br>> want to distinguish those types. On medium zoom levels, is this a<br>> two track<br>> thing and we loose the type distinction, or do we keep it?<br>
<br>The dual_carriageway and Junction relations would appear to the a good<br>way of doing such things. I realise that the 'dual carriageway' term<br>is not right and that other work would be required on the<br>specifications, however it would seem a better starting point.<br>
<br><a href="http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions" target="_blank">http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions</a><br><a href="http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways" target="_blank">http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways</a><br>
<br>A group of parallel tracks would be combined using 'dual carriageway'<br>and then a group short sections of track and nodes can be combined as<br>a 'Junction'. The render would then have a choice of drawing modes,<br>
either a single line and single point, or multiple lines/points.<br><br><br><br>Regards,<br><br><br><br>Peter<br><br><br>><br>><br>> Jochen<br>> --<br>> Jochen Topf <a href="mailto:jochen@remote.org">jochen@remote.org</a> <a href="http://www.remote.org/jochen/" target="_blank">http://www.remote.org/jochen/</a><br>
> +49-721-388298<br>><br>><br>> _______________________________________________<br>> Talk-transit mailing list<br>> <a href="mailto:Talk-transit@openstreetmap.org">Talk-transit@openstreetmap.org</a><br>> <a href="http://lists.openstreetmap.org/listinfo/talk-transit" target="_blank">http://lists.openstreetmap.org/listinfo/talk-transit</a><br>
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