Re: [Talk-transit] [Spam] Re: Multiple tracks
Choosing not to render a point because there's something else more important close by is relatively easy. Aggregating adjacent lines is much (much) harder. Identifying the number of lines that are adjacent is much (much) easier for the tagger than for the renderer. But I seem to be repeating myself; you either believe me or you don't. Richard On Tue, Jun 23, 2009 at 7:52 AM, Frankie Roberto fran...@frankieroberto.com wrote: On Mon, Jun 22, 2009 at 5:21 PM, Peter Miller peter.mil...@itoworld.comwrote: Can I suggest that as a start you create the detailed track layout and then we can look at different grouping strategies and see which ones the Mapnik people and routing people will find useful. Whatever you do should work for rail and trams and I see no reason for there not to be generality with roads. Lets not worry too much about the wrapping until we have stuff to wrap. I think this is a good approach. Using a tracks=1ofX tag could end up a complete waste of time if renderers can use the relations to dynamically pick whether to draw one track or more anyway. Mapnik seems to decide how many POIs to render based partly on how many it can fit on the map, so this doesn't seem infeasible. I'd like to see some discussion about strategies for tagging individual tracks though. I've attempted to do it in a few places, but mainly only at stations (where I've also drawn the platforms). Has anyone attempted to draw the switches where two lines meet? How about adding oneway=yes? Level crossings? Frankie -- Frankie Roberto Experience Designer, Rattle 0114 2706977 http://www.rattlecentral.com ___ 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
Re: [Talk-transit] [Spam] Re: Multiple tracks
On Wed, Jun 24, 2009 at 1:31 PM, Richard Mann richard.mann.westoxf...@googlemail.com wrote: Choosing not to render a point because there's something else more important close by is relatively easy. Aggregating adjacent lines is much (much) harder. Identifying the number of lines that are adjacent is much (much) easier for the tagger than for the renderer. But I seem to be repeating myself; you either believe me or you don't. I do believe you, and I haven't actually tried to implement such an algorithm myself. It's just my instinct that we should be tagging the data and letting the renderers worry about rendering algorithms later. However, I agree that there's a balance to be struck. Do relations solve the problem at all? If a track is part of a route relation, then could a renderer use that as a means of aggregating the tracks together? Are there any Mapnik people we can involve in this discussion? Frankie -- Frankie Roberto Experience Designer, Rattle 0114 2706977 http://www.rattlecentral.com ___ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
Re: [Talk-transit] [Spam] Re: Multiple tracks
On Wed, Jun 24, 2009 at 2:45 PM, Richard Mann richard.mann.westoxf...@googlemail.com wrote: Do relations solve the problem at all? If a track is part of a route relation, then could a renderer use that as a means of aggregating the tracks together? My hunch is that relations probably don't actually help much, unless you could rely on them being done consistently and accurately. Hmm... One idea another OSMer suggested a while back (when the idea of tagging tracks still sounded ridiculous) is to have some way of distinguishing between a 'track' and a railway line (or 'corridor' is perhaps a better word), so that renderers can choose which to display (and so that the data contains both conceptually different things). Not sure how best to implement this. The easiest thing would be to have the middle track double up as the way which represents the line, somehow. The hardest thing might be to have ways which mark both edges of the rail corridor (like how we do riverbanks). Frankie -- Frankie Roberto Experience Designer, Rattle 0114 2706977 http://www.rattlecentral.com ___ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
Re: [Talk-transit] [Spam] Re: Multiple tracks
The traditional method is to tag a node to be used as low zooms, and to tag various bits of detail to be used at high zooms. Using a relation for a point-location seems to be a rather more complicated way of achieving the same end (more complicated to create, more complicated to maintain). In the case of parallel ways, you could either: 1) create a further parallel way. This is what is done with house numbers (and to my mind would work for central reservations) 2) add information for the group to all the components (eg tracks=1of2). This works well if there's no obvious entity defining the centre line, but the components are very consistently located in respect of one another 3) create a relation for the group to hold group-level information (presumably this requires an algorithm to determine its geo-location, and could go a bit haywire if the component elements weren't strictly identical but offset, and would be complicated even if they were) The group-level information needs to be held somewhere (ie we can't just put tracks=1). But I don't think relations are the answer to all our problems. Richard On Mon, Jun 22, 2009 at 5:21 PM, Peter Miller peter.mil...@itoworld.comwrote: On 22 Jun 2009, at 12:53, Richard Mann wrote: 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. Can I suggest that as a start you create the detailed track layout and then we can look at different grouping strategies and see which ones the Mapnik people and routing people will find useful. Whatever you do should work for rail and trams and I see no reason for there not to be generality with roads. Lets not worry too much about the wrapping until we have stuff to wrap. For your interest, here is an example road interchange which can be rendered as a dot if required, or used in driving instructions as 'turn left at the 'Whitehouse Junction'. http://www.openstreetmap.org/browse/relation/2470 Here is a dual-carriageway example - just bind all the parallel ways together and a renderer can then do a line down the middle at some point. http://www.openstreetmap.org/browse/relation/2490 Here is a railway station where all the elements (including tracks, sidings, platforms, buildings, car parking, taxi ranks and cycle racks) are all part of a relation. http://www.openstreetmap.org/browse/relation/2522 And here is a sample rail junction wrapped up using a relation:- http://www.openstreetmap.org/browse/relation/162263 This should make it very easy for a renderer. The general rule is 'if you can't fit in all the detail on the map and it is part of a relation then do a single dot or single line for the whole thing. Regards, Peter Richard On Mon, Jun 22, 2009 at 10:45 AM, Roger Slevin ro...@slevin.plus.comwrote: 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
Re: [Talk-transit] [Spam] Re: Multiple tracks
On Mon, Jun 22, 2009 at 5:21 PM, Peter Miller peter.mil...@itoworld.comwrote: Can I suggest that as a start you create the detailed track layout and then we can look at different grouping strategies and see which ones the Mapnik people and routing people will find useful. Whatever you do should work for rail and trams and I see no reason for there not to be generality with roads. Lets not worry too much about the wrapping until we have stuff to wrap. I think this is a good approach. Using a tracks=1ofX tag could end up a complete waste of time if renderers can use the relations to dynamically pick whether to draw one track or more anyway. Mapnik seems to decide how many POIs to render based partly on how many it can fit on the map, so this doesn't seem infeasible. I'd like to see some discussion about strategies for tagging individual tracks though. I've attempted to do it in a few places, but mainly only at stations (where I've also drawn the platforms). Has anyone attempted to draw the switches where two lines meet? How about adding oneway=yes? Level crossings? Frankie -- Frankie Roberto Experience Designer, Rattle 0114 2706977 http://www.rattlecentral.com ___ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
Re: [Talk-transit] [Spam] Re: Multiple tracks
On 22 Jun 2009, at 12:53, Richard Mann wrote: 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. Can I suggest that as a start you create the detailed track layout and then we can look at different grouping strategies and see which ones the Mapnik people and routing people will find useful. Whatever you do should work for rail and trams and I see no reason for there not to be generality with roads. Lets not worry too much about the wrapping until we have stuff to wrap. For your interest, here is an example road interchange which can be rendered as a dot if required, or used in driving instructions as 'turn left at the 'Whitehouse Junction'. http://www.openstreetmap.org/browse/relation/2470 Here is a dual-carriageway example - just bind all the parallel ways together and a renderer can then do a line down the middle at some point. http://www.openstreetmap.org/browse/relation/2490 Here is a railway station where all the elements (including tracks, sidings, platforms, buildings, car parking, taxi ranks and cycle racks) are all part of a relation. http://www.openstreetmap.org/browse/relation/2522 And here is a sample rail junction wrapped up using a relation:- http://www.openstreetmap.org/browse/relation/162263 This should make it very easy for a renderer. The general rule is 'if you can't fit in all the detail on the map and it is part of a relation then do a single dot or single line for the whole thing. Regards, Peter 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.
