I do some mapping in SF too. The Muni Metro lines weirded me out when I first saw it, and I looked up the proper practice on the wiki as well as looking for a few examples in Europe, and it seems that the best practice is to just add railway tags and the proper relations to the street whenever it runs along a street, and as a way by itself when it runs in its own right-of-way (such as the J line's jog around a hill a little south of Dolores Park).
I'd support mapping the Muni Metro lines the European/more common way, if nobody else has any objections. On Apr 7, 2013 1:38 PM, "Martin Atkins" <[email protected]> wrote: > > Hi all, > > I do mapping in San Francisco, CA and I'm frustrated about the > inconsistent levels of detail we typically use when mapping urban > environments. > > For example, most highways are mapped in a network-oriented fashion with > one string of ways representing both directions of traffic, often > encapsulating other features like cycle lanes and sidewalks, and > intersections simply represented by crossing the streets at a single common > node. > > On the other hand, rail lines are most commonly mapped by their physical > shape, so the rail ways come in pairs. The people who mapped the tram lines > in San Francisco also mapped the curves of the rails at intersections, > rather than having them meet at a single node as with the highways. This > creates the following ridiculous effect in rendering: > http://osm.org/go/TZHvFT5aF-- > > Notice how the rails only just fit inside the rendered street on straight > sections, and cut the street corner completely at the intersection. > > However, here's how it actually looks on the ground (looking across the > intersection from east to west). Notice that the rails are completely > contained within this 4-lane intersection (all four being normal traffic > lanes with no physical separation except for the tram boarding platforms): > http://oi45.tinypic.com/**w6qsgh.jpg<http://oi45.tinypic.com/w6qsgh.jpg> > > (On the plus side, we're doing better than Google Maps, whose rendering > makes it look like the rails on Church street are both off to the west side > of the street! http://tinyurl.com/cedot4n ) > > This problem shows up in various other contexts too: it's impossible to > accurately tag a bench or bus stop on a sidewalk because the sidewalk > doesn't exist as a separate construct. Fences or buildings directly abut > the street end up rendering either over the street or set back from it > because the true width of the street is not represented. > > For most normal street mapping and vehicle routing purposes it seems > sufficient to just know simple landmark details that aid in orientation, > e.g. that whether particular street contains a railway or it passes > alongside a railway. Of course, more detail-oriented uses like 3D > renderings it'd be more important to have the full physical street layout > described, with separated lanes and proper physical relationships with > surrounding objects. > > How have others resolved this fundamental conflict? More detailed streets, > or less-detailed everything else? > > > ______________________________**_________________ > Tagging mailing list > [email protected] > http://lists.openstreetmap.**org/listinfo/tagging<http://lists.openstreetmap.org/listinfo/tagging> >
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