[Tagging] Mismatched Level of Detail in highways vs. other elements
John F. Eldredge
john at jfeldredge.com
Sun Apr 7 20:37:58 UTC 2013
Richard Mann <richard.mann.westoxford at gmail.com> wrote:
> You can always make a rendering with the streets drawn wider at zoom
> That would solve most of the problems.
> Mapping all the street as a series of parallel lines or areas will
> make a large mess of data that is a pain to decipher. It only really
> value at very high zoom, and it isn't a good idea to add complexity
> can't be easily ignored.
> On Sun, Apr 7, 2013 at 7:37 PM, Martin Atkins
> <mart at degeneration.co.uk>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
> > 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
> > node.
> > On the other hand, rail lines are most commonly mapped by their
> > 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
> > rather than having them meet at a single node as with the highways.
> > creates the following ridiculous effect in rendering:
> > http://osm.org/go/TZHvFT5aF--
> > Notice how the rails only just fit inside the rendered street on
> > sections, and cut the street corner completely at the intersection.
> > However, here's how it actually looks on the ground (looking across
> > intersection from east to west). Notice that the rails are
> > contained within this 4-lane intersection (all four being normal
> > lanes with no physical separation except for the tram boarding
> > (On the plus side, we're doing better than Google Maps, whose
> > 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
> > accurately tag a bench or bus stop on a sidewalk because the
> > doesn't exist as a separate construct. Fences or buildings directly
> > the street end up rendering either over the street or set back from
> > 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
> > 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
> > described, with separated lanes and proper physical relationships
> > surrounding objects.
> > How have others resolved this fundamental conflict? More detailed
> > or less-detailed everything else?
> > ______________________________**_________________
> > Tagging mailing list
> > Tagging at openstreetmap.org
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> Tagging at openstreetmap.org
The rendering convention that I have seen on most non-OSM maps is to show rail lines as a single cross-hatched line, regardless of the number of tracks, except for switching yards. The latter have multiple tracks shown, although usually fewer tracks than are physically present, since that level of detail isn't practical at a normal mapping scale.
John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for it is better to think wrongly than not to think at all." -- Hypatia of Alexandria
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