[Tagging] Mismatched Level of Detail in highways vs. other elements

LM_1 flukas.robot+osm at gmail.com
Sun Apr 7 18:58:27 UTC 2013


In my view the streets should be more detailed - after all having the
details dropped by computers is possible (even if not always easy). but
detail that is not there cannot be add in any simple way. This case might
depending on the precise conditions fulfil the requirements for separate
direction lanes. If not some more detailed scheme would have to be used -
mapping streets as areas. Eventually that will be the only viable option
city centres currently mapped in high detail with only the streets being
overly simplified...

Lukáš Matějka (LM_1)


2013/4/7 Martin Atkins <mart at degeneration.co.uk>

>
> 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?
>
>
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