[Talk-transit] Summary of Public Transport Proposal Criticism -> a real example from Zürich
Michael von Glasow
michael at vonglasow.com
Thu Feb 10 18:50:03 GMT 2011
On 02/10/2011 11:01 AM, Dominik Mahrer (Teddy) wrote:
> If I visit a bus stop by foot I can manage to map the pole/platform.
> So this could be level 1. But when I visit within the bus, I can only
> manage to map the stop position. So this would be level 1. What should
> be level 1 then?
All you need when mapping from within the bus is the information whether
the stop you've registered is on the left or on the right side of the
road (or two facing stops). Then simply place a highway=bus_stop on the
appropriate side of the road.
Admittedly, this is less precise than visiting the place on foot, but:
- when in a bus, the major source of imprecision is degradation of the
GPS signal, which often introduces errors of a few meters (more than the
width of the sidewalk) and dwarfs the imprecision introduced by
guesstimating the distance between the way and the stop node; the
location of the pole thus ends up in about the same range of imprecision
as the stop position itself
- if you have aerial imagery available (preferably from government
sources, which tend to be more precise than Bing and the like), in many
cases you can make out some features of the bus stop on the images - the
shelter, road markings, a widened/narrowed sidewalk - and fine-tune your
position with that
- when all else fails, you can always leave a fixme tag, explaining that
the position of the stop is approximate and other mappers should feel
free to correct it
As for defining the levels, I would define level 1 as the simplest
scheme in terms of learning curve, and when in doubt, opt for the tags
with the highest diffusion. So here I'd definitely go for
highway=bus_stop on level 1.
>>> And I do not think we (mappers) can replace an existing public
>>> routing solution like hafas (too complex and too dynamic).
>> There have been calls for this. IMO it is feasible, but as a layer on
>> OSM, not within.
> Maybe, you are right. But then the next question that pops up is: Do
> we then need the bus routes within OSM at all? Wouldn't it make more
> sense to move them to this new layer?
Transiki, as I have understood, aims to provide this layer on top of OSM
(in fact going even further than just routes). If you're looking for the
100% solution, maybe that's the place to develop it. On the other hand,
Transiki isn't there yet and I don't even know where it's going. What I
am certain of is that OSM can represent public transport routes,
possibly with some concessions on precision (such as not handling some
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