[Tagging] Pedestrian traffic through other areas? (Was: When does highway=footway become highway=pedestrian?)

[Minh Nguyen]

Vào lúc 16:08 2021-11-01, Graeme Fitzpatrick đã viết:
> On Mon, 1 Nov 2021 at 11:56, Minh Nguyen 
> <minh at nguyen.cincinnati.oh.us 
> <mailto:minh at nguyen.cincinnati.oh.us>> wrote:
> 
>     Vào lúc 01:15 2021-10-31, Martin Koppenhoefer đã viết:
>      > pedestrians can walk in any direction and on any side.
> 
>     Yes, pedestrians have more degrees of freedom than four-wheel vehicles
> 
>     area:*=* is for micromapping, while highway=* area=yes is for the
>     essence of the thing. The essence of a pedestrian plaza is its shape,
>     even if the ideal router would calculate a beeline dash through it
>     and a
>     less-than-ideal router still needs us to map that shortest path
>     manually. 
> 
> 
> Moving a semi-related question across to a new thread, how is pedestrian 
> routing through / inside areas such as parks or beaches supposed to work?
> 
> Here's 2 examples:
> 
> https://www.openstreetmap.org/directions?engine=fossgis_osrm_foot&route=-28.00772%2C153.38340%3B-28.00837%2C153.38337#map=18/-28.00817/153.38459 
> <https://www.openstreetmap.org/directions?engine=fossgis_osrm_foot&route=-28.00772%2C153.38340%3B-28.00837%2C153.38337#map=18/-28.00817/153.38459>
> 
> Instead of simply walking along the established grass path across the 
> causeway between the two ponds, you magically jump to the nearest path, 
> then follow that to the closest point to your destination, then jump 
> across to that spot.
> 
> https://www.openstreetmap.org/directions?engine=fossgis_osrm_foot&route=-28.15708%2C153.51028%3B-28.15919%2C153.51315#map=18/-28.15851/153.51212 
> <https://www.openstreetmap.org/directions?engine=fossgis_osrm_foot&route=-28.15708%2C153.51028%3B-28.15919%2C153.51315#map=18/-28.15851/153.51212>
> 
> & same thing - instead of just walking down the beach, you leave it, 
> walk along the path, then back down onto the beach.
> 
> Is there any way of fixing this so that you just walk the straight, 
> shortest, line to your destination?

In principle, a sophisticated router could automatically determine the 
shortest path between any two points within a pedestrian plaza. 
Unfortunately, there's scant support for computing a visibility graph in 
practice. [1] I'm also not sure that parks would be a good place for 
this automated approach, since some would have "Don't walk on grass" 
signs. So for now, if there are any common-sense paths through the area, 
your best bet is to map it explicitly. Mappers have been using tags like 
surface=grass and informal=yes for situations like your park example.

At the same time, you shouldn't feel obligated to manually map every 
possible shortest path that would be in a visibility graph. A pedestrian 
router ought to add proper support for routing through areas before 
marketing its use by autonomous electric skateboards. :-)

By the way, validators such as iD's assume that you've mapped some 
common-sense paths to keep the routing graph connected. However, there 
are inevitably cases where it's better to ignore the validator warning 
than to try to satisfy it with a pedantic path, such as a footbridge 
across a pond in someone's backyard. [2][3]

[1] 
https://lists.openstreetmap.org/pipermail/tagging/2021-October/062740.html
[2] https://www.openstreetmap.org/way/668194545
[3] https://www.openstreetmap.org/way/313191270

-- 
minh at nguyen.cincinnati.oh.us