[OSM-talk] routing across open spaces

[Anthony]

On Tue, Nov 30, 2010 at 5:22 PM, David Murn <davey at incanberra.com.au> wrote:
> On Tue, 2010-11-30 at 11:43 -0500, Anthony wrote:
>> On Tue, Nov 30, 2010 at 11:29 AM, David Murn <davey at incanberra.com.au> wrote:
>> > On Tue, 2010-11-30 at 15:30 +0000, Ed Avis wrote:
>> >> As a rough rule, leisure=park and landuse=grass could be considered walkable,
>> >> unless tagged access=no or access=private.
>> >
>> > You may also find timed access restrictions apply.  Some parks here for
>> > example, are gated off at night, which again may affect vehicle/bicycle
>> > traffic but not foot traffic, or it may affect everything.
>>
>> Fortunately, there are tags for all of this:
>>
>> http://wiki.openstreetmap.org/wiki/Access#Transport_mode_restrictions
>> http://wiki.openstreetmap.org/wiki/Access#Access_time_restrictions
>> http://wiki.openstreetmap.org/wiki/Barrier
>
> Thats great, what happens if someone traces the park from aerial
> imagery, and doesnt know/care about any of those?  Or for that matter,
> if someone tags it on-the-ground, but doesnt add all the details?

Then the mapping will be incomplete until someone else comes along and
fixes it.  Same as what happens if, for instance, someone traces a
street from aerial imagery and doesn't know/care about the one-way
tag, or the "no motorcycles" restriction.

> What defautls should routers use?  Should they assume all parks are flat
> and walkable, or should they assume theyre fenced, or that theyre 'stay
> off the grass' or 'stay on the grass' or what?

Personally, I'd assume that they're (relatively) flat and walkable.
>From the wiki:

"A park. Open, green area for recreation, usually municipal. These are
outdoor areas, typically grassy/green areas, set aside of leisure and
recreation.
Typically (or pretty much always) open to the public, but may be
fenced off, and may be closed e.g. at night time."

> This is the problem.  A way on the map, shows there is a right of
> passage.  If theres no way in an area, it might mean the area is
> passable, but it might also mean it hasnt been mapped.  Hence, the
> safest option is to not route unless theres a right of way to follow.

That's nonsense.  A way does not show a right of passage.  A
particularly tagged way shows a right of passage.  And a park is a
particularly tagged way.