[OSM-talk] routing across open spaces

[ce-test, qualified testing bv - Gert Gremmen]

I think you should just use the shape outline to create  2 possible
routes, and
present the geographic average between the 2. The average may be
weighted differently
if there are large differences in length between the 2.
Comments in the route description will show that an area is to be
crossed,
and so will the user act when he is actually presented with the area ;<)

-----Oorspronkelijk bericht-----
Van: talk-bounces at openstreetmap.org
[mailto:talk-bounces at openstreetmap.org] Namens David Murn
Verzonden: zondag 5 december 2010 2:36
Aan: Anthony
CC: OSM Talk
Onderwerp: Re: [OSM-talk] routing across open spaces

On Wed, 2010-12-01 at 00:00 -0500, Anthony wrote:

> Anyway, I looked around at a few places labelled leisure=park, and the
> usage is all over the place.  I'd say based on that very unscientific
> sample that it's probably best for routers to use a default of
> access=unknown for leisure=park areas, and only use parks for short
> cuts if they're explicitly tagged with something like foot=permissive.
> 
> Alternatively, I guess it wouldn't be horrible to add something like a
> highway=shortcut tag, so mappers could be explicit about it.  If we've
> gotta add foot=permissive by hand anyway, it's not that much more work
> to add a few extra ways.

I was thinking of this issue last night while playing with my routing
software.  One issue I thought about which makes this difficult, is
different shapes.  If youre trying to route across a square area or any
area which has a direct path from start to finish, routing in your
method is easy.  But I was thinking, what happens if youve got an
L-shaped park or even a U-shaped park.

  +-----+        +-------+
  |     |        |       |
  |     |        | +-C-+ |
A |     | B    A | |   | | B
  +-----+        +-+   +-+

Do you cross the open part of the area in the second example, in a
straight line from A to B?  Do you form an arc?  Do you simply go from A
to B, but go around the edge near C?  As an area is unlikely to be a
perfect oblong, this situation may arise more often than one would
think.

David


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