[OSM-talk] routing across open spaces
David Murn
davey at incanberra.com.au
Sun Dec 5 01:36:24 GMT 2010
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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