[Tagging] Status of oneway=cw oneway=ccw

[Peter Elderson]

*Oneway or not?*
*oneway=yes* is the simplest and already most used way to indicate that a
route is oneway. It does not matter if that's legal, customary, by design
or recommended. For ways, oneway is a legal thing; for routes it is not.
Routers look at the ways, not the routes. No clash there. It also does not
matter that it is physically possible to walk a route the other way.
Mappers in the wild seem to agree on this point.
You record what is there, and that is a route signed in one direction. In
fact the route only exists because of the waymarks; the line over the ways
is imaginary, not physical.

*Which direction?*
The direction cannot reliably be calculated from the relation, even when
the whole route is one relation, let alone for complex routes which are
hierarchies or collections of route relations.
A way with start role could help on simple linear routes, if sorting works
out. If not, you can't tell. On simple closed_loop routes, you would need
an end role as well, and the sorting requirement is still there.
If routes are composed of sub-relations each possibly having start and or
end roles, that would be a problem: which ones are to be used to determine
direction?

I think there is no other way then to assume that the route is ordered or
can be sorted with a standard sorting routine. If not, too bad, direction
cannot be determined. Flip a coin.

If it is or can be sorted, what always works to establish the direction, is
to mark two (any two) consecutive ways in the route relation as first and
second.

Vr gr Peter Elderson


Op vr 3 mei 2019 om 13:44 schreef Andy Townsend <ajt1047 at gmail.com>:

>
> On 03/05/2019 12:21, s8evq wrote:
> > But what's the alternative then?
> >
>
> Explicit start and/or finish nodes?
>
> As previously mentioned, you simply can't rely on route ways being ordered.
>
> Best Regards,
>
> Andy
>
>
>
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