[Routing] [motorway_link] description of direction

[Nic Roets]

On Mon, Jun 16, 2008 at 7:45 AM, Jon Bright <jon at siliconcircus.com> wrote:
>>> signpost=Dortmund, Münster

I assume the intention was that the routing program outputs some
instruction like 'Take the Dortmund exit' / 'Take the road makered
Dortmund'

> I don't really follow how "signpost" is motorcar or motorway-specific or
> why you couldn't add free-form strings there.  The numbers variant is

My idea is to allow extremely varied instructions including "Open the
gate on the left that appears to be locked, but isn't". We don't want
the software to change it to "Take the Open the gate on the left that
appears to be locked, but isn't exit"

> I don't mind adding relations, but looking ahead for signpost messages
> is a bad plan, imho.

The most complicated tagging I see is something like
<relation>
to=id type=way
via=id type=node // Redundant ?
from=id type=way
warn1=id type=node message='Keep right'
warn2=id type=node message='Take the middle lane'
warn3=id type=node message='Keep left'

The thing is that the routing program will need to know what the
ultimate destination is, which intermediate ways it has chosen and
from that determine what instructions to provide to the user.
Examining the intermediate ways to determine which relations are
active is what I describe as looking ahead.

>> Wuppertal can be tagged with "At the Acme junction, take the middle
>> lane for the exit marked 'Wuppertal'". For messages fitting a certain
>> layout, we can have machine translation into other languages e.g.
>> using 'sed'.
>
> If you're manually tagging, you're never going to get people to follow
> layouts strict enough to be sed-translateable.

I guess you're right.