Hi Johan,
I don't know about storing information for a router, I'm just speaking
from the perspective of myself as a mapper and saying that to me exit_to
on a junction node seems a simple and established way of recording exit
destination signs, so I don't see why I and other mappers using exit_to
should change from this. On a simple short one way motorway slip road
with just one road leading on to it, as in your example, I can see that
destination tagged on the way probably wouldn't be a problem. However on
longer and more complex ways you'd need to make sure that the roads were
split before every junction - to identify the point where the
destination is signed, as the destination(s) could change at different
points along that road.
Cheers,
Paul
On 20/11/12 23:02, Johan C wrote:
Well Paul, the fundamental question is: where do you store the
information needed for any router, in a node, in a way or in both? In
my opinion destination on a way can work very well, please take a look
at this example:
http://wiki.openstreetmap.org/wiki/User:It's_so_funny
<http://wiki.openstreetmap.org/wiki/User:It%27s_so_funny>
Cheers, Johan
ps no destination relation needed in this example, which makes it more
compliant to KISS
2012/11/20 Paul Williams <pjwde...@googlemail.com
<mailto:pjwde...@googlemail.com>>
I don't see any reason to deprecate exit_to, it seems to be the
simplest method of mapping a destination sign on a motorway
junction or similar exit. I use exit_to fairly frequently and it
has been a documented tag for a while (although on the motorway
junction page rather than it's own page) and is also used in JOSM
presets.
I feel it is a less ambiguous tag than destination (as a tag on a
way) as it shows the specific point where a destination is signed,
unlike destination tagged on a way. If you use destination as a
tag on a way then I think you'd need to be sure that at every
point along that way the destination(s) given is the same
throughout and if not or you didn't know you'd need to split the
way. The Taginfo stats also seem to show that exit_to is the most
popular of the three different ways of mapping destinations: a
destination relation, exit_to on a junction node, or destination
as a tag on a way.
A destination relation is also a clear way of mapping a
destination as the intersection and both the 'from' and 'to' ways
are part of the relation, and is particularly useful in mapping
situations where exit_to wouldn't work (like at a crossroads) so I
do also use this method. It is however more complex (and so is
unlikely to be a method that a new mapper would be able to use)
particularly where there are multiple destinations given on a sign
which requires a relation for each destination.
Cheers,
Paul Williams
(Paul The Archivist)
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