[Tagging] Branched and alternative roujtes

Paul Allen pla16021 at gmail.com
Mon Aug 19 14:59:11 UTC 2019


On Mon, 19 Aug 2019 at 15:13, Kevin Kenny <kevin.b.kenny at gmail.com> wrote:

> (Summary: What do the data *consumers* want to see in the tagging for
> route alternatives, circular routes, and routes that begin and end on
> dual carriageways?)
>

Since you've broadened the discussion to deal with more than just walking/
hiking/cycling routes, I'll take the opportunity to mention a bus route
(yes,
THAT one, yet again).  It may seem somewhat irrelevant to walking routes
as it has complications they (usually) do not, but a solution that handles
this bus route well would probably be useful for other bus routes and other
types of route.

It's a very messy circular route.  I don't see how any algorithm could
correctly
figure out the actual sequence of ways traversed unless they were sorted
correctly.  Three times it goes into a cul-de-sac, reverses into a side-road
(that is also a cul-de-sac) then goes forward in the opposite direction from
whence it came.  In one place it does the same reverse-turn trick in the
middle
of a very long road because it doesn't go all the way.  In another place it
goes around
four sides of a square, looping the loop.  In one place it traverses the
same sequence
of ways twice, about 30 minutes apart.  Even the drivers occasionally get it
wrong.  It's this: https://www.openstreetmap.org/relation/8592409

Even with a close inspection of the one-way streets along the route, it's
impossible to figure out exactly the sequence in which it traverses the
route.
And yet the information is there (I hope, but there may be errors) in the
ordering
of the relation.  We don't seem to have a tool that would let an ordinary
user
figure it out easily, but a user could (with a great deal of time and
effort)
use the query tool of standard carto to get the route, then work his or way
through
the list of ways in the route by clicking on them in turn, then returning
back to the list
each time. A slightly more savvy user would right-click on each way in turn
to open
it in a new tab, but it's still a lot of time and effort.

At this point I had a thought.  Given what we already have in standard
carto's query
tool, it would be a Simple Matter Of Programming[tm] to add a way of
dealing with
routes.  When I say "SMOP" it could be anything from an hour of trivial
coding to
weeks and weeks of a complete rewrite, but that's just a matter of details
and
some Dunning-Krugeresque hand waving on my part.

The way the query tool works is to return a list of nearby objects.  Hover
over any
object in the list and it is highlighted in a browny-orange.  Very useful.
Suppose
that sort of highlighting also worked with the list of ways in a route
relation (as in
the link above).  The whole route is highlighted in browny-orange.  But if
hovering
over a way in the list caused that way to be highlighted in a different
colour, you
could easily see the steps in the route and the sequence in which they are
traversed (assuming it was correctly sorted, of course), by hovering your
way through
the list.

Things get complicated with alternate routes and variant routes, but I'll
just
do some more Dunning-Krugeresque hand-waving here.

Of course, we're always going to have routes that aren't sorted.  Partly
because
some editors disordered routes (they seem not to do so these days, although
it's
possible they get confused by rare cases).  Partly because some mappers
don't
realize they should do so (although mappers would tend to add the ways of a
route
in sequence and a good editor would maintain that sequence).  Partly
because some
mappers think it's their mother's job to tidy their bedroom (sorry, I meant
the router's
job to make sense of what they've mapped).  I suspect that if standard
carto's query
permitted routes to be inspected that way, more mappers would take care to
ensure
their routes were sorted.

-- 
Paul
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