Re: [Tagging] Branched and alternative roujtes

[Warin]

On 20/08/19 00:11, Kevin Kenny 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?)

On Mon, Aug 19, 2019 at 3:47 AM Sarah Hoffmann  wrote:

We do happen to have a clear rule for unbroken linear routes: just assemble
in the obvious way, no matter if sorted or unsorted. We don't have any rule
for anything more complicated that mappers can follow to get the desired
effect. We already fail with something as simple as a directed unbroken
linear routes and circular routes. There is no single recommended way to
define the start point.

A circular route may not even have a start point.  Hikers doing the
Carnberry Lake 50 can start and end it anywhere and do it clockwise or
anti-clockwise (although there happen to be only a couple of good
places to get on and off the circular route).


Assuming we don't care what happens to really botched relations, all cases
except one that I listed initially are covered with one single simple
instruction to the mapper: sort your route.

What remains are routes which are split/have alternatives/access routes etc.
Gut feeling tells that roles will solve those cases but I get back to you
on that once I had a go at implementing it.

If I recall correctly, you're well on the way to handling role=forward
and role=backward splits - I seem to recall that WMT was fairly
graceful about the one or two of those I put in (to repair routes that
were broken altogether - I'm not in the habit of editing cycling
routes otherwise).

For hiking routes, the splits that I have and don't quite know how to
manage are:

- Short diversions. Some of the trails that I've mapped have short
segments for winter and summer routes, or marked alternatives for use
in case of high water, fire-season trail closures, or beaver activitty
(which, I suppose is a special case of high water).

- Access ways. Ordinarily these are marked separately from the main
trail and I just carry them as separate routes. The only case where
I've really wanted to make some sort of association is that the Green
Mountain Club, in addition to the 'end to end' award on the Long Trail
(for hiking the main stem) offers a much more difficult 'side to side'
award for hiking each of the approach trails. I have Absolutely No
Idea how to represent this, if I were to do so.

- Major diversions. For the 'end to end' award on New York's Long
Path, the suburban sections in Orange County are recognized to be a
problem for hikers, and a recognized alternative is to leave the Long
Path in Harriman Park, follow the Appalachian Trail to High Point, New
Jersey, and then the Shawangunk Ridge Trail to rejoin the Long Path in
Otisville.  I'm perfectly fine, though, with simply offering this as
narrative, and having the relations show this as three separate
trails. Hikers have to make their own decisions sometime!

- Trails that are waymarked only in one direction. I do this with
'oneway=yes' on the relation, and order the ways accordingly, but I
did encounter a circular route that seemed to be ambiguous however I
did it. (The trail maintainers rendered this one moot by installing
signs facing the other way.)

The same sort of things seem to infect road routes:

- Routes that begin and end at the interchanges among dual
carriageways, which give no single point that can be indentified as an
endpoint because the geographic endpoints are different in the two
directions. JOSM has a real problem sorting these.

- Multiple-carriageway routes, where there are grade-separated ways
between 'express' and 'local', or between 'auto' and 'hgv' or between
'vehicles with transponders' and 'vehicles paying cash'.  This is an
additional layer of split on top of 'forward' and 'backward' and is
even worse for messing up sorting.

- The same thing can happen on surface streets where there are
numbered routes that are bannered 'ALT, 'BUSINESS', 'TRUCK', etc. For
these, though, I'm perfectly fine with saying that the loops and spurs
are entirely separate routes. The signage is distinct, and people in
the affected areas are used to being directed onto 'US 20 Business' or
whatever.

We have 'forward' and 'backward' pretty much conquered (except for the
dual-carriageway case). WMT already appears to figure it out, (well,
mostly), and JOSM successfully sorts these, even when routes traverse
roundabouts.

I'd like to hear from data consumers in particular what tagging they'd
like to see for

- diversions and alternatives
- routes with different endpoints in the forward/backward directions
- spur routes
- one-way routes that may be circular


There needs to be roles for these (primarily a mapper here).

Are not diversions and alternatives the same thing? Or at least close enough 
that they can use the same OSM tags?

I see spurs differently from access tracks. Spurs may be dead ends off to a 
look out or camp site.

Access tracks provide access to the actual route, they 

Re: [Tagging] Branched and alternative roujtes

[Richard Fairhurst]

My use-case for cycle.travel is having a single polyline that I can make into
a route guide at https://cycle.travel/routes . Currently there’s two dozen:
I’d like there to be thousands. So:

> - diversions and alternatives 

Give them consistent roles so I can ignore them. 

> - routes with different endpoints in the forward/backward directions 

Not fussed. I only do the route in one direction. 

> - spur routes 

Again, consistent roles so I can filter them out. 

> - one-way routes that may be circular 

If there’s an agreed start point, then put the node in the relation with an
appropriate role. 

cheers
Richard



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Re: [Tagging] Branched and alternative roujtes

[Paul Allen]

On Mon, 19 Aug 2019 at 15:13, Kevin Kenny  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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