[Tagging] As the crow flies

A.Pirard.Papou A.Pirard.Papou at gmail.com
Sat Feb 23 18:53:47 UTC 2013

On 2013-02-22 12:10, Janko Mihelić wrote :
> I'm not entirely sure I understood your question, but you shouldn't 
> map non-ways. Routers could be developed that route through non-ways, 
> if there is no cliff or something else in the way. A router could 
> route along the contour lines, to make the hike through forest easier. 
> But if there is no path, don't map it.
On 2013-02-22 14:05, Volker Schmidt wrote :
> It happens often on mountain hiking routes. You have a signpost with 
> the red-white sign of the Alpine Club that indicates the direction 
> that you have to take across a meadow, for example. On the other side 
> you have to find a corresponding sign. In between there may not be any 
> visible path. In that case I would happily put a highway=path with 
> surface=grass as a straight line across the meadow.
On 2013-02-23 12:56, Martin Koppenhoefer wrote :
> maybe add the key "informal"=yes to the path? I do this for 
> "spontaneous" ways and it is also documented in the wiki: 
> http://wiki.openstreetmap.org/wiki/Key:informal
And the other suggestions, many thanks, sorry for not listing them all.
I'm looking for a general feature, not only a solution to my particular 

A non-way is not the best word to describe my idea and I also do not 
feel comfortable with it.
It's sort of a "secret [winding] little passage" that one must follow on 
So, more than "informal=yes" (which I don't understand well), it would 
be a straight "exists=no".
How could it be mapped, sort of dotted line, so that the human 
understands that he may follow a route for which there's no path under 
the conditions otherwise described (no cars in a meadow)?
But how could the automated router know if it must or not follow that 
secret passage?
Mind boggling, it needs more information.
And these thoughts led to the following reasoning...

In making a route (the relation), we are actually not mapping something 
(creating new map objects). We are relating existing objects of the map 
to be highlighted to show, well, a route to follow (other relations 
And it may, for many various reasons of which you found more, happen to 
be NO objects in the map to highlight and follow.  So, this problem is 
just, within the queue, aka file, of  members making up the route, to 
indicate somehow: this gap is not a mistake ("page intentionally left 
blank", JOSM don't complain): it means that you just must manage to go 
from here to there the best way you see fit, para-gliders included (1).
The first idea was to fill the gap with a dummy, but the second thought 
is that we simply could use the end nodes of the two ways the gap is 
striding to do so.
One node, repeated next to the way it belongs to, would have role 
/*gap_start*/, the other one /*gap_end*/.
Or /*jum*//*p_start*/, /*jump_end*/ (1).
No dummies needed.

Human routers (mapping a hike) just assemble these special instructions 
among the members.
Automated routers are driven by a human who simply breaks the route in 
segments (making "via" points), one of which uses no car, bike or 
pilgrim type but that funny little flying bird as the segment routing 
type. By definition of the crow segment, the router makes it of only two 
gap-start and gap-end nodes (it may use more nodes and, magically, we 
reinvent the GPS trace (we might use /*track_point*/ instead of gap_*, 
but that would lessen the possibility to detect routes broken by less 
capable editors).

I think it's a rather simple, best value for money, addition to the OSM 
tags I let you discuss.

To end my practical story, not only do the hike instructions loosely say 
that the hike starts and ends in the parking place (which is obviously 
the car segment of the hike!) but the bird segment starts wandering 
north in a drunkard fashion where there is no path, even breaking its 
way through the limit of an alleged cemetery.
I simply started on the road alongside the parking and cheated my way 
trough a small street detour.
They call that a walworkaround ;-)



(1) Yet another real case of possible exists=no routes coming to my mind 
errr... BTW.
Ski routes too.  Endless.

> 2013/2/21 A.Pirard.Papou <A.Pirard.Papou at gmail.com 
> <mailto:A.Pirard.Papou at gmail.com>>
>     Hello world,
>     It can happen for a hiking route, maybe others, to go across a
>     non-way.  One may for example get people across some land without
>     a path or officially start and end a hike in the middle of a
>     parking lot.
>     What must we do:
>       * create a pseudo way and what are the tags?
>       * more likely, leave a gap in the route relation, filled with
>         some element saying "fly to connect"?
>     The crow may be supposed to fly loosely following the roads too if
>     router software is unable to make a correct route or simply if the
>     user insists on being a crow.  This is not a mapping issue, but
>     the solution can be the same if the router builds the same
>     relation as ours as the output of its result.
>     I suggested several sites to add a flying bird to car, bike and
>     man to be chosen independently per segment.
>     This (unable), in addition to map bugs, is the case when using say
>     the Google router with an OSM map display.  e.g. openrunner.com
>     <http://www.openrunner.com/>'s doc says to use Cloudmade router
>     but soft only provides Google's on OSM.
>     (You'd do something nice reporting this bug).
>     I only found the following in close relation with this.
>     In two parts (yes, sometimes the gnus have to fly too ;-))
>     http://lists.openstreetmap.org/pipermail/talk/2010-November/055088.html
>     <http://www.openrunner.com/>
>     http://lists.openstreetmap.org/pipermail/talk/2010-December/055121.html
>     Cheers,
>     André.
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