[Tagging] Mapping nonexistent paths

Sinus Pi sinus+osmtag at sinpi.net
Tue Mar 23 15:13:00 UTC 2021

Bert wrote:

> Yes, easy for router. Horrible for a renderer ? I am not so sure.  What
is the intend or purposes of the renderer: render routes or mimic a
satellite imagery ? Or both ? If the surface of the square is mapped, it
looks awful if you want to mimic imagery.

The purpose is to display to users a map that will reflect reality. If the
square is just an open square, the renderer shouldn't show a "spider" with
routes connected in the middle, because that's not how it looks in real
life. Nor would it be ideal to show just the outer edge, because again,
that's not how an open square looks. It should, if possible, show something
that looks like a filled square, if it's a square in reality - thus best
with an "area". And even if routers are finally taught to use line-of-sight
routing on areas, not just traversing outer edges and properly finding
shortest paths through the area, they might still benefit from some
guidance: for example some pedestrian squares might have inclines or kerbs
impossible to cross for wheelchairs, and virtual paths could fill that void
by having access tags defining proper traversal of an otherwise open
terrain. Sure, one could micromap the whole square down to one paving
stone, but why bog routers with all that information, when one could just
as well "describe" the square's traversal to the router?

On Tue, 23 Mar 2021 at 15:35, Peter Elderson <pelderson at gmail.com> wrote:

> Can't wait!
> Vr gr Peter Elderson
> Op di 23 mrt. 2021 om 14:59 schreef Seth Deegan <jayandseth at gmail.com>:
>> There are nonexistent coastlines at river mouths, for example:
>>> https://www.openstreetmap.org/way/149550311
>> This is an intersection of 2 ways within each-other's realistic areas.
>> This will also be covered in my revised highway link proposal.
>> lectrician1 <https://wiki.openstreetmap.org/wiki/User:Lectrician1>
>> On Tue, Mar 23, 2021 at 8:31 AM Seth Deegan <jayandseth at gmail.com> wrote:
>>> Well Bert, I'll try to convince you why we really need them with my
>>> proposal.
>>> lectrician1 <https://wiki.openstreetmap.org/wiki/User:Lectrician1>
>>> On Tue, Mar 23, 2021 at 8:19 AM Bert -Araali- Van Opstal <
>>> bert.araali.afritastic at gmail.com> wrote:
>>>> On 23/03/2021 15:11, Mateusz Konieczny via Tagging wrote:
>>>> Mar 23, 2021, 12:57 by pelderson at gmail.com:
>>>> I tag lots of recreational routes as route relations. A route is a
>>>> continuous chain of connected ways. In lots of places I need a linking way
>>>> to keep the chain continuous, especially in hiking routes, because  there
>>>> is no actual official link or path.
>>>> E.g. Often a cycleway is present for a stretch along a road. Then it
>>>> just stops. Pedestrians and cyclists will continue on the side of the road.
>>>> If the path is mapped, it will connect, at the end, to the centerline of
>>>> the road with a virtual path, to provide a continuous chain for
>>>> routing (including "manual routing" in route relations). This gets more
>>>> complicated when footways and cycleways are both mapped separately, which
>>>> is an increasing trend.
>>>> The route or way doesn't stop, the pavement stops, the separation
>>>> stops. The route just continues.  Its perfectly OK to map those with our
>>>> current tagging scheme. Why would you want to use link here ? A link is
>>>> very distinguishable in it's function, use and most of the time
>>>> appearance.  It's not a "soft" link.
>>>> As you say, if there is no clear separate "link" don't use link. But
>>>> what does "virtual" add here ? Just use surface tagging if you feel the
>>>> need to indicate the different surface of those small links.
>>>> You could say it's tagging for the router
>>>> I would say that "there is connection between X and Y" is actually
>>>> mapping reality.
>>>> And it is often needed if people map footways/cycleways as separate
>>>> geometries
>>>> (and it is one of main drawbacks of doing it this way...)
>>>> , but it's standing practice to map for continuity. As soon as routers
>>>> and the standard OSM track export can be reasonably expected to deal with
>>>> non-continuous routes and route relations, i.e. finding a solution for
>>>> missing links which adequately deals with trajectory, access and other
>>>> characteristics of the terrain where a connection is needed, I am all for
>>>> mapping just what there is.
>>>> Note that is extremely unlikely - there are often small gaps where
>>>> there is an actual barrier and
>>>> no passage! Distinguishing this two is not easy and trying to guess
>>>> "there is connection here"
>>>> would result in massive number of false positives.
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