[Tagging] Mapping nonexistent paths

Bert -Araali- Van Opstal bert.araali.afritastic at gmail.com
Tue Mar 23 15:13:16 UTC 2021


Forgive me I am trying to answer all the questions here. Very few of the 
few of us here are going to read all the chit chat and we are using a 
lot of bandwidth. So I am going to try to answer multiple views and 
questions in one mail.

@zelonewolf:

> As I understand it, a "virtual" path is one that describes actual 
> usage (where people walk, and should therefore be routed on) but does 
> not manifest in any physical way.  Thus, a renderer could choose to 
> not render these virtual connections (as they do not physically appear 
> in the world) while routers can still use the data of "people walk 
> across this place where there is no path".
But they do manifest in a physical way, all the examples for highways 
do. I don't want to ask myself what was here first, the connecting paths 
and later someone made a paved square, or parking or paved junction on 
top of them, the paths are still there, under the square, they are not 
virtual. I still walk on the path on the square on top of it. A path 
across undeveloped land gets overgrown, but the path is still there, 
it's not virtual at all. I can't imagine any place, a square that has no 
highway=* to it, maybe some extreme cases of helipads where no one wants 
to get in or out the helicopter :).
> Without some kind of tagging like virtual (or whatever it gets 
> called), there is no way for renderers (who wish to differentiate such 
> things) to discern the habitual paths of humans across the ground from 
> physically manifested paths.
I explained this before.  Adding a virtual tag as a reference to render, 
to mimic imagery or unclutter tiles, will have the opposite effect, 
because in thousands of places the junctions, squares etc... are not 
mapped as areas, leading to lots of voids in the rendering.  The 
renderer should make that decision based on the presence of a landuse or 
landcover polygon, or on a surface tag in the highway=*. If there is no 
surface=* tag on a highway or no other polygon with surface designation, 
that's as virtual as it can get. No added value in a "virtual" tag.

@lectrician1:
>
>     There are nonexistent coastlines at river mouths, for example:
>     https://www.openstreetmap.org/way/149550311
>     <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.
Cover what ? That it's a logic line to close a polygon, a common 
practice in cartography and OSM? What does a "virtual" tag add here 
besides asking a mapper to add an additional tag. Is a renderer going to 
change it's rendering because you call it a virtual way ? A router to 
change that it knows you are on the river or on the lake when you cross 
the line, virtual or not is not going to change anything there ?
The only purpose in OSM where I could see an advantage of applying some 
kind of distinction is with boundaries.  To distinct physically present 
boundaries from those retrieved from official and reliable sources but 
not clearly verifiable in the field.
Boundaries for EEZ and territorial waters based on calculations.

But all other cases, no added value still.

@ael:
> I am coming around to path=link which seems somewhat clearer,
> although others uses of link are for more concrete ways.

If you abstract, every highway, every waterway is a link, a connection 
between two points.  The whole path is a link.

Greetings,

Bert Araali


On 23/03/2021 17:30, Peter Elderson wrote:
> Can't wait!
>
> Vr gr Peter Elderson
>
>
> Op di 23 mrt. 2021 om 14:59 schreef Seth Deegan <jayandseth at gmail.com 
> <mailto:jayandseth at gmail.com>>:
>
>         There are nonexistent coastlines at river mouths, for example:
>         https://www.openstreetmap.org/way/149550311
>         <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
>     <mailto: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
>         <mailto: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
>>             <mailto: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.
>>
>>             _______________________________________________
>>             Tagging mailing list
>>             Tagging at openstreetmap.org  <mailto:Tagging at openstreetmap.org>
>>             https://lists.openstreetmap.org/listinfo/tagging  <https://lists.openstreetmap.org/listinfo/tagging>
>             _______________________________________________
>             Tagging mailing list
>             Tagging at openstreetmap.org <mailto:Tagging at openstreetmap.org>
>             https://lists.openstreetmap.org/listinfo/tagging
>             <https://lists.openstreetmap.org/listinfo/tagging>
>
>     _______________________________________________
>     Tagging mailing list
>     Tagging at openstreetmap.org <mailto:Tagging at openstreetmap.org>
>     https://lists.openstreetmap.org/listinfo/tagging
>     <https://lists.openstreetmap.org/listinfo/tagging>
>
>
> _______________________________________________
> Tagging mailing list
> Tagging at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/tagging
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20210323/6ae2a462/attachment-0001.htm>


More information about the Tagging mailing list