[OSM-talk] [Talk-GB] Improving ref=* documentation

[Brian M. Sperlongano]

I'd like to put in a plug here for the route relation, specifically the
route=road relation:
https://wiki.openstreetmap.org/wiki/Tag:route%3Droad

These relations are really useful to data consumers because you're not
reliant on getting each and every way in a route tagged exactly right --
you can rely on the route relation as the central source for information on
a route and put a ref=*, unsigned_ref=*, networl=*, name=*, etc at that
level.  The American mapping community is getting very close to solving the
long-standing problem of linear highway shield rendering in vector maps.
The biggest challenge we have is that concurrent routes (a road is part of
more than one route) are very common in the US, and so it's not enough to
just draw a single icon on a road -- you need one for each route.  Having
accurate (and where concurrencies exist, overlapping) route relations with
a consistent network/ref scheme gives us a predictable data scheme that a
renderer can rely on.

There is of course nothing wrong with also repeating the multiple refs on
each way, and legacy data consumers probably rely on this style of tagging,
even though it's technically redundant where a route relation exists.

On Thu, Aug 5, 2021 at 7:19 AM Mateusz Konieczny via talk <
talk at openstreetmap.org> wrote:

>
>
>
> Aug 5, 2021, 09:20 by colin.smale at xs4all.nl:
>
> On 08/05/2021 5:02 AM stevea <steveaosm at softworkers.com> wrote:
>
>
> +1
>
> On Aug 4, 2021, at 5:30 PM, Joseph Eisenberg <joseph.eisenberg at gmail.com>
> wrote:
> > Two of the principles on the "Good Practice" page suggest that the
> real-world information, as found on signs or other physical evidence,
> rather than the laws in the register office somewhere, are considered the
> primary source. This advice has been in the wiki for over 10 years:
> https://wiki.openstreetmap.org/wiki/Good_practice...
>
>
> "Primary source" is not the same as "sole source." Where sources conflict,
> we exercise judgement. Which source is most likely to be "correct" in OSM
> terms?
>
> If you have a road which is signed (for example) "A12" for almost its
> entire length, but somewhere there is a one-off sign that says "A21", do we
> tag that bit of road as "A21"? Over what length? Or do we map following our
> cognitive processes, and assume that the sign is erroneous?
>
> If you have a road that in fact used to be the B2009 but was declassified
> years ago, but somewhere along its length there is a rusty fingerpost in
> the hedge that has the old number on it, does that road magically regain
> its number from 30 years ago?
>
> If we are not going to let many decades of data modelling experience get
> in the way of our tagging schema, we accept that there is only one "ref"
> for a road.
>
> In general I agree with your message (ground truth is true, but using
> brain to discard obviously
> invalid signs is needed).
>
> But road can have multiple refs at once, see ref=A4;7 at
>
> https://www.openstreetmap.org/?mlat=50.0818&mlon=19.8083#map=15/50.0818/19.8083
> <https://www.openstreetmap.org/?mlat=50.0818&mlon=19.8083#map=15/50.0818/19.8083&layers=N>
>
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20210805/682da96b/attachment.htm>