[Talk-us] Rewriting route direction documentation to emphasize subrelations

[Clifford Snow]

Do you know what portion of the Interstate system has been mapped with
route directions? What about US routes?

Clifford

On Fri, Jul 30, 2021 at 11:37 PM Minh Nguyen <minh at nguyen.cincinnati.oh.us>
wrote:

> The article has been rewritten according to the draft and renamed to
> reflect signage and tagging practices in Canada and New Zealand as well:
>
> https://wiki.openstreetmap.org/wiki/Route_directions
>
> Vào lúc 17:55 2021-07-24, Minh Nguyen đã viết:
> > Back in 2013, a discussion on this list [1] led to a wiki article
> > documenting how to indicate the cardinal direction along a route, such
> > as the "north" in northbound I-75. [2] I've drafted a rewrite of this
> > article at [3] and would like to get the community's feedback on it
> > before touching the original, which has often come up in discussion. The
> > rewrite attempts to clearly explain route directions for both domestic
> > and international audiences. These days, overseas mappers are very
> > active in navigation mapping, and route directions are also relevant to
> > some non-English-speaking regions.
> >
> > According to the original documentation, setting relation roles to
> > cardinal directions is preferred over creating a separate relation for
> > each direction and setting direction=* to the cardinal direction (and
> > joining the relations in a superrelation). The rewrite reverses this
> > guidance, placing more emphasis on subrelations and superrelations than
> > relation roles.
> >
> > The directional roles have had the advantage of being easier to
> > introduce than superrelations, especially for routes that only
> > occasionally run along divided highways. That was important early on,
> > when route relations were first being built out. However, it has tended
> > to result in routes that are only partly tagged with cardinal
> > directions, requiring data consumers to infer the cardinal direction
> > along ways with forward, backward, or unset roles. Additionally, editors
> > and quality assurance tools have not added specialized support for these
> > roles as they have for forward/backward, so existing coverage has been
> > fragile.
> >
> > Although subrelations and superrelations are initially more difficult to
> > create, they are easier to maintain in the long run and are already
> > well-established for major road routes as well as public transportation
> > routes. I see them as part of a natural progression in OSM towards
> > greater detail, coverage, and structure.
> >
> > This would only be a rewrite of documentation. I'm not proposing an
> > effort to systematically restructure existing route relations into
> > subrelations and superrelations. However, this documentation would
> > better support mappers who are interested in carrying out such
> > improvements themselves. Thanks for your attention.
> >
> > [1]
> >
> https://lists.openstreetmap.org/pipermail/talk-us/2013-November/thread.html#12165
> >
> > [2]
> >
> https://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States
> > [3]
> https://wiki.openstreetmap.org/wiki/User:Minh_Nguyen/Route_directions
>
> --
> minh at nguyen.cincinnati.oh.us
>
>
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> Talk-us at openstreetmap.org
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>


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