[Talk-us] ref tags

Chris Lawrence lordsutch at gmail.com
Tue Feb 12 21:16:02 GMT 2013

On Tue, Feb 12, 2013 at 2:18 PM, stevea <steveaOSM at softworkers.com> wrote:
> What this means is that ref tags (used at county, state and national levels)
> are and should be human readable, and route relations are a more machine
> parsable data structure for logically assembling together the various
> highway networks -- even where several exist in a single state, like Texas
> -- and assembling from existing infrastructure into larger wholes (at a
> national level, such as the Interstate System).
>  So, let's just assign sensible
> human meaning to ref tags and sensible machine parsable meaning to route
> relation tags.  This combination works to create all of the semantics we
> need for legal accuracy, local/county/state/federal variations, human
> readability, and logical parsability for software which routes or renders
> shields for display.

I largely agree with you (and Minh) that the ideal is for consumers to
move to using the route relations tags, since they are unambiguous
and, at this point, reasonably comprehensive.  The question then
arises: what to do with the existing on-route ref tags... to me there
are a few possibilities:

- Maximize compatibility with existing renderers that use the ref tag
for something more sophisticated than simply rendering the text in a
- Try to cram as much information in the ref tag as Mapnik* can
render, even if that means dropping prefixes (which I guess is where
the "bare numbers" that showed up in GA and FL came from).
- Apply local conventions, including prefixes like "SH" and "SR",
which may or may not be what is on blade signs or even in common use.
- Put something human readable in that Mapnik* can render, without
sacrificing readability, but omitting less important stuff if we get
too long (for example, dropping the redundant state route overlaps in
Georgia, using popular typographic conventions rather than standard
prefixes, combining route numbers with the same type "I-75/85" rather
than "I 75; I 85") - which basically where we were before
standardization a few years ago.

Personally I think the way forward may be to figure out editor tools
that will make route relations easier for people to use (maybe this is
as simple as adding some comboboxes to the JOSM tools to help people
find the right things to use for the various tags; I haven't used
Potlatch in years so no idea what needs to be done there, but probably
something similar) and maybe some automated system for detecting the
inevitable duplicates that will crop up.  Then maybe we can deprecate
the way ref tag in the US and find better things to do...

Chris Lawrence <lordsutch at gmail.com>

Website: http://www.cnlawrence.com/

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