[Talk-us] ref tags

Richard Welty rwelty at averillpark.net
Tue Feb 12 22:20:09 GMT 2013

On 2/12/13 4:16 PM, Chris Lawrence wrote:
>   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
> lozenge.
the existing ref tags need to be preserved at least a little while
the authors of the data consumers move to the relation based method
> - 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).
one major complaint i have about bare numbers is that they create
an ambiguity, and new mappers make mistakes. for example,

ref=US 9; 20

is this US 9 & US 20, or US 9 and some state route 20? a person not
yet well versed in OSM conventions might think the former. the question
is eliminated entirely if we include the prefix. it is also, of course,
eliminated if we move to well formed route relations which is a good
long term plan.
> - 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.
in the states which use the SR convention, it seems to be copying the
normal usage patterns of locals. here in New York, we talk about
"New York 7" to mean state highway 7, so the NY 7 ref tag makes
local sense. i did grow up in Florida, and the SR convention was pervasive.
i suspect you'll find that when the SR convention is used, it is for
that reason. i also don't think we should kill ourselves trying to shift 
locals to use of the postal code convention.
> - Put something human readable in that Mapnik* can render, without
> sacrificing readability,
i hate tagging just for mapnik, or even talking about such a thing. we
should tag in a manner that preserves the most information we can
for the use of all data consumers. in particular, we have a lot of routing
things of great potential value already out there or coming on pretty
fast (for example, garmin map generation and the OsmAnd GPS app
for Android devices.) whether or not mapnik can render decently with
a long ref tag should be a mapnik problem, and not cause a distortion
of the underlying data for convenience.


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