[Talk-us] US Highway Tagging, Was Changeset reverted...

Apollinaris Schoell aschoell at gmail.com
Sun Feb 28 20:46:22 GMT 2010

On 28 Feb 2010, at 11:50 , Mike N wrote:

> >yes, but the wiki isn't free of errors and can't be used as absolute reference. Who wrote it? was it based on wide agreement?
>    If it's in wide use for a long period of time with no objections, it is closer to a standard than any other convention.
> > don't tag for the renderer!
>    That's ok, as long we're not creating data that's usable by no one since there wouldn't be enough information otherwise.   (But then, are OSM'rs like mathematicians who are offended when one of their proofs actually has a real world application?)

yes, better to say: don't tag for a specific renderer instead make it generic enough for another renderer and not too cryptic for humans
and very important too: don't tag against the renderer

> >If it's absolutely needed use a special namespace e.g. hwshields:* and never hijack existing well defined tags.  
>   Agreed, but the ref tag is seemingly loosely defined for highway.  The Wiki states "Any valid syntax value" for ref=.  I don't see anything in highway tag that states a preferred convention.

the wiki isn't a good reference here. Let's face reality and ignore "don't map for the renderer" a bit and see what current renderer do. 
Mapnik, Osmarender, Cyclemap is currently what we all see most and it uses the ref tag from the way. Any change here will be seen immediately on the map.
problem comes in when we have shared routes. this is very common to have and one correct way in osm is to do as an example ref=US 101;CA 1 but rendering is ugly and in some places even >2 refs can be placed on a segment.
google maps do the right thing here http://maps.google.com/maps?f=q&ie=UTF8&ll=37.832531,-122.483912&spn=0.027421,0.03592&z=15
navi systems usually show a sorted by network priority list of routes which will be I, US, State, county …
the only way to achieve this is  probably with route relations but they are not rendered as of now

> >Which is where the network=* tag comes in, it tells you explicitly if
> it's national (network=I), state (network=S) or county (network=CO)
>   network= would be a good tag to way to address this for US highway tagging.  To date, the Wiki suggests its use only for relations, not highways themselves.

relation is where it belongs too. otherwise we end up again with multiple values on a highway segment.
and as soon it's implemented in any renderer it can be used for custom shields or standard highway labels instead the way ref.
But the current recommendation on the wiki is BS and can't be used for rendering

the old recommendation was 
network=I,US and some abbrev. for state, county … 
ref=<number only>

then someone without understanding that the state,country,county info can be put into (deprecated) is_in tags or better any renderer can calculate that from the country,state, county borders and changed it to
this is cryptic, hard to parse and absolutely no benefit.

optional we could help the lazy renderer with is_in tags
network=I,US and some abbrev. for state, county … 
ref=<number only>

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