I added the conversion table to maxspeed, as I do a lot of maxspeed tagging in my area. I read the maxspeed definition as needing a numeric value in km/h. While km/h doesn't mean a lot to me, I does to whatever app I use to draw speed limit signs (or, more likely, whatever app runs a satnav system and informs the user when they're over the stated maxspeed for the way they're on) The maxspeed needs to be computer-readable, so people tagging maxspeed=30 when the wiki states km/h is misleading, to my mind. People tagging as 30mph is fine, as that can be parsed to a consistent value anyway.
I think it should be in the database as rounded numeric km/h for the following reasons: 1) 30 mph/30mph/30 all meaning 48 is difficult to parse (or at least, more coding) 2) tagging in floating point is more accurate, but rounding the result to 0 dp seems sensible (I also did that because I didn't know if floating-points were approved in the database) 3) The conversion table is an accurate table to 0dp - some people according to the tags-in-use pages seem to have converted the value inaccurately, so I thought it'd save people doing bad math... (30mph != 50km/h, though if we get converted by europe it might change to that) 4) the wiki says km/h, as as previous suggested it's sometimes (often) unclear which unit was meant by mapper, and which unit is in use where the tag in (international waters/boundaries/ways crossing borders/etc And I'd welcome a sed-like change to the database to "fix" (imho) the maxspeed=30mph tags (I'd like them consistent. I not too bothered if we store millions of "mph" strings instead of just using km/h, as long as I can easily parse the data) Oh, and I tend to only tag ways with non-national speed limits on - I assume there's a country-wide default maxspeed per road type (though again the border problem raises it's head) Tristan 2008/10/8 Ed Loach <[EMAIL PROTECTED]> > Mark wrote: > > > Maybe <grin> this is calling out for a 'bot approach, to take > > maxspeed:mph & add a numeric maxspeed, to check out > > maxspeed=30's & mark > > them in some way (restricted to UK, obviously), and to check > > for entries > > of both=30 & fix them? > > <snip> > > > +1 on the namespace; I'm not generally keen on it, but here it > > makes > > sense. > > I'd argue that it doesn't make sense, in that if you allow both > maxspeed:mph and maxspeed as valid tags, a way may end up tagged > with both showing contradictory speed information. It makes more > sense to have maxspeed=<number><optional units; assume km/h if none > specified> to avoid the chance of that happening. It does make sense > for other situations, such as if opposite directions have different > limits (e.g. maxspeed:opposite=<number><optional units>), or if > different vehicle types have different limits (e.g. > maxspeed:psv=<number><optional units>) as these clearly can't lead > to contradictory information (assuming that if a vehicle type is > specified it overrides any other maxspeed tags). > > Ed > > > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk > -- Tristan Scott BSc(Hons) Yare Valley Technical Services www.yvts.co.uk 07837 205829
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