>Forgive me if I don't go around measuring the true height of each >bridge. (That's before we come to arched bridges.) > >Yes, the heights are advisory, but both are useful and I feel both >should be tagged. I don't believe I should be the one making the >decision on how to deal with dual signage; I should be gathering the >data that's there and leaving it up to the data users to work out what >to do with it.
That sort of what I meant - you note down the height on the sign itself - in both units if present. And tag for both units - because you cannot make a simple conversion. >I realise this started with how to tag in the UK, and is still on the >talk-gb list, but the UK isn't the only place being mapped, and I'm open >to other places having dual signage. If these Wikipedia pages[1][2] are >anything to go by, some places do, and both limits are rounded: > > "Houston, Texas has some signs in both SI and imperial units near > its airports and downtown." Well that's different. If there genuinely are two different signs - then you would have to tag both. The legal situation might also be technically slightly unclear. >It would be even more wrong of me to attempt to convert, potentially >losing accuracy. I never said do that. The whole point is that you *don't* lose any accuracy in converting from mph to km/h. 30mph is *exactly* equal to 48.28032 km/h. There's no approximation here, no rounding done - no loss of accuracy. It's an exact conversion - because the mile has been defined exactly in metric units (as well as most other imperial units). Similarly 40mph is exactly equal to 64.37376 km/h 50mph is exactly equal to 80.4672 km/h 60mph is exactly equal to 96.56064 km/h etc. Where there is one sign only - it makes absolutely no difference whether you tag as maxspeed=30mph or maxspeed=48.28032. The values relate to the same speed. I'm not saying you have to prefer one method over the other. That's up to you. _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
