This issue has come up as well with the height of mountain peaks; those of us 
who hike in the mountains in the US know peak heights *only* in feet, but OSM 
seems to reflect this in meters; this is entirely unhelpful to local hikers.  
Us locals think of Sierra Peak as 4050 feet, not 928 meters.

The discussion was strictly informal, but I think a number of us liked the idea 
to support a unit of measure, such as ele=4050ft or maxweight=10t

Steve

-----Original Message-----
From: Andy Townsend [mailto:[email protected]] 
Sent: Monday, November 02, 2015 1:59 PM
To: Talk Openstreetmap <[email protected]>
Subject: [Talk-us] Maxweight in the USA

Just a heads up...

There's a bit of a discussion going on at the moment as to whether it makes 
sense to store SI units (or actually a derivative - metric tons) in maxweight 
tags.  I noticed a few changes (initially to other values in the UK), and 
commented on
https://www.openstreetmap.org/changeset/35009662 , and the person making a 
changes (who's the author of one of the popular routers using OSM
data) wrote a diary entry here: 
https://www.openstreetmap.org/user/karussell/diary/36220 .

The argument in favour of the change is that storing an SI derivative makes the 
data easier to consume; my counter-arguments are that (a) it makes it harder 
for mappers to verify values and (b) anything consuming data shouldn't assume 
the data is valid anyway (for "Bobby Tables" 
reasons if for no other).

Whilst doing this I noticed that a bunch of other "x tons" weight limits had 
had values changed a while back (see for example 
http://www.openstreetmap.org/way/32719427/history ).  That's now been changed 
to "maxweight=4.5359237" which is at least not heavier than the actual posted 
restriction.  However there are still some other integer values without units 
which implies metric tons (see for example http://overpass-turbo.eu/s/cqw ).  
It may be that Pittsburgh has woken up one morning and decided to adopt SI 
units ahead of the rest of the country, but I doubt it.  Logically I'd expect a 
router encountering "maxweight=10" in the USA might want to interpret it as "10 
US tons" 
rather than 10,000 kg, but based on the above I suspect that at least one 
router isn't going to do that.

The relevant wiki page http://wiki.openstreetmap.org/wiki/Key:maxweight
does say "as of September 2014 only metric units of weight (metric tonnes or 
kilograms) are supported for this tag".  I'm unaware of any discussion prior to 
the 17 September 2014 change (not that that means that it didn't happen, just 
that I'm unaware of it).

I'm not from the US, and I'm not sure what the right answer is (if as a 
community you're happy entering maxweight=4.5359237 it'd certainly make 
everyone's lives easier), so I'm posting this here and then retiring back 
across the Atlantic :)

Cheers,

Andy (SomeoneElse)


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