[Talk-us] Maxweight in the USA

Steve Friedl steve at unixwiz.net
Mon Nov 2 22:12:14 UTC 2015

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


-----Original Message-----
From: Andy Townsend [mailto:ajt1047 at gmail.com] 
Sent: Monday, November 02, 2015 1:59 PM
To: Talk Openstreetmap <talk-us at openstreetmap.org>
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 :)


Andy (SomeoneElse)

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