[Talk-us] U.S. inland waterways

[Richard Fairhurst]

Nathan Edgars II wrote:
> I'm trying to do something like the European tagging: 
> http://www.itoworld.com/map/24
> But there they have some sort of international treaty that 
> defines configurations.

(puts day-job hat on)

For users of a waterway, the European (CEMT) waterway classes describe,
rather than define, the size of the limiting structures. They're
information, rather than regulation.

In other words, although a class Va waterway has a stated length of 110
metres, that doesn't mean that a river policeman will come and flag you down
for taking a 115m boat along the river. It's very possible that the locks
are (say) 120m long, and if you can get your boat through them, you're
absolutely entitled to do so.

This is particularly important at the smaller end of things where locks and
bridges may be a zillion and one different sizes. (Here in Britain people
routinely build boats to 60ft because there are certain locks that are 58ft
6in long... and if you put the boat in the lock diagonally, you can squeeze
that little bit of extra accommodation. There are other locks that have
subsided to become 1in too narrow for certain historic craft that would once
have used the locks. And so on.)

So the ideal is to tag each structure with its limiting dimensions, using
the familiar maxwidth=/maxheight=/etc. tags. This is never going to be
completely achieved, of course, because draught varies for each bit of the
riverbed. ;)

The next best thing is to tag the 'gauge' of a waterway - in other words,
the largest dimensions that will fit through all the structures on that
waterway. In Europe, tagging a waterway with the CEMT class would be a
quick-and-dirty-though-not-particularly-accurate way of stating the gauge.
(That said, the CEMT class would fit very well in the designation= tag.)

cheers
Richard



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