"HB" == Hendrik Boom <hendrik@...2611...> writes:
HB> I've once been told that the US is legally on the metric system and that HB> the inch is *defined* to be 2.54 cm., which makes 2.54 exact to as many HB> decimal places as you want. I'd like to know if this is actually true. HB> Anybody know?
Back in the 1950's the, IIRC, SI got annoyed that the inch/foot/mile system and SI were connected by the specification that:
1 metre == 39.37 inch
They felt that that made it look like the inch was the base standard and that the metre were defined by it.
So they inverted the conversion and rounded it so that:
1 foot == 0.3048 metres 1 inch == 2.54 centimetres
The new 2.54cm inch is formally the international inch.
The old 100/3937m inch is the (rarely used) US inch. The corresponding 1200/3937m foot is the US or survey foot, still used for land surveys, often as decimal feet (10.5 ft instead of 10ft 6in).
On the scale of a page of paper, the rounding is negligible. On the scale of a State-wide survey, it would be /very/ noticeable.
The US has at least signed and probably ratified a treaty which does require that everything be metric, but that never seems to be enforced on the States, Territories or Possessions and is usually poorly implemented by the Feds, too. (They write things like:
200 gallons (757.08236 Litres)
instead of rounding the conversion to match.)
Whether the inch to mtre conversion has ever been codified in law, though, I couldn't guess.
-JimC