🚀 go-pugleaf

In article <19930110.007@erik.naggum.no> Erik Naggum <enag@ifi.uio.no> writes:
 > [Alasdair Grant]
 > :
 > |   1 SI inch is 2.54mm _exactly_, not just to 7 decimal places.
 > 
 > There is no Systeme International "inch".
 > 
 > |   But the people who don't use ISO paper sizes don't use SI inches
 > |   either, they use NIST inches, which differ from SI inches well before
 > |   the 8th decimal place.  (I don't know the exact details - after all,
 > |   why should I know about American internal standards?)
 > 
 > "NIST" inches were aligned with the SI units well before 1982 (my earliest
 > reference to 1 inch = 2.54 cm), except for the US Survey foot, which is
 > ~1.000002 ft, and reflects the old inch, for very sound reasons.
 > 
Quoting from my basic reference on units %, subject yard:
	"... In England until 1963 the Imperial Standard Yard was the legal
	unit of length.  It was defined in the Weights and Measures Act of
	1878 as the distance between two points on a specified metal bar.
	In 1963 the yard was redefined as being equal to 0.9144 metres
	exactly.
	  In the United States the yard is specified by the Mendenhall order
	of 1893 as being equal to 3600/3937 metre and this makes the U.S.
	yard equal to 0.91440183 metres, i.e. it is about 0.7 * 10-4 inches
	longer than the 1963 Standard Yard.
	  In 1959 the International yard (0.9144 m) was adopted in the
	British Commonwealth and the United States of America for scientific
	purposes.  This yard has no legal status for trade but it is used as
	the unit of length both by the British Standards Institution and the
	American Standards Association.  The International yard is exactly
	the same as the British 1963 yard. ..."
What can we conclude?  The remarks of another poster chime with this (1 m =
39.37 US inch).  The US inch/foot is not only used for Survey but also in
Trade.  Only for scientific purposes the International inch is used.  The
US inch is *not* equal to the old Imperial inch.  While ASA (now ANSI)
standardized on the International Inch (for scientific purposes), I do
think that NIST did standardize the US inch.  The conversion factor Eric
gave is correct.  Now, while my reference is a bit outdated, I do not
think much has been changed.
--
%  H.G.Jerrard & D.B.McNeill, A Dictionary of Scientific Units.  Science
   Paperbacks, Chapman & Hall Ltd., London, 1966.
-- 
dik t. winter, cwi, kruislaan 413, 1098 sj  amsterdam, nederland
home: bovenover 215, 1025 jn  amsterdam, nederland; e-mail: dik@cwi.nl