Aha! Now we are getting somewhere. Thanks. What is the difference between the 1973 and the 1964 editions?
Is it available online? I also understand your point about using exact conversion factors during the calculation and only rounding the final result as required. A long time ago, I had a colleague who insisted on rounding at each step and consequently his calculations always had greater error than necessary. In addition, one of the most famous and respected anthropometric (body size) sources made the mistake of rounding the raw data to the nearest 5 mm. So now people like me that use the figures as input to calculations have to suffer from increased error in the output. However, I do not always follow your suggestion to match output precision to input precision. I judge output precision according to a variety of factors, input precision being only one of these. For example, measuring equipment may provide 6 significant figures and my judgement may be that the output only needs 4. -- Terry Simpson Human Factors Consultant [EMAIL PROTECTED] www.connected-systems.com Phone: +44 7850 511794 > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf > Of Gene Mechtly > Sent: 18 February 2003 02:00 > To: U.S. Metric Association > Subject: [USMA:24892] RE: Definitions of US non-metric units FW: U.S. > Customary Units > > On Mon, 17 Feb 2003, Terry Simpson wrote: > > ... Handbook 130 says it is 28.3495 g. Thus either FS376B is the > > superior source (for at least that unit) or there is a third document > > that we don't know about. > > Yes. See NASA SP 7012, US Government Printing Office. > Ask for the 1973 Edition, not the first 1964 Edition. > > SP 7012(1973) gives "ounce mass (avoirdupois)" = 28.349 523 125 grams > exact. > Try calculating this number yourself from the definition of the pound > mass. i.e. US pound mass (avoirdupois) = 0.453 592 37 kilogram exact. > > Note that "definitions" of almost all US non-metric units have not changed > since the inch was redefined as exactly 2.54 centimeters (or 25.4 mm if > you prefer) in all the major English speaking nations. > > Gene.
