In response to Terry's question, On Sun, 16 Feb 2003, Bill Potts wrote: > ... > The IEEE/ASTM SI 10-1997 document (for which you have to pay) has a > comprehensive list...
> Most of the "definitions" of non-metric units in NIST SP 811 and in SI 10(1977) were copied from NASA SP 7012 which I compiled in 1964. SP 7012 appeared in a series of editions and printings by the US Government Printing Office for use by the various NASA centers. SP 811 cites SP 7012 as the origin of the lists, but SI 10 (1977) fails to cite SP 7012 as its source. SI 10 (2002) may or may not cite SP 7012 as its original source. Through ASTM Committee E43 on SI practice, I requested restoration of the citation of SP 7012 as the original source, but do not yet know if my request was honored. SP 7012 gives a greater number of exact non-metric "definitions" (i.e. "conversion factors" which are in reality merely numerical multiples of SI units) without rounding than do either SP 811 or SI 10 both of which truncate many of the exact definitions. However, for most applications the full exact definitions are unnecessary and rounding is appropriate. As you probably know, Terry, the general rule is to use exact definitions first for calculations and then to round the final results appropriately as dictated by the precision of input data, neither increasing nor decreasing the number of significant digits in the results. Gene.
