It is a "rule" but a suggestion. Se SP811 section 6.2.5. It normally either agrees with ISO 31-0, or mentions the difference, so I assume ISO 31-0 takes the same position, but I don't have access to a copy.
________________________________ From: Pat Naughtin <pat.naugh...@metricationmatters.com> To: U.S. Metric Association <usma@colostate.edu> Sent: Fri, June 17, 2011 7:00:27 PM Subject: [USMA:50670] RE: cm vs. mm Dear Martin, Is there a rule or a protocol somewhere that it is preferable to use a denominator in a derived unit that does not contain a prefix? I have seen such a "rule" referred to but I have not seen it written anywhere that I can recall. Cheers, Pat Naughtin Geelong, Australia On 2011/06/17, at 17:43 , Martin Vlietstra wrote: > The underlying problem is that we have elected to works in multiples of > 1000, not 100. Multiples of 1000 work well for cubic measures, multiples of > 100 for superficial measures. This is a fact of life with which we must > live, just as the non-rational nature of pi is also a fact of life with > which we must live. > > -----Original Message----- > From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] On Behalf > Of Pierre Abbat > Sent: 17 June 2011 03:47 > To: U.S. Metric Association > Subject: [USMA:50660] RE: cm vs. mm > > On Wednesday 15 June 2011 13:51:28 Martin Vlietstra wrote: >> I disagree with you regarding the hectare - I would actually like to see >> the are being brought into general use as that would make: >> >> 1 are = 10^2 m^2 >> 1 ha = 10^4 m^2 >> 1 km^2 = 10^6 m^2 >> >> This would ensure that no unit need have four digits ahead of the decimal >> point. > > That wouldn't solve the problem. The problem is not that there are too many > digits; it's that, if the unit of length is the centimeter, or the unit of > area is the are or hectare, many calculations are going to require moving > the > decimal point. A gram per are is a centigram per square meter, and a gram > per > hectare, expressed as something per square meter, cannot be expressed with > any of the current prefixes. The base unit of area is the square meter. 1000 > > m² is a decare. 10^6 m² is a square kilometer, and 10^12 m² is a square > megameter, but 10^9 m² has no name, nor does 10^-3 m². > > Pierre > -- > I believe in Yellow when I'm in Sweden and in Black when I'm in Wales. > Pat Naughtin LCAMS Author of the ebook, Metrication Leaders Guide, see http://metricationmatters.com/MetricationLeadersGuideInfo.html Hear Pat speak at: http://www.youtube.com/watch?v=_lshRAPvPZY PO Box 305 Belmont 3216, Geelong, Australia Phone: 61 3 5241 2008 Metric system consultant, writer, and speaker, Pat Naughtin, has helped thousands of people and hundreds of companies upgrade to the modern metric system smoothly, quickly, and so economically that they now save thousands each year when buying, processing, or selling for their businesses. Pat provides services and resources for many different trades, crafts, and professions for commercial, industrial and government metrication leaders in Asia, Europe, and in the USA. Pat's clients include the Australian Government, Google, NASA, NIST, and the metric associations of Canada, the UK, and the USA. See http://www.metricationmatters.com for more metrication information, contact Pat at pat.naugh...@metricationmatters.com or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
