Dear John, Firstly, let me say how much I admire the thoroughness of your work on the NIST Handbook 44, Appendix C document.
However, like John Frewen-Lord, I wonder how far this gets us toward our ultimate goal of universal metrication. I don't know if I have ever found a process involving "metric conversion" that was ever successful. It seems to me that "metric conversion" has usually been used to dramatically slow what are otherwise inevitable metrication upgrades. It is interesting to note that the various USA attempts at "metric conversion" have all failed. And failed so dramatically that the public in the USA are now disillusioned and unprepared to take on another bout of "metric conversion". Metrication successes in the USA have all been processes involving "direct metrication" where "metric conversion" is not involved at all. Consider the upgrade to two litre drink bottles. A decision was made to use this size within the management structure of one of the drink companies (possibly because they could buy cheap moulding machines on the world market). No attempt was made to provide customary equivalents using "metric conversion" and none proved to be necessary. The public soon bought drinks in these bottles, got used to the two litre size, and then - in a few days - got on with their lives. Direct metrication, using millimetres, was also the approach used in the automotive industry. Although there were some delays that were often brought about by the use of "metric conversion" in the form of double-sided rulers and tapes. Direct metrication has been used in many other industries but, like the automotive industry, these have been hidden from the public. The words "metric conversion" owe the world a lot -- especially in the USA. As I mentioned, I don't think that "metric conversion" has never worked anywhere in the world, and more importantly "metric conversion" delays metrication upgrades dramatically. Another interesting point about metrication in the USA is that the metrication laws and regulations have invariably involved the words, "metric conversion" thus directly leading citizens into the "metric conversion" trap. With hindsight and a little historical research, it is easy to see that metric conversion has never produced a smooth metrication transition, and it has never produced a fast result. See the "Metric Conversion" web page at http://www.metricationmatters.com/metric_conversion.html where we quote the great American journalist, H. L. Mencken, who could have been talking about metric conversion as an approach to metrication, when he wrote: ... for every complex problem there is a solution that is clear, simple and wrong. Metric conversion in the USA is not producing any meaningful results at present, as it hasn't in the past, and it is reasonable to suppose that "metric conversion" will not be successful for the USA for a long time in to the future. See the article, "Approaches to metrication" that you will find at http://www.metricationmatters.com/docs/ApproachesToMetrication.pdf to consider the four possible approaches to metrication. The best choice is to take a few days to adopt a "direct metrication" approach and then get on with our lives without "metric conversion"; without having to train workers to use old pre-metric measuring words; without numerous errors due to "metric conversion"; and without corrective engineering to repair the "metric conversion" errors. By the way, I enjoyed the level of precision you used in reviewing NIST Handbook 44, Appendix C. I found the level of precision amazing. My best resource is an old Hewlett-Packard 11c with 10 digit accuracy, so next time you decide on another conversion factors review, I will stand well clear and leave you to it. Cheers, Pat Naughtin Geelong, Australia On 2010/11/19, at 04:56 , John M. Steele wrote: > A good question, to which I can't give a good answer. Much of it is notes > and markups of documents that go back years, but it is rarely more than a few > minutes on each observation, then record it. (It does require at least > double precision math, not a ten digit calculator.) I probably spent a > couple of hours on the letter and thinking about the idea that an "exact" > number is useful as a definition even if it requires an impractical number of > significant figures. Not everybody accepts that idea, but if you do, > essentially every conversion (except those involving pi or e) can be stated > exactly in decimal, or as a ratio of integers. > > Those extra digits of precision are not really useful if you are keying by > hand into a calculator, but they are useful as compiler constants in computer > programs. If every constant is expressed as a 53 bit significand in floating > point (about 15.9 digits), why use a wrong value when you can use a right > value? > > Even in a metric world, there will be a lot of old data that will need to be > understood. It is important to know how to convert from Customary (or > Imperial) to metric. It is NOT important and perhaps undesirable to know how > to do the reverse. However, except to idiots, it will be obvious you divide > instead of multiply. :) > > Obviously, real world conversion requires understanding the precision of your > input data, even if you use max. accuracy conversion constants. > > From: John Frewen-Lord <[email protected]> > To: U.S. Metric Association <[email protected]> > Sent: Thu, November 18, 2010 12:21:00 PM > Subject: [USMA:48884] Re: NIST Handbook 44, Appendix C > > John, how long did it take you to work out and write all this stuff? A fair > bit of time I would wager. > > None of this would be necessary in a metric only world. > > Gives some indication of the lost productivity experienced by the US (and to > some extent the UK) on a daily basis by having all these conversion factors, > not only between metric and non-metric, but between different units in > non-metric measures. > > John F-L > ----- Original Message ----- > From: John M. Steele > To: U.S. Metric Association > Sent: Thursday, November 18, 2010 5:05 PM > Subject: [USMA:48883] NIST Handbook 44, Appendix C > > NIST Handbook 44, Appendix C is a great compendium of information > inter-relating Customary, Imperial, and metric measure. However, the 5 > subsections can be a little confusing as conversions are stated to different > precisions, in different sections. A recent comment by Pat on confusion of > exact vs approximate values caused me to look closer. Section 4 is probably > the best source of exact conversions. However, some are not correctly marked > as exact or not, and in several cases the exact value can be deduced, but is > not explicitly stated. > > As a result of my review, I have submitted the comments below to the NIST > Weights & Measures office: > > Comments on NIST Handbook 44, Appendix C, 2010 Edition > > Handbook 44, Appendix C is an extremely useful resource for defining U.S. > Customary measure and its relation to the metric system. The data provided > has more than sufficient accuracy for any practical purposes. However, I > believe a few errors exist in the use of underlining to denote exactness. > Further, I offer a few suggestions for possible improvement. All comments > relate to section 4 of Appendix C; however, I have relied on some of the > other sections to define exactness in my reasoning. I did not do a > methodical review of prior versions, but these comments generally apply to > prior editions as well. > > Those figures which are underlined are intended to be exact, and may > therefore serve as definitional. I believe the following issues exist: > > 1) In the first table of length - International, the figures 12 in/ft, 36 > in/yd, 1 ft/ft, 3 ft/yd and 1 yd/yd are not underlined, but are exact. > Underlining should be added. > > 2) In units of capacity - liquid volume measures, it is not possible to state > exactly the volume of the minim decimally in terms of drams, ounces, or gills > (there is a division by three), yet they are underlined. Underlining should > be omitted. Note: The exact value of the minim can be stated as 0.003 759 > 765 625 in³ if desired. > > 3) In the cubic inch column of this table, the figures 1728 in³/ft³ and 1 > in³/in³ are not underlined, and should be. The value of 0.225 585 94 > in³/fluid dram is marked as exact, but is not. The underline should be > deleted, or the exact value stated and underlined, > 0.225 585 937 5 in³/fluid dram (this value can be calculated from other > entries in the table.) I recommend the exact value for completeness. > > 4) In the first table of Units of Volume, exact definitions of the cubic inch > and cubic foot in liters are given and underlined. However, these figures > are rounded (and not underlined) in the dry and liquid measure tables. The > use of two different values is somewhat distracting and confusing. I > recommend the exact values be used in the dry and liquid measure tables (also > in the milliliter column of these tables). > > I have some additional suggestions for exact values. They will involve more > significant figures than could ever matter in practical measurement. > However, they aid in the rigorous definition of US Customary measure in > metric terms and I urge their consideration: > > 5) Since the release of a new datum (NAD83) and related geodetic data, USGS > has allowed States to pass legislation and receive their geodetic data in > meters, International feet, or Survey feet, according to their preference. > This results in a mess; however, some States have adopted the International > foot. As a result, I believe the table for units of area - International > measure requires the addition of an International acre, 4046.856 4224 m², > exactly, based on 43560 International square feet. The link, chain, rod, > furlong, and related areas are perhaps sufficiently obsolete as to not > require "international" definition. Note: This issue may also indicate a > need for some rewrite of NIST SP811, Appendix B.6. > > 6) The gallon and bushel are defined as 231 in³ and 2150.42 in³ respectively. > By multiplying these values by (0.254 dm/in)³, it is possible to give exact > values in liters for these quantities, as 3.785 411 784 L, and 35.239 070 166 > 88 L. The first requires no more decimal places than the values for cubic > inch and cubic foot, already given, the value for bushel requires two more. > Starting from these values, each submultiple may also be stated exactly and > decimally, if desired. > > Pat Naughtin 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 [email protected] or to get the free 'Metrication matters' newsletter go to: http://www.metricationmatters.com/newsletter to subscribe.
