on 2003/06/03 05.25, Gillmann, Ralph at [EMAIL PROTECTED] wrote: > In trying to promote the specification of SI in standards, I've made the point > that if non-SI units are used, then a standard document should be referenced > which defines the system and its use. Since such documents don't seem to > exist, I then want to make the point that an engineering system of units needs > to be specified, not just a vague term such as "inch-pound units."
Dear Ralph, This is an updated version of a piece that I wrote to list the many ways to describe old ways of measuring. One of my favourites is the WOMBAT. Paul Trusten, a pharmacist, originally devised the acronym WOMBAT. It stands for �Ways Of Measuring Badly in America Today �or� Waste Of Money, Brains, And Time. The second expansion of the acronym accurately describes all non-SI units, and the first accurately describes all those used in the USA. WOMBAT has the advantages that it is a single word; and it is an acronym so it doesn't need to have a specific meaning. After Paul Trusten introduced WOMBAT to the United States Metric Association, it quickly became popular because it is short, humorous, sarcastic, and implies that the old units are structurally as primitive as Australian marsupial mammals. Another advantage of the acronym WOMBAT is that it is all-inclusive. You can use it for all the old non-SI units, for the old Imperial units and even for old metric but non-SI units such as calories and kilocalories. However, there is no such thing as a 'WOMBAT system' - it is just WOMBAT. With a little license, I have also used the acronym 'WOMBAT' for: 'Ways Of Measuring Badly in Australia Today.' The acronym, WOMBAT, is useful because there is a fundamental difficulty in discussing the old non-SI units that are still used in some parts of the world because there is no official, collective name for the old units we used in the past. To help organise my thoughts about old units I have made a list of other expressions that are used to describe old units. They are: American units The term, American units, is wrong because it is not synonymous with the old units. That assumption is patently false, since the USA has based the definitions of all their old units on metric units since 1893. This was when the USA Congress adopted the metre as a standard and defined the inch, foot, yard, and pound in relation to the metre and kilogram. 'American units' really means metric units or, more specifically, units of the International System or SI units. Bastard units Bastard units are those that are neither fish nor fowl. These are composite units made up from parts of various methods without definable parentage. Examples are grams per mile, pounds per tonne, watts per square inch, ounces per square metre, and micrograms per square foot. These are the worst kind of units and should be avoided at all times. British colonial units British Colonial has several advantages. It makes a useful distinction between British Colonial from British Imperial units. It is reasonably technically correct and it makes it clear where these units originated. However, having said all of this, British colonial units is neither accurate nor inclusive; the British colonies used Imperial units � not colonial units and not the USA Customary units that shared the same names. Colonial units Colonial units immediately identifies old units and sets them in a political context as being left-over remnants from the time of colonialism without too much of a political axe to grind against England or the United States. Customary units Customary units is wrong because most of them are no longer customary anywhere in the world, and they will become less customary in the future. USA customary units (USCU) are really SI units in disguise. USCU can not survive without SI and needs it absolutely in order to be applicable for high technology work. This is a misuse of SI standards to prop up a competing set of units. If barley corns, human feet and the length of arms were good enough for high level measurements then United States Customary units would not have to be propped up by SI standards. Decimal units Clearly, the modern metric system, the International System of Units (SI), is a decimal system with the idea of decimal numbers as its heart. However, it is not so well known that since the success of the metric system, from 1792, many attempts were made to decimalise bits and pieces of many old measuring methods. One of the earliest examples was Gunter's chain where Gunter divided the English chain (80 to the mile) into 100 links. Although this divided the chain into 100 lots of (the uncomfortable number) 7.92 inches, the advantages of a decimal number for calculation were so apparent that Gunter's chain was a major hit with the surveying community especially in the USA. Other examples of retrofitting decimal ideas to old units are mils (milli-inches), thous (thousandths of inches), decimal pounds at the butchers, decimal miles on the odometer of your car, and kiloyards (one thousand yards). Deprecated units Deprecated units is correct for a small group of units that have been deprecated by the world authority that controls the International System of Units � Conf�rence G�n�rale de Poids et Mesures (CGPM). However, most people do not know what deprecated means, they�ve never heard of the CGPM, and some non-SI units have not yet been officially deprecated by CGPM. Emu Emu meaning English mixture of units has the same problems as English units and Ye Olde English Mixture of units. English units English is neither accurate nor inclusive, and it is ambiguous as most non-SI units are not of English origin. The majority of so-called English units were originally developed by the Romans, Babylonians, medieval Europeans, various industries, businesses, and sometimes individual scientists and engineers. English units also confuses true English units (whatever they are) with Imperial units and USA units with the same name; for example an English ounce or a ton is not the same as an ounce or a ton in the USA. FFU FFU is an abbreviation of the words 'Fred Flintstone Units' and it was clearly designed as a derogatory term to mock old units when they are compared to the International System of Units. FFU was not meant as an alternative name for USA Customary units or for British Imperial units; it was meant as a catch-all phrase for all non-SI units, even old Chinese units. Generally however, FFU is taken to mean the combined hodge-podge of USA Customary units and British Imperial units because they are the only remaining measuring units still left that are seeking international acceptance. Imperial units Leaving aside the question of the demise of the Roman empire, Imperial units is neither accurate nor inclusive. It is a long time since there's been any empire that was able to set standards of measurement for the whole world or even for portions of it. Imperial units is even less appropriate for use in connection with units with old style names in the USA; Imperial units were never used in the USA as the Imperial units of the British Empire were developed, in England, after the USA became an independent nation. IP, fp, or ifp IP for inch-pound units, fp for foot-pound, or ifp for inch-foot-pound are neither accurate nor inclusive. These names are sometimes appropriate in an engineering context but they are of less use in other fields. They are also unsatisfactory on other grounds, since many old units, such as the gallon or acre, have little to do with either inches, feet, or pounds. Also, although many non-SI units are related to the pound they are not necessarily related to the inch. In legal terms the old measures were more likely to be based on the foot or the yard rather than the inch. These terms also have the drawback that they do not include any of the obsolete metric units. Non-SI Non-SI is accurate and inclusive but many people don't yet know what SI means. Besides non-SI is clumsy to say and it is too similar to SI. NSIU NSIU for non-SI units is technically correct but seems vague; it sounds more like the abbreviation of the name of a university. Old metric systems It took about 170 years (1790 to 1960) for the first metric system to evolve into the 'International System of Units � the modern metric system. During that time, the metric system took several forms, and these can, in hindsight, be thought of as evolutionary stages, as each of these metric systems were improvements on previous metric systems. The original metric system was devised, by an international committee, during the 1790s. The first major suggestion for improvement came from Karl Frederick Gauss who proposed that new electric units should be based on the millimetre, the milligram and the second in 1832. In 1873, the British Association for the Advancement of Science (BAAS) also realised that new units were needed to measure electrical properties. They proposed new electrical units based on the centimetre, the gram and the second. Historically, this became the cgs system (and sometimes the CGS system) when the first Congr�s International d'Electricit� formally adopted this system in 1881. By the end of the eighteenth century, a difference had developed between scientists and engineers. Scientists, such as chemists, were quite comfortable using centimetres and grams, but the engineers wanted to use much larger units such as kilograms or tonnes. Giovanni Giorgi, an Italian engineer, proposed a compromise in 1901. Giorgi's system was based on the metre, the kilogram and the second and he suggested that an electrical unit would need to be chosen to construct a fully coherent system of units. In the meantime, engineers in France were using � and lobbied for appropriate laws � a system based on the metre, the tonne, and the second (mts or MTS). The mts system could be used legally in France from 1919 to 1961. Engineers, all around the world, also devised another metric system based on the metre, the kilogram (of force not mass), and the second. From these competing systems, the Giorgi system was adopted by the Commission Electrotechnique Internationale, in 1935. Subsequently, in 1948, The Giorgi system was also adopted by the Conf�rence G�n�rale des Poids et Mesure (CGPM) and the amp�re was selected in 1950 as the electrical unit. This system became known as the mksA system. Considerable work followed to further develop the mksA system until 1960, when, with the addition of several other new units, the modern metric system was named the 'Syst�me International d'Unit�s' or, in English, the 'International System of Units'. The modern metric system is officially designated, and it is known in all nations, and in all languages, by its French initials, 'SI'. Old English (and USA) scientific and engineering 'systems' While the metric system was evolving into the 'International System of Units', many efforts were made to try to retrofit properties of the metric system on to older measuring methods. Several things should be noted about these old modified methods. Firstly, it is not correct to say that these old modified methods were 'systems', even though they are often called by that name. They are not 'systems' mostly because they are not complete methods of measures. For example, while mechanical engineers were devising their own 'system' they gave little thought to any issues faced by aeronautical or civil engineers. As a result, in any 'Gravitational System', there are aeronautical engineering, civil engineering, and mechanical engineering versions, and each of these has a distinct variety for the UK and another for the USA. And none of these 'systems' has anything to say about chemistry, medicine, nutrition, or any other of the remaining thousands of human activities. Secondly, these methods are unsupported by any international (or national) organisation, so there is very little information about what these old 'systems' actually are. These 'systems' are not documented, so it is quite difficult to find details about these old measuring methods. This can be a real problem if you are trying to cite a 'standard' that was used for a particular set of measures � often no such 'standard' exists. If there is no standard document that you can use as a reference to define the system � and the way it was used � then you can only vaguely say that they used 'inch-pound units' or they used 'foot-pound units'. You might find some documentation for the Absolute Units and for Engineering Units, although these can often be contradictory. For example, British Absolute Units, used mostly by physicists, had the pound as a unit of mass and the poundal as a unit of force, while British (and USA) Gravitational Units, used by engineers, employed a pound for force and a pound for mass. Naturally, the scientists and the engineers used different length units for their work. Even within engineering, aeronautical engineers used the pound for force and the slug for mass while mechanical engineers a pound for force and a pound for mass. When civil engineers used a foot as their unit of length, mechanical engineers used an inch as their unit of length. Over time, the different measuring methods became many measuring 'systems'. Thirdly, leaving aside the question of how you measure something as basic as length (you could choose to use international, nautical, statute, or survey methods), there is also the question of which length units you will use (thous, inches, links, feet, yards, rods, poles, perches, chains, miles, or leagues) when you decide on a measuring 'system'. There is no 'system' between these odd, historically generated, units. Fourthly, they are also not 'systems' because no attempt was ever made to form them into coherent measuring methods like the coherence of the metric systems. Overall, it is best never to use the word 'system' with old units. If you are examining an old measuring method where the inch and the pound are the dominant units, then say that it uses inch-pound units and ignore the other units in the set. If you are examining historical documents where the foot and the pound are the dominant units, then say that it uses foot-pound units and ignore the others. Names of old measuring methods that you might find include: Apothecaries Units, Avoirdupois Units, British Absolute Units, British Engineering Units, British Gravitational Units, English Engineering Units, Foot-Pound Units, Foot-Pound-Second Units, Foot-Pound-Second Units, Imperial Units, Inch-Pound Units, Inch-Pound-Second Units, Troy Units, and USA Customary Units. Don't forget that many of these sets of units might appear in UK and USA versions of aeronautical, civil, and mechanical engineering, as well as in surveying 'systems'. Olde English Mixture of units Olde English Mixture of units has the same problems as English units. It is also confusing because many non-SI units are recent inventions; they're not old. For example, the inch, the foot, and the yard did not have standard lengths until 1959; and even then they were only standardised for English speaking nations. The pouce, or French inch, still has no definition. PSIU PSIU for pre-SI units has the same problems as NSIU. Standard units Standard units, sometimes written as Std. and sometimes as USS for US Standard, is not appropriate, as it is not accurate. There is only one truly international system of standard units, and that is the International System of Units (SI). SI is the world standard in all countries in the world, and this has been true since the late nineteenth century. Even in the USA � the last country in the world to change to SI � the metre and the kilogram have been their only legal standards since 1893. System System as in 'English system', 'Imperial system' or �USA system� is totally wrong because there never was a complete system, just part systems or random mixtures of units. These terms should be avoided since most of the old units are unrelated and certainly do not constitute any sort of coherent 'system.' Unacceptable units Unacceptable units is too vague, but it may be useful in some circumstances, especially since it is technically accurate. At its simplest, if the units are not SI they are not acceptable. USC or US Customary USC for US Customary is not accurate or inclusive; for example it excludes Imperial units. Many SI units are also customary. Most citizens of the USA would recognise the SI units, second, litre, watt, volt, ampere, and hertz, and regard them as customary units in the USA. Ye olde imperial colonial English incoherent mix of non-system WOMBAT units Ye olde imperial colonial English incoherent mix of non-system WOMBAT units is probably a bit long. And what about: historical units (or hysterical units), (or prehistoric units), ancient units, archaic units, old units, incoherent units, old fashioned units, bad units, unsystematic units, old traditional units, old customary units, old standard units, or formerly traditional units, formerly customary units, formerly standard units, etc, etc, etc. An interesting question that arises when you consider these issues is 'What is (or was) the legal standard for old units? Of all of the old measurement units, which of them is the fundamental unit, and what is its official definition? What official standards exist (or have ever existed) for old measures? I wish you well if you have any international agreements that calls for (say) 'inch-pound' units. Leaving aside the discussions between scientists and engineers, you might also be on shaky legal ground. There is often no written standards or legal definitions of any of these 'systems' that would be accepted by a court. In my formal writing, I will continue to use 'non-SI,' or 'unacceptable units' but I suspect that from time to time the word colonial or the acronym WOMBAT will creep into my vocabulary. In the light of these not-so-good choices, it's not surprising that in the USA, as that nation changes to SI, many of their citizens have taken to using the acronym WOMBAT to describe all of the old ways of our enormous, chaotic, collection of non-SI units. In fact, if you include this acronym, WOMBAT, in your SI conversations, it may be one of the most constructive things you can do to help people to move toward adopting SI units exclusively. Cheers, Pat Naughtin LCAMS Geelong, Australia
