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A speedometer from an American car, showing the speed of the vehicle in miles per hour (outer, in white) and kilometres per hour (inner, in red)
A speedometer from an Australian car, showing the speed of the vehicle only in kilometres per hour.

Metrication refers to the introduction and use of the SI metric system, the international standard for physical measurements. This has involved a long process of independent and systematic conversions of countries from various local systems of weights and measures. Metrication began in France in the 1790s and spread widely during the following two centuries. The process is sometimes called metrification.

Contents

Overview

Only three countries (Burma (Myanmar), Liberia, and the United States) have yet to adopt the International System of Units as their official system of measurement.[1][2] However, a number of other jurisdictions have laws mandating or permitting other systems of measurement in some or all contexts, such as the United Kingdom.[3][4] Conversely the three countries named above as "non-metric" have indirectly adopted metric measures to some degree through international trade and standardisation.[2] The United States mandated the acceptance of the metric system in 1866 for commercial and legal proceedings, without requiring the use of the metric system.[5] Liberia and Myanmar are both substantially metric countries that trade internationally in metric units. Visitors to these places report that they also use metric units for most things internally with only a few exceptions like old petrol pumps calibrated in British Imperial gallons.[6] Most countries have adopted the metric system officially over a transitional period where both units are used for a set period of time. Some countries such as Guyana, for example, have officially adopted the metric system, but have had some trouble over time implementing it.[7] Antigua, also 'officially' metric, is moving toward total implementation of the metric system, but slower than expected.[8] Other Caribbean countries such as Saint Lucia are officially metric but are still in the process toward full conversion.[9]

In the European Union, with the Units of Measure Directive, the European Council (of Ministers) sought to achieve a common system of weights and measures to further the aims of the European Single Market. Throughout the 1990s, the European Commission helped accelerate the process for member countries to complete their conversion process to metric. As part of the negotiations towards the Directive, the United Kingdom secured permanent exemptions for the mile and yard in road markings, and (with Ireland) for the pint of beer sold in pubs[10] (see Metrication in the United Kingdom). In 2007, the European Commission also announced that (to facilitate trade with the United States) it was to abandon the requirement for metric-only labelling on packaged goods, and to allow dual metric-imperial marking to continue indefinitely.

Other countries using the old imperial system completed metrication during the second half of the 20th century. The most recent to complete this process was the Republic of Ireland, which began metric conversion in the 1970s and finalised it in early 2005.

In January 2007 the moon went metric after NASA bowed to pressure from other space agencies.[11]

The United States and the United Kingdom have some active opposition to metrication. Other countries, like France and Japan, that once had significant popular opposition to metrication, now have complete acceptance of metrication.[citation needed]

Before the metric system

In medieval Europe, local laws on weights and measures were set by trade guilds on a city-by-city basis. For example, the ell or elle was a unit of length commonly used in Europe, but its value varied from 40.2 centimetres in one part of Germany to 70 centimetres in The Netherlands to 94.5 centimetres in Edinburgh. A survey of Switzerland in 1838 revealed that the foot had 37 different regional variations, the ell had 68, there were 83 different measures for dry grain and 70 for fluids, and 63 different measures for "dead weights".[12] When Isaac Newton wrote Philosophiae Naturalis Principia Mathematica in 1687, he quoted his measurements in Parisian feet so readers could understand the size. Examples of efforts to have local intercity or national standards for measurements include the Scottish law of 1641, and the British standard Imperial unit system of 1845, which is still commonly used in the United Kingdom. At one time Imperial China had successfully standardised units for volume throughout its territory, but by 1936 official investigations uncovered 53 dimensions for the chi varying from 200 millimetres to 1250 millimetres; 32 dimensions of the cheng, between 500 millilitres and 8 litres; and 36 different tsin ranging from 300 grams to 2500 grams.[13] However, revolutionary France was to produce the definitive International System of Units which has come to be used by most of the world today.

The desire for a single international system of measurement derives from growing international trade and the need to apply common standards to goods. For a company to buy a product produced in another country, they need to ensure that the product will arrive as described. The medieval ell was abandoned in part because its value could not be standardised. It can be argued that the primary advantage of the International System of Units is simply that it is international, and the pressure on countries to conform to it grew as it became increasingly an international standard. SI is not the only example of international standardisation; several powerful international standardisation organisations exist for various industries, such as the International Organisation for Standardisation, the International Electrotechnical Commission, and the International Telecommunication Union.

Forerunners of the metric system

Decimal numbers are an essential part of the metric system. Although the Indians used decimal numbers for mathematical computations, it was Simon Stevin who in 1585 first advocated the use of decimal numbers for everyday purposes in his booklet De Thiende (Dutch for 'the tenth'). He also declared that it would only be a matter of time before decimal numbers were used for currencies and measurements. His notation for decimal fractions was clumsy, but was overcome by the introduction of the decimal point, generally attributed to Bartholomaeus Pitiscus who used this notation in his trigonometrical tables (1595).

In his Essay towards a Real Character and a Philosophical Language, published in 1668, John Wilkins proposed a system of measurement that was very similar in concept to today's metric system. He proposed retaining the second as the basic unit of time and proposed that the length of a pendulum which had a period of one second should be the base unit of length. This length, for which he proposed the name "standard", would have been 994 mm. His base unit of mass, which he proposed calling a "hundred", would have been the mass of a cubic standard of distilled rainwater. The names that he proposed for decimal multiples and subunits of his base units of measure were the names of units of measure that were in use at the time.

In 1670, Gabriel Mouton published a proposal that was in essence similar to Wilkins' proposal, except that his base unit of length would have been 1/1000 of a minute of arc (about 2.04 m). He proposed calling this unit the virga. Rather than using different names for each unit of length, he proposed a series of names that had prefixes, rather like the prefixes found in SI.

In 1790, Thomas Jefferson submitted a report to the United States Congress in which he proposed the adoption of a decimal system of coinage and of weights and measures. His proposed base unit of length was the foot which he suggested should be either 3/10 or 1/3 of the length of a pendulum that had a period of one second – that is 3/10 or 1/3 of the "standard" proposed by Wilkins over a century previously. His base unit of mass was to be the bushel, which would have been the mass of a cubic foot of water. Like Wilkins, the names that he proposed for multiples and subunits of his base units of measure were the names of units of measure that were in use at the time.

Conversion process

Countries by date of metrication

The metric system was officially introduced in France in 1799. In the 19th century, the metric system was adopted by the following European countries: Portugal (1814)[14], Netherlands, Belgium and Luxembourg (1820), Switzerland (1835), Spain (1850s), Italy (1861), Germany (1870, legally from 1 January 1872), Austria (1876, but the law was adopted in 1871). Denmark adopted the metric system in 1907.

There are three common routes that nations take in converting from traditional measurement systems to the metric system. The first is a quick, so called "Big-Bang" route which was used by India in the 1960s and several other nations including Australia and New Zealand since then. The second route is to phase in units over time and progressively outlaw traditional units. This method, favoured by some industrial nations, is slower and generally less complete. The final route is to redefine traditional units in metric terms. This method has been used successfully where traditional units were ill-defined and had regional variations.

The first route, "Big-Bang", is to simultaneously outlaw the use of pre-metric measurement, metricate, reissue all government publications and laws, and change education systems to metric. India's changeover lasted from 1 April 1960, when metric measurements became legal, to 1 April 1962, when all other systems were banned. The Indian model was extremely successful and was copied over much of the developing world.

The second way, the phase-in route, is to pass a law permitting the use of metric units in parallel with traditional ones, followed by education of metric units, then progressively banning the use of the older measures. This has generally been a slow route to metric. The British Empire permitted the use of metric measures in 1873, but the changeover was not completed in most countries until the 1970s and 1980s when governments took an active role in the now-independent parts of the former empire, now Commonwealth. Japan, too, followed this route and did not complete the changeover for 70 years. In the United Kingdom, the process is still incomplete. By law, loose goods sold with reference to units of quantity have to be weighed and sold using the metric system. In 2001 the EU directive 80/181/EEC stated that supplementary units (imperial units alongside metric including labelling on packages) would become illegal from the beginning of 2010. In September 2007[10] a consultation process was started which resulted in the direcitve being modifed to permit supplementary units to be used indefinitely.

A third method is to redefine traditional units in terms of metric values. These redefined "quasi-metric" units often stay in use long after metrication is said to have been completed. Resistance to metrication in post-revolutionary France convinced Napoleon to revert to mesures usuelles (usual measures) and to some extent the names remain throughout Europe. In 1814, Portugal adopted the Metric system but with the names of the units substituted by Portuguese traditional ones. In this system the basic units were the mão-travessa (hand) = 1 decimeter (10 mão-travessas = 1 vara (yard) = 1 meter), the canada = 1 liter and the libra (pound) = 1 kilogram [14]. In the Netherlands, 500 g is informally referred to as a pond (pound) and 100 g as an ons (ounce), and in Germany and France 500 g is informally referred to respectively as ein Pfund and une livre ("one pound").[15] In Denmark, the re-defined pund (500 g) is occasionally used, particularly among older people and (older) fruit growers, since these were originally paid according to the number of pounds of fruit produced. In Sweden and Norway a mil (Scandinavian mile) is informally equal to 10 km, and this has continued to be the predominantly used unit in conversation when referring to geographical distances. In the 19th century, Switzerland had a non-metric system completely based on metric terms (e.g. 1 fuss (foot) = 30 cm, 1 zoll (inch) = 3 cm, 1 linien (line) = 3 mm). In China the jin now has a value of 500 g and the liang is 50g.

It is difficult to judge the degree to which ordinary people change to using metric in their daily lives. In countries that have recently changed, older segments of the population tend to still use the older units. Also, local variations abound in which units are round metric quantities or not. In Canada, for example, ovens and cooking temperatures are usually measured in degrees Fahrenheit and Canadians almost invariably use Fahrenheit for cooking, which may be due to the overwhelming influence of the neighbouring United States; similarly, Canadians often use non-metric measurements in day-to-day discussions of height and weight, and for clothing sizes, which are invariably measured in inches, though driver's licences and other official government documents record weight and height only in metric. In the United Kingdom, Fahrenheit is seldom encountered (except when some people talk about hot summer weather) while other metric units are often used in conjunction with older measurements, and road signs use miles rather than kilometres. Another example is "hard" and "soft" metric. Canada converted liquid dairy products to litres, 500 g and 250 g sizes, which caused some complaining at time of conversion, as a litre of milk is 35 imperial ounces, while the former imperial quart used in Canada was 40 ounces. This is a "hard" metric conversion. Conversely, butter in Canada is sold primarily in a 454 g package, which converts to one Imperial pound. This is considered "soft" metric. Such countries could be said to be "semi-metric".

Exceptions

As of 2007, in most countries of the world the metric system officially dominates; but traditional units are still used in many places and industries. For example, automobile tyre pressure is measured as psi in countries such as Brazil, Argentina, Australia and Chile which are otherwise completely metric. Office space is often rented in traditional units, such as square foot in Hong Kong, tsubo in Japan or pyeong in Korea. Traditional measurements are still used in some areas: e.g., in plumbing the diameters of pipes are still measured in inches in some countries (in the United Kingdom all new pipes are metric). Automotive wheel diameters are still set as whole inch measurements (although tyre widths are measured in millimetres) and dots per inch continues to be used in describing graphical resolution in the computer industry. Television and monitor screen diameters are still commonly cited in inches in many countries; however, in Australia and South Africa, centimetres are often used for television sets, whereas CRT computer monitors and all LCD monitors are measured in inches. The only exception to the metrication process in Ireland was the pint in bars, pubs, and clubs; although alcohol sold in any other location is in metric units (usually 330 ml (canned beer), 500 ml (bottled beer), 750 ml (wine), or 1 l (spirit)). In Australia, a pint of beer was redefined to 570 ml (see Australian beer glasses). In both metric and non-metric countries, racing bicycle frames are generally measured in centimetres, while mountain bicycle frames are measured in either or both. In Spain and former colonies i.e. Americas and Philippines certain pre-metric units are still used e.g. the quiñón for land measurement in the Philippines, the fanega, ferrado and atahúlla to name three used in Spain and other former possessions. The pulgada (inch) is 23 mm so 2 mm shorter than the English inch.

An example of metrication of British consumer products. Two of the four items are purely metric. Milk is often sold as "1.136 litres / 2 pints". The sausages are labelled "340 g / 12 oz"

In some countries (such as Antigua, see above), the transition is still in progress. The Caribbean island nation of Saint Lucia announced metrication programs in 2005 to be compatible with CARICOM.[16] In the United Kingdom, the metric system is compulsory in most, but not all, industries. In the United Kingdom, the metric system had been legal for nearly a century before metrication efforts began in earnest. The government had been making preparations for the conversion of the Imperial unit since the 1862 Select Committee on Weights and Measures recommended the conversion[17] and the Weights and Measures Act of 1864 and the Weights and Measures (Metric System) Act of 1896 legalised the metric system.[18] In 1965, with lobbying from British industries and the prospects of joining the European Community, the government set a 10 year target for full conversion and created the Metrication Board in 1969. Metrication did occur in many areas during this time period, including the re-surveying of Ordnance Survey maps in 1970, decimalisation of the currency in 1971, and teaching the metric system in schools. However, no date was set for making the use of the metric system compulsory, and the Metrication Board was abolished in 1980 following a change in government.[19] The 1989 European Units of Measurement Directive (89/617/EEC) required all member states to make the metric system compulsory; however, the British negotiated certain derogations (delayed switchovers), including miles for road signs, and pints for draught beer, cider, and milk sales.[20] and because physical repackaging into rounded metric numbers could lead to reducing the quantity of goods sold for the same price.[21] It should, however, be noted that some items have been rounded up during metric changeover; for example, spirits were changed from 1/6 of a gill (23.7 ml) to 25 ml and the standard loaf from 14 ounces (396.9 g) to 400 g.

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United States

A measuring cup, manufactured and sold in the U.S. (circa 1980) features graduations in both metric and U.S. Customary systems. Held in the right-hand, a person would have the metric graduations in front, facing them.

As previously mentioned, the United States has been influenced by metric over time through international trade and standardisation. The use of the metric system was made legal as a system of measurement in 1866[22] and the United States was a founding member of the International Bureau of Weights and Measures in 1875.[23] The system was officially adopted by the federal government in 1975 for use in the military and government agencies.[24] In 1985, the metric system was made the preferred (but predominantly voluntary) system of weights and measures for United States trade and commerce (see Metrication in the United States). It has remained voluntary for federal and state road signage to use metric units, despite attempts in the 1990s to make it a requirement.[25] A 1992 amendment to the Fair Packaging and Labeling Act (FPLA), which took effect in 1994, required labels on federally regulated "consumer commodities"[26] to include both metric and U.S. customary units. As of June 2007, all but two US states (New York and Alabama) have passed laws permitting metric-only labels for the products they regulate.[27] Likewise, Canada also legally allows for dual labelling of goods provided that the metric unit is listed first and that there is a distinction of whether a liquid measure is a U.S. or a Canadian (Imperial) unit.[28] Today, the American public and much of the private business and industry still use U.S. customary units despite many years of informal or optional metrication.[29] At least two states, Kentucky and California, have even moved towards demetrication of highway construction projects.[30][31][32]

Air and sea transport

In air and sea transport the nautical mile is used. This approximates to one minute of arc of latitude along any meridian and is precisely defined as 1852 metres (about 1.151 miles). It is a non-SI unit (although accepted for use in the SI by the BIPM). The prime unit of speed for maritime and air navigation remains the knot (nautical mile per hour).

The prime unit of measure for aviation (altitude) is usually estimated based on air pressure values and, in many countries, is still described in nominal feet though many others employ nominal metres. A vertical spacing of 1,000 feet (305 m) has become the standard measure for safety and clarity for purposes of air traffic control.[citation needed] The policies of the International Civil Aviation Organization (ICAO) relating to measurement are:

  • there should be a single system of units throughout the world
  • the single system should be SI
  • the use of the foot for altitude is a permitted variation

Consistent with ICAO policy, aviation has undergone a significant amount of metrication over the years; for example, runways are usually given in metres. The United States metricated the data interchange format (METAR) for temperature reports in 1996.[33] Metrication is also gradually taking place in cargo weights/dimensions and fuel volume/weight.

Accidents and incidents

Confusion over units during the process of metrication can sometimes lead to accidents. One of the most famous examples is the 1983 Gimli Glider incident, where a Canadian Boeing 767 ran out of fuel due, in large part, to confusion at Air Canada during Canada's metrication.[34]

While not strictly an example of national metrication, the use of two different systems was a contributing factor in the loss of the Mars Climate Orbiter in 1998. NASA specified metric units in the contract. NASA and other organisations worked in metric units but one subcontractor, Lockheed Martin, provided thruster performance data to the team in pound force seconds instead of newton seconds. The spacecraft was intended to orbit Mars at about 150 kilometres (93 mi) altitude but the incorrect data meant that it descended to about 57 kilometres (35 mi) and probably burned up in the Martian atmosphere.

On 25 September 2009, the British Department for Transport published a draft version of legislation to amend the Traffic Signs Regulations and General Directions 2002[35] for comment. Amongst the proposed changes is an amendment to existing legislation to make dual unit height and width warning and restriction signs mandatory. This is justified in Paragraph 53 of the Impact Analysis[36] by the text "... Based on records from Network Rail’s incident logs since April 2008, approximately 10 – 12% of bridge strikes involved foreign lorries. This is disproportionately high in terms of the number of foreign lorries on the road network."

Opposition

As the birthplace of the metric system, France experienced a rough start to metrication. The traditional French measuring system was chaotic, with size of units differing in each small town, and often even within towns. Lyon had two different values of pound in general use, one of 14 ounces, and another of 15 ounces, the latter only being used for measuring silk. The revolutionary government, which saw the newly conceived metric system (commissioned by the previous king) as a good fit for its ideology of "pure reason", first attempted a quick conversion, legalising metric units in 1795 and, just four years later, banning the use of traditional units. Massive popular opposition led Napoleon, after he came to power, to roll back these reforms. He publicly denounced the previous government for "tormenting people with trifles". It appears that it was decimalisation that disturbed the people most, as, although Napoleon decreed that there should be "such fractions and multiples as were generally used", he redefined the old base units in metric terms (mesures usuelles), thereby ensuring a sound definition for the system of weights and measures.. The original metric system was made law again in France in 1837.[12]

The introduction of metrication in Japan was met with some resistance in the 1920s, where opponents believed that the adoption of a foreign measuring system would have a bad influence on national sentiment, cause dislocations in public life and needless expense to the nation, prove disadvantageous to foreign trade, and hurt the national language and culture. In 1933, the government postponed first conversion stage by five years, and the second stage by ten years. The U.S. occupation resulted in a temporary conversion to U.S. customary units. The post-war manufacturing boom required an international standard measurement system and the issue was pursued again in the 1950s and 1960s. The metrication process was completed in 1969. Some traditional units are used for measurements of sake and the area of land and apartments. Nevertheless, local units had been defined in terms of metric units (e.g., 1 shaku = 10/33 metre) as early as 1891. For the measurement of sake, 10 Japanese cups (180 millilitres each) equal 1 shō (traditional flask size of 1.8 litre capacity). Rice cookers are typically sold as having capacities such as 5 cups or 10 cups. (Note that the traditional Japanese cup is 180 millilitres while the American cup is 237 millilitres.[37] )

Few countries have experienced significant popular opposition to metrication. Australia successfully converted to the metric system from 1970 to 1988, replacing Imperial Units of measurement that were inherited from the British Empire. Some, such as 19th century European countries, Russia, India and China, converted before most of their populations were literate, so the initial conversion affected few people. For others, such as Ireland, the previous system (i.e., imperial) was seen as foreign.[12] Metrication in the United Kingdom is opposed by some who espouse the traditional or Imperial units of measurement.

See also

Notes

  1. ^ "Appendix G – Weights and Measures". The World Factbook. CIA. 2006. https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html. Retrieved 8 August 2006. 
  2. ^ a b "Metric usage and metrication in other countries". US Metric Association. 2009. http://lamar.colostate.edu/~hillger/internat.htm. Retrieved 23 May 2009. 
  3. ^ "Department for Transport statement on metric road signs". British Weights and Measures Association. 2002. http://www.bwmaonline.com/Transport%20-%20DfT%20memo.htm. Retrieved 23 May 2009. 
  4. ^ "Units of Measurement and Permitted Symbols or Abbreviations of Units of Measurement Lawful for Use for Trade". Hong Kong Weights and Measures Ordinance. 1997. http://www.legislation.gov.hk/blis_ind.nsf/d2769881999f47b3482564840019d2f9/ca7c0e7895c7f088c82564760077b0c9?OpenDocument. Retrieved 23 May 2009. 
  5. ^ "Metric Act of 1866". Metric Program, Weights and Measures Division, United States National Institute of Standards, Technology and Technology. http://ts.nist.gov/WeightsAndMeasures/Metric/upload/HR-596-Metric-Law-1866.pdf. Retrieved 10 November 2009. 
    "U.S. Metric System (SI) Legal Resources". Metric Program, Weights and Measures Division, United States National Institute of Standards, Technology and Technology. http://ts.nist.gov/WeightsAndMeasures/Metric/Federal_Metric_Policy.cfm#legal. Retrieved 11 November 2009. 
  6. ^ Pat Naughtin (2005). "Editorial". Metrication Matters Number 31. http://www.metricationmatters.com/mm-newsletter-2005-12.html#editorial. Retrieved 23 May 2009. 
  7. ^ Warwick Cairns (2007). About the Size of It. Pan Macmillan. p. 145. ISBN 978-0230016286. 
  8. ^ "Improving Trade Conformity in Antigua and Barbuda". Commonwealth News and Information Service Issue 225. Commonwealth Secretariat. 2005. http://www.thecommonwealth.org/news/142849/improving_trade_conformity_in_antigua_and_barbuda.htm. Retrieved 5 November 2007. 
  9. ^ Associated Press (2005). "St Lucia begins drive to implement metric system to catch up with region". The Jamaica Observer. http://www.jamaicaobserver.com/news/html/20050322T200000-0500_77361_OBS_ST_LUCIA_BEGINS_DRIVE_TO_IMPLEMENT_METRIC_SYSTEM_TO_CATCH_UP_WITH_REGION.asp. Retrieved 5 November 2007. 
  10. ^ a b "EU gives up on 'metric Britain". BBC News. 2007. http://news.bbc.co.uk/1/hi/uk/6988521.stm. Retrieved 23 May 2009. 
  11. ^ "Metric Moon". NASA. 2007. http://science.nasa.gov/headlines/y2007/08jan_metricMoon.htm. Retrieved 05 Feb 2010. 
  12. ^ a b c Thomas McGreevy, Peter Cunningham (1995). The Basis of Measurement: Historical Aspects. Picton Publishing. ISBN 0-948251-82-4. 
  13. ^ Witold Kula (1986). "For all peoples; for all time". Measures and Men. Richard Szreter (trans.). Princeton University Press. ISBN 0691054460. 
  14. ^ a b Fátima Paixão, Fátima Regina Jorge, Sucess and constraints in adoption of the metric system in Portugal, The Global and the Local: History of Scinece and the Cultural Integration of Europe, 2006
  15. ^ Hubert Fontaine. "Confiture de rhubarbe". http://www.hubertlejardinier.com/confiture.htm. Retrieved 5 November 2007.  (French) "1 zeste de citron par livre (500g) de rhubarbe"
  16. ^ "St Lucia moving to metric system". Caribbean Net News. 2005. http://www.caribbeannetnews.com/2005/03/17/moving.shtml. Retrieved 27 August 2006. 
  17. ^ "Report (1862) from the Select Committee on Weights and Measures" (PDF). Department of Trade and Industry, United Kingdom. 1862. http://www.metric.org.uk/Docs/DTI/met1862.pdf. Retrieved 23 May 2009. 
  18. ^ "Metrication Timeline". UK Metric Association. 2008. http://www.metric.org.uk/Press/metrictimeline.aspx. Retrieved 23 May 2009. 
  19. ^ Jim Humble. "Historical perspectives by the last Director of the UK Metrication Board". UK Metric Association. http://www.metric.org.uk/Press/Articles.aspx?ID=7. Retrieved 27 May 2009. 
  20. ^ "Consumer Affairs". Statutory Instrument 1995 No. 1804. United Kingdom. 1995. http://www.opsi.gov.uk/si/si1995/Uksi_19951804_en_1.htm. Retrieved 27 August 2006. 
  21. ^ "The Great Metric Rip-Off". British Weights and Measures Association. http://www.bwmaonline.com/Metric%20Downsizing.htm. Retrieved 27 August 2006. 
  22. ^ U.S. Metric Association. Metric Act (Kasson Act) of 1866. Retrieved on 27 August 2006.
  23. ^ U.S. Metric Association. Metric Convention of 1875. Retrieved on 27 August 2006.
  24. ^ U.S. Metric Association. Metric Conversion Act of 1975. Retrieved on 27 August 2006.
  25. ^ U.S. Metric Association. National Highway System Designation Act of 1995. Retrieved on 27 August 2006.
  26. ^ U.S. Metric Association. Sec. 1459. Definitions Fair Packaging and Labeling Act. Retrieved on 27 August 2006.
  27. ^ USMA:38845 Fwd: Re: New Jersey Announces that it will Permit Metric-Only Labeling. Retrieved on 10 Feb 2010
  28. ^ Chapter 2 — Basic Labelling Requirements. Canadian Food Inspection Agency. pp. (also available in French). http://www.inspection.gc.ca/english/fssa/labeti/guide/ch2e.shtml. Retrieved 16 May 2007. 
  29. ^ Zengerle, Jason (January/February 1999). Waits and Measures. Mother Jones.
  30. ^ Kentucky Transportation Cabinet (1998). Metric to English Conversion.
  31. ^ State of California, Department of Transportation (2004). Metric to U.S. Customary Units (English) Transition.
  32. ^ Richard D. Land, Chief Engineer (16 June 2006) (pdf). Declaration of Units of Measure - "Metric" or "English" Project. State of California, Department of Transportation. http://www.dot.ca.gov/hq/oppd/design/UOM-Metric_or_English.pdf. Retrieved 5 November 2007. 
  33. ^ "Frequently Asked Questions about METAR/SPECI and TAF". National Weather Service METAR/TAF Information. http://www.nws.noaa.gov/oso/oso1/oso12/faq.htm. Retrieved 21 August 2009. 
  34. ^ Merran Williams ((July-August 2003)) (pdf). The 156-tonne GIMLI GLIDER. Flight Safety Australia. pp. 22, 25. http://www.casa.gov.au/fsa/2003/jul/22-27.pdf. Retrieved 5 November 2007. 
  35. ^ "The Traffic Signs (Amendment) Regulations and General Directions 2010 (Draft)". Department for Transport. http://www.dft.gov.uk/consultations/open/trafficsignsamendmentregs/annexa.pdf. Retrieved 8 December 2009. 
  36. ^ "Impact Assessment of the Traffic Signs (Amendment) Regulations and General Directions 2010 and of the Traffic Signs (Temporary Obstructions) (Amendment) Regulations 2010.". Department for Transport. http://www.dft.gov.uk/consultations/open/trafficsignsamendmentregs/annexd.pdf. Retrieved 8 December 2009. 
  37. ^ Conversion for US cup can be found in NIST (1995) Guide to SI Units Appendix B8

External links

Websites supporting metrication
Books supporting metrication
  • Metric Signs Ahead (UKMA) (2005) by Robin Paice (ISBN 0955235123)
  • A Very British Mess (UKMA) (2004) by Robin Paice (ISBN 0750310146)
Websites opposing metrication
Books opposing metrication

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