Metrication
Metrication, or metrification, isprocessconverting fromvarious older systemsunits used throughoutworld (especially"Imperial" or "American" systems that derived fromUnited Kingdom), tometric or SI system.Metrication involves not only changingunitswhich quantitiesmeasured, but also redesigning standardsuse rational metric sizes. For example,1 inch isrational size forbolt ifbolt isbe measuredinches, butmetric equivalent25.40 mmnotrational size,thusmetric size25 mmsubstituted. This requiresredesign not only ofbolt, but alsomany other productsstructures that would containbolt.
All countries inworld usemetric system togreater or lesser extent,most have abolishedusenon-metric unitsalmost all purposes. However infew specific areas, non-metric measures retain worldwide dominance. Thesenotably airsea transport, whereknot remainsprime unitvelocitymaritime navigation,for safetyflexibility reasons aircraft flying heightsuniversally calculatedfeet rather than metres.
The main exceptionstandardised metrication isUnited States. Although metrication isofficial policy ofUnited States,progressmetrication has been much slower inUnited States than inrest ofworld. The nonmetric units continuebe frequently usedeveryday life,in commerceengineering. However, change has happened: most products withinU.S.now labelledboth metricnonmetric units;an increasing numbercompaniesgovernment agenciesswitchingmetric standards. The U.S. continuesuse only milesroad distance signs. Originally U.S. legislation set October 2000 asdeadline by which states must undertake construction workstatisticsmetricstatesbe eligibleFederal funding, but that requirement has since been rescinded. Some states, such as California, have experimentedmetric road signs, but thereas yet no planslarge-scale conversion. Metric unitsgenerally usedscientific applications inUSAsome few exceptions like BTUscalories.
Europe generally uses metric unitsalmost all purposes,uses metric standards. Although some nonmetric unitsstill popularly usedsome countries,have no legal status. The United KingdomIreland aremain exception, whichstill inprocessphasing outlegal statusnonmetric units. Thususemixturemetricnonmetric unitsdifferent purposes. The United Kingdomcurrently inprocessabolishingusenonmetric units; as2000, all loose goods sold by mass must be sold using metric units,process that has been resisted by some leadingactsvandalism such asdefacementmetric road signs. UK policy iseliminate almost all nonmetric units by 2009, exceptroad signs. Irelandgenerally more advanced thanUnited Kingdom, but still lags behindrestEurope; conversionspeed limit signskilometres per hour was not completed until 2001. Metricationall EU member statesrequired under EU law, withtarget date2009 by which all productsEurope must be sold only by metric units,some limited exceptions.
Canada has converted tometric systemmost purposes, including temperatureweather reports, speed limits, road signs,sizesmost products. However therestill significant usenonmetric unitsstandardssome sectors ofCanadian economy, mainly due toclose proximity toUnited States. Notable among thesestationeryconstruction lumbergyproc. Retrofitting metric sized wallboard on old 16" spaced studs can be significantly difficult.
AustraliaNew Zealand have largely converted tometric system, but nonmetric unitsstill sometimes usedpopular conversation, especiallymeasure body height or mass. (Many Australians know their heightfeetinches but their masskilograms.)
Withever increasing importanceglobal trade, increasing harmonizationunitsmeasurementstandards,thus further advancesmetrication,both necessaryinevitable. Metrication generally requires legislative action, i.e. legal requirementsuse metric unitscommerce, andeventual prohibition ofusenonmetric units. Thisbecause businesses which convertmetric standards frequently cannot competethose which do not, due topreferenceconsumers forfamiliar. Those countries which have attemptedengineervoluntary conversion tometric system, such asUnited States, have been largely unsucessful comparedthose which have mademetric system legally compulsory.
Usemultiple standardsunits leadlosshundredsmillionsdollars whenMars Climate Orbiter crashed into Mars. The manufacturer ofspacecraft had designednavigation systembe programmedEnglish measurements. Butnavigation team at NASA's Jet Propulsion LaboratoryPasadena, California incorrectly assumedspacecraft required metric units.
See also: anti-metrication, conversionunits, decimalization
