World Geodetic System
The World Geodetic System is a standard for use in cartography and satellite navigation including GPS. This standard includes the definition of the coordinate system's fundamental and derived constants, the ellipsoidal Earth Gravitational Model, a description of the associated World Magnetic Model, a current list of local datum transformations; the latest revision is WGS 84, established in 1984 and last revised in 2004. Earlier schemes included WGS 72, WGS 66, WGS 60. WGS 84 is the reference coordinate system used by the Global Positioning System; the coordinate origin of WGS 84 is meant to be located at the Earth's center of mass. The WGS 84 meridian of zero longitude is the IERS Reference Meridian, 5.3 arc seconds or 102 metres east of the Greenwich meridian at the latitude of the Royal Observatory. The WGS 84 datum surface is an oblate spheroid with equatorial radius a = 6378137 m at the equator and flattening f = 1/298.257223563. The polar semi-minor axis b equals a × = 6356752.3142 m. WGS 84 uses the Earth Gravitational Model 2008.
This geoid defines the nominal sea level surface by means of a spherical harmonics series of degree 360. The deviations of the EGM96 geoid from the WGS 84 reference ellipsoid range from about −105 m to about +85 m. EGM96 differs from the original WGS 84 geoid, referred to as EGM84. WGS 84 uses the World Magnetic Model 2015v2; the new version of WMM 2015 became necessary due to extraordinarily large and erratic movements of the north magnetic pole. The next regular update will occur in late 2019. Efforts to supplement the various national surveying systems began in the 19th century with F. R. Helmert's famous book Mathematische und Physikalische Theorien der Physikalischen Geodäsie. Austria and Germany founded the Zentralbüro für die Internationale Erdmessung, a series of global ellipsoids of the Earth were derived. A unified geodetic system for the whole world became essential in the 1950s for several reasons: International space science and the beginning of astronautics; the lack of inter-continental geodetic information.
The inability of the large geodetic systems, such as European Datum, North American Datum, Tokyo Datum, to provide a worldwide geo-data basis Need for global maps for navigation and geography. Western Cold War preparedness necessitated a standardised, NATO-wide geospatial reference system, in accordance with the NATO Standardisation AgreementIn the late 1950s, the United States Department of Defense, together with scientists of other institutions and countries, began to develop the needed world system to which geodetic data could be referred and compatibility established between the coordinates of separated sites of interest. Efforts of the U. S. Army and Air Force were combined leading to the DoD World Geodetic System 1960; the term datum as used here refers to a smooth surface somewhat arbitrarily defined as zero elevation, consistent with a set of surveyor's measures of distances between various stations, differences in elevation, all reduced to a grid of latitudes and elevations. Heritage surveying methods found elevation differences from a local horizontal determined by the spirit level, plumb line, or an equivalent device that depends on the local gravity field.
As a result, the elevations in the data are referenced to the geoid, a surface, not found using satellite geodesy. The latter observational method is more suitable for global mapping. Therefore, a motivation, a substantial problem in the WGS and similar work is to patch together data that were not only made separately, for different regions, but to re-reference the elevations to an ellipsoid model rather than to the geoid. In accomplishing WGS 60, a combination of available surface gravity data, astro-geodetic data and results from HIRAN and Canadian SHORAN surveys were used to define a best-fitting ellipsoid and an earth-centered orientation for each of selected datum; the sole contribution of satellite data to the development of WGS 60 was a value for the ellipsoid flattening, obtained from the nodal motion of a satellite. Prior to WGS 60, the U. S. Army and U. S. Air Force had each developed a world system by using different approaches to the gravimetric datum orientation method. To determine their gravimetric orientation parameters, the Air Force used the mean of the differences between the gravimetric and astro-geodetic deflections and geoid heights at selected stations in the areas of the major datums.
The Army performed an adjustment to minimize the difference between astro-geodetic and gravimetric geoids. By matching the relative astro-geodetic geoids of the selected datums with an earth-centered gravimetric geoid, the selected datums were reduced to an earth-centered orientation. Since the Army and Air Force systems agreed remarkably well for the NAD, ED and TD areas, they were consolidated and became WGS 60. Improvements to the global system included the Astrogeoid of Irene Fischer and the astronautic Mercury datum. In January 1966, a World Geodetic System Committee composed of representatives from the United States Army and Air Force was charged with developing an improved WGS, needed to satisfy mapping and geodetic requirements. Additional surface gravity observa
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Denmark the Kingdom of Denmark, is a Nordic country and the southernmost of the Scandinavian nations. Denmark lies southwest of Sweden and south of Norway, is bordered to the south by Germany; the Kingdom of Denmark comprises two autonomous constituent countries in the North Atlantic Ocean: the Faroe Islands and Greenland. Denmark proper consists of a peninsula, an archipelago of 443 named islands, with the largest being Zealand and the North Jutlandic Island; the islands are characterised by flat, arable land and sandy coasts, low elevation and a temperate climate. Denmark has a total area of 42,924 km2, land area of 42,394 km2, the total area including Greenland and the Faroe Islands is 2,210,579 km2, a population of 5.8 million. The unified kingdom of Denmark emerged in the 10th century as a proficient seafaring nation in the struggle for control of the Baltic Sea. Denmark and Norway were ruled together under one sovereign ruler in the Kalmar Union, established in 1397 and ending with Swedish secession in 1523.
The areas of Denmark and Norway remained under the same monarch until Denmark -- Norway. Beginning in the 17th century, there were several devastating wars with the Swedish Empire, ending with large cessions of territory to Sweden. After the Napoleonic Wars, Norway was ceded to Sweden, while Denmark kept the Faroe Islands and Iceland. In the 19th century there was a surge of nationalist movements, which were defeated in the 1864 Second Schleswig War. Denmark remained neutral during World War I. In April 1940, a German invasion saw brief military skirmishes while the Danish resistance movement was active from 1943 until the German surrender in May 1945. An industrialised exporter of agricultural produce in the second half of the 19th century, Denmark introduced social and labour-market reforms in the early 20th century that created the basis for the present welfare state model with a developed mixed economy; the Constitution of Denmark was signed on 5 June 1849, ending the absolute monarchy, which had begun in 1660.
It establishes a constitutional monarchy organised as a parliamentary democracy. The government and national parliament are seated in Copenhagen, the nation's capital, largest city, main commercial centre. Denmark exercises hegemonic influence in the Danish Realm, devolving powers to handle internal affairs. Home rule was established in the Faroe Islands in 1948. Denmark negotiated certain opt-outs, it is among the founding members of NATO, the Nordic Council, the OECD, OSCE, the United Nations. Denmark is considered to be one of the most economically and developed countries in the world. Danes enjoy a high standard of living and the country ranks in some metrics of national performance, including education, health care, protection of civil liberties, democratic governance and human development; the country ranks as having the world's highest social mobility, a high level of income equality, is among the countries with the lowest perceived levels of corruption in the world, the eleventh-most developed in the world, has one of the world's highest per capita incomes, one of the world's highest personal income tax rates.
The etymology of the word Denmark, the relationship between Danes and Denmark and the unifying of Denmark as one kingdom, is a subject which attracts debate. This is centered on the prefix "Dan" and whether it refers to the Dani or a historical person Dan and the exact meaning of the -"mark" ending. Most handbooks derive the first part of the word, the name of the people, from a word meaning "flat land", related to German Tenne "threshing floor", English den "cave"; the -mark is believed to mean woodland or borderland, with probable references to the border forests in south Schleswig. The first recorded use of the word Danmark within Denmark itself is found on the two Jelling stones, which are runestones believed to have been erected by Gorm the Old and Harald Bluetooth; the larger stone of the two is popularly cited as Denmark's "baptismal certificate", though both use the word "Denmark", in the form of accusative ᛏᛅᚾᛘᛅᚢᚱᚴ tanmaurk on the large stone, genitive ᛏᛅᚾᛘᛅᚱᚴᛅᚱ "tanmarkar" on the small stone.
The inhabitants of Denmark are there called "Danes", in the accusative. The earliest archaeological findings in Denmark date back to the Eem interglacial period from 130,000–110,000 BC. Denmark has been inhabited since around 12,500 BC and agriculture has been evident since 3900 BC; the Nordic Bronze Age in Denmark was marked by burial mounds, which left an abundance of findings including lurs and the Sun Chariot. During the Pre-Roman Iron Age, native groups began migrating south, the first tribal Danes came to the country between the Pre-Roman and the Germanic Iron Age, in the Roman Iron Age; the Roman provinces maintained trade routes and relations with native tribes in Denmark, Roman coins have been found in Denmark. Evidence of strong Celtic cultural influence dates from this period in Denmark and much of North-West Europe and is among other things reflected in the finding of the Gundestrup cauldron; the tribal Danes came from the east Danish islands and Scania and spoke an early form of North Germanic.
Historians believe that before their arrival, most of Jutland and the nearest islands were settled by tribal J
The mile is an English unit of length of linear measure equal to 5,280 feet, or 1,760 yards, standardised as 1,609.344 metres by international agreement in 1959. With qualifiers, "mile" is used to describe or translate a wide range of units derived from or equivalent to the Roman mile, such as the nautical mile, the Italian mile, the Chinese mile; the Romans divided their mile into 5,000 roman feet but the greater importance of furlongs in pre-modern England meant that the statute mile was made equivalent to 8 furlongs or 5,280 feet in 1593. This form of the mile spread to the British-colonized nations some of which continue to employ the mile; the US Geological Survey now employs the metre for official purposes but legacy data from its 1927 geodetic datum has meant that a separate US survey mile continues to see some use. While most countries replaced the mile with the kilometre when switching to the International System of Units, the international mile continues to be used in some countries, such as Liberia, the United Kingdom, the United States, a number of countries with fewer than one million inhabitants, most of which are UK or US territories, or have close historical ties with the UK or US.
The mile was abbreviated m. in the past but is now sometimes written as mi to avoid confusion with the SI metre. However, derived units, such as miles per hour or miles per gallon, continue to be universally abbreviated as mph and mpg, respectively; the modern English word mile derives from Middle English myl and Old English mīl, cognate with all other Germanic terms for "miles". These derived from apocopated forms of the Latin mīlia or mīllia, the plural of mīle or mīlle "thousand" but used as a clipped form of mīlle passus or passuum, the Roman mile of one thousand paces; the present international mile is what is understood by the unqualified term "mile". When this distance needs to be distinguished from the nautical mile, the international mile may be described as a "land mile" or "statute mile". In British English, the "statute mile" may refer to the present international miles or to any other form of English mile since the 1593 Act of Parliament, which set it as a distance of 1,760 yards.
Under American law, the "statute mile" refers to the US survey mile. Foreign and historical units translated into English as miles employ a qualifier to describe the kind of mile being used but this may be omitted if it is obvious from the context, such as a discussion of the 2nd-century Antonine Itinerary describing its distances in terms of "miles" rather than "Roman miles"; the mile has been variously abbreviated—with and without a trailing period—as m, M, ml, mi. The American National Institute of Standards and Technology now uses and recommends mi in order to avoid confusion with the SI metre and millilitre. However, derived units such as miles per hour or miles per gallon continue to be abbreviated as mph and mpg rather than mi/h and mi/gal. In the United Kingdom road signs use m as the abbreviation for mile though height and width restrictions use m as the abbreviation for the metre, which may be displayed alongside feet and inches; the BBC style holds that "There is no acceptable abbreviation for'miles'" and so it should be spelt out when used in describing areas.
The Roman mile consisted of a thousand paces as measured by every other step—as in the total distance of the left foot hitting the ground 1,000 times. The ancient Romans, marching their armies through uncharted territory, would push a carved stick in the ground after each 1,000 paces. Well-fed and harshly driven Roman legionaries in good weather thus created longer miles; the distance was indirectly standardised by Agrippa's establishment of a standard Roman foot in 29 BC, the definition of a pace as 5 feet. An Imperial Roman mile thus denoted 5,000 Roman feet. Surveyors and specialized equipment such as the decempeda and dioptra spread its use. In modern times, Agrippa's Imperial Roman mile was empirically estimated to have been about 1,617 yards in length. In Hellenic areas of the Empire, the Roman mile was used beside the native Greek units as equivalent to 8 stadia of 600 Greek feet; the mílion continued to be used as a Byzantine unit and was used as the name of the zero mile marker for the Byzantine Empire, the Milion, located at the head of the Mese near Hagia Sophia.
The Roman mile spread throughout Europe, with its local variations giving rise to the different units below. Arising from the Roman mile is the "milestone". All roads radiated out from the Roman Forum throughout the Empire – 50,000 miles of stone-paved roads. At every mile was placed a shaped stone, on, carved a Roman numeral, indicating the number of miles from the center of Rome – the Forum. Hence, one always knew; the Italian mile was traditionally considered a direct continuation of the Roman mile, equal to 1000 paces, although its actual value over time or between regions could vary greatly. It was used in international contexts from the Middle Ages into the 17th century and is thus known as the "geographical mile", although the geographical mile is now a separate standard unit; the Arabic mile was not the common Arabic unit of length. The Arabic mile was, used by medieval geographers and scientists and constituted a kind of precursor to the nautical or geographical mile, it extended the Roman mile to fit an astronomical approximatio
The metre or meter is the base unit of length in the International System of Units. The SI unit symbol is m; the metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second. The metre was defined in 1793 as one ten-millionth of the distance from the equator to the North Pole – as a result the Earth's circumference is 40,000 km today. In 1799, it was redefined in terms of a prototype metre bar. In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted; the imperial inch is defined as 0.0254 metres. One metre is about 3 3⁄8 inches longer than a yard, i.e. about 39 3⁄8 inches. Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations except the United States and the Philippines, which use meter. Other Germanic languages, such as German and the Scandinavian languages spell the word meter. Measuring devices are spelled "-meter" in all variants of English.
The suffix "-meter" has the same Greek origin as the unit of length. The etymological roots of metre can be traced to the Greek verb μετρέω and noun μέτρον, which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism; this range of uses is found in Latin, French and other languages. The motto ΜΕΤΡΩ ΧΡΩ in the seal of the International Bureau of Weights and Measures, a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as "Use measure!", thus calls for both measurement and moderation. In 1668 the English cleric and philosopher John Wilkins proposed in an essay a decimal-based unit of length, the universal measure or standard based on a pendulum with a two-second period; the use of the seconds pendulum to define length had been suggested to the Royal Society in 1660 by Christopher Wren. Christiaan Huygens had observed that length to be 39.26 English inches. No official action was taken regarding these suggestions.
In 1670 Gabriel Mouton, Bishop of Lyon suggested a universal length standard with decimal multiples and divisions, to be based on a one-minute angle of the Earth's meridian arc or on a pendulum with a two-second period. In 1675, the Italian scientist Tito Livio Burattini, in his work Misura Universale, used the phrase metro cattolico, derived from the Greek μέτρον καθολικόν, to denote the standard unit of length derived from a pendulum; as a result of the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. On 7 October 1790 that commission advised the adoption of a decimal system, on 19 March 1791 advised the adoption of the term mètre, a basic unit of length, which they defined as equal to one ten-millionth of the distance between the North Pole and the Equator. In 1793, the French National Convention adopted the proposal. In 1791, the French Academy of Sciences selected the meridional definition over the pendular definition because the force of gravity varies over the surface of the Earth, which affects the period of a pendulum.
To establish a universally accepted foundation for the definition of the metre, more accurate measurements of this meridian were needed. The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which attempted to measure the distance between a belfry in Dunkerque and Montjuïc castle in Barcelona to estimate the length of the meridian arc through Dunkerque; this portion of the meridian, assumed to be the same length as the Paris meridian, was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator. The problem with this approach is that the exact shape of the Earth is not a simple mathematical shape, such as a sphere or oblate spheroid, at the level of precision required for defining a standard of length; the irregular and particular shape of the Earth smoothed to sea level is represented by a mathematical model called a geoid, which means "Earth-shaped". Despite these issues, in 1793 France adopted this definition of the metre as its official unit of length based on provisional results from this expedition.
However, it was determined that the first prototype metre bar was short by about 200 micrometres because of miscalculation of the flattening of the Earth, making the prototype about 0.02% shorter than the original proposed definition of the metre. Regardless, this length became the French standard and was progressively adopted by other countries in Europe; the expedition was fictionalised in Le mètre du Monde. Ken Alder wrote factually about the expedition in The Measure of All Things: the seven year odyssey and hidden error that transformed the world. In 1867 at the second general conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth; the conference recommended the adoption of the metre and the creation of an internatio
The system of imperial units or the imperial system is the system of units first defined in the British Weights and Measures Act of 1824, refined and reduced. The Imperial units replaced the Winchester Standards, which were in effect from 1588 to 1825; the system came into official use across the British Empire. By the late 20th century, most nations of the former empire had adopted the metric system as their main system of measurement, although some imperial units are still used in the United Kingdom and other countries part of the British Empire; the imperial system developed from what were first known as English units, as did the related system of United States customary units. The Weights and Measures Act of 1824 was scheduled to go into effect on 1 May 1825. However, the Weights and Measures Act of 1825 pushed back the date to 1 January 1826; the 1824 Act allowed the continued use of pre-imperial units provided that they were customary known, marked with imperial equivalents. Apothecaries' units are mentioned neither in the act of 1824 nor 1825.
At the time, apothecaries' weights and measures were regulated "in England and Berwick-upon-Tweed" by the London College of Physicians, in Ireland by the Dublin College of Physicians. In Scotland, apothecaries' units were unofficially regulated by the Edinburgh College of Physicians; the three colleges published, at infrequent intervals, the London and Dublin editions having the force of law. Imperial apothecaries' measures, based on the imperial pint of 20 fluid ounces, were introduced by the publication of the London Pharmacopoeia of 1836, the Edinburgh Pharmacopoeia of 1839, the Dublin Pharmacopoeia of 1850; the Medical Act of 1858 transferred to The Crown the right to publish the official pharmacopoeia and to regulate apothecaries' weights and measures. Metric equivalents in this article assume the latest official definition. Before this date, the most precise measurement of the imperial Standard Yard was 0.914398415 metres. In 1824, the various different gallons in use in the British Empire were replaced by the imperial gallon, a unit close in volume to the ale gallon.
It was defined as the volume of 10 pounds of distilled water weighed in air with brass weights with the barometer standing at 30 inches of mercury at a temperature of 62 °F. In 1963, the gallon was redefined as the volume of 10 pounds of distilled water of density 0.998859 g/mL weighed in air of density 0.001217 g/mL against weights of density 8.136 g/mL, which works out to 4.546096 l or 277.4198 cu in. The Weights and Measures Act of 1985 switched to a gallon of 4.54609 L. These measurements were in use from 1826, when the new imperial gallon was defined, but were abolished in the United Kingdom on 1 January 1971. In the US, though no longer recommended, the apothecaries' system is still used in medicine in prescriptions for older medications. In the 19th and 20th centuries, the UK used three different systems for weight. Troy weight, used for precious metals; the distinction between mass and weight is not always drawn. A pound is a unit of mass, although it is referred to as a weight; when a distinction is necessary, the term pound-force may be used to refer to a unit of force rather than mass.
The troy pound was made the primary unit of mass by the 1824 Act. The Weights and Measures Act 1855 made the avoirdupois pound the primary unit of mass. In all the systems, the fundamental unit is the pound, all other units are defined as fractions or multiples of it. Although the 1824 act defined the yard and pound by reference to the prototype standards, it defined the values of certain physical constants, to make provision for re-creation of the standards if they were to be damaged. For the yard, the length of a pendulum beating seconds at the latitude of Greenwich at Mean Sea Level in vacuo was defined as 39.01393 inches. For the pound, the mass of a cubic inch of distilled water at an atmospheric pressure of 30 inches of mercury and a temperature of 62° Fahrenheit was defined as 252.458 grains, with there being 7,000 grains per pound. However, following the destruction of the original prototypes in the 1834 Houses of Parliament fire, it proved impossible to recreate the standards from these definitions, a new Weights and Measures Act was passed in 1855 which permitted the recreation of the prototypes from recognized secondary standards.
The imperial system is one of many systems of English units. Although most of the units are defined in more than one system, some subsidiary units were used to a much greater extent, or for different purposes, in one area rather than the other; the distinctions between these systems are not drawn precisely. One such distinction is that between these systems and older British/English units/systems or newer additions; the term imperial should not be applied to English units that were outlawed in the Weights and Measures Act 1824 or earlier, or which had fallen out of use by that time, nor to post-imperial inventions, such as the slug or poundal. The US customary system is derived from the English units that were in use at the time of settlement; because the United States was independent at the time, these units were unaffected b