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Link (unit)
The link (usually abbreviated as "l.", "li." or "lnk."), sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. In US customary units modern definition, the link is exactly of a US survey foot, or exactly 7.92 inches or approximately 20.12 cm. The unit is based on Gunter's chain, a metal chain 66 feet long with 100 links, that was formerly used in land surveying. Even after the original tool was replaced by later instruments of higher precision, the unit was commonly used throughout the English-speaking world, for example in the United States customary units and the Imperial system. The length of the foot, and hence the link, varied slightly from place to place and time to time. In modern times the difference between the US survey foot and the international foot is two parts per million. The link fell out of general use in the 20th century. Proportions to other customary units :Twenty-five links make a rod, pole or perch ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NMAH DC - IMG 8738
The National Museum of American History: Kenneth E. Behring Center collects, preserves, and displays the heritage of the United States in the areas of social, political, cultural, scientific, and military history. Among the items on display is the original Star-Spangled Banner. The museum is part of the Smithsonian Institution and located on the National Mall at 14th Street and Constitution Avenue NW in Washington, D.C. History The museum opened in 1964 as the Museum of History and Technology. It was one of the last structures designed by the renowned architectural firm McKim Mead & White. In 1980, the museum was renamed the National Museum of American History to represent its mission of the collection, care, study, and interpretation of objects that reflect the experience of the American people. The museum site had previously held two temporary war buildings constructed in 1942. In May 2012, John Gray became the new director. He retired from the post in May 2018 and w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foot (unit)
The foot ( feet), standard symbol: ft, is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, , is a customarily used alternative symbol. Since the International Yard and Pound Agreement of 1959, one foot is defined as 0.3048 meters exactly. In both customary and imperial units, one foot comprises 12 inches and one yard comprises three feet. Historically the "foot" was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits. The United States is the only industrialized nation that uses the international foot and the survey foot (a customary unit of length) in preference to the meter in its commercial, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Millimetre
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter. The millimetre (American and British English spelling differences#-re, -er, international spelling; International System of Units, SI unit symbol mm) or millimeter (American and British English spelling differences#-re, -er, American spelling) is a Units of measurement, unit of length in the International System of Units (SI), equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre. One millimetre is equal to micrometres or nanometres. Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is equal to exactly (≈ 0.03937) of an inch. Definition Since 1983, the metre has been defined as "the length of the path travelled by light in vacuum during a time interval of of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
English Units
English units are the units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications. Use of the term "English units" can be ambiguous, as, in addition to the meaning used in this article, it is sometimes used to refer to the units of the descendent Imperial system as well to those of the descendant system of United States customary units. The two main sets of English units were the Winchester Units, used from 1495 to 1587, as affirmed by King Henry VII, and the Exchequer Standards, in use from 1588 to 1825, as defined by Queen Elizabeth I. In England (and the British Empire), English units were replaced by Imperial units in 1824 (effective 1 January 1826) by a Weights and Measures Act, which retained many though not all of the unit names and redefined ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Institute Of Standards And Technology
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into Outline of physical science, physical science laboratory programs that include Nanotechnology, nanoscale science and technology, engineering, information technology, neutron research, material measurement, and physical measurement. From 1901 to 1988, the agency was named the National Bureau of Standards. History Background The Articles of Confederation, ratified by the colonies in 1781, provided: The United States in Congress assembled shall also have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States. Article 1, section 8, of the Constitution of the United States, ratified in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangulation
In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle measurements at known points, rather than measuring distances to the point directly as in trilateration; the use of both angles and distance measurements is referred to as triangulateration. In computer vision Computer stereo vision and optical 3D measuring systems use this principle to determine the spatial dimensions and the geometry of an item. Basically, the configuration consists of two sensors observing the item. One of the sensors is typically a digital camera device, and the other one can also be a camera or a light projector. The projection centers of the sensors and the considered point on the object's surface define a (spatial) triangle. Within this triangle, the distance between the sensors is the base ''b'' and must be k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Datum
The North American Datum (NAD) is the horizontal datum now used to define the geodetic network in North America. A datum is a formal description of the shape of the Earth along with an "anchor" point for the coordinate system. In surveying, cartography, and land-use planning, two North American Datums are in use for making lateral or "horizontal" measurements: the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). Both are geodetic reference systems based on slightly different assumptions and measurements. Vertical measurements, based on distances above or below Mean High Water (MHW), are calculated using the North American Vertical Datum of 1988 (NAVD 88). NAD 83, along with NAVD 88, is set to be replaced with a new GPS- and gravimetric geoid model-based geometric reference frame and geopotential datum in 2022. First North American Datum of 1901 In 1901 the United States Coast and Geodetic Survey adopted a national horizon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Yard And Pound
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. The agreement defined the yard as exactly and the avoirdupois pound as exactly . History In October 1834, the United Kingdom Houses of Parliament were destroyed in a fire. Among the items lost were the objects that defined the imperial standards of length and mass. New prototypes were subsequently created to replace the items lost in the fire, among them a new "yardstick" ruler in 1855, and with it a new formal definition of the yard. Two copies of the ruler were subsequently presented to the United States, which in turn adopted the measure for the United States national standard yard. In 1866, the U.S. Congress passed a law that allowed, but did not require, the use of the metric system in trade and commerce. Included in the law ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mendenhall Order
The Mendenhall Order marked a decision to change the fundamental standards of length and mass of the United States from the customary standards based on those of England to metric standards. It was issued on April 5, 1893, by Thomas Corwin Mendenhall, superintendent of the U.S. Coast and Geodetic Survey, with the approval of the United States Secretary of the Treasury, John Griffin Carlisle. The order was issued as the Survey's ''Bulletin No. 26 – Fundamental Standards of Length and Mass''. Standards before the order In October 1834, the United Kingdom Houses of Parliament were destroyed in a fire, and the British standards of length and mass were also destroyed. "When the new imperial standards to replace them were completed in 1855, two copies of the yard and one copy of the avoirdupois pound were presented to the United States". These were superior to the yard then in use, so one of them was adopted as the United States national standard yard. These yards were taken to E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weights And Measures Acts Of The United Kingdom
Weights and measures acts are acts of the British Parliament determining the regulation of weights and measures. It also refers to similar royal and parliamentary acts of the Kingdoms of England and Scotland and the medieval Welsh states. The earliest of these were originally untitled but were given descriptive glosses or titles based upon the monarch under whose reign they were promulgated. Several omnibus modern acts are entitled the Weights and Measures Act and are distinguished by the year of their enactment. Background There have been many laws concerned with weights and measures in the United Kingdom or parts of it over the last 1,000 or so years. The acts may catalogue lawful weights and measures, prescribe the mechanism for inspection and enforcement of the use of such weights and measures and may set out circumstances under which they may be amended. Modern legislation may, in addition to specific requirements, set out circumstances under which the incumbent minis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
English System
English units are the units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications. Use of the term "English units" can be ambiguous, as, in addition to the meaning used in this article, it is sometimes used to refer to the units of the descendent Imperial system as well to those of the descendant system of United States customary units. The two main sets of English units were the Winchester Units, used from 1495 to 1587, as affirmed by King Henry VII, and the Exchequer Standards, in use from 1588 to 1825, as defined by Queen Elizabeth I. In England (and the British Empire), English units were replaced by Imperial units in 1824 (effective 1 January 1826) by a Weights and Measures Act, which retained many though not all of the unit names and redefined ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edmund Gunter
Edmund Gunter (158110 December 1626), was an English clergyman, mathematician, geometer and astronomer of Welsh descent. He is best remembered for his mathematical contributions which include the invention of the Gunter's chain, the Gunter's quadrant, and the Gunter's scale. In 1620, he invented the first successful analogue device which he developed to calculate logarithmic tangents. He was mentored in mathematics by Reverend Henry Briggs and eventually became a Gresham Professor of Astronomy, from 1619 until his death. Biography Gunter was born in Hertfordshire in 1581. He was educated at Westminster School, and in 1599 he matriculated at Christ Church, Oxford. He took orders, became a preacher in 1614, and in 1615 proceeded to the degree of bachelor in divinity. He became rector of St. George's Church in Southwark. Mathematics, particularly the relationship between mathematics and the real world, was the one overriding interest throughout his life. In 1619, Sir Henry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
