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Airy Modified
The Airy spheroid or Airy ellipsoid is a mathematical model of the Earth, an Earth ellipsoid, designed to fit the well for the British Isles. It is named after its inventor George Biddell Airy, a nineteenth century English mathematician. Airy 1830 ellipsoid The Airy 1830 ellipsoid has an equatorial radius of 6,377,563.396 m, a polar radius of 6,356,256.909 m and an inverse flattening of 299.3249646. The original definition was in feet - using the 1796 definition of the foot, an equatorial radius of 20,923,713 ft and a polar radius of 20,853,810 ft. When the Ordinance Survey retriangulated in 1936 they defined a conversion to metres, namely a ratio of (10^0.48401603)/10 which is approximately 1 ft = 0.3048007491 m. Airy Modified 1849 The 1849 ellipsoid (EPSG:7002), known as Airy Modified 1849, is the 1830 ellipsoid scaled by 0.999965 to better fit the primary triangulation of Ireland. See also * Ordnance Survey National Grid * Irish grid reference system The Irish grid refer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Ellipsoid
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations. It is a spheroid (an ellipsoid of revolution) whose minor axis (shorter diameter), which connects the geographical North Pole and South Pole, is approximately aligned with the Earth's axis of rotation. The ellipsoid is defined by the ''equatorial axis'' () and the ''polar axis'' (); their radial difference is slightly more than 21 km, or 0.335% of (which is not quite 6,400 km). Many methods exist for determination of the axes of an Earth ellipsoid, ranging from meridian arcs up to modern satellite geodesy or the analysis and interconnection of continental geodetic networks. Amongst the different set of data used in national surveys are several of special importance: the Bessel ellipsoid of 1841, the international Hayfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Isles
The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebrides, Outer Hebrides, the Northern Isles (Orkney and Shetland), and over six thousand smaller islands. They have a total area of and a combined population of almost 72 million, and include two sovereign states, the Republic of Ireland (which covers roughly five-sixths of Ireland), and the United Kingdom, United Kingdom of Great Britain and Northern Ireland. The Channel Islands, off the north coast of France, are normally taken to be part of the British Isles, even though geographically they do not form part of the archipelago. Under the UK Interpretation Act 1978, the Channel Islands are clarified as forming part of the British Islands, not to be confused with the British Isles. The oldest rocks are 2.7 billion years old and are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
George Biddell Airy
Sir George Biddell Airy (; 27 July 18012 January 1892) was an English mathematician and astronomer, as well as the Lucasian Professor of Mathematics from 1826 to 1828 and the seventh Astronomer Royal from 1835 to 1881. His many achievements include work on planetary orbits, measuring the mean density of the Earth, a method of solution of two-dimensional problems in solid mechanics and, in his role as Astronomer Royal, establishing Greenwich as the location of the prime meridian. Biography Airy was born at Alnwick in Northumberland, one of a long line of Airys who traced their descent back to a family of the same name residing at Kentmere, in Westmorland, in the 14th century. The branch to which he belonged, having suffered in the English Civil War, moved to Lincolnshire and became farmers. Airy was educated first at elementary schools in Hereford, and afterwards at Colchester Royal Grammar School. An introverted child, Airy gained popularity with his schoolmates through his grea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foot (unit)
The foot (standard symbol: ft) is a Units of measurement, unit of length in the imperial units, British imperial and United States customary units, United States customary systems of metrology, measurement. The prime (symbol), prime symbol, , is commonly used to represent the foot. In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since international yard and pound, an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters. Historically, the "foot" was a part of many local systems of units, including the Ancient Greek units of measurement, Greek, Ancient Roman units of measurement, Roman, Chinese units of measurement, Chinese, Units of measurement in France before the French Revolution, French, and English units, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordinance Survey
The Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of 1745. There was also a more general and nationwide need in light of the potential threat of invasion during the Napoleonic Wars. Since 1 April 2015, the Ordnance Survey has operated as Ordnance Survey Ltd, a government-owned company, 100% in public ownership. The Ordnance Survey Board remains accountable to the Secretary of State for Science, Innovation and Technology. It was also a member of the Public Data Group. Paper maps represent only 5% of the company's annual revenue. It produces digital map data, online route planning and sharing services and mobile apps, plus many other location-based products for business, government and consumers. Ordnance Survey mapping is usually classified as either " large-scale" (in other words, more detailed) or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
