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Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
10 cm = 1.0 dm – wavelength of the highest UHF radio frequency, 3 GHz; 12 cm = 1.2 dm – wavelength of the 2.45 GHz ISM radio band; 21 cm = 2.1 dm – wavelength of the 1.4 GHz hydrogen emission line, a hyperfine transition of the hydrogen atom; 100 cm = 10 dm – wavelength of the lowest UHF radio frequency, 300 MHz
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
The reverse conversion is harder: given X-Y-Z can immediately get longitude, but no closed formula for latitude and height exists. See "Geodetic system." Using Bowring's formula in 1976 Survey Review the first iteration gives latitude correct within 10-11 degree as long as the point is within 10,000 meters above or 5,000 meters below the ellipsoid.
Length, in meters Reference The classical electron radius r e: 2.817 940 285 (31) × 10 −15 [18] The Compton wavelength of the electron λ C: 2.426 310 215 (18) × 10 −12 [18] The reduced Compton wavelength of the electron λ C: 3.861 592 6764 (18) × 10 −13 [19] The Compton wavelength (or reduced Compton wavelength) of any fundamental ...
Distance from the Earth to the Sun: â„“: Radius of the Moon: s: Radius of the Sun: t: Radius of the Earth: D: Distance from the center of Earth to the vertex of Earth's shadow cone d: Radius of the Earth's shadow at the location of the Moon n: Ratio, d/â„“ (a directly observable quantity during a lunar eclipse) x: Ratio, S/L = s/â„“ (which is ...
Posidonius calculated the Earth's circumference by reference to the position of the star Canopus.As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7 + 1 ⁄ 2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes).
Later arc measurements aimed at determining the flattening of the Earth ellipsoid by measuring at different geographic latitudes. The first of these was the French Geodesic Mission , commissioned by the French Academy of Sciences in 1735–1738, involving measurement expeditions to Lapland ( Maupertuis et al.) and Peru ( Pierre Bouguer et al.).