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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).
In 2019, 39 million km 2 (15 million sq mi) of Earth's land surface consisted of forest and woodlands, 12 million km 2 (4.6 million sq mi) was shrub and grassland, 40 million km 2 (15 million sq mi) were used for animal feed production and grazing, and 11 million km 2 (4.2 million sq mi) were cultivated as croplands. [272]
Geopotential height or geopotential altitude is a vertical coordinate referenced to Earth's mean sea level (assumed zero geopotential) that represents the work involved in lifting one unit of mass over one unit of length through a hypothetical space in which the acceleration of gravity is assumed constant. [1]
Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). [1] Treating the Earth as a sphere, its circumference would be its single most important measurement. [2]
where R is evaluated from Earth's azimuthal radius of curvature and h are ellipsoidal heights are each point. The first term on the right-hand side of the equation accounts for the mean elevation and the second term for the inclination. A further reduction of the above Earth normal section length to the ellipsoidal geodesic length is often ...
The angular velocity of the Earth is defined to be ω = 72.921 15 × 10 −6 rad/s. [11] This leads to several computed parameters such as the polar semi-minor axis b which equals a × (1 − f) = 6 356 752.3142 m, and the first eccentricity squared, e 2 = 6.694 379 990 14 × 10 −3. [11]
The ellipsoid is defined by the equatorial axis (a) and the polar axis (b); their radial difference is slightly more than 21 km, or 0.335% of a (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 ...
Geocentric circular orbit with an altitude of 35,786 km (22,236 mi). The period of the orbit equals one sidereal day, coinciding with the rotation period of the Earth. The speed is approximately 3 km/s (9,800 ft/s). High Earth orbit (HEO) Geocentric orbits with altitudes at apogee higher than that of the geosynchronous orbit. A special case of ...