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Hypsometry (from Ancient Greek ὕψος (húpsos) 'height' and μέτρον (métron) 'measure') [1] [2] is the measurement of the elevation and depth of features of Earth's surface relative to mean sea level. [3] On Earth, the elevations can take on either positive or negative (below sea level) values.
Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum. Pressure altitude divided by 100 feet (30 m) is the flight level , and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions).
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]
Elevation is defined as the vertical distance between an object and sea level, while altitude is defined as the vertical distance from an object to Earth's surface. [38] The elevation of Earth's land surface varies from the low point of −418 m (−1,371 ft) at the Dead Sea, to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount ...
Typically, due to aerodynamic drag, there is a wind gradient in the wind flow ~100 meters above the Earth's surface—the surface layer of the planetary boundary layer. Wind speed increases with increasing height above the ground, starting from zero [4] due to the no-slip condition. [5]
Therefore, the altitude and azimuth of an object in the sky changes with time, as the object appears to drift across the sky with Earth's rotation. In addition, since the horizontal system is defined by the observer's local horizon, [ a ] the same object viewed from different locations on Earth at the same time will have different values of ...
In astronomy, the altitude in the horizontal coordinate system and the zenith angle are complementary angles, with the horizon perpendicular to the zenith. The astronomical meridian is also determined by the zenith, and is defined as a circle on the celestial sphere that passes through the zenith, nadir, and the celestial poles .
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).