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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 .
Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon. The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth.
The Kármán line, at an altitude of 100 kilometres (62 mi) above sea level, by convention defines represents the demarcation between the atmosphere and space. [7] The thermosphere and exosphere (along with the higher parts of the mesosphere) are regions of the atmosphere that are conventionally defined as space.
A circle is divided into 360 degrees; subdivisions of the degree include the minute (1 ⁄ 60 of one degree) and the second (1 ⁄ 3600 of one degree). Degrees are commonly used to divide the roughly spherical shape of the Earth for geographic and cartographic purposes, e.g. when reporting latitudes and longitudes. [1] degree day
Even with these restrictions, if the polar angle (inclination) is 0° or 180°—elevation is −90° or +90°—then the azimuth angle is arbitrary; and if r is zero, both azimuth and polar angles are arbitrary. To define the coordinates as unique, the user can assert the convention that (in these cases) the arbitrary coordinates are set to zero.
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).
ICAO further defines: elevation: "the vertical distance of a point or a level, on or affixed to the surface of the earth, measured from mean sea level." [2] I.e., elevation would be the altitude of the ground or a building.
The angle of climb can be defined as the angle between a horizontal plane representing the Earth's surface, and the actual flight path followed by the aircraft during its ascent. The speed of an aircraft type at which the angle of climb is largest is called V X. It is always slower than V Y, the speed for the best rate of climb. As the latter ...