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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.
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 .
Pressure altitude is the elevation above a standard datum air-pressure plane (typically, 1013.25 millibars or 29.92" Hg). Pressure altitude is used to indicate "flight level" which is the standard for altitude reporting in the U.S. in Class A airspace (above roughly 18,000 feet).
The International Civil Aviation Organization (ICAO) offers similar definitions: [2] altitude: "the vertical distance of a level, a point or an object considered as a point, measured from the mean sea level (MSL);" [2] height: "the vertical distance of a level, a point or an object considered as a point, measured from a specific datum." [2]
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 seked is proportional to the reciprocal of our modern measure of slope or gradient, and to the cotangent of the angle of elevation. [2] Specifically, if s is the seked, m the slope (rise over run), and ϕ {\displaystyle \phi } the angle of elevation from horizontal, then:
It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane. [1] [2] At solar noon, the zenith angle is at a minimum and is equal to latitude minus solar declination angle. This is the basis by which ancient mariners navigated the oceans. [3]
A height finder radar is a type of 2-dimensional radar that measures altitude of a target.. The operator slews the antenna toward a desired bearing, identifies a target echo at a desired range on the range height indicator display, then bisects the target with a cursor that is scaled to indicate the approximate altitude of the target. [7]