Construct · 4 fields · 5 citations
One name. Different field. Different construct. One map.
● jingle · one word, four reference directions Nearest construct by meaningamplitudecompare the meaningsEvery construct on the map is compared with every other by the meaning of its definitions, and the closest one is surfaced here. The nearest construct to azimuth is amplitude.
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In the horizontal coordinate system used in astronomy and celestial navigation, azimuth is the compass bearing of a celestial body: the angle measured around the observer's horizon, in modern convention clockwise from due north, to the point directly below the body. Paired with altitude, the height above the horizon, it fixes where a star, the Sun, or a planet appears for an observer at a given place and moment. The Explanatory Supplement to the Astronomical Almanac (Urban and Seidelmann, 2013) sets out this frame and notes that older works reckon the very same angle from due south instead. The referent is the direction to a point of light on the sky, tied to the observer's local horizon and to north, not the orientation of a line on the ground, the direction of a sound at the ear, or the bearing a gun is laid to.[1]
In surveying and geodesy, the azimuth of a line is the horizontal angle from a reference meridian, clockwise, to the line joining two points on the ground. A forward azimuth runs from the first point to the second and a back azimuth in the reverse direction, and on the curved Earth the two differ by close to, but not exactly, 180 degrees. Which meridian counts is a standing hazard: a true azimuth is referenced to the geographic pole, a grid azimuth to the map projection's north, and a magnetic azimuth to the compass, and the three can disagree by degrees. Vincenty's (1975) equations for geodesics on the ellipsoid compute these forward and back azimuths precisely, and Karney's (2013) algorithms refine them. The referent is the orientation of a line between ground marks, not a direction to a star, a sound, or a target.[2][3]
In acoustics and psychoacoustics, the azimuth of a sound source is its horizontal direction relative to the listener's head: the angle in the horizontal plane from straight ahead, around toward one ear. The listener recovers it not from a chart but from the differences between the two ears, the small gap in arrival time and the difference in loudness that a source off to one side produces. Rayleigh's (1907) duplex theory established that low frequencies are located mainly by interaural time and high frequencies by interaural level. The referent is a perceived direction anchored to the head itself, an egocentric angle that moves when the listener turns, unlike a star's bearing from north, a survey line's bearing from a meridian, or a firing bearing on a grid.[4]
In gunnery and fire control, azimuth is the horizontal bearing a weapon is laid to: the angle, referenced to grid north or to an aiming point, that points the piece toward the target in the horizontal plane, paired with elevation to complete the firing solution. Field artillery doctrine such as the U.S. Army's Field Artillery Manual Cannon Gunnery (2016) works this bearing through deflection settings and corrects it for effects such as drift and wind. The referent is a commanded pointing direction for a weapon, computed and applied to a mount, not the position of a body on the sky, the orientation of a ground line, or the perceived direction of a sound.[5]
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