Azimuthal angle

An azimuth (/ˈæzɪməθ/) (from the pl. form of the Arabic noun "السَّمْت" as-samt, meaning "the direction") is an angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and a reference vector on the reference plane is called the azimuth.

An example of azimuth is the angular direction of a star in the sky. The star is the point of interest, the reference plane is the local horizontal area (e.g. a circular area 5 km in radius around an observer at sea level), and the reference vector points north. The azimuth is the angle between the north vector and the star's vector on the horizontal plane.

Azimuth is usually measured in degrees (°). The concept is used in navigation, astronomy, engineering, mapping, mining, and ballistics.

In land navigation, azimuth is usually denoted alpha, α, and defined as a horizontal angle measured clockwise from a north base line or meridian.Azimuth has also been more generally defined as a horizontal angle measured clockwise from any fixed reference plane or easily established base direction line.

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