Azimuth
From Wikipedia, the free encyclopedia
Azimuth is the horizontal component of a direction (compass direction), measured around the horizon, from the north toward the east (i.e., clockwise) in astronomy and geodesy and from the south toward the west (i.e., clockwise) in surveying. It is usually expressed in degrees.
| From North | From South | ||
|---|---|---|---|
| North | 0° or 360° | South | 0° or 360° |
| East | 90° | West | 90° |
| South | 180° | North | 180° |
| West | 270° | East | 270° |
In the horizontal coordinate system, also used in celestial navigation and satellite dish installation, azimuth is one of the two coordinates. The other is altitude, sometimes called elevation above the horizon. See also: Sat finder.
There are a wide variety of azimuthal map projections. They all have the property that directions (the azimuths) from a central point are preserved.
In three-dimensional polar coordinate systems, including cylindrical coordinates and spherical coordinates, the azimuth of a point is the angle between the positive x-axis and the projection of the vector from the origin to the point onto the xy-plane (the component of the vector in the xy-plane). In cylindrical coordinate, theta θ is almost universally used to represent the azimuth. Although there are several conventions in spherical coordinates, the azimuth is usually denoted by either theta θ or phi φ.
Azimuth is often — some consider incorrectly — referred to as a bearing. Nowadays in astronomy, azimuth is nearly always measured from the north. In former times, it was common to refer to azimuth from the south, as it was then zero at the same time the hour angle of a star was zero. This assumes, however, that the star (upper) culminates in the south, which is only true for most stars in the Northern Hemisphere.
In aviation, azimuth is used to determine headings or the direction in which to fly.
For magnetic tape drives, azimuth refers to the angle between the tape head(s) and the tape medium.
The word 'azimuth' is derived from the Arabic 'as-sumūt' which means 'the ways', referring to the ways or directions that you can face.
