Azimuth is a mathematical concept defined as the angle, usually measured in degrees (°), between a reference plane and a point. This concept is used in many practical applications including navigation, astronomy, mapping, mining and artillery. The word azimuth is derived from the Arabic السمت ('assumūt') which means the ways, referring to the ways or directions a person faces.
Navigation
In navigation, the reference plane is typically
true north and is considered 0° azimuth. Moving
clockwise, a point due east would have an azimuth of 90°, south 180°, and west 270°. Some navigation systems use south as the reference plane. However, any direction can serve as the plane of reference, as long as it is clearly defined for everyone using that system.
True northbased azimuths
From North

North
 0° or 360°  South
 180°

NorthNortheast
 22.5°  SouthSouthwest
 202.5°

Northeast
 45°  Southwest
 225°

EastNortheast
 67.5°  WestSouthwest
 247.5°

East
 90°  West
 270°

EastSoutheast
 112.5°  WestNorthwest
 292.5°

Southeast
 135°  Northwest
 315°

SouthSoutheast
 157.5°  NorthNorthwest
 337.5°

Mapping
There are a wide variety of
azimuthal map projections. They all have the property that directions (the azimuths) from a central point are preserved. Some navigation systems use south as the reference plane like in the Philippine practice. However, any direction can serve as the plane of reference, as long as it is clearly defined for everyone using that system.
Astronomy
Azimuth is often, some consider incorrectly, referred to as a
bearing. However, in modern
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.
Other uses
Azimuth is used to determine headings or the direction in which to fly. In
artillery, it is the direction of fire.
Azimuth is also terms used in mining for a similar, but slightly different angle: azimuths and meridian angles are used to name any angle measured clockwise from any meridian.
For tape and cassette tape decks, azimuth refers to the angle between the tape head(s) and tape. For magnetic tape drives, azimuth refers to the angle between the tape head(s)
In sound localization experiments and literature, the azimuth refers to the angle the sound source makes compared to the imaginary straight line that is drawn from within the head through the area between the eyes.
An azimuth thruster in shipbuilding is a propeller that can be rotated horizontally.
Other systems
Right Ascension
If instead of measuring from and along the horizon the angles are measured from and along the
celestial equator, the angles are called
right ascension if referenced to the Vernal Equinox, or hour angle if referenced to the Prime Meridian.
Horizontal coordinate
In the
horizontal coordinate system, 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.
Polar coordinate
In threedimensional
polar coordinate systems, including
cylindrical coordinates and
spherical coordinates, the azimuth of a point is the
angle between the positive xaxis and the projection of the
vector onto the xy
plane (the component of the vector in the xyplane). In cylindrical coordinates,
phi $phi$ is almost universally used to represent the azimuth in mathematical applications, whereas physical applications may denote the azimuth using the symbol
phi,
$phi$. Although there are several conventions in spherical coordinates, the azimuth is usually denoted by either theta,
$theta$ or phi,
$phi$. elec 4503
See also