azimuths

Azimuths are a type of directional angle used to specify the direction of a point on the horizontal plane relative to a reference direction. Typically defined as the angle measured clockwise from north, an azimuth ranges from 0° to 360°. In the common convention, 0° corresponds to true north, 90° to east, 180° to south, and 270° to west.

Azimuths are used across several fields, including navigation, surveying, astronomy, and geographic information systems. In navigation and surveying, an azimuth indicates the direction from a location to a target or line, and it can be combined with distance to plot position. In astronomy, azimuth accompanies altitude to specify the position of celestial objects in the local sky, with the object’s projection on the horizon determining its azimuth.

Measurement and variants: An azimuth can be expressed as a true azimuth, measured relative to geographic (true) north, or as a magnetic azimuth, measured relative to magnetic north. Magnetic north shifts over time and location, so magnetic azimuths may require correction to obtain true azimuths for precise work. Instruments such as compasses, theodolites, or satellite-based devices are used to measure azimuths, often converting between azimuth and other coordinate forms.

Relation to bearing and notation: In practice, azimuth is closely related to bearing, which may be given as a quadrant notation (for example, N50°E) or as an azimuth in degrees. While azimuth uses a single 0–360° measure, quadrant bearings describe direction with reference to the cardinal directions. Azimuths are a fundamental component of the horizontal coordinate system, and when combined with altitude (or elevation), they form the common azimuth–elevation coordinate pair used to locate objects in the sky or on the ground.