Azimuth is an angular measurement used to describe the horizontal direction of an object relative to a chosen reference direction. In its most common form in navigation, astronomy, surveying, and engineering, azimuth is the angle measured clockwise along a horizontal plane from a reference direction, usually true north, to the direction of the object or line being measured. The angle is expressed in degrees, with a full circle divided into 360 degrees. A direction exactly north has an azimuth of 0°, east has an azimuth of 90°, south has an azimuth of 180°, and west has an azimuth of 270°.
In astronomy, azimuth is one of the two coordinates used in the horizontal coordinate system to locate objects in the sky. The other coordinate is altitude (or elevation), which describes the angle above the horizon. An object's azimuth describes where it appears along the horizon when viewed from an observer’s location on Earth. Because azimuth is based on the observer’s location and time, the azimuth of a celestial object changes continuously as Earth rotates.
In surveying and civil engineering, azimuth is used to define the orientation of lines, boundaries, roads, pipelines, and structures. A surveyor may specify the direction of a property boundary or alignment by its azimuth measured from a reference meridian. The reference direction may be true north, grid north, or magnetic north, depending on the surveying method and required accuracy. When magnetic north is used, corrections may be required because Earth’s magnetic field does not align exactly with geographic north and changes over time.
In geology, geophysics, and petroleum engineering, azimuth is used to describe the horizontal orientation of features such as fractures, boreholes, and directional wells. For a directional well, the azimuth of the wellbore describes the compass direction in which the well is being drilled. Azimuth is commonly measured together with inclination, which describes the angle at which the well deviates from vertical.
