Azimuthkulma

Azimuthkulma, commonly called azimuth, is the angular coordinate used in the horizontal coordinate system to specify the direction of a distant object projected onto the local horizontal plane. It is defined as the angle between a reference direction (usually true north) and the projection of the object on the horizon, measured along the horizon in a specified sense, typically clockwise.

The azimuth is commonly given in degrees from 0° to 360°. In the standard convention, 0° corresponds to north, 90° to east, 180° to south, and 270° to west. Some fields or regions use different reference directions or measure in the opposite sense, so it is important to note the convention when reporting azimuth values.

Azimuth is paired with altitude (or elevation) to locate an object in the sky or on the ground. Altitude is the angle above the horizon, while azimuth indicates the direction along the horizon. Together, azimuth and altitude define the position of celestial bodies, aircraft, satellites, or landmarks from a given observation point.

In practice, azimuth is time-dependent for celestial objects because of Earth's rotation. It depends on the observer's latitude, longitude, local time, and the object's celestial coordinates (such as declination and hour angle). Calculations involve spherical trigonometry and are used in astronomy, navigation, solar energy calculations, and surveying.

Notes: the term can also describe the bearing of a line relative to a reference meridian in surveying. Observed azimuths near the horizon can be affected by atmospheric refraction and obstacles, so reporting conventions should always specify the reference direction and measurement method.