Azimuth

Azimuth, the horizontal direction of an object, measured clockwise in degrees, minutes, and seconds of arc from true north or south along the theoretical horizon. (The theoretical horizon is the horizon as it would appear if the earth were perfectly smooth, with no surface features.)

In astronomy, azimuth is used together with altitude, which is measured up from the theoretical horizon, to define the position of a celestial object. Azimuth is also used in navigation, in surveying, and in directing artillery fire.