ALTITUDE AND AZIMUTH

in astronomy, gunnery, navigation, and other fields, two coordinates describing the position of an object above the Earth. Altitude in this sense is expressed as angular elevation (up to 90) above the horizon. Azimuth, in astronomical measurement, is the number of degrees clockwise from due south (usually) to the object's vertical circle (i.e., a great circle through the object and the zenith). For nonastronomical purposes, azimuth (or bearing) is generally measured clockwise from due north.