Azimuth

AZIMUTH (from the Arabic word "as-sunut", which is the plurAzimuthal of the word "as-samt", which means "way, direction"; EN: azimuth; DE: Azimut, Marschrichtungszahl; FR: azimut; ES: azimut; RU: азимут) is the dihedral angle between the plane of the meridian of the point of the observation and the vertical plane, which is passing in the given direction, which is measured clockwise from the direction to the north (from 0 to 360 degrees).

They distinguish the astronomical (true) azimuth, which is formed by the plane of the astronomical meridian, and passing through the plumb line in the point of the observations; the geodesic azimuth, which is formed by the plane, which passes through the normal to the ellipsoid; the magnetic azimuth, which is formed by the plane of the magnetic meridian. The difference in the values of the first two is non-significant (several seconds) due to the difference of the directions of the plumb line and the normal to the ellipsoid, which are drawn in one point. The magnetic azimuth differs from the true one by the value of the declination of the magnetic needle (Figure).