magnetic variation

deviation in the direction of magnetic attraction

"Magnetic North" redirects here, for other uses see Magnetic North (disambiguation)The magnetic declination (also known as grid magnetic angle in military circles) at any point on the Earth is the angle between the local magnetic field -- the direction the north end of a compass points -- and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is equivalent, and is more often used in aeronautical and other forms of navigation. Isogonic lines are where the declination has the same value, and the lines where the declination is zero are called agonic lines.
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Noun
1. the angle (at a particular location) between magnetic north and true north
(synonym) magnetic declination, variation
(hypernym) angle

1. In navigation, at a given place and time, the horizontal angle between the true north and magnetic north measured east or west according to whether magnetic north lies east or west of true north. 2. In cartography, the annual change in direction of the horizontal component of the earth's magnetic field. See also declination; magnetic declination. 1/11/86

Angle horizontal, en un lieu et un temps donnés, entre la direction du nord géographique et celle du nord magnétique. La déclinaison magnétique est qualifiée est ou ouest selon que le nord magnétique se trouve à l'est ou à l'ouest du nord géographique. Voir aussi déclinaison astronomique; variation magnétique. 1/9/71

Variation annuelle en direction de la composante horizontale du champ magnétique terrestre. Voir aussi déclinaison astronomique; déclinaison magnétique. 1/11/86