Magnetic north biography
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Magnetic declination
Angle on the horizontal plane between magnetic north and true north
Magnetic declination (also called magnetic variation) is the angle between magnetic north and true north at a particular location on the Earth's surface.
Magnetic north biography
The angle can change over time due to polar wandering.
Magnetic north is the direction that the north end of a magnetized compass needle points, which corresponds to the direction of the Earth's magnetic field lines. True north is the direction along a meridian towards the geographic North Pole.
Somewhat more formally, Bowditch defines variation as "the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north.
The angle between magnetic and grid meridians is called grid magnetic angle, grid variation, or grivation."[1]
By convention, declination is positive when magnetic north is east of true north, and neg