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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 ...
The local angular difference between magnetic north and true north is called the magnetic declination. Most map coordinate systems are based on true north, and magnetic declination is often shown on map legends so that the direction of true north can be determined from north as indicated by a compass. [28]
If the reference direction is north (either true north, magnetic north, or grid north), the bearing is termed an absolute bearing. In a contemporary land navigation context, true, magnetic, and grid bearings are always measured in this way, with true north, magnetic north, or grid north being 0° in a 360-degree system. [5]
True south is the direction opposite to the true north. It is important to make the distinction from magnetic north, which points towards an ever changing location close to the True North Pole determined Earth's magnetic field. Due to fundamental limitations in map projection, true north also differs from the grid north which is marked by the ...
Compass needles in the Northern Hemisphere point toward the magnetic North Pole, although the exact location of it changes from time to time as the contours of Earth’s magnetic field also change.
1 - True North 2 - Heading, the direction the vessel is "pointing towards" 3 - Magnetic north, which differs from true north by the magnetic variation. 4 - Compass north, including a two-part error; the magnetic variation (6) and the ship's own magnetic field (5) 5 - Magnetic deviation, caused by vessel's magnetic field.
The magnetic pole moved along the northern Canadian shore for centuries, Dr Brown said. It drifted into the Arctic Ocean in the 1990s, and after that, it accelerated and headed towards Siberia.
3 – Magnetic north, which differs from true north by the magnetic variation. 4 – Compass north, including a two-part error; the magnetic variation (6) and the ship's own magnetic field (5) 5 – Magnetic deviation, caused by vessel's magnetic field. 6 – Magnetic variation, caused by variations in Earth's magnetic field.