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Magnetic declination. Angle on the horizontal plane between magnetic north and true north. Example of magnetic declination showing a compass needle with a "positive" (or "easterly") variation from geographic north. N g is geographic or true north, N m is magnetic north, and δ is magnetic declination. Magnetic declination (also called magnetic ...
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]
World Magnetic Model. Magnetic declination map at sea-level for the year 2010 derived from WMM2010. The World Magnetic Model (WMM) is a large spatial-scale representation of the Earth's magnetic field. It was developed jointly by the US National Geophysical Data Center and the British Geological Survey. The data and updates are issued by the US ...
Maps typically include information on the declination as an angle or a small diagram showing the relationship between magnetic north and true north. Information on declination for a region can be represented by a chart with isogonic lines (contour lines with each line representing a fixed declination).
Magnetic dip, dip angle, or magnetic inclination is the angle made with the horizontal by Earth's magnetic field lines. This angle varies at different points on Earth's surface. Positive values of inclination indicate that the magnetic field of Earth is pointing downward, into Earth, at the point of measurement, and negative values indicate ...
An azimuth compass (or azimuthal compass) is a nautical instrument used to measure the magnetic azimuth, the angle of the arc on the horizon between the direction of the Sun or some other celestial object and the magnetic north. This can be compared to the true azimuth obtained by astronomical observation to determine the magnetic declination ...
The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. The locations of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation. The effect of this means a map with the latest declination information should be used. [9]
South magnetic pole. Coordinates: 64.081°S 135.866°E. Observed south dip poles during 1903–2000 are yellow squares. IGRF-12 Modeled pole locations from 1590 to 2020 are circles progressing from blue to yellow. [1] The south magnetic pole, also known as the magnetic south pole, is the point on Earth's Southern Hemisphere where the ...