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With a local declination of 14°E, a true bearing (i.e. obtained from a map) of 54° is converted to a magnetic bearing (for use in the field) by subtracting declination: 54° – 14° = 40°. If the local declination was 14°W (−14°), it is again subtracted from the true bearing to obtain a magnetic bearing: 54°- (−14°) = 68°.
Changes in Earth's magnetic field on a time scale of a year or more are referred to as secular variation. Over hundreds of years, magnetic declination is observed to vary over tens of degrees. [13] The animation shows how global declinations have changed over the last few centuries. [34] The direction and intensity of the dipole change over time.
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 .
This image shows magnetic declination, or the angle between magnetic and geographic north, according to the World Magnetic Model released in 2025. Red is magnetic north to the east of geographic ...
File:Magnetic grid declination diagram.svg. Add languages. ... English: Magnetic declination diagram as used in USGS maps, including grid north. Based on actual USGS ...
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. [29]
In mid-December of 2024, scientists officially updated the World Magnetic Model (WMM), which helps keep track of our planet’s magnetic north and its chaotic and relatively unpredictable movements.
English: This is a world map of magnetic declination created by the National Geophysical Data Center at NOAA. Français : Carte mondiale de la déclinaison magnétique terrestre créé par le centre national des donnée géophysiques ( NGDC ) de l'agence américaine responsable de l'étude de l'océan et de l'atmosphère ( NOAA ).