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The magnetic declination in a given area may (most likely will) change slowly over time, possibly as little as 2–2.5 degrees every hundred years or so, depending on where it is measured. For a location close to the pole like Ivujivik, the declination may change by 1 degree every three
Magnetic compass adjustment and correction is one of the subjects in the examination curriculum for a shipmaster's certificate of competency. The sources of magnetic deviation vary from compass to compass or vehicle to vehicle. However, they are independent of location, and thus the compass can be calibrated to accommodate them.
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. 7 - Compass heading or compass course, before correction for magnetic deviation or magnetic variation.
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.
It should be very close to the magnetic bearing. The difference between a magnetic bearing and a compass bearing is the deviation caused to the compass by ferrous metals and local magnetic fields generated by any variety of vehicle or shipboard sources (steel vehicle bodies/frames or vessel hulls, ignition systems, etc.) [4]
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.
As of early 2019, the magnetic north pole is moving from Canada towards Siberia at a rate of approximately 55 km (34 mi) per year. [19] NOAA gives the 2024 location of the magnetic north pole as 86 degrees North, 142 degrees East. By 2025, it will have drifted to 138 degrees East (same latitude). [20]
The Enhanced Magnetic Model (EMM) is a sister product of the NGDC featuring a much higher amount of data to degree and order 790, giving a wavelength of 51 km as opposed to the 3000 km of WMM. At this resolution, it is not only able to model the Earth's magnetic field at the core-mantle boundary ("main field"), but also take into account ...