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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°.
A magnetic bearing. A magnetic bearing is a type of bearing that supports a load using magnetic levitation. Magnetic bearings support moving parts without physical contact. For instance, they are able to levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear. Magnetic bearings support the highest ...
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]
By the 1940s, magnetic north had moved northwest from its 1831 position by about 250 miles (400 kilometers). In 1948, it reached Prince Wales Island, and by 2000 it had departed Canadian shores.
The resulting bearing indicated is the magnetic bearing to the target. Again, if one is using "true" or map bearings, and the compass does not have preset, pre-adjusted declination, one must additionally add or subtract magnetic declination to convert the magnetic bearing into a true bearing. The exact value of the magnetic declination is place ...
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. Over the last two centuries the dipole strength has been decreasing at a rate of about 6.3% per century ...
The magnetic azimuth is the arc between the point on the horizon below the heavenly body and the direction of magnetic north. [1] When the latitude and date are known, the bearing of the sun at sunrise or sunset relative to true north can be readily determined. [2]
Non-magnetic methods of taking bearings, such as with gyrocompass, astronomical observations, satellites (as GPS) or radio navigation, are not subject to magnetic deviation. Thus, a comparison of bearings taken with such methods with the bearing given by a compass can be used to compute local magnetic deviation.