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In surveying, bearings can be referenced to true north, magnetic north, grid north (the Y axis of a map projection), or a previous map, which is often a historical magnetic north. [citation needed] If navigating by gyrocompass, the reference direction is true north, in which case the terms true bearing and geodetic bearing are used.
18th-century azimuthal compass held in the National Archaeological Museum of Spain. 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.
The declination in the example is 14°E (+14°). If, instead, the declination was 14°W (−14°), you would still “add” it to the magnetic bearing to obtain the true bearing: 40°+ (−14°) = 26°. Conversely, local declination is subtracted from a true bearing to obtain a magnetic bearing. With a local declination of 14°E, a true ...
Back staff, the best known of which is the Davis' quadrant. It could measure the altitude of the Sun without having the navigator directly observe the Sun. Cross staff, an older instrument long out of use. Kamal Very simple instrument used primarily by Arabian navigators. It consists of a small board with a knotted piece of twine through the ...
The XII position is true north. A clock position, or clock bearing, is the direction of an object observed from a vehicle, typically a vessel or an aircraft, relative to the orientation of the vehicle to the observer. The vehicle must be considered to have a front, a back, a left side and a right side.
The correct quadrants for φ and θ are implied by the correctness of the planar rectangular to polar conversions. These formulae assume that the two systems have the same origin, that the spherical reference plane is the Cartesian xy plane, that θ is inclination from the z direction, and that the azimuth angles are measured from the Cartesian ...
The first two columns give the number of points and degrees clockwise from north. The third gives the equivalent bearing to the nearest degree from north or south towards east or west. The "CW" column gives the fractional-point bearings increasing in the clockwise direction and "CCW" counterclockwise. The final three columns show three common ...
The "bearing compass" was eventually sited in a fixed position in a binnacle with, as far as possible, an all round view and acquired the name "standard compass". It would nonetheless have a different deviation from the "steering compass", so the compass heading shown on the "steering compass" would be different from the compass heading shown ...