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A compass rose, showing absolute bearings in degrees. In nautical navigation the absolute bearing is the clockwise angle between north and an object observed from the vessel. If the north used as reference is the true geographical north then the bearing is a true bearing whereas if the reference used is magnetic north then the bearing is a ...
A bearing compass, is a nautical instrument used to determine the bearing of observed objects. (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore). (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore).
It is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any celestial body, crosses the observer's assumed latitude. [1] In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle (Celestial Longitude ...
Loxodrom′ic Line is a curve which cuts every member of a system of lines of curvature of a given surface at the same angle. A ship sailing towards the same point of the compass describes such a line which cuts all the meridians at the same angle. In Mercator's Projection (q.v.) the Loxodromic lines are evidently straight. [3]
Traverse tables use three values for each of the crooked course segments – the Distance (Dist.), Difference of Latitude (D.Lat., movement along N–S axis) and the Departure (Dep., movement along E–W axis), the latter two calculated by the formulas: Difference of latitude = distance × cos θ Departure = distance × sin θ
If a navigator begins at P 1 = (φ 1,λ 1) and plans to travel the great circle to a point at point P 2 = (φ 2,λ 2) (see Fig. 1, φ is the latitude, positive northward, and λ is the longitude, positive eastward), the initial and final courses α 1 and α 2 are given by formulas for solving a spherical triangle
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.
Magnetic deviation is the angle from a given magnetic bearing to the related bearing mark of the compass. Deviation is positive if a compass bearing mark (e.g., compass north) is right of the related magnetic bearing (e.g., magnetic north) and vice versa.