Compass: Difference between revisions

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Compasses used in or near trucks, cars or other mechanized vehicles are particularly difficult to use accurately, even when corrected for deviation by the use of built-in magnets or other devices. Large amounts of ferrous metal combined with the on-and-off electrical fields caused by the vehicle's ignition and charging systems generally result in significant compass errors.
Compasses used in or near trucks, cars or other mechanized vehicles are particularly difficult to use accurately, even when corrected for deviation by the use of built-in magnets or other devices. Large amounts of ferrous metal combined with the on-and-off electrical fields caused by the vehicle's ignition and charging systems generally result in significant compass errors.


At sea, a ship's compass must also be corrected for errors, called [[Magnetic deviation|deviation]], caused by [[iron]] and [[steel]] in its structure and equipment. The ship is ''swung'', that is rotated about a fixed point while its heading is noted by alignment with fixed points on the shore. A compass deviation card is prepared so that the navigator can convert between compass and magnetic headings. The compass can be corrected in three ways. First the [[lubber line]] can be adjusted so that it is aligned with the direction in which the ship travels, then the effects of permanent magnets can be corrected for by small magnets fitted within the case of the compass. The effect of [[ferromagnetism|ferromagnetic]] materials in the compass's environment can be corrected by two iron balls mounted on either side of the compass binacle. The coefficient <math>a_0</math> representing the error in the lubber line, while <math>a_1,b_1</math> the ferromagnetic effects and <math>a_2,b_2</math> the non-ferromagnetic component.
At sea, a ship's compass must also be corrected for errors, called [[Magnetic deviation|deviation]], caused by [[iron]] and steel in its structure and equipment. The ship is ''swung'', that is rotated about a fixed point while its heading is noted by alignment with fixed points on the shore. A compass deviation card is prepared so that the navigator can convert between compass and magnetic headings. The compass can be corrected in three ways. First the [[lubber line]] can be adjusted so that it is aligned with the direction in which the ship travels, then the effects of permanent magnets can be corrected for by small magnets fitted within the case of the compass. The effect of [[ferromagnetism|ferromagnetic]] materials in the compass's environment can be corrected by two iron balls mounted on either side of the compass binacle. The coefficient <math>a_0</math> representing the error in the lubber line, while <math>a_1,b_1</math> the ferromagnetic effects and <math>a_2,b_2</math> the non-ferromagnetic component.


Fluxgate compasses can be calibrated automatically, and can also be programmed with the correct local compass variation so as to indicate the true heading.
Fluxgate compasses can be calibrated automatically, and can also be programmed with the correct local compass variation so as to indicate the true heading.
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