CE 134 Lecture Notes - Lecture 8: Compass, True North, Declination
27 Apr 2016
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Document Summary
True north is a fixed point in space that does not vary with time. The earth"s magnetic field has north and south poles that are very close to the true directions of. Annual variation: the yearly rate of variation of the magnetic north. Magnetic declination: the angle between the true north and the magnetic north at a given time for a given location (can be east or west) Isogonic charts map the magnetic declination and annual variation of declination. Sometimes, local variations of the magnetic field occur and the magnetic north observed, or declination, will not correspond to the charts: due to high concentration of certain minerals in certain regions that bend the magnetic field locally. The magnetic compass is the instrument that is used to identify the magnetic north. Metallic objects and direct-current electricity cause a local attraction that affect the main magnetic field.
