Magnetic Definitions for Land Surveyors

magnetic annual change—See annual change.

magnetic annual variation—See annual variation.

magnetic azimuth—See azimuth, magnetic; North, true.

magnetic bearing—See bearing; azimuth, magnetic; North, true.

magnetic chart—See chart, magnetic.

magnetic compass—See compass, magnetic.

magnetic daily variation—See magnetic diurnal variation.

magnetic declination—See declination (definition 2).

magnetic deviation—See deviation, magnetic.

magnetic dip—Angular distance between the horizontal and the direction of a line of force of the Earth’s magnetic field at any point. Also known as “dip” or “magnetic inclination.

magnetic dip circle—An instrument for measuring the magnetic dip by the use of a needle and a graduated vertical circle.

magnetic dip needle—1A dip circle or the needle thereof. 2 A needle arranged to disclose intense local anomaly of the magnetic dip; useful in the recovery of lost iron monuments.

magnetic dip or inclination—The angle which a freely suspended, symmetrically magnetized needle that is not influenced by transient artificial magnetic disturbance will make with the plane of the horizon.

magnetic disturbance—See magnetic storms.

magnetic diurnal variation—The transient change in the magnetic field of the Earth associated with the apparent daily motions of the sun and the moon. In most places the solar daily variation follows a fairly consistent Pattern although with appreciable and unpredictable changes in form and amplitude

magnetic equator—See equator, magnetic.

magnetic isoporic line—A line on the Earth’s surface traversing all the points at which the magnetic annual change uniformly has a certain value at a given time.

magnetic map—See chart, magnetic.

magnetic meridian—See meridian, magnetic.

magnetic north—See north, magnetic.

magnetic pole—See pole, magnetic.

magnetic secular change—The change from year to year. usually extending for many decades in the same direction, of magnetic declination, dip, or intensity.

magnetic storms—Disturbances in the Earth’s magnetic field associated with abnormal solar activity and capable of seriously affecting both radio and wire transmission.

magnetic variation—See variation.

Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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