magnetic declination


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magnetic declination

[mag′ned·ik ‚dek·lə′nā·shən]
(astronomy)

Declination, Magnetic

 

(D), the angle between the magnetic and the true (geographic) meridians at a given point on the earth’s surface. The direction of the true meridian is usually determined with a gyroscopic theodolite or by astronomical observations. The direction of the magnetic meridian is found with the aid of instruments, such as magnetic declinometers and magnetometers, that make it possible to determine the position of a magnetic needle at the measurement site. If the north end of the magnetic needle is deflected to the east of the direction of the true meridian, the magnetic declination is called east, or positive; if it is deflected to the west, the magnetic declination is called west, or negative.

Magnetic declination is widely used in navigation, in geodetic and mine surveying, and in military work. Lines on a map connecting points with equal values of magnetic declination are called isoclinic lines. Since magnetic declination does not remain constant over long periods of time but undergoes slow changes, maps of magnetic declination are periodically revised based on measurements repeated every five to six years.

IU. A. BURTSEV

magnetic declination

At a particular location, the horizontal angle between true meridian (true north-south line) and magnetic meridian (direction of compass needle).

magnetic declination

magnetic declinationclick for a larger image
The angle between the magnetic and geographical meridians at any place, expressed in degrees east or west to indicate the direction of magnetic north from true north. Also called a magnetic variation.
References in periodicals archive ?
Some plasma parameters are the density [N.sub.e0] = 7.94 x [10.sup.17] [m.sup.-3], the magnetic declination angle [[theta].sub.B] = 45[degrees] and the collision frequency [v.sub.en] = 1 GHz.
Propagation and Polarization Characteristics Affected by Magnetic Declination Angle
Figure 8(a) shows that whatever the magnetic declination angle is, there is a turning point around the cyclotron frequency at which [P.sub.r_co] comes to extreme small value.
It can be seen from 8(e) that the relationship between normalized absorbed power [P.sub.a] and incidence frequency also possesses a similar variation trend to that shown in Sections 3.3-3.6 in spite of arbitrary magnetic declination angle.
An analytical technique named propagator matrix method (PMM) is presented to study the propagation and polarization characteristics of EM waves through nonuniform magnetized plasma slab with arbitrary magnetic declination angle.
When the magnetic declination angle is set as 90[degrees], the phenomenon of the transformation of EM wave polarization vanishes in the case of normal wave incidence on the plasma slab.
The great-circle route between the VORs is found and then the VOR station's magnetic declination is added (or subtracted).
Even as the earth's magnetic poles shift, VOR magnetic declination values don't change until they are significantly off--up to four degrees off, in fact.