The angular difference between the magnetic meridian and the geographic meridian at a particular location.

Related Terms

ADJUSTABLE DIFFERENTIAL

A means of changing the difference between the control cut-in and cut-out points.

ARMATURE DEMAGNETIZATION

The reduction in the effective magnetic lines of force, produced by the armature current.

AIR GAP

The space between magnetic poles, or between the rotating and stationary assemblies in a motor or generator.

GREENWICH HOUR ANGLE

Angular distance west of the Greenwich celestial meridian; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of the Greenwich celestial meridian and the hour circle of a point on the celestial sphere, measured westward from the Greenwich celestial meridian throug

HALF-POWER POINTS

Power ratios used to define the angular width of a radar beam. One convention defines beam width as the angular width between points at which the field strength is 71 percent of its maximum value. Expressed in terms of power ratio, this convention defines beam width as the angular width between half-power points. A second convention defines beam width as the angular width between points at which the field strength is 50 percent of its maximum value. Expressed in terms of power ratio, the latter convention defines beam width as the angular width between quarter- power points.

HALVING

The process of adjusting magnetic compass correctors so as to remove half of the deviation on the opposite cardinal or adjacent intercardinal headings to those on which adjustment was originally made when all deviation was removed. This is done to equalize the error on opposite headings.

HEELING MAGNET

A permanent magnet placed vertically in a tube under the center of a marine magnetic compass, to correct for heeling error.

HIGH WATER INEQUALITY

The difference between the heights of the two high waters during a tidal day

GRID MAGNETIC ANGLE

Angular difference in direction between grid north and magnetic north. It is measured east or west from grid north. Grid magnetic angle is sometimes called GRID VARIATION or GRIVATION.

GRID MAGNETIC ANGLE

Angular difference in direction between grid north and magnetic north. It is measured east or west from grid north. Grid magnetic angle is sometimes called GRID VARIATION or GRIVATION.

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