# magnetic deviation

(redirected from Magnetic-deviation)

## magnetic deviation

[mag′ned·ik ‚dē·vē′ā·shən]
The angle between the magnetic meridian and the axis of a compass card, expressed in degrees east or west to indicate in which direction the end of the compass card is offset from magnetic north.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Deviation, Magnetic

the deviation of the movable system of a compass from the position fixing the direction toward the earth’s magnetic pole (in the case of a magnetic compass) or to the geographical pole (in the case of a gyrocompass). The deviation of a ship’s magnetic compass is due to the action of local magnetized bodies (for example, the steel hull of a boat) and the electromagnetic fields of ships’ electrical and radio equipment. Deviation is eliminated by means of auxiliary magnets that create a system of compensating magnetic fields. Corrections for residual deviation are made using tables. A gyrocompass is free from magnetic deviation, but its readings are affected by changes in course, speed, and geographical latitude of the position (velocity deviation); motion with acceleration (ballistic deviation); and rolling, particularly with northeast and northwest courses (quadrantal deviation). Deviation of a gyrocompass is limited or compensated for by correctors.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

## magnetic deviation

The angular difference between the magnetic heading and the compass heading, expressed in degrees east or west to indicate in which direction the end of the compass heading is offset from the magnetic heading. It is one of the errors in a magnetic compass caused by local magnetic fields in the aircraft especially by the “iron” of the aircraft. The error is not constant and depends on the “magnetic environment” and heading of the aircraft. This error is corrected by use of small compensating magnets, and any residual deviation is calculated during a compass swing and indicated on a compass deviation card.