magnetic deviation

plural magnetic deviations

1. countableuncountableUsed other than figuratively or idiomatically: see magnetic, deviation.

   Preliminary experiments with radium of activity 1000 showed that it was very difficult to determine the magnetic deviation of the α rays.

   1904, Ernest Rutherford, Radio-activity, Dover, published 2004, page 117

2. countableuncountableThe difference in angle between magnetic north and the north shown by a compass at any given location and time, caused by interference from local magnetic fields.
3. countableuncountableMagnetic declination.

   This angular difference is the local magnetic deviation (Figure C.2). Navigation systems normally work relative to True North and therefore must remove the local magnetic deviation.

   1998, John R. Ellis, Objectifying Real-Time Systems, page 483