magnetic deviation

magnetic deviation (countable and uncountable, plural magnetic deviations)

1. Used other than figuratively or idiomatically: see magnetic,‎ deviation.
   • 1904, Ernest Rutherford, Radio-activity, Dover, published 2004, page 117:

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

2. Magnetic declination.
   • 1998, John R. Ellis, Objectifying Real-Time Systems, page 483:

     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.

• (magnetic declination): magnetic declination, magnetic variation