quadrantal deviation

quadrantal deviation

[kwä′drant·əl ‚dē·vē′ā·shən]
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Deviation which changes its sign (E or W) approximately each 90° change of heading; caused by induced magnetism in horizontal soft iron present near the compass.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.