compass correction card
compass correction card
[′käm·pəs kə′rek·shən ‚kärd] (navigation)
A card posted in a holder near the magnetic compass, on which there is recorded the difference between the readings of the compass and the correct geomagnetic directions; these errors (deviations) are given for at least the four cardinal points; sometimes the card lists the compass bearings to be flown when it is desired to fly corresponding magnetic headings.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
compass correction card

Compass correction/deviation card.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved