reduction to the meridian

reduction to the meridian

[ri′dək·shən tüthə mə′rid·ē·ən]
(navigation)
The process of applying a correction to an altitude observed when a body is near the celestial meridian of the observer, for the purpose of finding the altitude at meridian transit.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.