geographic vertical[¦jē·ə¦graf·ik ′vərd·ə·kəl]
A line perpendicular to the surface of the geoid; it is the direction in which the force of gravity acts.
The direction of a line normal to the surface of the geoid. Also known as map vertical.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.