The four intersections of the horizon with the meridian and the prime vertical circle (or simply the prime vertical). The intersection with the meridian is designated north and south, and the intersection with the prime vertical is designated east and west. The cardinal points are 90° apart; they lie in a plane with each other and correspond to the cardinal regions of the heavens. The four basic directions—north, south, east, and west—are collectively known as cardinal points. The four intermediate points—northeast, southeast, northwest, and southwest—are called collateral, quadrantal, or intercardinal points.
The directions northeast (045°), southeast (135°), northwest (225°), and southwest (315°). Also called intercardinal points.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved