A-scope in which the time base is circular. The display appears as a circle with the transmitted pulse at the top. The scanning proceeds clock-wise at a rapid rate. Echoes appear as radial pips. The greater the distance or range to the target, the farther clock-wise the pip appears. This type of display is commonly used in radar altimeters. In this case, the target is the ground and the scope indicating the range of the target (i.e., the height of the aircraft above the ground or the obstruction). Also called a J-scan, J-scope, or J-indicator. See also A-scope.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved