observing angle
observing angle
[əb′zər·viŋ ‚aŋ·gəl] (ordnance)
Angle at the target between a line to the observer and a line to the gun or battery; the angular distance of an observer from the gun or battery.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.