A classified method of reporting position by wireless telegraphy used by the military. Each whole degree of latitude and longitude is allotted a pair of letters that are secretly changed from time to time. The position of a place is first referred to the nearest intersection of the meridian and the parallel of latitude for the whole number of degrees southwest of the place. This is the four-lettered group. Then, the change of latitude and longitude between the places and this intersection is expressed in minutes. The minute of change in latitude is given first followed by the change in longitude.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved