VLF Multirange Navigation Errors

The fix error, for long-distance XIF navigation systems in which the distances to two or three ground-based stations are determined, is a function of the "angles of cut" of the lines of position, the standard deviation of the errors in determination of the distances (ranges) to the stations, and the degree of correlation of these distance determinations. An analysis is made of the errors which occur in a range determination. n. Estimates, applicable when comparing constant-error contours (isograms), are given. The equations for the constant-error contours are derived (based on a spherical earth) as a function of baseline length (and orientation where three stations are used) and the angles of cut of the lines of position. n. Various error isograms were computed and plotted through the use of a digital computer. A number of examples are presented. A method for determining the area covered acceptably by two stations is given and three-station coverage characteristics are discussed.