
Accession Number : AD0621677
Title : VLF MULTIRANGE NAVIGATIONFIX ERROR CONTOURS.
Descriptive Note : Final rept.,
Corporate Author : NATIONAL AVIATION FACILITIES EXPERIMENTAL CENTER ATLANTIC CITY NJ RESEARCH DI V
Personal Author(s) : Braff, Ronald ; Braverman, Nathaniel
Report Date : MAY 1965
Pagination or Media Count : 64
Abstract : A study was made of the accuracy and coverage of longdistance navigation systems which employ verylowfrequencies (in the range from ten to fourteen kilocycles per second) and which are based upon the determination of the distances from the vehicle to two or three groundbased stations. The fix error (actually precision), for such systems, may be expressed statistically in terms of the precise bivariate equiprobability error density ellipse or by the simpler, but conservatively approximate, drms circle. This error 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. Estimates, applicable when computing constanterror contours (isograms), are given. Error isograms are available for the twostation case but are based on a flat earth approximation. Proposed VLF systems would employ long baselines where the flat earth approximation is shown to cause appreciable discrepancies. The equations for the constanterror 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. 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 threestation coverage characteristics are discussed. (Author)
Descriptors : *NAVIGATIONAL AIDS, VERY LOW FREQUENCY, LORAN, POSITION FINDING, RADIO NAVIGATION, ERRORS, STATISTICAL ANALYSIS, NAVIGATION.
Subject Categories : Aerodynamics
Distribution Statement : APPROVED FOR PUBLIC RELEASE