Accession Number : ADA119309

Title :   Fixed Site Comparison of P and C/A Code Ranging Performance Using GPS X-Sets.

Descriptive Note : Final rept. Jul-Dec 81,

Corporate Author : JOHNS HOPKINS UNIV LAUREL MD APPLIED PHYSICS LAB

Personal Author(s) : Bailey,Gregory D

PDF Url : ADA119309

Report Date : Apr 1982

Pagination or Media Count : 63

Abstract : The NAVSTAF Global Positioning System (GPS) is a satellite-based navigation system under development by the Department of Defense. Satellites transmit a precise (P) code and a clear/acquisition (C/A) code which are used to calculate satellite to user range. Ranges from three or more satellites are then used to determine the user's position. The Johns Hopkins University Applied Physics Laboratory (APL) has two identical receivers, each of which is capable of tracking either code. The purpose of the study was to examine the characteristics of the C/A code as it might be used by a marine user with a low-cost GPS receiver. The study found that the single-frequency P and C/A code range residuals and navigation errors show the same basic characteristics, except for expected higher noise levels in the C/A code, and possible multi-path interference in the C/A code of one satellite as it set. The dual-frequency P code phase delay measurements provided ionospheric corrections that appeared reasonable in character and value. The ionospheric contribution to position error was found to be largest when two or four satellites were at low elevation. At other times the ionospheric effect on position error appeared negligible.

Descriptors :   *Global positioning system, *Navigation satellites, *Multipath transmission, *Interference, Coding, Receivers, Position(Location), Range finding, Errors, Ionosphere, Low elevation, User needs, Coast Guard equipment, Performance(Engineering)

Subject Categories : Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE