Fixed Site Comparison of P and C/A Code Ranging Performance Using GPS X-Sets.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1982
- Accession Number
- ADA119309
Entities
People
- Gregory D. Bailey
Organizations
- Johns Hopkins University