Precise GPS Surveying After Y-Code

Javad Ashjaee and Robert Lorenz

Abstract:	Although it’s not a foregone conclusion, man Dierendonck, 19911, it is accepted that data from both the Ll and L2 frequencies is necessary for efficient high accuracy GPS survey. It may come as a piercing insight into the obvious that the way to increase survey efficiency and accuracy begins with the three basic premises: 1) Use all available observables. 2) Measure them accurately. 3) Use optimal signal processing techniques which offer the best SNR (Signal-to-Noise Ratio), jam immunity and multipath rejection. When the P-code is available, the above suggests we correlate with the P-code on Ll and L2, and use this range and phase data in conjunction with that derived from the CIA code processing. Without exception, no codeless technique recovers GPS signal information as well as one which makes use of the modulating code. When AS (Anti-Spoofing) is activated, the P-code on the Ll and L2 carriers is replaced with Y-code. This precludes the use of traditional P-code correlation techniques. The Y-code is the modulo two sum of the P-code and the encryption code W. This paper compares four fundamental approaches to recovering L2 carrier and code phases in the presence of AS: 1) Squaring 2) Cross-correlation 3) Code-correlation followed by squaring 4) Tracking the underlying P-code and W-code in the Y-code
Published in:	Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992) September 16 - 18, 1992 Albuquerque, NM
Pages:	657 - 659
Cite this article:	Ashjaee, Javad, Lorenz, Robert, "Precise GPS Surveying After Y-Code," Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992), Albuquerque, NM, September 1992, pp. 657-659.
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