Error Models for Precision Landing with GBAS Using New GNSS Signals

S. Monrocq, J-P. Arethens

Abstract:	In the context of precision landing with GNSS for aircraft, GBAS is needed to be able to reach high level of performances, particularly if CAT II/III operations are considered. The goal of this study is to include the use of new GNSS signals to derive the new suitable ranging sources error models and to determine whether these new signals will enable intended operations without the use of other augmentation systems. The study derives error models for corrected ranging sources supposing pseudo-range correction yielded by a GBAS ground station. The error models in the context of CAT I operation with L1 C/A signals are known results, and this work extends these results for new GNSS signals and CAT II/III operations. The error models include new aspects that may be of great importance for reaching better performances in the high precision landing, like GALILEO and modernized GPS signals, and the new possibilities offered by the bifrequency signals. Also, the study focuses of the main sources of error for the ranging sources, which is the multipath effect from the ground. The methodology used here is based on a simulation tool that describes the multipath environment likely to be found on airport sites. The study analyses the influence of the multipath effect in the correlation process. A comparison of the performances between the new signals and the current GPS L1 C/A is carried out to highlight the influences of signal characteristics such as power, chipping rate and modulation; this for different correlation techniques such as the narrow correlator, or the double-delta correlator. Also with the bi-frequency signals, new techniques of carrier aided code loop can be investigated. After validating the different error models to obtain the total differentially-corrected pseudo-range error computed in the airborne unit, we can assess the feasibility of a CAT II/III landing with a bi-frequency, bi-constellation GBAS. 5th PCRD Growth Research Programme GIFT "GNSS Inertial Future Landing Techniques" and GALILEO Internal Studies supported by European Commission have sustained these studies.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	1775 - 1791
Cite this article:	Monrocq, S., Arethens, J-P., "Error Models for Precision Landing with GBAS Using New GNSS Signals," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 1775-1791.
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