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Analysis of the feasibility of using GPS carrier phase ambiguity resolution techniques for precision approaches

Abstract : The US Global Positioning System (GPS) provides an accurate positioning service anywhere in the world at any time, but its features are far from being sufficient for it to constitute the Global Navigation Satellite System (GNSS) expected by the civil aviation community. The horizontal accuracy is below 100 m 95% of the time, which is adequate for oceanic, enroute and non precision approaches phases of flight, although additional autonomous integrity monitoring is required to improve safety. The position estimate is computed by measuring the distance to all the visible satellites of the constellation, from the observations of pseudo random noise code modulations. When corrected using a ground reference station, the GPS code pseudorange measurements should provide an accuracy of a few meters. This is sufficient for low accuracy precision approaches (Category I), but guidance during the high accuracy precision approaches (Category II and III) requires the use of a sub-meter positioning system with a high integrity. Since the beginning of the years 1980s, the GPS carrier phase measurements have been used in geodetic applications to pinpoint the location of the survey sites with a centimeter accuracy, after res- olution of the intrinsic ambiguities of these measurements. Such techniques are attractive to the civil aviation community as they appear to have the accuracy required for its most demanding applications. However, as the ambiguity resolution process appears to be fragile especially in real-time kinematic applications, several questions remain unanswered about the reliability of these specific techniques, called AROF (Ambiguity Resolution On-the-Fly) procedures. The aim of this study is to contribute to the analysis of the feasibility of using GPS carrier phase measurements ambiguity resolution procedures during precision aircraft landings. The starting point of this analysis is the presentation of the requirements for a GNSS based precision landing system, and the determination of a model for the carrier phase measurements. Then, the data pre-processing oper- ations are reviewed, and the resulting quality of the data is assessed. Then, a classification of AROF procedures is proposed, and theoretical principles of several techniques, including the new MAPAS procedure developed during this study, are described. Next, the characteristics of AROF procedures are identified, enabling the determination of the requirements of AROF procedures. Afterwards, the difficulty of the determination of theoretical performance is discussed, and mathematical expressions of the performance parameters of MAPAS are presented. Next, the performance of AROF procedures is evaluated on a practical basis using simulated measurements, using measurements collected from a Nortel GPS signal generator, and using field measurements. Finally the characteristics are checked against the constraints, and a conclusion is drawn from this study.
Keywords : GPS GNSS
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Christophe Macabiau. Analysis of the feasibility of using GPS carrier phase ambiguity resolution techniques for precision approaches. Signal and Image processing. INPT, 1997. English. ⟨tel-02895882⟩

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