A systematic investigation of optimal carrier-phase combinations for modernized triple-frequency GPS |
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Authors: | Marc Cocard Stéphanie Bourgon Omid Kamali Paul Collins |
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Institution: | (1) Center for Research in Geomatics, Laval University, Pavillon Louis-Jacques-Casault, Quebec City, QC, Canada, G1K 7P4;(2) Geodetic Survey Division, Natural Resources Canada, 615 Booth Street, Ottawa, ON, Canada, K1A 0E9 |
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Abstract: | The upcoming modernization of the GPS signals will allow for measurements on an additional third frequency L5 located at 1176.45 MHz.
To take advantage of carrier-phase measurements on this new signal, the strategies for integer ambiguity resolution, required
for centimeter-level accuracy, may need to be revised. The Least-squares Ambiguity Decorrelation Adjustment method remains
perhaps the most powerful tool for finding the best combinations based on a complete decorrelation of the variance–covariance
matrix related to the ambiguities. However, the computational load of that method plus the opportunity to comprehensively
study the interaction of multiple frequencies suggest a reconsideration of approaches using predefined combinations between
frequencies is not out of place. In this paper a systematic investigation is made of all possible triple-frequency geometry-free
carrier-phase combinations which retain the integer nature of the ambiguities. The concept of the lane-number is presented
to unambiguously describe the wavelength of a particular combination. The propagation of the observation noise and of the
ionospheric bias on these combinations is presented. These noise and ionospheric amplification factors are analysed with respect
to the resulting wavelength, in an effort to highlight optimal combinations characterized by a long wavelength, low noise
and limited ionospheric impact. |
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Keywords: | GPS L5 Third frequency Integer ambiguity Carrier-phase combinations Noise factor |
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