Fractional cycle bias estimation and ambiguity resolution for Galileo triple-frequency uncombined PPP

Galileo already has 28 in-orbit satellites, with precise positioning capabilities on a global scale. All Galileo satellites are capable of broadcasting multi-frequency signals, and multi-frequency integration is expected to further improve the performance of precise point positioning (PPP) ambiguity-fixed solutions. In this paper, the fractional cycle bias (FCB) estimation method and ambiguity resolution (AR) method for Galileo triple-frequency uncombined (UC) PPP are developed, and the derived results are compared with those of dual-frequency UC PPP ambiguity-fixed and ambiguity-float solutions. The results indicate that the standard deviation (STD) of UC FCB series on a single frequency is better than 0.04 cycles using datasets from 155 globally distributed ground tracking stations. The convergence time of Galileo dual-frequency PPP float solutions in the east, north and up directions is 32.0 min, 10.0 min and 43.5 min, respectively, and the corresponding statistic of dual-frequency PPP fixed solutions is reduced to 30.5 min, 8.5 min and 32.0 min in the three directions, respectively. The convergence time of triple-frequency PPP fixed solutions is further shortened to 16.5 min, 8.0 min and 32.0 min in the three directions, respectively.