Abstract
The Galileo constellations are characterized by transmitting GNSS signals on multi-frequencies, which can benefit the robustness and accuracy of the solutions. However, the dual-frequency E1/E5a combinations are generally used for precise point positioning (PPP). In this paper, the performance of Galileo static and kinematic PPP using different dual- and multi-frequency combinations are assessed using observations from the European region. Overall, the accuracy of daily PPP achieved by the dual-frequency GPS, Galileo, and BDS is better than 5 mm in the horizontal direction and better than 10 mm in the vertical direction. Though the number of observed Galileo satellites is less than GPS, the horizontal accuracy can reach 1.6 mm/2.3 mm/5.7 mm on North/East/Up component, which is improved by 59.0% and 12.3% compared to the GPS in the north and up direction. Then, the accuracy of Galileo static PPP is analyzed using different dual- and multi-frequency combinations. Results indicate that the Galileo E1/E5b PPP can degrade the accuracy due to the inter-frequency clock biases between the E1/E5a and E1/E5b combinations. Best accuracy can be achieved for the triple- and four-frequency PPP, which is 4.8 mm in the up direction. The hourly accuracy for the static PPP can reach 5.6 mm/9.2 mm/12.6 mm in the north/east/up direction using the GPS/Galileo/GLONASS/BDS combinations. Finally, a positioning convergence ratio (PCR) indicator, which represents the accuracy of PPP over a period, is used to analyze the convergence time of kinematic PPP. Results indicated that the multi-frequency Galileo observations contribute minorly to the convergence of kinematic PPP. However, Galileo shows the best convergence performance for the single GNSS positioning, and the GPS/Galileo combined PPP achieved the best performance for the PPP using different GNSS combinations.
Highlights
Precise point positioning (PPP) can achieve high positioning accuracy on regions such as mountains, deserts, or oceans without the support of external reference stations [1]
The analysis focused on the convergence time precise point positioning (PPP), which is critical for the kinematic PPP solutions
We focus on analyzing the performance of dual-frequency to five-frequency Galileo PPP and the factors affecting precision improvement
Summary
Precise point positioning (PPP) can achieve high positioning accuracy on regions such as mountains, deserts, or oceans without the support of external reference stations [1]. The BDS-3 and Galileo constellations provide observation frequency on more than three frequencies, which bring opportunities to improve the performance of PPP. The use of the triple-frequency BDS and Galileo observations can achieve comparable results as the dual-frequency PPP model and is not affected by the time-dependent phase hardware delays [13]. If proper spatial and temporal ionospheric constraints are available, the triple-frequency PPP with the raw observation model can achieve better performance than the traditional dual-frequency ionospheric-free PPP [15]. An optimal linear combination model is proposed by [16] using triple-frequency observations to improve the ambiguity resolution performance and timeto-first fix of PPP. A unified modeling strategy for triple-frequency PPP AR was proposed by [17] and indicated that that the contribution of the third frequency observations can improve the float PPP solutions and the reliability of PPP AR.
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