Performance of BDS-2/3, GPS, and Galileo Time Transfer with Real-Time Single-Frequency Precise Point Positioning

Single-frequency receivers are low cost and portable, thus being widely applied in engineering; the extended Kalman filter (EKF) is commonly used to perform single-frequency precise point positioning (SF-PPP). However, the positioning performance of SF-PPP is seriously influenced by various errors. Due to the large process noise and initial variance of the estimated parameters, the weight matrix of state parameters will be ill-conditioned, and since the noise of the pseudo-range is much higher than that of the carrier phase, the weight matrix of observations presents as ill-conditioned. Additionally, the condition number of the normal matrix will jump on the conditions of cycle slip, new emerging satellites, and signal outages. To reduce the condition number of the normal matrix, the regularized Kalman filter (RKF) algorithm is proposed, with additional support for the maximum variance matrix and singular value decomposition, thereby improving the accuracy and stability of SF-PPP. Through static and dynamic experiments, it is found that the proposed method can reduce both the ill-conditioning of the weight matrices of the observations and the state parameters. The condition number of the normal matrix is < 500 per epoch, and the convergence time is shortened by > 40%. Compared with the SF-PPP using EKF, centimeter-level static positioning accuracies of 1.13, 0.73, and 2.92 cm and decimeter-level kinematic positioning accuracies of 12.5, 10.8, and 27.3 cm in the east, north, and vertical components, respectively, using RKF; this yielded 38.3, 29.8, and 45.2% and 39.6, 41.9, and 21.3% improvement in the static and kinematic scenarios, respectively.

Section: Introductionmentioning

confidence: 99%

A reduced-condition-number algorithm for single-frequency precise point positioning based on regularized Kalman filter

Li,

Yang,

Jia

2024

“…Benefited from real-time products from IGS ACs, scholars have carried out extensive research on RTPPP time transfer. Research shows that based on GPS/BDS-3, the accuracy of RTPPP time transfer can reach sub-nanosecond level [11,13,14]. Compared with IGS final precise products, using real-time products from CNES, the accuracy of RTPPP time transfer of multi-GNSS (GPS + GLONASS + Galileo) can reach within 0.1 ns, and the performance by multi-GNSS can be improved above 10.7%, 37.6% and 19.4%, compared with GPS, GLONASS and Galileo, respectively [15].…”

Section: Introductionmentioning

confidence: 99%

Impacts of satellite clock errors on GPS/BDS/Galileo real-time PPP time transfer

Zheng,

Wang,

Zhang

et al. 2024

By utilizing the real-time precise orbit and clock products provided by International GNSS Service (IGS), it is feasible to calculate real-time PPP (RTPPP) time and frequency transfer. The quality of these real-time precise products has a significant effect on the performance of clock comparisons and time transfer. This paper focuses on real-time clock comparisons with IGS real-time multi-GNSS precise products, which tries to explore the potential of GNSS RTPPP time transfer in time and frequency community. By using real-time precise satellite orbit and clock products from two IGS analysis centers, i.e., CNES and WHU, the clock comparisons and time transfer performance of four time links are comprehensively investigated. It is shown that the statistical uncertainty of real-time clock comparison based on Multi-GNSS is within 0.15 ns, and GPS RTPPP provides time transfer results with better performance than BDS-3 and Galileo. In addition, the deviations occur in remote time links results of BDS-3 and Galileo-only between using CNES and WHU, the maximum difference can reach up to 1.10 ns. It is shown that real-time BDS-3 and Galileo satellite products of CNES and WHU are inconsistent, and will affect the time transfer performance. The paper also investigates the receiver clock offset solutions determined by using different available satellites. The results show that there are significant satellite-related biases between different satellites, especially for BDS-3 and Galileo. Thus, the reference time scales determined by using different satellites are inconsistent, and further, the time transfer for long baseline time links will be affected as there are few common view satellites for remote stations.

“…The study revealed that the peak-to-peak value of time transfer error is less than 1 nanosecond, and the frequency stability of time transfer reaching 1 × 10 −16 [6]. Xiao et al studied the feasibility of single-frequency PPP time transfer method and concluded that it can meet sub-nanoseconds time transfer accuracy requirements [7]. Zhang et al confirmed that the Beidou PPP time transfer accuracy can reach nanoseconds or sub-nanoseconds precision, with the daily stability at the 1 × 10 −15 order of magnitude [8].…”

Section: Introductionmentioning

confidence: 99%

Study of high-precision time transfer method enhanced by PPP-AR/PPP-RTK

Liu,

Tu,

Chen

et al. 2024

Self Cite

With the ongoing advancements in the Global Navigation Satellite System (GNSS), the technology for high-precision time transfer facilitated by GNSS has also become increasingly refined. This paper aims to investigate the contribution of information-enhanced GNSS PPP to time transfer performance, with a focus on the comprehensive evaluation and analysis of the time transfer performance of PPP-AR and PPP-RTK. Using GPS as a case study, experimental results indicate that the average success fixing rate of PPP integer ambiguity resolution across five stations is 94%. Using the standard deviation for stability assessment, the analysis reveals that the stability of the station clock offset sequence of PPP-AR is superior to that of PPP floating solution. In comparison to the PPP floating solution, the average improvement of PPP-AR stability is 17%. Furthermore, using PPP-AR for time transfer improves the stability of the time transfer link clock offset sequence and also reduces its noise level. Moreover, different types of time transfer links exhibit varying degrees of improvement. The stability has been increased by 14% on average, and the noise level has been improved by 9% on average. Additionally,` the Allan deviation is employed to assess the frequency stability. The findings indicate that the frequency stability of the fixed solution is superior to that of the float solution. PPP-RTK also enhances the stability, noise level and frequency stability of time transfer even better than PPP-AR. Nevertheless, as the reference network scale increases, the accuracy of the interpolated atmospheric delay correction diminishes, impacting the performance of PPP-RTK.