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Following several performance enhancements, GPS has provided a stable signal-in-space range error (SISRE) of about 50 cm (RMS) for more than a decade. As of early 2024, a major SISRE reduction by about 30% could be noted that helps to maintain the competitiveness of GPS in comparison with the Chinese BeiDou system and reduces the performance difference with respect to the European Galileo system. Based on analyses of onboard clock stability and broadcast navigation messages, the SISRE enhancement can be attributed to a combination of clock switches on selected satellites as well as an overall reduction of the mean time between navigation data uploads. The additional adoption of new transmit antenna phase center offsets in the control segment has no immediate performance impact but affects the comparison of broadcast and precise orbits. Following the aforementioned operational changes, SISRE values for dual-frequency P(Y)-code positioning with the legacy navigation message (LNAV) were found to decrease to roughly 30 cm from March 2024 onward, and marginally worse results are obtained for users of the civil L1/L2 signals and the L2 civil navigation (CNAV) message. Single-frequency LNAV users, on the other hand, experience only a minor benefit, since orbit and clock information improvements are largely masked by the non-availability of group delay information for the L1 C/A signal relative to the L1 P(Y) signal. [ABSTRACT FROM AUTHOR]

The Galileo High Accuracy Service (HAS) has undergone substantial development in recent years, offering users free access to GPS and Galileo satellite orbit, clock, and code bias corrections for Precise Point Positioning (PPP) on a global scale. This paper explores the use of the currently available HAS corrections for smartphone positioning. Due to hardware disparities and limited tracking capabilities, smartphone processing with only two GNSS constellations struggles to ensure satisfactory satellite geometry and sufficient observations in realistic user environments. To fully harness all observed measurements and the orbit and clock information directly disseminated from satellites, this study introduces a new PPP algorithm combing HAS corrections and broadcast ephemerides (HAS and BRDC PPP) for smartphone processing. Through four vehicle experiments in urban environments, the proposed HASandBRDC PPP solutions demonstrated a notable reduction in positioning errors. Specifically, the horizontal rms and 95th percentile error decreased from 2.0 and 3.3 m to 1.6 and 2.4 m, respectively, when compared to the HAS PPP solutions. These results are highly comparable to four-constellation PPP solutions utilizing Centre National d'Etudes Spatiales (CNES) ultra-rapid products, which can achieve a horizontal rms of 1.4 m. Additionally, the inclusion of smartphone inertial measurement unit (IMU) measurements results in a notable 59% average reduction in PPP gross errors. This study provides an original comparison of the 2022 and 2023 HAS corrections, demonstrating the feasibility of real-time lane-level navigation with smart devices even in remote areas without Internet connectivity, which has not been previously explored. [ABSTRACT FROM AUTHOR]

Since 2020, the BeiDou Navigation Satellite System (BDS) has launched new precise point positioning service which provides precise correction of GPS and BDS-3 satellites to help users realize real-time precise point positioning, known as PPP-B2b service. After being fully operational for more than one year, this contribution comprehensively analyzes the performance of PPP-B2b in terms of correction availability, clock and orbit quality and positioning accuracy with PPP-B2b messages of nearly 48 weeks from 2021 to 2022. The results show that in the PPP-B2b service, the orbit radial differences of BDS-3 MEO, GPS, and BDS-3 IGSO satellites are 0.056 m, 0.069 m, and 0.172 m, respectively, compared to the GFZ final orbit, while the difference of along-track and cross-track is more than three times the radial. For BDS-3 MEO satellites from different manufacturers, the RMS of Satellite Laser Ranging (SLR) residuals is different, with a maximum of 0.11 m. Restricted by the regional tracking network, the correction series of PPP-B2b service are discontinuous, and there are constant satellite-specific clock biases in different arcs of the satellite. Thus, the STD and RMS of satellite clock offset and signal-in-space ranging error (SISRE) are calculated using the method of weighting by arcs. The STD of SISRE for BDS-3 MEO, GPS and BDS-3 IGSO are 0.059 m, 0.092 m and 0.174 m, respectively. A total of 108 days of observation data from 12 MGEX stations of the East Asia region are selected to analyze the positioning performance of PPP-B2b. The results of day-by-day static PPP are stable at the centimeter level, while the average convergence time of GPS-only (61.65 min) is longer than BDS-3-only (45.12 min), which the constant bias in clock offset may cause. To analyze the effect of this bias, the bias is calculated and used as a correction to the PPP-B2b clocks. The convergence time of BDS-3 and GPS positioning is reduced by 48.7% and 65.9%, respectively, after correcting this bias, which confirms the influence of clock constant bias on positioning convergence. [ABSTRACT FROM AUTHOR]

A consistent analysis of signal-in-space ranging errors (SISREs) is presented for all current satellite navigation systems, considering both global average values and worst-user-location statistics. The analysis is based on 1 year of broadcast ephemeris messages of the Global Positioning System (GPS), GLONASS, Galileo, BeiDou and QZSS collected with a near-global receiver network. Position and clock values derived from the navigation data are compared against precise orbit and clock products provided by the International GNSS Service and its multi-GNSS experiment. Satellite laser ranging measurements are used for a complementary and independent assessment of the orbit-only SISRE contribution. The need for proper consideration of antenna offsets is highlighted and block-/constellation-specific radial antenna offset values for the center-of-mass correction of broadcast orbits are derived. Likewise, the need for application of differential code biases in the comparison of broadcast and precise clock products is emphasized. For GPS, the analysis of the legacy navigation message is complemented by a discussion of the CNAV message performance based on the first CNAV test campaign in June 2013. Global average SISRE values for the individual constellations amount to 0.7 ± 0.02 m (GPS), 1.5 ± 0.1 m (BeiDou), 1.6 ± 0.3 m (Galileo), 1.9 ± 0.1 m (GLONASS), and 0.6 ± 0.2 m (QZSS) over a 12-month period in 2013/2014. [ABSTRACT FROM AUTHOR]