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Global Navigation Satellite System (GNSS) products, including satellite orbit and clock corrections, ionospheric and tropospheric delay models, and multi-frequency data, are fundamental to modern geodesy and numerous scientific and industrial applications. The exploitation of these products facilitates the achievement of precise positioning, navigation, and timing (PNT) across a diverse range of fields, including transportation, geodesy, agriculture, and disaster management. Nevertheless, numerous challenges remain, including signal degradation due to multipath effects, atmospheric interference, and vulnerabilities to jamming and spoofing. Recent developments seek to address these limitations and enhance the utility of GNSS products. International collaboration, spearheaded by organizations such as the International GNSS Service (IGS), is crucial for standardizing and distributing GNSS products, facilitating global accessibility and addressing challenges such as climate monitoring and disaster resilience. This review emphasizes the indispensable role of GNSS products in advancing science and industry, highlights persistent challenges, and explores innovative solutions that promise to enhance their accuracy, resilience, and accessibility for addressing global needs. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The field of satellite navigation has seen significant advancements due to the fast development of multi-constellation Global Navigation Satellite Systems (GNSS). Around 150 satellites will be in service when all six systems – GPS, GLONASS, Galileo, BeiDou, QZSS, and NAVIC – are launched by 2030, offering both enormous potential and advantages for research and engineering applications. This study used an experiment on the accuracy, particularly for short, medium, long baselines (Wide Lane ambiguity solution) of the BeiDou, QZSS and QZSS/BeiDou combinations. It showed that with the integration of BeiDou/QZSS static measurements in the study region millimetre-centimetre accuracy for short, medium, and long baselines can be attained. Based on the results of this study, it can be concluded that the 1st (QZSS/BeiDou), 2nd (BeiDou), and 3rd (QZSS) strategies feature different horizontal accuracies for all categories. The obtained results with different satellite configurations for the Fixed-Wide-Lane integer ambiguity solution are compared with each other. Accuracy at the short baseline (BeiDou, QZSS, and BeiDou/QZSS satellites) was obtained in the range of 0.5–0.7 cm. For the medium baseline, it was computed around 1.8–82 cm. For the long baseline, the accuracy was 5.6–13.3 cm. [ABSTRACT FROM AUTHOR]

It is essential to provide high-integrity navigation information for safety-critical applications. Global navigation satellite systems (GNSSs) play an important role in these applications because they can provide global, high-accuracy, all-weather navigation services. Therefore, it has been a hot topic to improve GNSS integrity performance. This paper focuses on an initial proposal of the next-generation BeiDou Navigation Satellite System (BDS) integrity subsystem, with the aim of providing high-quality and global integrity services for the BDS. This paper first reviews the current status of the third-generation BDS integrity service. Following this, this paper proposes a space–ground integrated integrity monitoring design for the BDS that integrates the traditional ground-based integrity monitoring method, the advanced satellite autonomous integrity monitoring (A-SAIM) method, and the augmentation from low-earth-orbit (LEO) satellites. Specifically, this work offers an initial design of the A-SAIM method, which considers both single-satellite autonomous integrity monitoring and multi-satellite joint integrity monitoring. In addition, this work describes two different ways to augment BDS integrity with LEO satellites, i.e., (a) LEO satellites act as space monitoring stations and (b) LEO satellites act as navigation satellites. Simulations are carried out to validate the proposed design using CAT-I operation in civil aviation as an example. Simulation results indicate the effectiveness of the proposed design. In addition, simulation results suggest that if the fault probability of LEO satellites is worse than 1 × 10−4, LEO satellites can contribute more to BDS integrity performance improvement by acting as space monitoring stations; otherwise, it would be better to employ LEO satellites to broadcast navigation signals. The results also suggest that after taking LEO satellites into account, the global coverage of CAT-I can be potentially improved from 67% to 99%. This work is beneficial to the design of the next-generation BDS integrity subsystem. [ABSTRACT FROM AUTHOR]

For decades, GNSS code measurements were much noisier than phase ones, limiting their applicability to ionospheric total electron content (TEC) studies. Ultra-wideband AltBOC signals changed the situation. This study revisits the Galileo E5 and BeiDou B2 AltBOC signals and their potential applications in TEC estimation. We found that TEC noises are comparable for the single-frequency AltBOC phase-code combination and those of the dual-frequency legacy BPSK/QPSK phase combination, while single-frequency BPSK/QPSK TEC noises are much higher. A two-week high-rate measurement campaign at the ACRG receiver revealed a mean 100 sec TEC RMS (used as the noise proxy) of 0.26 TECU, 0.15 TECU, and 0.09 TECU for the BeiDou B2(a+b) AltBOC signal and satellite elevations 0–30°, 30–60°, and 60–90°, correspondingly, and 0.22 TECU, 0.14 TECU, and 0.09 TECU for the legacy B1/B3 dual-frequency phase combination. The Galileo E5(a+b) AltBOC signal corresponding values were 0.25 TECU, 0.14 TECU, and 0.09 TECU; for the legacy signals' phase combination, the values were 0.19 TECU, 0.13 TECU, and 0.08 TECU. The AltBOC (for both BeiDou and Galileo) SNR exceeds those of BPSK/QPSK by 7.5 dB-Hz in undisturbed conditions. Radio frequency interference (the 28 August 2022 and 9 May 2024 Solar Radio Burst events in our study) decreased the AltBOC SNR 5 dB-Hz more against QPSK SNR, but, due to the higher initial SNR, the threshold for the loss of the lock was never broken. Today, we have enough BeiDou and Galileo satellites that transmit AltBOC signals for a reliable single-frequency vTEC estimation. This study provides new insights and evidence for using Galileo and BeiDou AltBOC signals in high-precision ionospheric monitoring. [ABSTRACT FROM AUTHOR]

Abstract The optimal design of Global Navigation Satellite System (GNSS) software receivers should enable the accurate estimation of the receiver's position, velocity, and time under various environmental conditions. The software receivers consist of three sections: acquisition, tracking, and navigation. This paper specifically centers on the acquisition sections of the Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), BeiDou, and Galileo satellite navigation systems. The acquisition stage necessitates the prompt and precise transmission of the satellite list within the receiver's view, along with Doppler frequency estimation and phase code offset, to facilitate a seamless transition to the tracking stage with the utmost speed and accuracy. Conventional acquisition demonstrates commendable speed, but lacks accuracy, especially in environments with a low Carrier-to-Noise Ratio (CNR). Contrastingly, precise acquisition methods will impede the speed of the acquisition stage. In this paper, a novel acquisition method is proposed. By integrating concepts like resampling, two-stage acquisition, and fine-acquisition, this method enables the attainment of higher accuracy without compromising speed. The results demonstrate that the proposed method enhances accuracy by 7.275% compared to conventional methods and boosts speed by 76.97% compared to methods focused on accuracy improvement.

The optimal design of Global Navigation Satellite System (GNSS) software receivers should enable the accurate estimation of the receiver's position, velocity, and time under various environmental conditions. The software receivers consist of three sections: acquisition, tracking, and navigation. This paper specifically centers on the acquisition sections of the Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), BeiDou, and Galileo satellite navigation systems. The acquisition stage necessitates the prompt and precise transmission of the satellite list within the receiver's view, along with Doppler frequency estimation and phase code offset, to facilitate a seamless transition to the tracking stage with the utmost speed and accuracy. Conventional acquisition demonstrates commendable speed, but lacks accuracy, especially in environments with a low Carrier-to-Noise Ratio (CNR). Contrastingly, precise acquisition methods will impede the speed of the acquisition stage. In this paper, a novel acquisition method is proposed. By integrating concepts like resampling, two-stage acquisition, and fine-acquisition, this method enables the attainment of higher accuracy without compromising speed. The results demonstrate that the proposed method enhances accuracy by 7.275% compared to conventional methods and boosts speed by 76.97% compared to methods focused on accuracy improvement. [ABSTRACT FROM AUTHOR]

In order to study and explore the role of automated monitoring technology in subway construction and maintenance, this paper adopted a combination of theoretical analysis and engineering cases. In terms of theoretical analysis, on the basis of introducing the application background and significance of automated monitoring technology in the subway industry, the main methods and technical means of automatic monitoring of subway deformation were summarized by analyzing cutting-edge sensor technology and data processing methods, including monitoring methods based on sensor technology, data management based on the Internet of Things technology, and artificial intelligence platforms based on big data. In terms of engineering cases, this paper demonstrated the progressiveness of automated monitoring based on the case of a subway bridge with monitoring duration 2 h per time, and the monthly personnel input can be reduced by 420 man days with obvious economic benefits. The results show that, introducing advanced technology for traditional industy could enhance automated data management and research platform, and improve the automation level and efficiency. [ABSTRACT FROM AUTHOR]

In January 2023, the International Laser Ranging Service (ILRS) approved the tracking of 20 additional BeiDou-3 Medium Earth Orbit (BDS-3 MEO) satellites, integrating them into the ILRS tracking network. Before that, only 4 BDS-3 MEO satellites had been tracked. BDS satellites employ highly advanced GNSS components and technological solutions; however, microwave-based orbits still contain systematic errors. Satellite Laser Ranging (SLR) tracking is thus crucial for better identification and understanding of orbit modeling issues. Orbit improvements are necessary to consider BDS in future realizations of terrestrial reference frames, supporting the determination of global geodetic parameters and utilizing them for the co-location of GNSS and SLR in space. In this study, we summarize the first 6 months of SLR tracking 24 BDS-3 MEO satellites. The study indicates that the ILRS network effectively executed the request to track the entire BDS-3 MEO constellation. The number of observations is approximately 1300 and 450 for high- and low-priority BDS-3 satellites, respectively, over the 6 months. More than half of the SLR observations to BDS-3 MEO satellites were provided by 5 out of the 24 laser stations, which actively measured GNSS targets. For 14 out of 24 BDS-3 MEO satellites, the standard deviation of SLR residuals is at the level of 19–20 mm, which is comparable with the quality of the state-of-the-art Galileo orbit solutions. However, the SLR validation of the individual satellites revealed that the BDS-3 MEO constellation consists of more ambiguous groups of satellites than originally reported in the official metadata files distributed by the BDS operators. For 8 BDS-3 satellites, the quality of the orbits is noticeably inferior with a standard deviation of SLR residuals above 100 mm. Therefore, improving orbit modeling for BDS-3 MEO satellites remains an urgent challenge for the GNSS community. [ABSTRACT FROM AUTHOR]

The Global Positioning System (GPS) is a GNSS constellation, but GNSS is not always GPS. GPS is one of the GNSS constellations used around the world. The GNSS constellations include GPS (US), QZSS (Japan), Beidou/BDS (China), Galileo (EU), and GLONASS (Russia). In 1999, the European Commission (EC) proposed the European Galileo satellite navigation system for the first time. A four-phase development was proposed, including public and private sector finance. Galileo was intended for both civilian and government use, and is managed and controlled by civil authorities. Galileo is made up of 30 satellites, a number of globally distributed ground stations, and a ground control and monitoring system, all of which are extremely similar to the structure, format, and layout of GPS. In this study, we investigate GPS/GLONASS/Galileo/Beidou/IRNSS/QZSS Navigation Satellite System integration algorithm for long baselines ranging from 1500km to 3000km in China, Japan and Mongolia. The positioning performance with GPS/GLONASS/Galileo/BDS/IRNSS/QZSS, GPS-only, Galileo-only, GLONASS-only and BDS-only, etc. is compared in terms of the positioning accuracy. An improvement of positioning accuracy over long baselines can be found with GPS/GLONASS/Galileo/BDS/QZSS/IRNSS compared with that of GPS-only and that of BDS-only. The obtained differences of the two baselines (Topcon Magnet Tools Software (Multi-GNSS)-(CSRS-PPP (GPS/GLONASS), (Trimble-RTX (GPS/GLONASS), (AUSPOS (GPS/GLONASS)) Online Processing Software) by using GPS/GLONASS/Galileo/BDS/QZSS/IRNSS signals is between 40cm and 111.5cm on three days.

Velocity estimation has a key role in several applications; for instance, velocity estimation in navigation or in mobile mapping systems and GNSSs is currently a common way to achieve reliable and accurate velocity. Two approaches are mainly used to obtain velocity based on GNSS measurements, i.e., Doppler observations and carrier phases differenced in time (that is, TDCP). In a benign environment, Doppler-based velocity can be estimated accurately to within a few cm/s, while TDCP-based velocity can be estimated accurately to within a few mm/s. On the other hand, the TDCP technique is more prone to availability shortage and the presence of blunders. In this work, the two mentioned approaches are tested, using three devices of different grades: a high-grade geodetic receiver, a high-sensitivity receiver, and a GNSS chip mounted on a smartphone. The measurements of geodetic receivers are inherently cleaner, providing an accurate solution, while the remaining two receivers provide worse results. The case of smartphone GNSS chips can be particularly critical owing to the equipped antenna, which makes the measurements noisy and largely affected by blunders. The GNSSs are considered separately in order to assess the performance of the single systems. The analysis carried out in this research confirms the previous considerations about receiver grades and processing techniques. Additionally, the obtained results highlight the necessity of adopting a diagnostic approach to the measurements, such as RAIM-FDE, especially for low-grade receivers. [ABSTRACT FROM AUTHOR]

With the development of Beidou navigation satellite system, a large number of studies have been conducted on the application data transmission of Beidou short messages in areas with frequent geological disasters. How to analyze its safety has become the key to engineering application. In this paper, FMEA is used to provide an application data safety analysis method based on Beidou short messages. In order to ensure the correctness of data as the starting point, possible failure modes are analyzed, especially the risks caused by data changes. According to the failure mode, the corresponding risk mitigation measures are given to prevent or mitigate the risks. This will provide safety assistance for the wide application of Beidou short message in the future rail transit field to improve the overall safety of the system. [ABSTRACT FROM AUTHOR]

The Global Navigation Satellite System Occultation Sounder II (GNOS-II) payload onboard the Chinese Fengyun-3E (FY-3E) satellite is the world's first operational spaceborne mission that can utilize reflected signals from multiple navigation systems for Earth remote sensing. The satellite was launched into an 836-km early-morning polar orbit on 5 July 2021. Different GNSS signals show different characteristics in the observations and thus require different calibration methods. With an average data latency of less than 3 h, many near real-time applications are possible. This article first introduces the FY-3E/GNOS-II mission and instrument design, then describes the extensive calibration methods for the multi-GNSS measurements, and finally presents application results in the remote sensing of ocean surface winds, land soil moisture and sea ice extent. Especially, the ocean surface wind product has been used in operational applications such as assimilation in the numerical weather prediction model and monitoring of tropical cyclones. Currently, GNOS-II has been carried by FY-3E, FY-3F (launched in August 2023) and FY-3G (launched in April 2023). It will be also carried by future follow-on FY series and a more complete multi-GNSS reflectometry constellation will be established. [ABSTRACT FROM AUTHOR]

The European Commission (EC) originally proposed ideas for a European Galileo satellite navigation system in 1999. A four-phase development is planned, involving investment from both the public and commercial sectors. Galileo is intended for both public and government use; the system is administered and operated by civil administration. Galileo will consist of a constellation of 30 satellites, a number of globally situated ground stations, and a ground control and monitoring system - all of which are quite similar to the structure, format, and layout of GPS. This document discusses an experiment at the project site that used the static approach to integrate GPS, GLONASS, GALILEO, Beidou, and QZSS signals. This research analyses the possible precision of GPS-only and GPS/GLONASS/GALILEO/Beidou/QZSS. These results suggest that combining a GPS system with GALILEO, GLONASS Beidou, and QZSS is preferable for surveying purposes. Integrating GPS/GLONASS/GALILEO/Beidou/QZSS static measurements in the study region with 0-120 millimetre accuracy looks to be possible in three days. [ABSTRACT FROM AUTHOR]

With the widespread global application of BeiDou navigation, BeiDou B1C signaling based on Quadrature Multiplexed Binary Offset Carrier (QMBOC) modulation is expected to be extensively used in urban environments due to its wider signal bandwidth, smaller code pseudorange measurement errors, and stronger multipath capabilities. Despite offering higher positioning accuracy and secondary modulation characteristics of the BeiDou, B1C signals introduce the challenge of multiple peaks in the autocorrelation function. This leads to phase ambiguity during signal acquisition and tracking, resulting in positioning deviations of tens or even hundreds of meters. In urban environments, such deviations give rise to significant practical application issues. To address this problem, we have designed a multi-loop structure for the synchronous tracking of B1C signals and proposed a multi-peak phase-deblurring algorithm specifically tailored for the BeiDou B1C signal in urban environments. This algorithm considers the coupling relationship between the code and the carrier loops, and by matching the structural design of multiple loops, it achieves a precise and unambiguous phase estimation of the pseudocode, enabling the stable tracking of the entire loop for the BeiDou B1C signal. Simulation and actual testing demonstrate that the algorithm exhibits an error less than 0.03 for chip intervals when the signal-to-noise ratio is greater than −20 dB. Additionally, the accuracy can be improved by adjusting the set conditions, making it suitable for urban environments. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The ability to provide precise orbit prediction of Global Navigation Satellite System (GNSS) satellites is essential in a wide range of applications in space geodesy and Earth sciences, including near real-time and real-time GNSS applications, forming broadcast ephemerides, or supporting Satellite Laser Ranging stations in tracking. In this study, we evaluate the impact of orbit modeling strategies on the accuracy of orbit predictions on short (one-day), and long (multi-day) time scales, focusing on the selection of the optimal approach for handling solar radiation pressure (SRP), the effects of including pseudo-stochastic parameters, and the impact of the arc length used for the initial orbit fit. The analysis includes 300 days of predictions in 2021 and the satellites belonging to the GPS, Galileo, GLONASS, BeiDou-3, (BDS-3), and QZSS constellations. Fitting an initial 2-day orbit arc is the optimal solution for all analyzed navigation satellite constellations. When official satellite construction metadata are available, e.g. for Galileo/QZSS, the hybrid strategy of combining both empirical and physical models, i.e. the extended Empirical CODE Orbit Model (ECOM2) with box-wing models, leads to the best results. Otherwise, using only the ECOM2 is a better choice. Finally, the results indicate that for all navigation satellites, the introduction of pseudo-stochastic parameters deteriorates the prediction quality. When using the optimal prediction strategy, the 95th percentiles of the position errors after the 1st/4th/9th day of prediction are equal to 0.09/0.93/4.52, 0.22/1.71/9.69, 0.20/2.19/11.30, 0.23/1.80/9.39, 0.23/2.28/7.78m for GPS-IIF, Galileo FOC, GLONASS-M, BDS-3 CAST, and QZSS, respectively. • Optimize GNSS orbit prediction quality for up to nine days. • Handling of solar radiation pressure depends on the satellite type. • Fitting an initial 2-day orbit arc is the optimal solution for navigation satellites. • Pseudo-stochastic orbit parameters deteriorate prediction quality. [ABSTRACT FROM AUTHOR]

Since 2014, China has embarked on the process of building its own national continuously operating reference system (CORS), called the ground-based augmentation system (GAS), as one of the seven planning services of the BeiDou global navigation satellite system (BDS-3). The performance specifications for GAS were released, and the system has begun to render open services formally in May 2021. This paper involves a comprehensive introduction to GAS, from the aspects of its system composition, reference time system, and coordinate reference frame. The performance specifications and service products of GAS are presented and discussed. Performance tests of GAS services including wide-area and regional real-time augmentation positioning service and postprocessing data service were been carried out. The results show that wide-area real-time augmentation positioning service can realize meter-level to decimeter-level positioning for pseudo-range and carrier-phase positioning, respectively, while for regional real-time service, it can provide centimeter-level positioning within seconds, for postprocessing data service, it can realize millimeter-level positioning in mainland China. Overall, the performance test results of GAS service show that the service performance can well meet the design requirements and indicate the broad application prospects of GAS in the future. [ABSTRACT FROM AUTHOR]

The Gaussian mixture model (GMM) is commonly used to model the heavy tail of the ground-based augmentation system (GBAS) range error distribution. In practice, Gaussian over-bounding based on a GMM is used to over-bound the heavy tail of the ranging errors, but the GBAS protection levels (PLs) based on the Gaussian over-bounding tend to be overestimated. Based on the idea of solution separation and overcoming the shortcoming of its direct reference to GBAS, this paper analyses the constraint conditions and objective functions of the optimal protection level based on solution separation under a GMM distribution, and proposes that multi-hypothesis solution set classification can effectively reduce the computational complexity. At the same time, least squares optimization and dynamic allocation of integrity risk are used to further reduce the protection level. This paper verifies the validity of the parameters of the GMM based on actual airport GBAS data, performs simulation verification of the typical scenarios of CAT I and CAT II/IIIa global GBAS under the Beidou 3 constellation, and analyses the performance improvement effect under different solution set traversal depths. The results show that when the traversal depths of CAT I and CAT II/IIIa are 4 and 6, the vertical protection level component of the ground ranging error is reduced by 14% and the total vertical protection level is reduced by 10%. [ABSTRACT FROM AUTHOR]

The subject of this paper is the analysis of the stability of BeiDou system clocks; currently only signals from two blocks, BSD-2 and BDS-3, are available. For elaboration, 30 s clock corrections from the 2014 to 2020 period for 37 satellites were used (9 IGSO, 28 MEO). Four different Allan variances were used to determine stability, and additionally, the type of noise characteristic for each satellite was also determined. Based on the calculations, it was shown that the BDS-2 segment has a significantly lower stability than BDS-3. Moreover, it was possible to notice a difference in the course of the graphs of the same satellites using different variances. BDS-2 satellites were mostly characterised by the presence of WFM noise, while BDS-3 satellites were characterised by WFM noise for the shortest averaging times and RWFM for the other intervals. Accuracy varies between 10−10 s to 10−6 s for a rubidium clocks in general, in case of the hydrogen masers in is between 10−14 s to 10−10 s. [ABSTRACT FROM AUTHOR]

With the large-scale use of BeiDou navigation and 5G technology worldwide, integrating BeiDou navigation and communication has become a hot research topic in navigation and positioning technology. Low-cost, miniaturized, and susceptible mixed-signal receivers will become the future receiver technology development trend. However, the current receiver technology still faces the challenge of further improving the positioning service capability and communication quality, which includes the lack of practical analysis of the compatibility between signals and the lack of mixed-signal processing capability of the receiver baseband key technology. To address these problems, we start by analyzing the signal part of 5G out-of-band signals falling into the BD B1 signal band, conduct a detailed analysis of the mixed signal regime and frequency planning, and design a hybrid receiver architecture compatible with both signals, and propose an SC-PMF-FFT fast capture algorithm based on strong correlation, which takes advantage of the strong correlation of signals broadcast on the BD B1 frequency point from B1I to B1C, and reuses the structure of the CDMA system signal capture algorithm to complete the fast capture of 5G signals using an OFDM system. The experiments show that the method can capture the BeiDou B1 signal with a sensitivity of −154 dBm and a whole constellation capture time of no more than 40 ms with the inlet power of the 5G signal not exceeding −45 dBw. [ABSTRACT FROM AUTHOR]

In the multi-GNSS solutions integrating GPS, GLONASS, Galileo, and BeiDou, the receiver clock may be treated twofold; the clock parameter may be estimated for each GNSS separately or the common clock can be estimated, e.g., for GPS, with inter-system biases (ISBs) for other systems. The latter strategy reduces the number of estimated independent clock parameters per epoch almost by a factor of four because the clock parameters are estimated epoch-wise, whereas ISBs are estimated as constant values for the entire day or month. Due to the discontinuities in reference satellite clocks, the estimated ISBs and receiver clock parameters have also to be reinitialized at day boundaries. This raises questions about whether only the common clock has to be reset or all ISB values and what is the impact of the reinitialization of clock parameters with covariance values when estimating system-specific clock parameters. We analyze the effects of different types of stochastic modeling applied to the parameters of clocks and ISBs. In this study, we test five different strategies to clock handling in multi-GNSS kinematic Precise Point Positioning derived continuously for one month. We found that two solutions can be considered equivalent: (1) estimating system-specific clocks and (2) estimating the common clock with ISB and resetting at day boundaries the common clock parameter and ISBs. Oppositely, resetting only the common clock parameter or assuming that the ISB keep their stabilities over long periods is insufficient to obtain superior results of station coordinates and reliable time transfer results. [ABSTRACT FROM AUTHOR]

Against the background of the intensive development and implementation of satellite technologies for position determination, navigation, and time synchronization, one of the central threats to critical industries is the creation of intentional interference to the signals of global navigation satellite systems. It is shown that the use of small-sized antenna arrays in navigation systems consisting of satellite constellations of GPS, GLONASS, GALILEO, BEIDOU, QZSS, or their combinations makes it possible to detect and suppress interfering signals by forming zeros of the antenna array directional pattern in the directions of their arrival. The interfering signal suppression is supplemented with detection procedures while maintaining the ability of navigation by using from one to four satellite systems according to criteria of the required number of satellites in the line of sight and the permissible geometric factor. The process of suppressing the interfering signal from four directions is illustrated by three scenarios, the initial data for which are signals from 35 satellites in the line of sight collected in real-time from five systems. It has been shown that the use of five systems and 35 satellites ensures the suppression of the interfering signal. At the same time, 22 satellites are involved in solving the navigation problem, 13 satellites are below the detection threshold, and the geometric factor is 1.18. When using GPS, GLONASS, and 19 satellites, the interfering signal is suppressed. In this case, 10 satellites are involved in solving the navigation problem, 9 are below the detection threshold, and the geometric factor is 2.1. When using only GPS, the interfering signal suppression is also ensured. This time 7 satellites are involved in solving the navigation problem, 4 are below the detection threshold, and the geometric factor is 1.76. [ABSTRACT FROM AUTHOR]

The orbit maneuver detection is crucial in Global Navigation Satellite System (GNSS) precise orbit determination, which is necessary for adjusting data processing strategies. The frequency of orbit maneuvers for the BeiDou Navigation System is significantly higher than that of other navigation systems, especially for geosynchronous orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites. We propose a novel real-time and postprocessing method for detecting orbit maneuvers for BeiDou satellites based on the orbit differences between the epoch-updated orbit estimated using square root information (SRIF) and the predicted orbit according to the precise orbit estimated during non-maneuver period, as well as the orbital state difference during maneuver and non-maneuver periods. This method has significant advantages over using observation residuals and it is not affected by observation outliers, thus improving the accuracy and timeliness of orbit maneuver detection. We demonstrated that 32 orbit maneuver events of BeiDou satellites were successfully detected in 2022, of which 1 was for medium Earth orbit (MEO), 7 were for IGSO with an average detected maneuvering time of 7–8 min, and 24 were for GEO satellites with an average detected time of 4–5 min. Moreover, our method can be easily integrated into current real-time filter-based precise orbit determination (POD) processing without any extra task line, which simplifies the overall data processing. The data used in this method can be accessed easily, including GNSS observation data, broadcast ephemeris, and other open-source information files. [ABSTRACT FROM AUTHOR]

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ABSTRACTChina’s foremost national goal is to become a major space power by 2030. Consequently, President Xi Jinping has made the launch of the BeiDou navigation satellite system (BDS) and promotion of a “BDS global network” a national priority.BDS represents a frontier technology of the “fourth industrial revolution” which ushered in the digital age. Using BeiDou as a case study, this paper attempts to analyze the structural features of China’s frontier technology strategy and its impact on China’s global influence. Significantly, BDS has both military and civilian applications, which is a prominent feature of today’s cutting edge technologies. Therefore, a focus on BDS will deepen our understanding of how China is exploring these new types of dual-purpose technologies to expand its global reach.The paper argues that by dramatically restructuring its decision-making process under Xi Jinping, China has been able to adopt a state-led national strategy for using BeiDou domestically, while expanding its global reach through a market-driven approach. This strategy has facilitated the penetration of Chinese BDS applications into the economies and societies of many developing (and some developed) countries.

In this study, the latest contribution of the BeiDou-3 FOC satellites to GPS/GLONASS/Galileo/BDS-2 combined static and kinematic precise point positioning (PPP) is investigated over a one-month period in 2021 considering the three different cut-off angles (7°, 15°, and 30°). The results show that the contribution of BDS-3 to GPS/GLONASS/Galileo PPP is generally marginal for 7° and 15° cut-off angles. The largest BeiDou-3 contributions to static and kinematic positioning accuracy are found to be 9%, 6%, and 19% (for 3-h sessions with the 15° cut-off angle) and 9%, 15%, and 8% (with the 30° cut-off angle) for the north, east, and up components, respectively. The largest reductions in static and kinematic convergence time by adding BDS-3 to GPS/GLONASS/Galileo are found to be 13%, 10%, and 6% (for the 30° cut-off angle) and 17%, 7%, and 6% (for the 30° cut-off angle) for the north, east, and up components, respectively. [ABSTRACT FROM AUTHOR]

In the middle of 2011, Trimble introduced the RTX correction service to support RT-PPP applications. In this study, the performance of Trimble RTX correction service is investigated over a one-month period using five different GNSS constellations – namely, GPS-only, GPS + GLONASS, GPS + Galileo, GPS + GLONASS + Galileo, and GPS + GLONASS + Galileo + BeiDou. The results show that positioning accuracy and convergence time are significantly improved with the use of the multi-GNSS constellation compared with the GPS-only solution. The result of the converged positioning accuracy indicates that the GPS + GLONASS + Galileo + BeiDou combination improves the accuracy by 63%, 54%, and 60% for north, east, and up components, respectively, compared with the GPS-only solution. The mean convergence time is reduced by the GPS + GLONASS+ Galileo + BeiDou combination by 70%, 71%, and 38.6% compared with the GPS-only solution in the north, east, and up components, respectively. 1.2 (north), 1.5 (east), and 2.3 cm (up) root mean square errors (RMSEs) of converged positioning from the GPS + GLONASS + Galileo + BeiDou combination are computed. [ABSTRACT FROM AUTHOR]

This study aims to verify whether the open-source software may provide Precise Point Positioning (PPP) with high accuracy. In this way, we address a question on the potential usability of open-source software for PPP analysis. On 31 July 2020, the full constellation of BeiDou satellites (SV) was announced. Over the European area, however, the number of visible BeiDou SVs is significantly smaller than in Asian-Pacific regions. Additionally, the system is in a modernization process, which may result in difficulties in utilizing its full potential. Ten days of multi-GNSS data were processed using the open-source software GAMP to determine how the accuracy of a derived three-dimensional PPP coordinates depends on observation session length and satellite systems used. The time series of position components of selected EUREF Permanent Network (EPN) stations generated from sub-daily (30 min and longer) solutions were analyzed. The obtained results prove that adding BeiDou observations, even in the case of using an incomplete constellation, leads to visible improvements, which can be observed both in the reduction of differences between estimated and true coordinates, as well as in the reduction of the standard deviation (SD). Improved accuracy caused by adding BeiDou data is especially noticeable for short observation sessions (in the range of 0.5 to 2.0 h) and in the case of a joint solution with GLONASS or Galileo observations. Finally, the open-source software GAMP proved to be a useful tool for multi-GNSS data processing and analysis. [ABSTRACT FROM AUTHOR]