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Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo

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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Satellite Missions for Earth and Planetary Exploration".

Deadline for manuscript submissions: closed (15 November 2022) | Viewed by 19863

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Special Issue Editors

Dr. Shengfeng Gu

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GNSS Research Center, Wuhan University, Luoyu Road 129, Wuhan 430079, China
Interests: GNSS real-time precise data processing; GNSS ionospheric delay modeling; navigation
Special Issues, Collections and Topics in MDPI journals

Dr. Xiaopeng Gong

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GNSS Research Center, Wuhan University, Luoyu Road 129, Wuhan 430079, China
Interests: GNSS real-time clock estimation; precise positioning; signal bias estimation
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Yidong Lou

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GNSS Research Center, Wuhan University, 129 Luoyu Road, Wuhan 430079, China
Interests: GNSS precise data processing; navigation
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Chuang Shi

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Guest Editor

School of Electronic and Information Engineering, Beihang University, Beijing 100191, China
Interests: GNSS precise data processing; navigation; timing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The potential of global navigation satellite systems (GNSS) as an efficient tool in providing precise positioning has been widely recognized. Especially, the precise point positioning (PPP) technique is receiving increasing interest due to its cost-effectiveness, global coverage and high accuracy. In addition, the emergence of multiple satellite navigation systems, including BDS, Galileo, modernized GPS, and GLONASS, brings great opportunities and challenges for PPP. For instance, the additional frequency as well as the new signal of BDS-3 and Galileo enables the fast convergence of PPP by efficient ambiguity resolution (AR). More recently, besides the standard point positioning, BDS, Galileo as well as QZSS has also provided the satellite-based PPP service. Obviously, the development of multi-frequency multi-GNSS and their build-in PPP service has popularized the use of PPP as an efficiency technique in navigation, timing as well as geoscience applications.

This special issue aims at different algorithms and applications of PPP with either GNSS build-in high-precision service or IGS high-precision product. Topics may cover anything from the classical ionospheric-free PPP, to undifferenced uncombined PPP, and from the float ambiguity PPP, to fixed ambiguity PPP. Hence, code and phase observation-specific bias estimation and correction, atmosphere augmentation PPP with multiscale networks or studies of PPP and multi-sensor integration navigation, among other issues, are welcome.

Dr. Shengfeng Gu
Dr. Xiaopeng Gong
Prof. Dr. Yidong Lou
Prof. Dr. Chuang Shi
Guest Editors

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Keywords

multi-GNSS PPP
multi-frequency PPP
PPP with ambiguity resolution
PPP with atmosphere augmentation
PPP based on BDS-3 B2b, Galileo HAS and QZSS CLAS
PPP applications in navigation and timing
PPP convergence
PPP in urban environment

Published Papers (10 papers)

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22 pages, 11960 KiB

Open AccessArticle

Analysis of Regional Satellite Clock Bias Characteristics Based on BeiDou System

by Wenxuan Liu, Hu Wang, Hongyang Ma, Yingyan Cheng, Pengyuan Li, Bo Li and Yingying Ren

Remote Sens. 2022, 14(23), 6047; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14236047 - 29 Nov 2022

Viewed by 1286

Abstract

With the continuous development of the Global Navigation Satellite System (GNSS), the calculation theory and strategy of the global Satellite Clock Bias (SCB) tends to be mature. However, in some eventualities with restricted conditions, the calculation and application of the global SCB are limited; hence, the application of regional SCB is derived. This paper focuses on the quality of regional SCB products in different regions, calculates three groups of regional SCB products, and analyzes their properties and application effects. We expand the double-differenced assessment method for SCB and extend satellite clock accuracy assessment to regional satellite clock products. Additionally, the Regional Effect Bias (REB) is introduced to analyze the influence of the relative position of satellite geometry on the SCB products due to the regional effects. The conclusions are as follows: (1) In low-latitude regions, SCB products have a high degree of completeness and a large number of satellite observations, which is conducive to expanding the positioning application range of regional SCB; (2) the low-latitude regions SCB will be affected by ionospheric activity, and the accuracy will be slightly lower than that of satellite clocks deviation in mid-latitudes; (3) in this paper, the REB in this area is in the level of 10⁻⁷. The experiment displays the result that the values of REB in low-latitude areas are larger, leading to fluctuated Precise Point Position (PPP) results. However, there are fewer stations in the mid-latitude regions, which will also affect the accuracy of PPP; (4) the accuracy of the positioning results of the regional satellite clock deviation in the Chinese region is higher than that of the global clock. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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17 pages, 3676 KiB

Open AccessArticle

Evaluation of Real-time Precise Point Positioning with Ambiguity Resolution Based on Multi-GNSS OSB Products from CNES

by Shi Du, Bao Shu, Wei Xie, Guanwen Huang, Yulong Ge and Pan Li

Remote Sens. 2022, 14(19), 4970; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14194970 - 6 Oct 2022

Cited by 7 | Viewed by 2051

Abstract

Ambiguity resolution (AR) is a core technology that helps to speed up convergence time and increase positioning accuracy for precise point positioning (PPP), and the performance of PPP-AR is based on the quality of ambiguity resolution products. Real-time PPP-AR becomes a reality as users can now obtain publicly accessible real-time observable-specific signal bias (OSB) products from the Centre National d’Etudes Spatiales (CNES). Therefore, an analysis of the quality of OSB products and an evaluation of the performance of PPP-AR are required to promote the application of real-time positioning. For a total of 31 days between day of year (DOY) 121 and 151 in 2021, observation data were collected from 90 stations, and the OSB products were used to assess the experiments. As for the quality of the OSB products, the data availability (DA) of the GPS and Galileo satellites was greater than 97%, whereas that of BDS was less than 60%; the maximum fluctuation value (MAX) and standard deviation (STD) of the GPS, Galileo, and BDS satellites were 0.045 and 0.012; 0.081 and 0.028; and 0.292 and 0.085 cycles, respectively. In terms of ambiguity residuals using the OSB products, the wide-lane (WL) residual percentages within ±0.25 cycles for the GPS, Galileo, BDS-2, and BDS-3 systems were more than 92%, and the narrow-lane (NL) residual percentages within ±0.25 cycles for the four systems were 92%, 89%, 79%, and 60%, respectively. With regard to the performance of PPP-AR, the GPS+Galileo solution showed the best performance in the kinematic positioning mode, in which the mean root mean square (RMS) of positioning accuracy was 1.06, 1.27, and 2.85 cm for the east (E), north (N), and up (U) components, respectively, and the mean convergence time reached 9.6 min. In the static positioning mode, the mean convergence times of the GPS-only and GPS+Galileo solutions were 11.4 min and 8.0 min, respectively, and both of their mean RMS for positioning accuracy reached 0.79, 0.95, and 1.48 cm for the E, N, and U components, respectively. However, the addition of BDS did not further enhance the performance of multi-GNSS PPP-AR in either the kinematic or static positioning mode due to the poor quality of the real-time BDS products. More importantly, a prediction method was proposed to avoid re-convergence and to enhance the reliability of PPP-AR in the event of short-time missing real-time OSB products and to improve the positioning accuracy and the ambiguity fixed rate. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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21 pages, 8959 KiB

Open AccessArticle

Analyses of GLONASS and GPS+GLONASS Precise Positioning Performance in Different Latitude Regions

by Yanli Zheng, Fu Zheng, Cheng Yang, Guigen Nie and Shuhui Li

Remote Sens. 2022, 14(18), 4640; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14184640 - 16 Sep 2022

Cited by 4 | Viewed by 2887

Abstract

The orbital inclination angle of the GLONASS constellation is about 10° larger than that of GPS, Galileo, and BDS. Theoretically, the higher orbital inclination angle could provide better observation geometry in high latitude regions. A wealth of research has investigated the positioning accuracy of GLONASS and its impact on multi-GNSS, but rarely considered the contribution of the GLONASS constellation’s large orbit inclination angle. The performance of GLONASS in different latitude regions is evaluated in both stand-alone mode and integration with GPS in this paper. The performance of GPS is also presented for comparison. Three international GNSS service (IGS) networks located in high, middle, and low latitudes are selected for the current study. Multi-GNSS data between January 2021 and June 2021 are used for the assessment. The data quality check shows that the GLONASS data integrity is significantly lower than that of GPS. The constellation visibility analysis indicates that GLONASS has a much better elevation distribution than GPS in high latitude regions. Both daily double-difference network solutions and daily static Precise Point Positioning (PPP) solutions are evaluated. The statistical analysis of coordinate estimates indicates that, in high latitude regions, GLONASS has a comparable or even better accuracy than that of GPS, and GPS+GLONASS presents the best estimate accuracy; in middle latitude regions, GPS stand-alone constellation provides the best positioning accuracy; in low latitude regions, GLONASS offers the worst accuracy, but the positioning accuracy of GPS+GLONASS is better than that of GPS. The tropospheric estimates of GLONASS do not present a resemblance regional advantage as coordinate estimates, which is worse than that of GPS in all three networks. The PPP processing with combined GPS and GLONASS observations reduces the convergence time and improves the accuracy of tropospheric estimates in all three networks. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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19 pages, 6458 KiB

Open AccessArticle

Assessment of Real-Time GPS/BDS-2/BDS-3 Single-Frequency PPP and INS Tight Integration Using Different RTS Products

by Jie Lv, Zhouzheng Gao, Qiaozhuang Xu, Ruohua Lan, Cheng Yang and Junhuan Peng

Remote Sens. 2022, 14(17), 4367; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14174367 - 2 Sep 2022

Cited by 3 | Viewed by 1350

Abstract

Due to the virtues of low-cost and high positioning accuracy, Single-Frequency Precise Point Positioning (SF-PPP) is becoming a prospective technique. However, SF-PPP is not as widely used as dual-frequency and triple-frequency PPP at present, owing to the effect of ionospheric delay residuals after model rectification. In recent years, with the evolution of multi-constellation Global Navigation Satellite Systems (multi-GNSS, i.e., GPS, BDS-2, and BDS-3), it has become possible to obtain credible and continuous positioning results using SF-PPP. However, such performance would be significantly degraded in challenging environments (i.e., boulevards, tunnels, and tall buildings). Under these circumstances, GNSS signals are obstructed, and it is difficult to provide sufficient observations for SF-PPP. Therefore, the Inertial Navigation System (INS) is employed to promote the positioning performance of SF-PPP. The PPP/INS integration is regarded as one of the most efficient approaches in GNSS-denied environments. To satisfy the request of supplying real-time positioning information, the Real-Time Services (RTS) of the International GNSS Service (IGS) provide real-time precise orbit and clock products for globally distributed users through the internet. In this paper, a real-time GPS/BDS-2/BDS-3 SF-PPP and INS tight integration model is proposed, and it is assessed using the data gathered by vehicle and real-time products afforded by CAS (Chinese Academy of Sciences), GFZ (Deutsche GeoForschungsZentrum), and WHU (Wuhan University). The outcomes illustrate the following: (1) GPS + BDS SF-PPP/INS can provide more accurate and continuous positioning solutions compared with those of GPS + BDS SF-PPP, with improvements of 52.8%, 31.1%, and 42.8% in the north, east, and vertical components, respectively. (2) In general, the orbit and clock products’ accuracies in terms of GPS afforded by the three analysis centers are consistent with each other. For BDS, the orbit product from WHU is more accurate compared to those of CAS and GFZ. However, the accuracy of the clock product afforded by WHU is lower compared with those provided by the other two centers, especially for BDS-2 satellites. (3) The positioning accuracy in terms of Root Mean Square (RMS) values based on GFZ products are much higher than the results based on CAS and WHU products in the three directions. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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22 pages, 6256 KiB

Open AccessArticle

Integration of Multi-GNSS PPP-RTK/INS/Vision with a Cascading Kalman Filter for Vehicle Navigation in Urban Areas

by Shengfeng Gu, Chunqi Dai, Feiyu Mao and Wentao Fang

Remote Sens. 2022, 14(17), 4337; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14174337 - 1 Sep 2022

Cited by 12 | Viewed by 2132

Abstract

Precise point positioning (PPP) has received much attention in recent years for its low cost, high accuracy, and global coverage. Nowadays, PPP with ambiguity resolution and atmospheric augmentation is widely regarded as PPP-RTK (real-time kinematic), which weakens the influence of the long convergence time in PPP and regional service coverage in RTK. However, PPP-RTK cannot work well in urban areas due to limitations of non-line-of-sight (NLOS) conditions. Inertial navigation systems (INS) and vision can realize continuous navigation but suffer from error accumulation. Accordingly, the integration model of multi-GNSS (global navigation satellite system) and PPP-RTK/INS/vision with a cascading Kalman filter and dynamic object removal model was proposed to improve the performance of vehicle navigation in urban areas. Two vehicular tests denoted T01 and T02 were conducted in urban areas to evaluate the navigation performance of the proposed model. T01 was conducted in a relatively open-sky environment and T02 was collected in a GNSS-challenged environment with many obstacles blocking the GNSS signals. The positioning results show that the dynamic object removal model can work well in T02. The results indicate that multi-GNSS PPP-RTK/INS/vision with a cascading Kalman filter can achieve a positioning accuracy of 0.08 m and 0.09 m for T01 in the horizontal and vertical directions and 0.83 m and 0.91 m for T02 in the horizontal and vertical directions, respectively. The accuracy of the velocity and attitude estimations is greatly improved by the introduction of vision. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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14 pages, 3501 KiB

Open AccessArticle

GPS, BDS-3, and Galileo Inter-Frequency Clock Bias Deviation Time-Varying Characteristics and Positioning Performance Analysis

by Yibiao Chen, Jinzhong Mi, Shouzhou Gu, Bo Li, Hongchao Li, Lijun Yang and Yuqi Pang

Remote Sens. 2022, 14(16), 3991; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14163991 - 16 Aug 2022

Cited by 5 | Viewed by 1592

Abstract

Multi-frequency observations are now available from GNSSs, thereby bringing new opportunities for precise point positioning (PPP). However, they also introduce new challenges, such as inter-frequency clock bias (IFCB) between the new frequencies and the original dual-frequency observations due to triple-frequency observations, which severely impact the PPP. In this paper, we studied the estimation and correction methods of uncombined inter-frequency clock bias of GPS, BDS-3, and Galileo, analyzed the time-varying characteristics and short-term stability of IFCB, and analyzed the influence of IFCB on the positioning of the GPS, BDS-3, and Galileo, based on a triple-frequency un-differential non-combined PPP model. The obtained results show that the amplitude of Block IIF satellites of the GPS can reach up to 10–20 cm, and the IFCB in BDS-3, Galileo, and GPS Block III satellites can be neglected. After correction by IFCB, the 3D positioning accuracy of the GPS triple-frequency PPP was 1.73 cm and 4.75 cm in the static and kinematic modes, respectively, while the convergence time was 21.64 min and 39.61 min. Compared with the triple-frequency GPS PPP without any correction with IFCB, the static and kinematic 3D positioning accuracy in this work was improved by 27.39% and 17.34%, and the corresponding convergence time was improved by 10.55% and 15.22%, respectively. Furthermore, the delayed IFCB was also used for positioning processing, and it was found that a positioning performance comparable to that of the same day can be obtained. The standard deviation of IFCB for a single satellite was found to be no more than 1 cm, when the IFCB value of a neighboring day was subtracted from the IFCB value of same day, which proves the short-term stability of IFCB. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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18 pages, 3134 KiB

Open AccessArticle

Satellite Clock Batch Estimation Accuracy Analysis and Its Impacts on PPP

by Menghao Li, Weiquan Huang, Hui Li, Renlong Wang and Peng Cui

Remote Sens. 2022, 14(16), 3932; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14163932 - 13 Aug 2022

Cited by 2 | Viewed by 1210

Abstract

The ultra-rapid satellite clock product based on the satellite clock batch estimation is commonly used for high-precision and reliable precise point positioning (PPP) services. In order to clarify the effect of different ranging errors on the satellite clock batch estimation accuracy, the source of the satellite clock bias induced by the batch observation model is classified into the initial clock bias (ICB) and time-dependent bias (TDB). In addition to the effect of the ICB and TDB, the analytic relationship between the observation redundancy and the satellite clock batch estimation accuracy are derived and verified. The suitable number of stations is suggested to be 40 for the satellite clock batch estimation to achieve the counterbalance between the efficiency and saturable accuracy. For the PPP based on the batch-estimated satellite clock, the impacts of the ICB and TDB on PPP are clarified. The satellite clock batch estimation and PPP experiments are carried out to investigate the impacts of the ICB and TDB on the satellite clock batch estimation accuracy and the PPP performance. The ICB causes a significant bias for the batch-estimated satellite clock. The TDB is impacted by the assimilation ability of the batch-estimated satellite clock to the satellite orbit error. The convergence time and the positioning accuracy after the convergence of PPP are primarily affected by the ICB and TDB, respectively. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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17 pages, 3408 KiB

Open AccessArticle

Performance of Multi-GNSS in the Asia-Pacific Region: Signal Quality, Broadcast Ephemeris and Precise Point Positioning (PPP)

by Mengyuan Li, Guanwen Huang, Le Wang, Wei Xie and Fan Yue

Remote Sens. 2022, 14(13), 3028; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14133028 - 24 Jun 2022

Cited by 5 | Viewed by 2066

Abstract

Since BeiDou Navigation Satellite System (BDS) and Japan’s Quasi-Zenith Satellite System (QZSS) have more visible satellites in the Asia-Pacific region, and navigation satellites of Global Positioning System (GPS), Galileo satellite navigation system (Galileo), and GLONASS satellite navigation system (GLONASS) are uniformly distributed globally, the service level of multi-mode Global Navigation Satellite System (GNSS) in the Asia-Pacific region should represent the best service capability. Based on the observation data of 10 Multi-GNSS Experiment (MGEX) stations, broadcast ephemeris and precision ephemeris from 13 to 19 October 2021, this paper comprehensively evaluated the service capability of multi-GNSS in the Asia-Pacific region from three aspects of observation data quality, broadcast ephemeris performance, and precision positioning level. The results show that: (1) the carrier-to-noise-density ratio (C/N0) quality of the GPS and Galileo is the best, followed by BDS and GLONASS, and QZSS is the worst. GPS, BDS-2, GLONASS, and QZSS pseudorange multipath values range from 0 to 0.6 m, while Galileo system and BDS-3 pseudorange multipath values range from 0 to 0.8 m. (2) In terms of broadcast ephemeris accuracy, BDS-3 broadcast ephemeris has the best orbit, and the three-dimensional (3D) Root Mean Square (RMS) is 0.21 m; BDS-2 was the worst, with a 3D RMS of 1.99 m. The broadcast ephemeris orbits of GPS, Galileo, QZSS, and GLONASS have 3D RMS of 0.60 m, 0.62 m, 0.83 m, and 1.27 m, respectively. For broadcast ephemeris clock offset: Galileo has the best performance, 0.61 ns, GLONASS is the worst, standard deviation (STD) is 3.10 ns, GPS, QZSS, BDS-3 and BDS-2 are 0.65 ns, 0.75 ns, and 1.72 ns, respectively. For signal-in-space ranging errors (SISRE), the SISRE results of GPS and Galileo systems are the best, fluctuating in the range of 0 m–2 m, followed by QZSS, BDS-3, Galileo, and BDS-2. (3) GPS, BDS, GLONASS, Galileo, GPS/QZSS, and BDS/QZSS were used for positioning experiments. In static PPP, the convergence time and positioning accuracy of GPS show the best performance. The positioning accuracy of GPS/QZSS and BDS/QZSS is improved compared with that of GPS and BDS. In terms of kinematic PPP, the convergence time and positioning accuracy of GPS/QZSS and BDS/QZSS are improved compared with that of GPS and BDS. In addition to GLONASS and Galileo systems, the other combinations outperformed 3 cm, 3 cm, and 5 cm in the east, north, and up directions. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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16 pages, 5987 KiB

Open AccessArticle

Performance Assessment of BDS-3 PPP-B2b/INS Loosely Coupled Integration

by Xiaofei Xu, Zhixi Nie, Zhenjie Wang, Boyang Wang and Qinghuai Du

Remote Sens. 2022, 14(13), 2957; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14132957 - 21 Jun 2022

Cited by 11 | Viewed by 1822

Abstract

The BeiDou global navigation satellite system (BDS-3) has been officially providing a real-time precise point positioning (PPP) augmentation service, known as the PPP-B2b service, since 2020. Decimeter-level positioning accuracy is expected to be achieved based on the PPP-B2b service. It shows great potential for global navigation satellite system (GNSS) real-time applications, including, for example, vehicle positioning on land. However, the application of the PPP-B2b service is still full of challenges in the urban environment because of GNSS signal blockage. The inertial navigation system (INS) is a popular technology which can provide continuous positions under GNSS challenging scenarios. In this study, we constructed a BDS-3 PPP-B2b/INS loosely coupled integration system for vehicle positioning and evaluated its performance through two automotive experiments. In the first experiment, four periods of 30 s GNSS outages were simulated to evaluate the performance of PPP-B2b/INS loosely coupled integration during GNSS outages. During the simulated GNSS outages, PPP-B2b positioning did not work. Nevertheless, PPP-B2b/INS loosely coupled integration provided continues solution through INS mechanization. The averaged positioning errors at the last epoch of outages were 300.6/498.0/41.0 cm for PPP-B2b/MEMS-IMU and 18.6/21.8/6.1 cm for PPP-B2b/Tactical-IMU loosely coupled integration, in the east, north and up directions, respectively. In the second experiment, we drove the land vehicle in a complex urban environment for 15 min. During this period, two GNSS signal interruptions occurred due to the occlusion of bridges, lasting 15 s and 5 s, respectively. The results show that the improvement of positioning accuracy in the east, north, and up components were 64.1%, 77.8%, and 73.8% respectively for PPP-B2b/MEMS-IMU loosely coupled integration, and 63.9%, 79.5%, and 74.4% respectively for PPP-B2b/Tactical-IMU loosely coupled integration, as compared to the positioning accuracy of PPP-B2b only. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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Open AccessTechnical Note

Preliminary Analysis of Intersystem Biases in BDS-2/BDS-3 Precise Time and Frequency Transfer

by Pengfei Zhang, Rui Tu, Linlin Tao, Bing Wang, Yuping Gao and Xiaochun Lu

Remote Sens. 2022, 14(18), 4594; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14184594 - 14 Sep 2022

Cited by 2 | Viewed by 1172

Abstract

The Chinese BeiDou global satellite system (BDS-3) and regional system (BDS-2) are predicted to coexist over the next decade. Intersystem biases (ISBs) in BDS-2/BDS-3 play a key role in maintaining the consistency and continuity from the BDS-2 to BDS-3 time transfer. Here, we discuss the temporal characteristics, parameter composition, generation mechanism, and the effect of ISBs in BDS-2/BDS-3 on time and frequency transfer. The satellite orbits and clock products from three international GNSS service analysis centers, namely Wuhan University (WUM, China), GeoForschungsZentrum Potsdam (GFZ, Germany), and the Center for Orbit Determination in Europe (CODE), were employed to investigate the time-transfer stability of ISBs when BDS-2 and BDS-3 were used in combination. We analyzed the intrinsic characteristics of ISBs, the receiver types, antennas, and frequency standards. Our first results showed that ISBs are stable for different analysis center products, although the mean values of daily results differed markedly for the three analysis centers. With respect to the relationship between station attribution and ISB difference for a time link, the receiver type, antenna, and frequency standard influence the ISB differences in time and frequency transfer. The effect of three ISB stochastic models was evaluated with respect to time and frequency transfer. The “walk” and “constant” schemes were slightly superior to “noise”, with the improvement in their frequency stability being approximately 5% compared with that of “noise”. Full article

(This article belongs to the Special Issue Precise Point Positioning with GPS, GLONASS, BeiDou, and Galileo)

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