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Journal of Global Positioning Systems Vol. 21, No. 1, 2025 |
Cover |
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Journal of Global Positioning Systems
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JGPS Team Structure, Copyright and Table of Contents |
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JGPS Team Structure, Copyright
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Letter from the Guest Editor |
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Dr. Junping Chen
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1. In-orbit phase center corrections calibration for BDS-3 satellite B1C/B2a signals in the IGS20 frame |
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Bingchen Fu, Jianghui Geng
Addressing the inaccuracies in the ground-calibrated phase center offsets (PCOs) provided by the China Satellite Navigation Office (CSNO) for BeiDou-3 (BDS-3) satellites and the absence of phase center variations (PCVs), this study performs in-orbit calibration of the B1C/B2a antenna phase centers for BDS-3 MEO and IGSO satellites under the IGS20 frame. Using ionosphere-free combination observations from 155 global IGS/MGEX stations spanning 2021 to 2024, we demonstrate high consistency in PCV estimates for satellites of the same type, with most nadir-angle PCV differences below 1 mm and an overall standard deviation of approximately 0.3 mm. Horizontal PCO estimates align with igs20.atx values at the centimeter level. After aligning the Z-PCO estimates with the IGS20 frame, the mean differences with respect to the igs20.atx values are -9.5 cm for MEO satellites and 40 cm for IGSO satellites. Compared to the igs20.atx model, the phase center correction (PCC) model derived in this study improves the orbit overlap accuracy for BDS-3 MEO satellites by 0.43% to 7.03%. Furthermore, using the estimated B1C/B2a PCC model, the mean scale factor difference for BDS-3 solutions relative to the IGS20 frame is 0.16 ppb, confirming successful alignment with IGS20. The BDS-3 PCC results have been submitted to the International GNSS Service (IGS) through the Chinese Academy of Sciences (CAS) Analysis Center, contributing to integrated analysis and promoting the high-precision international application of the BeiDou Navigation Satellite System.
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2. Demystifying spatiotemporal relationship between GNSS-derived precipitable water vapor and ENSO index and its applications on floods and droughts |
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Yumeng Hao, Kefei Zhang
The El Niño-Southern Oscillation (ENSO) is a complex ocean-atmosphere interaction phenomenon that drives extreme weather events globally, with water vapor playing a crucial role in its evolution. Recently, Global Navigation Satellite
Systems (GNSSs) have emerged as an effective tool for retrieving water vapor with high accuracy, high spatial and temporal resolution, and all-weather capability. However, GNSS-derived precipitable water vapor (PWV) has not been well researched for its potential in the study of ENSO, particularly regarding their lead-lag relationships. This study investigates the spatiotemporal response relationship between PWV variations and the Oceanic Niño Index (ONI) using 12 years of coastal GNSS-derived PWVdata. Multichannel singular spectrum analysis (MSSA) was employed to extract nonlinear trends of PWV anomalies, followed by Pearson correlation and
lead-lag correlation analyses with ONI. The results reveal a moderate negative correlation in the western Pacific and positive correlations in the eastern Pacific and western Indian Ocean. Notably, stations closer to
the Niño 3.4 region exhibited stronger correlations. Moreover, more than half of the stations showed absolute correlation coefficients exceeding 0.4 at optimal lag times, indicating that ENSO exerts a lagged influence on PWV at most stations. A case study at the COCO station near Indonesia (2015-2017) demonstrated that PWV and precipitation anomalies lagged ONI by approximately 8 months, consistent with the severe drought in 2015 and flooding in 2016. These findings suggest that
GNSS-derived PWV serves as a valuable indicator for monitoring ENSO dynamics and could enhance early warning systems for ENSO-related drought and flood risks.
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3. Analysis of GPS Network Inversion Filtering Algorithms for Fault Slip |
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Zhengdong Luo, Tieding Lu, Qianru Chen, Xiwen Sun and Weijian Hu
Our study employs GPS coordinate time series and the NIF method to invert postseismic deformation, investigate the spatiotemporal evolution of fault slip, and evaluate the inversion efficiency of the NIF method under various parameter settings, thereby providing prior information for future research on earthquakes and fault slip. Taking the GPS coordinate time series from the Tokai region of Japan during 2009-2021 as an example, we conducted an analysis using the NIF method. The results indicate that the fault slip following the 2011 earthquake was primarily concentrated in the northeastern part of Tokai region (34.8°N-35.8°N, 137.2°E-138.4°E), with a maximum cumulative slip of 9.31 cm at depths ranging from 20 to 60 km. In terms of model parameter analysis, the inversion time and memory cost increase with the number of sub-faults, while the maximum cumulative slip approaches a stable value. Variations in the proportion of local benchmark motion proportion parameter do not affect the inversion time or memory cost but are negatively correlated with the maximum cumulative slip. The time scale of the GPS coordinate time series has no significant impact on the NIF inversion. In contrast, higher time resolution of the GPS coordinate time series results in longer inversion times and greater memory cost, with the maximum cumulative slip gradually stabilizing.
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4. Enhanced Low-Cost GNSS RTK Positioning with an Adaptive Threshold |
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Yalong Wang, Yuting Gao, Qingzhi Zhao, Shurong Xue, Bopeng Sun and Feng Zhou
Fault detection and identification algorithm is essential to ensure the reliability of global navigation satellite systems (GNSS) systems for high-precision intelligent applications. Low-cost receivers always suffers from GNSS pseudorange gross-error detection and carrier-phase cycle-slip anomaly in complex environments, which would degrade positioning accuracy. To address these issues, this paper proposes an enhanced low-cost RTK precise-positioning algorithm with an adaptive strategy, designed to detect multiple pseudorange gross errors and carrier-phase cycle slips. By leveraging time differenced darrier phase (TDCP) observations, the proposed method dynamically adjusts detection thresholds in real time, thereby minoring multiple faults and improving positining accuracy. To evaluate the performance of the proposed algorithm, a dynamic vehicle experiment equipped with ublox and BeiYun low-cost GNSS devices was conducted. Four schemes including GL, GLF, GLFTC, and GLFTA methods are compared. Results show that the 3D RMS positioning errors of the proposed GLFTA method achieves maximum 19.34% improvement. That is because the proposed GLFTA method incorporating an adaptive strategy can detect small carrier phase cycle slips than the GL, GLF, and GLFTC methods, thereby enhancing RTK positioning performance in complex environments.
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5. Optimizing window and component selection in SSA for GNSS coordinate time series offset detection |
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Zhiwei Yang, Guangyu Xu, Aiping Zhao and Xiaowei Xie
Addressing the challenge of extracting coseismic offset signals from GNSS coordinate time series using earthquake catalog information, this study introduces a method based on optimized window and component selection in Singular Spectrum Analysis (SSA). The proposed approach automatically selects relevant components for time series reconstruction according to the magnitude of eigenvalues and the contribution rate of each component, without relying on prior information or assumptions. This effectively overcomes the limitations associated with arbitrary decomposition and reconstruction of time series in conventional SSA. By subtracting the reconstructed series from the original data, a residual time series is obtained, from which reliable offset signals can be extracted as comprehensively as possible. Through simulation tests and an application to the March 9, 2011, Mw7.3 earthquake event in Japan, comparative experiments were conducted to evaluate different window lengths and varying numbers of reconstructed components. The results indicate that a window length of 365 days, combined with the selection of principal components whose cumulative contribution rate exceeds 95%, constitutes the most suitable strategy for detecting offset signals in GNSS residual time series.
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6. Statistical Analysis of Ionospheric Scintillation in Low-Latitude Regions |
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Lingqiao Zeng, Xiaomin Luo, Biyan Chen, Wei Xiang, Ankang Xie, Jing Wang and Kamarul Hawari Bin Ghazali
With the arrival of the maximum phase of Solar Cycle 25, ionospheric scintillation phenomena have become increasingly frequent, which severely impacts the capabilities of GNSS positioning, navigation, and timing services. This study collected 30-second sampling rate data from 6 GNSS stations in low-latitude regions of Asia, Oceania, the Pacific, Africa, and South America spanning the period 2014-2024. Using S4c as the criterion for identifying low-latitude amplitude ionospheric scintillation, the statistical characteristics of ionospheric scintillation in various regions were analyzed. The results demonstrated a significant positive correlation between the occurrence of ionospheric scintillation in various regions and solar activity. During solar maximum years, ionospheric scintillations at the KOUG station mainly occurred in winter, spring, and autumn, while those at the other stations are predominantly observed in spring and autumn annually. Scintillation at all stations predominantly takes place between 8:00 p.m. and 2:00 a.m. local time. In low solar activity years, both the frequency and duration of ionospheric scintillation at each station decrease significantly. With the exception of the KOUG station, where scintillation remained severe, the other stations show no obvious seasonal or local time patterns. The directional distribution of ionospheric scintillation exhibits a distinct relationship with the latitude of the stations. Furthermore, the study indicates that due to the distinct meridional distribution characteristics and latitude-dependent variations of equatorial plasma bubbles, the scintillation intensity at different locations during high solar activity years follows the order from strongest to weakest: South America (near the Atlantic Ocean), Africa, the Pacific region adjacent to South America, Asia, and Oceania.
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ABSTRACTS OF PHD DISSERTATIONS |
1. High-accuracy Smartphone RTK Positioning: Major Challenges and Innovative Solutions |
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Yang Jiang
The integration of high-accuracy navigation into smartphones has immense potential for enabling transformative applications in industries such as autonomous driving, pedestrian navigation, and augmented reality. However, achieving centimeterlevel Real-Time Kinematic (RTK) positioning with smartphones faces challenges stemming from hardware limitations, noisy GNSS measurements, and GNSS-challenging environments. This thesis proposes innovative methodologies to overcome these barriers and enhance smartphone RTK positioning accuracy and reliability.
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2. Precise Smartphone Positioning Based on PPP-RTK Techniques |
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Yan Zhang
The proliferation of smartphones in recent decades has driven advancements in technology for navigation applications. The traditional positioning methods to enable precise positioning service are precise point positioning (PPP) and real-time kinematic (RTK) techniques. But without precise corrections to the atmospheric effects, PPP has long convergence time and RTK requires high-rate data. It has been extensively demonstrated that PPP-RTK technology can realize fast or even instant ambiguity resolution for users with precise atmosphere information from the reference station. Previous approaches, such as Continuously Operating Reference Stations (CORS), are characterized by high installation and maintenance costs. This thesis therefore focuses on this issue and evaluating smartphone precise positioning using PPP-RTK techniques.
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3. Research on Key Technologies and Applications of GNSS-R Sea Surface Altimetry and Eddy Detection |
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Jin Xing
The global detection of ocean eddies is typically conducted using satellite remote sensing of sea surface height data, combined with eddy kinetic energy fields and flow fields to identify eddy centers and radii, which is crucial for climate monitoring and resource development. Ocean eddies, as circulation structures with dynamic effects, have evolution and dissipation processes that are closely related to variations in sea surface height. Global Navigation Satellite System-Reflectometry (GNSS-R), with its advantages of short revisit periods and extensive coverage, has increasingly become an efficient method for measuring sea surface height. However, factors such as sea state and satellite orbit introduce challenges in achieving precise sea surface height measurements, while the indistinct boundaries of oceanic eddies further complicate accurate eddy contour identification. To address these challenges, this thesis proposes a GNSS-R-based sea surface height measurement method. First, the along-track sea surface height for each reflection event is obtained. Then, the along-track data is processed through gridding to generate a daily mean sea surface height map. Finally, eddy height features are utilized to extract ocean eddy information from this map. This study utilized GNSS-R altimetry results to detect eddies and validated the effectiveness of the proposed method based on spaceborne measured data and simulated Asymmetric Constant Envelope Binary Offset Carrier (ACE-BOC) high-bandwidth signals, providing crucial support for global ecological and environmental protection.
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4. Ground and Marine Resilient Integration Technology of Multi-Source Sensors for Navigation and Positioning |
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Mowen Li
Integration of multi-source sensor is the main development direction of modern technology to meet the growing demand for the high-accuracy, high-reliability and high-stability Positioning, Navigation and Timing (PNT) information in multiple scenes. With the establishment of Global Navigation Satellite System (GNSS), the benchmark of spatial-temporal information service has been guaranteed, which further promotes the research on the resilient integration technology for multi-source PNT sensors. In the PNT information service, GNSS can provide users with a unified spatio-temporal datum and full-time, accurate navigation and positioning information, but it is easy to be obstructed and interfered by the surroundings or equipment. Thanks to the good independence and anti-interference ability, Inertial Navigation System (INS) has the ability to navigate without external information, but it needs external information to calibrate and suppress error accumulation from time to time. Long Baseline sonar (LBL) system fills the blank of underwater PNT services for GNSS, but its positioning accuracy and stability, especially for the elevation, is limited by the observation geometry. The Conductivity/Temperature/Depth profile (CTD) can.provide additional elevation information for LBL positioning, and salinity to determine the overwater and underwater scene of the rover. The resilient integration of multi-source sensor can address the limitations and dependencies of the single sensor on the application scenes, and achieve the cooperative work and complementarity among each sensor. This capacity will provide users with continuous, stable and reliable PNT information.
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5. Theory and methods of testing and integrity monitoring for multiple gross errors |
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Yangkang Yu
In the fields of mathematical statistics, geodetic surveying, and satellite navigation, the handling of outliers has always been a crucial aspect in ensuring the accuracy of models and the reliability of systems. An outlier is defined as an observation that significantly differs from other observations in terms of scale, frequency, or generation mechanism. Outliers typically have a significant impact on parameter estimation results based on the least squares method, leading to biased parameter estimates, inaccurate confidence intervals, and reduced model prediction capabilities. Consequently, this directly affects the precision and reliability of coordinate calculations, deformation monitoring, and frame maintenance in practical applications, and even poses a threat to the integrity and safety of systems in fields such as aerospace, transportation, and disaster monitoring. For measurement data, outliers are mainly caused by gross errors. Therefore, the key to addressing outlier issues in measurement data lies in in-depth research and effective management of gross errors.
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6. Research on Key Issues of Refining GNSS-based Terrestrial Reference Frame |
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Ruyuan Wang
Space geodetic techniques play a crucial role in constructing and maintaining modern reference frames, with the Global Navigation Satellite System (GNSS) providing essential data through high-precision coordinate time series. Advances in GNSS technology have significantly enhanced observational precision and spatiotemporal resolution, enabling the precision and stability improvement of the GNSS-based terrestrial reference frame. This study focuses on refining the reference frame based on GNSS data and introduces three key methods for its maintenance and densification: common-mode error (CME) filtering, long-term Precise Point Positioning with Ambiguity Resolution (PPP-AR), and the integration of Low Earth orbit (LEO) satellites with GNSS for PPP-based long-term coordinate solutions.
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Back Cover |
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Journal of Global Positioning Systems
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