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GNSS Data Processing and Navigation
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GNSS Data Processing and Navigation

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Remote Sensors".

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 49169

Special Issue Editors

Dr. Adrià Rovira-Garcia

E-Mail Website
Guest Editor
Research Group of Astronomy and Geomatics (gAGE), Department Mathematics, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Interests: high-accuracy navigation; ionospheric modeling; multi-constellation and multi-frequency GNSS; fast precise point positioning (Fast-PPP)
Dr. José Miguel Juan Zornoza

E-Mail Website
Guest Editor
Research Group of Astronomy and Geomatics (gAGE), Department Physics, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Interests: wide area real time kinematics (WARTK); precise point positioning (PPP); ionospheric modelling; scintillation; space weather; radio occultations

Special Issue Information

Dear Colleagues,

The number of devices equipped with Global Navigation Satellite Systems (GNSS) is expected to grow to 8 billion by 2020. This is related to the increasing number of GNSS satellite constellations. Two constellations have already declared their full operational capability. Namely, the Global Positioning System (GPS; U.S. Air Force), completed in 1994; the Global Navigation Satellite System (GLONASS; Russian Federal Space Agency) completed in 1995 (and restored in 2011). Two additional constellations are being completed—the BeiDou Navigation Satellite System (BDS; China National Space Administration) and the Galileo (European Commission).

Together, these four GNSSs account for more than 100 satellites. This fact constitutes an unprecedented frame to improve radio-navigation and atmospheric-sounding techniques, in which the processing of GNSS data is of the utmost importance. This Special Issue targets the study of all of the aspects that can improve satellite-based navigation, with a focus on real-time and on exploiting the multi-constellation paradigm.

Dr. Adrià Rovira-Garcia
Dr. José Miguel Juan Zornoza
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Real-time precise point positioning (PPP)
  • Real-time kinematic (RTK)
  • Integer ambiguity resolution (IAR) user strategies and products
  • Algorithms for cycle-slip detection and correction in real-time
  • Satellite clock stability
  • Multi-GNSS satellite orbit and clock determination in real-time
  • Atmospheric modelling for high-precision navigation

Published Papers (15 papers)

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Editorial

Jump to: Research

3 pages, 179 KiB  
Editorial
Special Issue on GNSS Data Processing and Navigation
by Adria Rovira-Garcia and José Miguel Juan Zornoza
Sensors 2020, 20(15), 4119; https://0-doi-org.brum.beds.ac.uk/10.3390/s20154119 - 24 Jul 2020
Viewed by 1426
Abstract
Global Navigation Satellite System (GNSS) data can be used in a myriad of ways. The current number of applications exceed by far those originally GNSS was designed for. As an example, the present Special Issue on GNSS Data Processing and Navigation compiles 14 [...] Read more.
Global Navigation Satellite System (GNSS) data can be used in a myriad of ways. The current number of applications exceed by far those originally GNSS was designed for. As an example, the present Special Issue on GNSS Data Processing and Navigation compiles 14 international contributions covering several aspects of GNSS research. This Editorial summarizes the whole special issue grouping the contributions under four different, but related topics. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)

Research

Jump to: Editorial

14 pages, 2752 KiB  
Article
A Fine-Tuned Positioning Algorithm for Space-Borne GNSS Timing Receivers
by Xi Chen, QiHui Wei, YaFeng Zhan and TianYi Ma
Sensors 2020, 20(8), 2327; https://0-doi-org.brum.beds.ac.uk/10.3390/s20082327 - 19 Apr 2020
Cited by 2 | Viewed by 2156
Abstract
To maximize the usage of limited transmission power and wireless spectrum, more communication satellites are adopting precise space–ground beam-forming, which poses a rigorous positioning and timing requirement of the satellite. To fulfill this requirement, a space-borne global navigation satellite system (GNSS) timing receiver [...] Read more.
To maximize the usage of limited transmission power and wireless spectrum, more communication satellites are adopting precise space–ground beam-forming, which poses a rigorous positioning and timing requirement of the satellite. To fulfill this requirement, a space-borne global navigation satellite system (GNSS) timing receiver with a disciplined high-performance clock is preferable. The space-borne GNSS timing receiver moves with the satellite, in contrast to its stationary counterpart on ground, making it tricky in its positioning algorithm design. Despite abundant existing positioning algorithms, there is a lack of dedicated work that systematically describes the delicate aspects of a space-borne GNSS timing receiver. Based on the experimental work of the LING QIAO (NORAD ID:40136) communication satellite’s GNSS receiver, we propose a fine-tuned positioning algorithm for space-borne GNSS timing receivers. Specifically, the proposed algorithm includes: (1) a filtering architecture that separates the estimation of satellite position and velocity from other unknowns, which allows for a first estimation of satellite position and velocity incorporating any variation of orbit dynamics; (2) a two-threshold robust cubature Kalman filter to counteract the adverse influence of measurement outliers on positioning quality; (3) Reynolds averaging inspired clock and frequency error estimation. Hardware emulation test results show that the proposed algorithm has a performance with a 3D positioning RMS error of 1.2 m, 3D velocity RMS error of 0.02 m/s and a pulse per second (PPS) RMS error of 11.8ns. Simulations with MATLAB show that it can effectively detect and dispose outliers, and further on outperforms other algorithms in comparison. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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14 pages, 2322 KiB  
Article
Analyzing the Satellite-Induced Code Bias Variation Characteristics for the BDS-3 Via a 40 m Dish Antenna
by Ju Hong, Rui Tu, Rui Zhang, Lihong Fan, Pengfei Zhang, Junqiang Han and Xiaochun Lu
Sensors 2020, 20(5), 1339; https://0-doi-org.brum.beds.ac.uk/10.3390/s20051339 - 29 Feb 2020
Cited by 6 | Viewed by 2568
Abstract
The satellite-induced code bias variation of geostationary satellite orbit satellites and medium earth orbit satellites of the second-generation BeiDou Navigation Satellite System (BDS-2) exceeds 1 m, which severely affects the accuracy and stability of the ambiguity resolution and high-precision positioning. With the development [...] Read more.
The satellite-induced code bias variation of geostationary satellite orbit satellites and medium earth orbit satellites of the second-generation BeiDou Navigation Satellite System (BDS-2) exceeds 1 m, which severely affects the accuracy and stability of the ambiguity resolution and high-precision positioning. With the development of the third-generation BDS (BDS-3) with a new system design and new technology, analysis of the satellite-induced code variation characteristics of BDS-3 has become increasingly important. At present, many scholars have explored the satellite-induced code bias of BDS-3, but most of them focus on BDS-3 experimental satellites via normal geodetic antenna. Compared to normal geodetic antenna, the 40-m dish antenna from the National Time Service Center can accurately detect satellite-induced code variations with low noise and high gain. Thus, observational data from fifteen BDS-3 medium earth orbit satellites are collected with the B1I/B2b/B3I/B1C/B2a frequency bands on the day of year (DOY) 199–206 in 2019, the PRN numbers of which are C19/C20/C21/C22/C23/C24/C25/C26/C27/C28/C30/C32/C33 /C35/C37, via the 40 m dish antenna to analyze the code bias variation characteristics. The results show that the obvious satellite-induced elevation‑dependent code bias variations exist in the B1I/B2b/B3I/B1C/B2a frequency bands of C28, compared with other satellites. Similarly, the multipath (MP) combination of B3I has an obvious elevation‑dependent variation within a range of 0.1 m for C21/C24/C27/C28/C37 and elevation‑dependent variation of the B2a and B2b frequency bands also exists in most satellites with a range of 0.1 m. However, the MP combination values of some satellites are asymmetric with respect to elevation, which is different from BDS-2 satellites and especially obvious for BDS-3 satellites B1I and BIC frequency bands with elevation‑dependent variations of 0.2 m, indicating that the code bias variation is not uniquely related to elevation, especially for the B1I/BIC frequency bands. What’s more, the satellite-induced code bias variation of the BDS-3 satellites is greatly reduced compared with that of the BDS-2 satellites. In addition, the similar code bias variation appears at the Xia1 station with a normal geodetic antenna of B1I/B1C/B3I/B2a/B2b of C21, B3I/B2a/B2b of C24 and B2b of C28 among B1I/B1C/B3I/B2a/B2b of C21/C24/C27/C28/C37. The influence of the BDS-3 satellite-induced elevation‑dependent code bias on precision positioning and ambiguity fixing is worth further study using different antennas or receivers. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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23 pages, 4073 KiB  
Article
The Application of Robust Least Squares Method in Frequency Lock Loop Fusion for Global Navigation Satellite System Receivers
by Mengyue Han, Qian Wang, Yuanlan Wen, Min He and Xiufeng He
Sensors 2020, 20(4), 1224; https://0-doi-org.brum.beds.ac.uk/10.3390/s20041224 - 23 Feb 2020
Cited by 3 | Viewed by 2848
Abstract
The tracking accuracy of a traditional Frequency Lock Loop (FLL) decreases significantly in a complex environment, thus reducing the overall performance of a satellite receiver. In order to ensure high tracking accuracy of a receiver in a complex environment, this paper proposes a [...] Read more.
The tracking accuracy of a traditional Frequency Lock Loop (FLL) decreases significantly in a complex environment, thus reducing the overall performance of a satellite receiver. In order to ensure high tracking accuracy of a receiver in a complex environment, this paper proposes a new tracking loop combining the vector FLL (VFLL) with a robust least squares method, which accurately matches the weights of received signals of different qualities to ensure high positioning accuracy. The weights of received signals are selected at the signal level, not at the observation level. In this paper, the ranges of strong and weak signals of the loop are determined according to the different expressions of the distribution function at different signal strengths, and the concept of loop segmentation is introduced. The segmentation results of the FLL are taken as a basis of the weight selection, and then combined with the Institute of Geodesy and Geophysics (IGGIII) weight function to obtain the equivalent weight matrix; the experiments are conducted to prove the advantages of the proposed method over the traditional methods. The experimental results show that the proposed VFLL tracking method has strong denoising capability under both normal- signal and harsh application environment conditions. Accordingly, the proposed model has a promising application perspective. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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25 pages, 10331 KiB  
Article
Evaluating the Vulnerability of Several Geodetic GNSS Receivers under Chirp Signal L1/E1 Jamming
by Matej Bažec, Franc Dimc and Polona Pavlovčič-Prešeren
Sensors 2020, 20(3), 814; https://0-doi-org.brum.beds.ac.uk/10.3390/s20030814 - 03 Feb 2020
Cited by 16 | Viewed by 4440
Abstract
Understanding the factors that might intentionally influence the reception of global navigation satellite system (GNSS) signals can be a challenging topic today. The focus of this research is to evaluate the vulnerability of geodetic GNSS receivers under the use of a low-cost L1/E1 [...] Read more.
Understanding the factors that might intentionally influence the reception of global navigation satellite system (GNSS) signals can be a challenging topic today. The focus of this research is to evaluate the vulnerability of geodetic GNSS receivers under the use of a low-cost L1/E1 frequency jammer. A suitable area for testing was established in Slovenia. Nine receivers from different manufacturers were under consideration in this study. While positioning, intentional 3-minute jammings were performed by a jammer that was located statically at different distances from receivers. Furthermore, kinematic disturbances were performed using a jammer placed in a vehicle that passed the testing area at various speeds. An analysis of different scenarios indicated that despite the use of an L1/E1 jammer, the GLONASS (Russian: Globalnaya Navigatsionnaya Sputnikovaya Sistema) and Galileo signals were also affected, either due to the increased carrier-to-noise-ratio (C/N0) or, in the worst cases, by a loss-of-signal. A jammer could substantially affect the position, either with a lack of any practical solution or even with a wrong position. Maximal errors in the carrier-phase positions, which should be considered a concern for geodesy, differed by a few metres from the exact solution. The factor that completely disabled the signal reception was the proximity of a jammer, regardless of its static or kinematic mode. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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17 pages, 2209 KiB  
Article
Helmert Variance Component Estimation for Multi-GNSS Relative Positioning
by Mowen Li, Wenfeng Nie, Tianhe Xu, Adria Rovira-Garcia, Zhenlong Fang and Guochang Xu
Sensors 2020, 20(3), 669; https://0-doi-org.brum.beds.ac.uk/10.3390/s20030669 - 25 Jan 2020
Cited by 18 | Viewed by 3198
Abstract
The Multi-constellation Global Navigation Satellite System (Multi-GNSS) has become the standard implementation of high accuracy positioning and navigation applications. It is well known that the noise of code and phase measurements depend on GNSS constellation. Then, Helmert variance component estimation (HVCE) is usually [...] Read more.
The Multi-constellation Global Navigation Satellite System (Multi-GNSS) has become the standard implementation of high accuracy positioning and navigation applications. It is well known that the noise of code and phase measurements depend on GNSS constellation. Then, Helmert variance component estimation (HVCE) is usually used to adjust the contributions of different GNSS constellations by determining their individual variances of unit weight. However, HVCE requires a heavy computation load. In this study, the HVCE posterior weighting was employed to carry out a kinematic relative Multi-GNSS positioning experiment with six short-baselines from day of year (DoY) 171 to 200 in 2019. As a result, the HVCE posterior weighting strategy improved Multi-GNSS positioning accuracy by 20.5%, 15.7% and 13.2% in east-north-up (ENU) components, compared to an elevation-dependent (ED) priori weighting strategy. We observed that the weight proportion of both code and phase observations for each GNSS constellation were consistent during the entire 30 days, which indicates that the weight proportions of both code and phase observations are stable over a long period of time. It was also found that the quality of a phase observation is almost equivalent in each baseline and GNSS constellation, whereas that of a code observation is different. In order to reduce the time consumption of the HVCE method without sacrificing positioning accuracy, the stable variances of unit weights of both phase and code observations obtained over 30 days were averaged and then frozen as a priori information in the positioning experiment. The result demonstrated similar ENU improvements of 20.0%, 14.1% and 11.1% with respect to the ED method but saving 88% of the computation time of the HCVE strategy. Our study concludes with the observations that the frozen variances of unit weight (FVUW) could be applied to the positioning experiment for the next 30 days, that is, from DoY 201 to 230 in 2019, improving the positioning ENU accuracy of the ED method by 18.1%, 13.2% and 10.6%, indicating the effectiveness of the FVUW. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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16 pages, 6520 KiB  
Article
The Prediction of Geocentric Corrections during Communication Link Outages in PPP
by Joanna Janicka, Dariusz Tomaszewski, Jacek Rapinski, Marcin Jagoda and Miloslawa Rutkowska
Sensors 2020, 20(3), 602; https://0-doi-org.brum.beds.ac.uk/10.3390/s20030602 - 21 Jan 2020
Cited by 6 | Viewed by 2154
Abstract
The International GNSS Service (IGS) real-time service (RTS) provides access to real-time precise products. State-Space Representation (SSR) products are disseminated through the Internet using the Networked Transport of the RTCM (Radio Technical Commission for Maritime Services) via the Internet Protocol (NTRIP). However, communication [...] Read more.
The International GNSS Service (IGS) real-time service (RTS) provides access to real-time precise products. State-Space Representation (SSR) products are disseminated through the Internet using the Networked Transport of the RTCM (Radio Technical Commission for Maritime Services) via the Internet Protocol (NTRIP). However, communication outages caused by a loss of the communication link during ephemeris changes can occur. Unfortunately, any break in providing orbit and clock corrections affects the possibility to perform precise point positioning. To eliminate this problem, various methods have been developed and presented in the literature. The solution proposed by the authors is to directly predict geocentric corrections. This manuscript presents the results and analysis of geocentric correction predictions under two scenarios: the first between the IODE (issue of data ephemeris) value change and the second where prediction must be done for epochs containing a change in IODE ephemeris. In this case, the prediction uses data from a previous message. The Root Mean Square (RMS) values calculated based on the differences between the true correction values and the predicted geocentric corrections using a linear function, a second-degree polynomial and a constant value do not differ significantly. The numerical results show that, in most cases, maintaining the constant value of the last registered SSR correction is the best option. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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18 pages, 15968 KiB  
Article
Spatial and Temporal Variations of Polar Ionospheric Total Electron Content over Nearly Thirteen Years
by Hui Xi, Hu Jiang, Jiachun An, Zemin Wang, Xueyong Xu, Houxuan Yan and Can Feng
Sensors 2020, 20(2), 540; https://0-doi-org.brum.beds.ac.uk/10.3390/s20020540 - 19 Jan 2020
Cited by 7 | Viewed by 3014
Abstract
It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the [...] Read more.
It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5–3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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24 pages, 8422 KiB  
Article
Kinematic and Dynamic Vehicle Model-Assisted Global Positioning Method for Autonomous Vehicles with Low-Cost GPS/Camera/In-Vehicle Sensors
by Haigen Min, Xia Wu, Chaoyi Cheng and Xiangmo Zhao
Sensors 2019, 19(24), 5430; https://0-doi-org.brum.beds.ac.uk/10.3390/s19245430 - 09 Dec 2019
Cited by 46 | Viewed by 8985
Abstract
Real-time, precise and low-cost vehicular positioning systems associated with global continuous coordinates are needed for path planning and motion control in autonomous vehicles. However, existing positioning systems do not perform well in urban canyons, tunnels and indoor parking lots. To address this issue, [...] Read more.
Real-time, precise and low-cost vehicular positioning systems associated with global continuous coordinates are needed for path planning and motion control in autonomous vehicles. However, existing positioning systems do not perform well in urban canyons, tunnels and indoor parking lots. To address this issue, this paper proposes a multi-sensor positioning system that combines a global positioning system (GPS), a camera and in-vehicle sensors assisted by kinematic and dynamic vehicle models. First, the system eliminates image blurring and removes false feature correspondences to ensure the local accuracy and stability of the visual simultaneous localisation and mapping (SLAM) algorithm. Next, the global GPS coordinates are transferred to a local coordinate system that is consistent with the visual SLAM process, and the GPS and visual SLAM tracks are calibrated with the improved weighted iterative closest point and least absolute deviation methods. Finally, an inverse coordinate system conversion is conducted to obtain the position in the global coordinate system. To improve the positioning accuracy, information from the in-vehicle sensors is fused with the interacting multiple-model extended Kalman filter based on kinematic and dynamic vehicle models. The developed algorithm was verified via intensive simulations and evaluated through experiments using KITTI benchmarks (A project of Karlsruhe Institute of Technology and Toyota Technological Institute at Chicago) and data captured using our autonomous vehicle platform. The results show that the proposed positioning system improves the accuracy and reliability of positioning in environments in which the Global Navigation Satellite System is not available. The developed system is suitable for the positioning and navigation of autonomous vehicles. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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17 pages, 2977 KiB  
Article
Characteristics and Performance Evaluation of QZSS Onboard Satellite Clocks
by Wei Xie, Guanwen Huang, Bobin Cui, Pingli Li, Yu Cao, Haohao Wang, Zi Chen and Bo Shao
Sensors 2019, 19(23), 5147; https://0-doi-org.brum.beds.ac.uk/10.3390/s19235147 - 24 Nov 2019
Cited by 19 | Viewed by 3380
Abstract
In the Global Navigation Satellite System (GNSS) community, the Quasi-Zenith Satellite System (QZSS) is an augmentation system for users in the Asia-Pacific region. However, the characteristics and performance of four QZSS satellite clocks in a long-term scale are unknown at present. However, it [...] Read more.
In the Global Navigation Satellite System (GNSS) community, the Quasi-Zenith Satellite System (QZSS) is an augmentation system for users in the Asia-Pacific region. However, the characteristics and performance of four QZSS satellite clocks in a long-term scale are unknown at present. However, it is crucial to the positioning, navigation and timing (PNT) services of users, especially in Asia-Pacific region. In this study, the characteristics and performance variation of four QZSS satellite clocks, which including the phase, frequency, frequency drift, fitting residuals, frequency accuracy, periodic terms, frequency stability and short-term clock prediction, are revealed in detail for the first time based on the precise satellite clock offset products of nearly 1000 days. The important contributions are as follows: (1) It is detected that the times of phase and frequency jump are 2.25 and 1.5 for every QZSS satellite clock in one year. The magnitude of the frequency drift is about 10−18. The periodic oscillation of frequency drift of J01 and J02 satellite clocks is found. The clock offset model precision of QZSS is 0.33 ns. (2) The two main periods of QZSS satellite clock are 24 and 12 hours, which is the influence of the satellite orbit; (3) The frequency stability of 100, 1000 and 10,000 s are 1.98 × 10−13, 6.59 × 10−14 and 5.39 × 10−14 for QZSS satellite clock, respectively. The visible “bump” is found at about 400 s for J02 and J03 satellite clocks. The short-term clock prediction accuracy of is 0.12 ns. This study provides a reference for the state monitoring and performance variation of the QZSS satellite clock. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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15 pages, 466 KiB  
Article
Tensor-Based Subspace Tracking for Time-Delay Estimation in GNSS Multi-Antenna Receivers
by Caio C. R. Garcez, Daniel Valle de Lima, Ricardo Kehrle Miranda, Fábio Mendonça, João Paulo C. L. da Costa, André L. F. de Almeida and Rafael T. de Sousa, Jr.
Sensors 2019, 19(23), 5076; https://0-doi-org.brum.beds.ac.uk/10.3390/s19235076 - 20 Nov 2019
Cited by 7 | Viewed by 2461
Abstract
Although Global Navigation Satellite Systems (GNSS) receivers currently achieve high accuracy when processing their geographic location under line of sight (LOS), multipath interference and noise degrades the accuracy considerably. In order to mitigate multipath interference, receivers based on multiple antennas became the focus [...] Read more.
Although Global Navigation Satellite Systems (GNSS) receivers currently achieve high accuracy when processing their geographic location under line of sight (LOS), multipath interference and noise degrades the accuracy considerably. In order to mitigate multipath interference, receivers based on multiple antennas became the focus of research and technological development. In this context, tensor-based approaches based on Parallel Factor Analysis (PARAFAC) models have been proposed in the literature, providing optimum performance. State-of-the-art techniques for antenna array based GNSS receivers compute singular value decomposition (SVD) for each new sample, implying into a high computational complexity, being, therefore, prohibitive for real-time applications. Therefore, in order to reduce the computational complexity of the parameter estimates, subspace tracking algorithms are essential. In this work, we propose a tensor-based subspace tracking framework to reduce the overall computational complexity of the highly accurate tensor-based time-delay estimation process. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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14 pages, 9063 KiB  
Article
Improving the GRACE Kinematic Precise Orbit Determination Through Modified Clock Estimating
by Xingyu Zhou, Weiping Jiang, Hua Chen, Zhao Li and Xuexi Liu
Sensors 2019, 19(19), 4347; https://0-doi-org.brum.beds.ac.uk/10.3390/s19194347 - 08 Oct 2019
Cited by 10 | Viewed by 2928
Abstract
Utilizing global positioning system (GPS) to determine the precise kinematic orbits for the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) plays a very important role in the earth’s gravitational and other scientific fields. However, the orbit quality is highly depended [...] Read more.
Utilizing global positioning system (GPS) to determine the precise kinematic orbits for the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) plays a very important role in the earth’s gravitational and other scientific fields. However, the orbit quality is highly depended on the geometry of observed GPS satellites. In this study, we propose a kinematic orbit determination method for improving the GRACE orbit quality especially when the geometry of observed GPS satellites is weak, where an appropriate random walk clock constraint between adjacent epochs is recommended according to the stability of on-board GPS receiver clocks. GRACE data over one month were adopted in the experimental validation. Results show that the proposed method could improve the root mean square (RMS) by 20–40% in radial component and 5–20% in along and cross components. For those epochs with position dilution of precision (PDOP) larger than 4, the orbits were improved by 50–70% in radial component and 17–50% in along and cross components. Meanwhile, the Allan deviation of clock estimates in the proposed method was much closer to the reported Allan deviation of GRACE on-board oscillator. All the results confirmed the improvement of the proposed method. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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12 pages, 4080 KiB  
Article
Height Variation Depending on the Source of Antenna Phase Centre Corrections: LEIAR25.R3 Case Study
by Andrzej Araszkiewicz, Damian Kiliszek and Anna Podkowa
Sensors 2019, 19(18), 4010; https://0-doi-org.brum.beds.ac.uk/10.3390/s19184010 - 17 Sep 2019
Cited by 8 | Viewed by 2925
Abstract
In this study, we compared two sets of antenna phase center corrections for groups of the same type of antenna mounted at the continuously operating global navigation satellite system (GNSS) reference stations. The first set involved type mean models provided by the International [...] Read more.
In this study, we compared two sets of antenna phase center corrections for groups of the same type of antenna mounted at the continuously operating global navigation satellite system (GNSS) reference stations. The first set involved type mean models provided by the International GNSS Service (release igs08), while the second set involved individual models developed by Geo++. Our goal was to check which set gave better results in the case of height estimation. The paper presents the differences between models and their impact on resulting height. Analyses showed that, in terms of the stability of the determined height, as well as its variability caused by increasing the facade mask, both models gave very similar results. Finally, we present a method for how to estimate the impact of differences in phase center corrections on height changes. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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20 pages, 2721 KiB  
Article
Effective Efficiency Advantage Assessment of Information Filter for Conventional Kalman Filter in GNSS Scenarios
by Yanning Zheng, Siyou Wang and Shengli Wang
Sensors 2019, 19(18), 3858; https://0-doi-org.brum.beds.ac.uk/10.3390/s19183858 - 06 Sep 2019
Cited by 1 | Viewed by 1796
Abstract
The Global Navigation Satellite System (GNSS) is a widely used positioning technique. Computational efficiency is crucial to applications such as real-time GNSS positioning and GNSS network data processing. Many researchers have made great efforts to address this problem by means such as parameter [...] Read more.
The Global Navigation Satellite System (GNSS) is a widely used positioning technique. Computational efficiency is crucial to applications such as real-time GNSS positioning and GNSS network data processing. Many researchers have made great efforts to address this problem by means such as parameter elimination or satellite selection. However, parameter estimation is rarely discussed when analyzing GNSS algorithm efficiency. In addition, most studies on Kalman filter (KF) efficiency commonly have defects, such as neglecting application-specified optimization and limiting specific hardware platforms in the conclusion. The former reduces the practicality of the solution, because applications that need such analyses on filters are often optimized, and the latter reduces its generality because of differences between platforms. In this paper, the computational cost enhancement of replacing the conventional KF with the information filter (IF) is tested considering GNSS application-oriented optimization conditions and hardware platform differences. First, optimization conditions are abstracted from GNSS data-processing scenarios. Then, a thorough analysis is carried out on the computational cost of the filters, considering hardware–platform differences. Finally, a case of GNSS dynamic differencing positioning is studied. The simulation shows that the IF is slightly faster for precise point positioning and much faster for the code-based single-difference GNSS (SDGNSS) with the constant velocity (CV) model than the conventional KF, but is not a good substitute for the conventional KF in the other algorithms mentioned. The real test shows that the IF is about 50% faster than the conventional KF handling code-based SDGNSS with the CV model. Also, the information filter is theoretically equivalent to and can produce results that are consistent with the Kalman filter. Our conclusions can be used as a reference for GNSS applications that need high process speed or real-time capability. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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14 pages, 4632 KiB  
Article
A New Asynchronous RTK Method to Mitigate Base Station Observation Outages
by Yuan Du, Guanwen Huang, Qin Zhang, Yang Gao and Yuting Gao
Sensors 2019, 19(15), 3376; https://0-doi-org.brum.beds.ac.uk/10.3390/s19153376 - 01 Aug 2019
Cited by 8 | Viewed by 3258
Abstract
Real-time kinematic (RTK) positioning is a satellite navigation technique that is widely used to enhance the precision of position data obtained from global navigation satellite systems (GNSS). This technique can reduce or eliminate significant correlation errors via the enhancement of the base station [...] Read more.
Real-time kinematic (RTK) positioning is a satellite navigation technique that is widely used to enhance the precision of position data obtained from global navigation satellite systems (GNSS). This technique can reduce or eliminate significant correlation errors via the enhancement of the base station observation data. However, observations received by the base station are often interrupted, delayed, and/or discontinuous, and in the absence of base station observation data the corresponding positioning accuracy of a rover declines rapidly. With the strategies proposed till date, the positioning accuracy can only be maintained at the centimeter-level for a short span of time, no more than three min. To address this, a novel asynchronous RTK method (that addresses asynchronous errors) that can bridge significant gaps in the observations at the base station is proposed. First, satellite clock and orbital errors are eliminated using the products of the final precise ephemeris during post-processing or the ultra-rapid precise ephemeris during real-time processing. Then the tropospheric error is corrected using the Saastamoinen model and the asynchronous ionospheric delay is corrected using the carrier phase measurements from the rover receiver. Finally, a straightforward first-degree polynomial function is used to predict the residual asynchronous error. Experimental results demonstrate that the proposed approach can achieve centimeter-level accuracy for as long as 15 min during interruptions in both real-time and post-processing scenarios, and that the accuracy of the real-time scheme can be maintained for 15 min even when a large systematic error is projected in the U direction. Full article
(This article belongs to the Special Issue GNSS Data Processing and Navigation)
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