Publications
83 results found
Chen J, Zhi N, Liao H, et al., 2022, Global forecasting of ionospheric vertical total electron contents via ConvLSTM with spectrum analysis, GPS Solutions, Vol: 26, ISSN: 1080-5370
The widely used GNSS correction services for high precision positioning take advantage of accurate real-time TEC forecasting based on vertical total electron content (VTEC) maps. The methods for modeling and forecasting are mainly based on overly simplified assumptions, which in principle cannot reflect the real situations due to limitations of the mathematical formulations. Therefore, these methods cannot comprehensively capture the features of ionospheric TEC in spatial–temporal series. To overcome the problems caused by such assumptions, we combine ConvLSTM (convolutional long short-term memory) with spectrum analysis. The method allows the extraction of high-resolution spatial–temporal patterns of the ionospheric VTEC maps and accelerates the convergence time of neural networks. Extensive experiments have been carried out for short- and long-term forecasting and demonstrated that the performance of our method is better than other state-of-the-art models developed for various time series analysis methods. Based on the data from global ionospheric maps (GIMs) products, the results show that the root-mean-square error (RMSE) of global VTEC forecasting by our method substantially improves for two hours intervals over the years 2015, 2016, 2017 and 2019 compared to existing methods, specifically, 20–50% reduction on 1 or 2 h forecasting in terms of RMSE. In addition, the method is sufficient to support real-time forecasting since it takes less than one second to output global forecasting solutions. With these properties, we can facilitate real-time and highly accurate ionosphere correction services beneficial to numerous GNSS correct services and positioning terminals.
Yang F, Zhao L, Li L, et al., 2019, Performance Evaluation of Kinematic BDS/GNSS Real-Time Precise Point Positioning for Maritime Positioning, JOURNAL OF NAVIGATION, Vol: 72, Pages: 34-52, ISSN: 0373-4633
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Wang E, Jia C, Feng S, et al., 2018, A New Satellite Selection Algorithm for a Multi-Constellation GNSS Receiver, 31st International Technical Meeting of the Satellite-Division-of-The-Institute-of-Navigation (ION GNSS), Publisher: INST NAVIGATION, Pages: 3802-3811, ISSN: 2331-5911
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Qin F, Sun R, Ochieng WY, et al., 2017, Integrated GNSS/DR/road segment information system for variable road user charging, Transportation Research Part C: Emerging Technologies, Vol: 82, Pages: 261-272, ISSN: 0968-090X
Road User Charging (RUC) is designed to reduce congestion and collect revenue for the maintenance of transportation infrastructure. In order to determine the charges, it is important that appropriate Road User Charging Indicators (RUCI) are defined. This paper focusses on Variable Road User Charging (VRUC) as the more dynamic and flexible compared to Fixed Road User Charging (FRUC), and thus is a better reflection of the utility of the road space. The main issues associated with VRUC are the definition of appropriate charging indicators and their measurement. This paper addresses the former by proposing a number of new charging indicators, considering the equalization of the charges and marginal social cost imposed on others. The measurement of the indicators is addressed by a novel data fusion algorithm for the determination of the vehicle state based on the integration of Global Navigation Satellite Systems (GNSS) with Dead Reckoning (DR) and road segment information. Statistical analyses are presented in terms of the Required Navigation Performance (RNP) parameters of accuracy, integrity, continuity and availability, based on simulation and field tests. It is shown that the proposed fusion model is superior to positioning with GPS only, and GPS plus GLONASS, in terms of all the RNP parameters with a significant improvement in availability.
Zhang Z, Zhan X, Feng S, et al., 2017, Sensitivity Analysis of the Vestigial Signal Defense Based Civil GPS Spoofing Detection Method, IET Radar, Sonar & Navigation, Vol: 11, Pages: 861-872, ISSN: 1751-8784
The vestigial signal defence (VSD) method is used widely for GNSS spoofing detection through monitoring the vestigial signals within the receiver. Though the VSD has been extensively investigated in the open literature, its sensitivity in terms of detection and false alarm probabilities has not been analysed. This is addressed in this study. The sensitivity models including the vestigial signal-to-interference and noise ratio (SINR) and the detection and false alarm probabilities are mathematically formulated. The models are used to quantify and characterise the SINR and the detection and false alarm probabilities. It shows that the VSD is vulnerable to relatively strong spoofing signals. Strong spoofing signals significantly increase the noise floor in turn greatly decreasing the vestigial SINR, resulting in an unacceptable VSD detection performance. It also shows that the sensitivity could be improved with a higher sampling frequency and a longer integration time. It is therefore recommended to use a scheme that combines a long integration time and noise floor monitoring. The sensitivity models together with the recommendation scheme are validated by simulation.
Zhang X, Zhan X, Feng S, et al., 2017, An Analytical Model for BDS B1 Spreading Code Self-Interference Evaluation Considering NH Code Effects, SENSORS, Vol: 17, ISSN: 1424-8220
The short spreading code used by the BeiDou Navigation Satellite System (BDS) B1-I or GPS Coarse/Acquistiion (C/A) can cause aggregately undesirable cross-correlation between signals within each single constellation. This GPS-to-GPS or BDS-to-BDS correlation is referred to as self-interference. A GPS C/A code self-interference model is extended to propose a self-interference model for BDS B1, taking into account the unique feature of the B1-I signal transmitted by BDS medium Earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites—an extra Neumann-Hoffmann (NH) code. Currently there is no analytical model for BDS self-interference and a simple three parameter analytical model is proposed. The model is developed by calculating the spectral separation coefficient (SSC), converting SSC to equivalent white noise power level, and then using this to calculate effective carrier-to-noise density ratio. Cyclostationarity embedded in the signal offers the proposed model additional accuracy in predicting B1-I self-interference. Hardware simulator data are used to validate the model. Software simulator data are used to show the impact of self-interference on a typical BDS receiver including the finding that self-interference effect is most significant when the differential Doppler between desired and undesired signal is zero. Simulation results show the aggregate noise caused by just two undesirable spreading codes on a single desirable signal could lift the receiver noise floor by 3.83 dB under extreme C/N0 (carrier to noise density ratio) conditions (around 20 dB-Hz). This aggregate noise has the potential to increase code tracking standard deviation by 11.65 m under low C/N0 (15–19 dB-Hz) conditions and should therefore, be avoided for high-sensitivity applications. Although the findings refer to Beidou system, the principle weakness of the short codes illuminated here are valid for other satellite navigation systems.
Zeng Q, Meng Q, Liu J, et al., 2016, Acquisition and loop control of ultra-tight INS/BeiDou integration system, Optik, Vol: 127, Pages: 8082-8089, ISSN: 0030-4026
Focus on the ultra-tight INS/GNSS integration, the NH code evasion method is proposed in BeiDou baseband signal process. An ultra-tight INS/BeiDou integration model based on vector tracking loop is built to analyze the coupling mechanism and control scheme between loop measurements and INS navigation data. Two control schemes are derived, including the relationship between code phase difference and the INS positioning error, the relationship between frequency difference and INS velocity error. A prototype based on BeiDou software-defined receiver and MEMS is designed and the model is tested.
Meng Q, Liu JY, Zeng QH, et al., 2016, Neumann-Hoffman code evasion and stripping method for BeiDou software-defined receive, Journal of Navigation, Vol: 70, Pages: 101-119, ISSN: 0373-4633
The acquisition and tracking strategies of the BeiDou navigation satellite signals are affected by the modulation of Neumann-Hoffman code (NH code), which increases the complexity of receiver baseband signal processing. Based on the analysis of probability statistics of the NH code, a special sequence of incoming signals is proposed to evade the bit transitions caused by the NH code, and an NH Code Evasion and Stripping method (NCES) based on the NH-pre-modulated code is proposed. The NCES can be applied in both 20-bit NH code and 10-bit NH code. The fine acquisition eliminates the impact of NH code on the traditional tracking loop. These methods were verified with a BeiDou PC-based software-defined receiver using the actual sampled signals. Compared with other acquisition schemes which try to determine or ignore the NH code phase, the NCES needs fewer incoming signals and the actual runtime is greatly reduced without sacrificing much time to search in the secondary code dimension, and the success rate of acquisition is effectively improved. An extension of Fast Fourier Transform (FFT)-based parallel code-phase search acquisition gives the NCES an advantage in engineering applications.
Sun Z, Wang X, Feng S, et al., 2016, Design of an adaptive GPS vector tracking loop with the detection and isolation of contaminated channels, GPS Solutions, Vol: 21, Pages: 701-713, ISSN: 1080-5370
In vector tracking loop (VTL), the relativity among received signals is exploited to deeply integrate the entire information within signal processing channels. However, the tracking error in one channel may corrupt other channels and lead to an increasing degradation in the tracking performance. An adaptive GPS vector tracking loop with the detection and isolation of contaminated channels is proposed to suppress the propagation of tracking error and to make the vector-based receiver less vulnerable in poor signal quality environments resulting from signal attenuation, interference and jamming. The vectorial transfer function models and the noise bandwidths of both the vector frequency lock loop and the vector delay lock loop are established to accurately calculate bandwidths and optimally design parameters for VTL. The autonomous fault detection algorithm based on uniformly most powerful test for VTL is designed to detect and isolate contaminated channels (with large tracking error due to the poor signal quality) by monitoring the bandwidth statistics of all tracking loops. The results of trials in harsh situations show that the proposed adaptive VTL is superior to baseline VTL, allowing the accuracy, the availability and the reliability of the vector-based receiver to be improved. In conclusion, the proposed adaptive VTL with the detection and isolation of contaminated channels is a powerful method for applications in GPS-challenged environments.
Gillieron P-Y, Ruotsalainen L, Peyret F, et al., 2016, The SaPPART COST Action: Towards Positioning Integrity for Road Transport, European Navigation Conference (ENC), Publisher: IEEE
Global Navigation Satellite Systems (GNSS) is becoming one of the main components supporting Intelligent Transport Systems (ITS) and value-added services in road transport and personal mobility. The use of GNSS is expected to grow significantly due to improvements in positioning performance, with positive impacts such as: finding the optimal route; improving traffic and travel efficiency as well as safety and security; reducing congestion and optimizing fuel consumption. The deployment of mission critical applications needs high reliability in the positioning information. However, the positioning reliability is not easy to achieve because of the heterogeneous quality of the GNSS signal, which is highly influenced by the road environment and the operational scenario of the application. It is important to understand the requirements and performance GNSS can achieve for various road transport applications. This paper is presenting the SaPPART COST Action on the Satellite Positioning Performance Assessment for Road Transport. It introduces the goal and the framework of the Action with the research programme and some related activities dedicated to dissemination and supporting standardisation working groups.
Kirkko-Jaakkola M, Feng S, Xue Y, et al., 2016, Effect of antenna location on GNSS positioning for ITS applications, European Navigation Conference (ENC), Publisher: IEEE
The proliferation of GNSS-receiving mobile devices in the consumer market and the growth of the Intelligent Transportation Systems sector have raised a lot of interest in low-cost precise positioning. However, GNSS signal quality is degraded inside the metal body of a vehicle, which is where the antenna of a portable device is to be located. This article investigates the effect of antenna location on precise low-cost GNSS positioning for a road vehicle. We compare a roof-mounted GNSS receiver with an identical receiver having the antenna on the dashboard and a tailored smartphone also located inside the cabin; both the availability of raw carrier phase measurements and the resulting horizontal precise point positioning accuracy are evaluated. The test results show that the 90 % circular error probable is degraded by several meters inside the vehicle. Moreover, most of the evaluated accuracy metrics indicate that the low-cost GNSS receiver with antenna inside the cabin achieved a positioning accuracy at least 50 % better than the smartphone located next to it when using the same satellite systems.
Meng Q, Zeng QH, Liu JY, et al., 2016, Positioning strategy of GEO satellite in BeiDou software-defined receiver, Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology, Vol: 24, Pages: 349-354, ISSN: 1005-6734
GEO satellites play the roles of basic navigation, enhancement and forwarding in GNSS. In this paper, the specialty and compatibility of BeiDou GEO positioning are studied. The D2 navigation data in BeiDou system are analyzed. The quadratic function approximation in base-band signal process is proposed, and GEO position and velocity computational formulas are derived. A GEO pseudorange corrected algorithm based on fuzzy control is designed which improved the versatility and compatibility of the signal processing channel. Corresponding algorithms and strategy are successfully tested and verified by using actual BeiDou B1I signal based on DSP+FPGA software-defined receiver, which realize the Doppler shift accuracy of <50Hz without the fine acquisition, and reduce the workload of pseudorange measurement by 50%. The above methods have favorable application value.
Xue Y, Feng S, Ochieng WY, et al., 2016, The Improvement of the Positioning Accuracy in Search and Rescue with Two Satellites, 7th China Satellite Navigation Conference (CSNC), Publisher: Springer Verlag (Germany), Pages: 255-261, ISSN: 1876-1100
The efficiency of search and rescue (SAR) heavily relies on the positioning accuracy, so high positioning accuracy is very important in the procedure of SAR, especially when searched and rescued object (SARO) dropped into the place where the number of the visible satellites is very small. It is necessary to know the position of the SARO using as less satellites as possible because of the signal sheltered. Combining with the principle of time and frequency difference of arrival (TDOA and FDOA, respectively) and differential technology of positioning error correction in global positioning system (GPS), pseudorange differential positioning method basing on TDOA and FDOA is put forward in the procedure of SAR with two satellites. By choosing the proper reference object (RO), the pseudorange correction of RO is used to correct pseudorange of the SARO so that more accurate position of SARO is solved. Finally, simulation results show that the positioning accuracy can be improved and can precede 5 km after differential by selecting RO and SARO which are within 1000 km apart for pseudorange differential technology.
Zhang X, Zhang Z, Ochieng W, et al., 2016, A Reverse Approach to Antenna Specifications for London Buses Next-generation Positioning System, 29th International Technical Meeting of The-Satellite-Division-of-the-Institute-of-Navigation (ION GNSS+), Publisher: INST NAVIGATION, Pages: 1927-1936, ISSN: 2331-5911
Gu S, Liu J, Zeng Q, et al., 2015, Dynamic Allan Variance Analysis Method with Time-Variant Window Length Based on Fuzzy Control, Journal of Sensors, Vol: 2015, ISSN: 1687-7268
To solve the problem that dynamic Allan variance (DAVAR) with fixed length of window cannot meet the identification accuracy requirement of fiber optic gyro (FOG) signal over all time domains, a dynamic Allan variance analysis method with time-variant window length based on fuzzy control is proposed. According to the characteristic of FOG signal, a fuzzy controller with the inputs of the first and second derivatives of FOG signal is designed to estimate the window length of the DAVAR. Then the Allan variances of the signals during the time-variant window are simulated to obtain the DAVAR of the FOG signal to describe the dynamic characteristic of the time-varying FOG signal. Additionally, a performance evaluation index of the algorithm based on radar chart is proposed. Experiment results show that, compared with different fixed window lengths DAVAR methods, the change of FOG signal with time can be identified effectively and the evaluation index of performance can be enhanced by 30% at least by the DAVAR method with time-variant window length based on fuzzy control.
Feng S, Jokinen A, 2015, Integer ambiguity validation in GNSS positioning, Gps Solutions, Vol: 21, Pages: 79-87, ISSN: 1521-1886
Carrier phase observations are required for high accuracy positioning with Global Navigation Satellite Systems (GNSS). This requires that the correct number of whole carrier cycles in each observation (integer ambiguity) is determined. The existing methods have been shown to perform differently depending on the observables. Subsequently, the ratio test used for ambiguity validation was developed further including combining it with the Integer Aperture (IA) concept. The key challenges in using the ratio test are the existence of biases in float solutions and stochastic dependence between the two elements of the ratio. The current methods either make assumptions of independence and non-existence of biases or use simulations together with the bias-free assumption. We propose a new method taking into account both challenges which result in an unknown distribution of the ratio test statistic. A Doubly Non-Central F distribution (DNCF) is proposed for the determination of threshold. The Cumulative Distribution Function (CDF) of DNCF over-bounds the CDF of ratio test statistic distribution in case there is a bias in the float solution and a correlation between the two elements of the ratio. The Precise Point Positioning (PPP) method with products from CNES and measurement data from 10 NOAA stations are used to verify the proposed method. The test results show that the proposed method improves the performance of ambiguity resolution achieving a lower rate of wrong fixing than current state-of-the-art.
Xie F, Liu J, Li R, et al., 2015, A simultaneous multiple BeiDou signal acquisition algorithm for a software-based GNSS receiver, Optik, Vol: 127, Pages: 1607-1614, ISSN: 0030-4026
The time needed for a Global Navigation Satellite System (GNSS) receiver to acquire satellite signals is one of the key parameters to assess the performance of a receiver. This presents a challenge for a software receiver in which more frequency bins and satellite codes are required to search using conventional methods. In order to speed up the acquisition process of the BeiDou software receiver in a cold start, this paper proposes a simultaneous multiple Code Division Multiple Access (CDMA) signal acquisition algorithm. The time for searching satellites is reduced by constructing new local codes to enable the capability of detecting the presence of multiple BeiDou satellites. Besides, the individual phase identification approach for each visible satellite is further presented with multiple satellites acquisition. So a search within the PRNs used for the generation of local combined code is performed. Finally, the test results show that the proposed acquisition algorithm can effectively detect multiple BeiDou satellites simultaneously. In addition, the test results show that signal acquisition time can be reduced by 8.7% to 24.1% depending on different combination numbers and different numbers of visible satellites in the combination list.
Sun R, Ochieng W, Fang C, et al., 2015, A New Algorithm for Lane Level Irregular Driving Identification, Journal of Navigation, Vol: 68, Pages: 1173-1194, ISSN: 1469-7785
Global Navigation Satellite Systems (GNSS) are used widely in the provision of Intelligent Transportation System (ITS) services. Today, there is an increasing demand on GNSS to support applications at lane level. These applications required at lane level include lane control, collision avoidance and intelligent speed assistance. In lane control, detecting irregular driving behaviour within the lane is a basic requirement for safety related lane level applications. There are two major issues involved in lane level irregular driving identification: access to high accuracy positioning and vehicle dynamic parameters, and extraction of erratic driving behaviour from this and other related information. This paper proposes an integrated algorithm for lane level irregular driving identification. Access to high accuracy positioning is enabled by GNSS and its integration with an Inertial Navigation System (INS) using filtering with precise vehicle motion models and lane information. The identification of irregular driving behaviour is achieved by algorithms developed for different types of events based on the application of a Fuzzy Inference System (FIS). The results show that decimetre level accuracy can be achieved and that different types of lane level irregular driving behaviour can be identified.
Institut français des sciences et technologies des transports DLEDR, 2015, SaPPART white paper better use of global navigation satellite systems for safer and greener transport, Publisher: IFSTTAR, ISBN: 978-2-85782-707-8
Transport and mobility services are crucial to the society that faces important challenges.Up to date, transport facilities and services have been fundamental to economic growth.However, there have significant and unacceptable negative impacts on the environmentincluding pollution, noise and climate change. Therefore, it is paramount that theefficiency of the transport system is improved significantly including lower consumptionof energy. A way of achieving this is through the concept of smart transport that exploitsIntelligent Transport Systems (ITS) technology. ITS are built on three technology pillars:information, communication and positioning technologies.Of the three technologies, positioning could be argued to be the least familiar amongsttransport stakeholders. However, a quick investigation reveals that there are awide variety of transport and related services often associated with communicationtechnologies that are supported by positioning. Currently, the positioning is provided inthe majority of the cases by Global Navigation Satellite System (GNSS), among whichthe Global Positioning System (GPS) is the pioneer and still the most widely usedsystem. The other current fully operational stand-alone system is Russia’s GLONASS.As these operational systems were not originally and specifically designed for transportapplications, the actual capabilities and limitations of the current GNSS are not fullyunderstood by many stakeholders. Therefore, better knowledge of these limitations andtheir resolution should enable a much more rapid deployment of ITS.This white paper is produced by the members of the COST Action SaPPART with twoprincipal aims. The first is to explain the principles, state-of-the-art performance ofGNSS technology and added value in the field of transport. The second aim is to deliverkey messages to the stakeholders to facilitate the deployment of GNSS technology andthus contribute to the development of smarter and greener transport systems.Th
Sun R, Ochieng WY, Feng S, 2015, An integrated solution for lane level irregular driving detection on highways, Transportation Research Part C: Emerging Technologies, Vol: 56, Pages: 61-79, ISSN: 1879-2359
Global Navigation Satellite Systems (GNSS) has been widely used in the provision of Intelligent Transportation System (ITS) services. Current meter level system availability can fulfill the road level applications, such as route guide, fleet management and traffic control. However, meter level of system performance is not sufficient for the advanced safety applications. These lane level safety applications requires centimeter/decimeter positioning accuracy, with high integrity, continuity and availability include lane control, collision avoidance and intelligent speed assistance, etc. Detecting lane level irregular driving behavior is the basic requirement for these safety related ITS applications. The two major issues involved in the lane level irregular driving identification are accessing to high accuracy positioning and vehicle dynamic parameters and extraction of erratic driving behaviour from this and other related information. This paper proposes an integrated solution for the lane level irregular driving detection. Access to high accuracy positioning is enabled by GNSS and Inertial Navigation System (INS) integration using filtering with precise vehicle motion models and lane information. The detection of different types of irregular driving behaviour is based on the application of a Fuzzy Inference System (FIS). The evaluation of the designed integrated systems in the field test shows that 0.5 m accuracy positioning source is required for lane level irregular driving detection algorithm and the designed system can detect irregular driving styles.
Mao Q, Zhang L, Li Q, et al., 2015, A Least Squares Collocation Method for Accuracy Improvement of Mobile LiDAR Systems, Remote Sensing, Vol: 7, Pages: 7402-7424, ISSN: 2072-4292
In environments that are hostile to Global Navigation Satellites Systems (GNSS), the precision achieved by a mobile light detection and ranging (LiDAR) system (MLS) can deteriorate into the sub-meter or even the meter range due to errors in the positioning and orientation system (POS). This paper proposes a novel least squares collocation (LSC)-based method to improve the accuracy of the MLS in these hostile environments. Through a thorough consideration of the characteristics of POS errors, the proposed LSC-based method effectively corrects these errors using LiDAR control points, thereby improving the accuracy of the MLS. This method is also applied to the calibration of misalignment between the laser scanner and the POS. Several datasets from different scenarios have been adopted in order to evaluate the effectiveness of the proposed method. The results from experiments indicate that this method would represent a significant improvement in terms of the accuracy of the MLS in environments that are essentially hostile to GNSS and is also effective regarding the calibration of misalignment.
Wang X, Ji X, Feng S, et al., 2015, A high-sensitivity GPS receiver carrier-tracking loop design for high-dynamic applications, GPS Solutions, Vol: 19, Pages: 225-236, ISSN: 1080-5370
In order to enhance the tracking performance of global positioning system (GPS) receivers for weak signal applications under high-dynamic conditions, a high-sensitivity and high-dynamic carrier-tracking loop is designed. The high-dynamic performance is achieved by aiding from a strapdown inertial navigation system (SINS). In weak signal conditions, a dynamic-division fast Fourier transform (FFT)-based tracking algorithm is proposed to improve the sensitivity of GPS receivers. To achieve the best performance, the tracking loop is designed to run either in the conventional SINS-aided phase lock loop mode (time domain) or in the frequency-domain-tracking mode according to the carrier-to-noise spectral density ratio detected in real time. In the frequency-domain-tracking mode, the proposed dynamic-division FFT algorithm is utilized to estimate and correct the error of the SINS aiding. Furthermore, the optimal values of the dynamic-division step and the FFT size are selected to maximize the signal-to-noise ratio gain. Simulation results demonstrate that the designed loop can significantly improve the tracking sensitivity and robustness for weak GPS signals without compromising the dynamic performance.
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Feng S, Wang S, Liu J, et al., 2015, A beidou based multiple-GNSS positioning algorithm for mission critical applications, Pages: 143-155, ISSN: 1876-1100
With the development of the Global Navigation Satellite Systems (GNSS), countries that own a GNSS have realised that critically national infrastructures using Position Navigation and Timing (PNT) services and a portion of the national economy associated with GNSS applications should not be over reliant on other countries. Recently, both China and Russia have made their systems mandatory for some applications. This paper addresses this issue and proposes a Beidou based multiple-GNSS positioning algorithm. It involves three stages: (1) Understanding of the quality of Beidou solutions. This was achieved by Receiver Autonomous Integrity Monitoring (RAIM) embedded in the Beidou positioning algorithm. (2) A real time validation and modelling algorithm for the measurements from the other constellations if Beidou solution is proved good in stage 1. The measurement residual errors relative to the Beidou position solution are assessed. (3) Introduction of measurements from the other constellations if there is not enough Beidou measurements. At this stage, the models derived in stage 2 are applied to the non-Beidou measurements. The tests were carried out using the Beidou and GPS data from a reference station. The signal blockage of Beidou and GPS constellation is simulated. The test results show that the proposed methods can benefit from the validated measurements from the GPS constellation. The performance can be significantly improved in terms of accuracy, continuity, integrity and availability in difficult environments. It can be extended for critical applications where any constellation is mandated.
Zhao YX, Li W, Feng S, et al., 2014, An Improved Differential Evolution Algorithm for Maritime Collision Avoidance Route Planning, Abstract and Applied Analysis, Vol: 2014, ISSN: 1687-0409
High accuracy navigation and surveillance systems are pivotal to ensure efficient ship route planning and marine safety. Based on existing ship navigation and maritime collision prevention rules, an improved approach for collision avoidance route planning using a differential evolution algorithm was developed. Simulation results show that the algorithm is capable of significantly enhancing the optimized route over current methods. It has the potential to be used as a tool to generate optimal vessel routing in the presence of conflicts.
Li Q, Zhang L, Mao Q, et al., 2014, Motion field estimation for a dynamic scene using a 3D LiDAR, Sensors, Vol: 14, Pages: 16672-16691, ISSN: 1424-2818
This paper proposes a novel motion field estimation method based on a 3D light detection and ranging (LiDAR) sensor for motion sensing for intelligent driverless vehicles and active collision avoidance systems. Unlike multiple target tracking methods, which estimate the motion state of detected targets, such as cars and pedestrians, motion field estimation regards the whole scene as a motion field in which each little element has its own motion state. Compared to multiple target tracking, segmentation errors and data association errors have much less significance in motion field estimation, making it more accurate and robust. This paper presents an intact 3D LiDAR-based motion field estimation method, including pre-processing, a theoretical framework for the motion field estimation problem and practical solutions. The 3D LiDAR measurements are first projected to small-scale polar grids, and then, after data association and Kalman filtering, the motion state of every moving grid is estimated. To reduce computing time, a fast data association algorithm is proposed. Furthermore, considering the spatial correlation of motion among neighboring grids, a novel spatial-smoothing algorithm is also presented to optimize the motion field. The experimental results using several data sets captured in different cities indicate that the proposed motion field estimation is able to run in real-time and performs robustly and effectively.
Guan X, Wang X, Fang J, et al., 2014, An innovative high accuracy autonomous navigation method for the Mars rovers, Acta Astronautica, Vol: 104, Pages: 266-275, ISSN: 0094-5765
Autonomous navigation is an important function for a Mars rover to fulfill missions successfully. It is a critical technique to overcome the limitations of ground tracking and control traditionally used. This paper proposes an innovative method based on SINS (Strapdown Inertial Navigation System) with the aid of star sensors to accurately determine the rovers position and attitude. This method consists of two parts: the initial alignment and navigation. The alignment consists of a coarse position and attitude initial alignment approach and fine initial alignment approach. The coarse one is used to determine approximate position and attitude for the rover. This is followed by fine alignment to tune the approximate solution to accurate one. Upon the completion of initial alignment, the system can be used to provide real-time navigation solutions for the rover. An autonomous navigation algorithm is proposed to estimate and compensate the accumulated errors of SINS in real time. High accuracy attitude information from star sensor is used to correct errors in SINS. Simulation results demonstrate that the proposed methods can achieve a high precision autonomous navigation for Mars rovers. © 2014 IAA.
Jing S, Zhan X, Lu J, et al., 2014, Characterisation of GNSS Space Service Volume, Journal of Navigation, Vol: 68, Pages: 107-125, ISSN: 0373-4633
There is increasing demand for navigation capability for space vehicles. The idea to extend the application of Global Navigation Satellite Systems (GNSS) from terrestrial to space applications by the use of main beam and side lobe signals has been shown to be feasible. In order to understand the performance and the potential space applications GNSS can support, this paper characterises the Space Service Volume (SSV) in terms of the four parameters of minimum received power, satellite visibility, pseudorange accuracy and Geometric Dilution of Precision (GDOP). This new definition enables the position errors to be estimated. An analytical methodology is proposed to characterise minimum received power for the worst location. Satellite visibility and GDOP are assessed based on grid points at different height layers (to capture the relationship between height and visibility) for single and multiple GNSS constellations, the former represented by BeiDou III (BDS III) and the latter, BDS III in various combinations with GPS, GLONASS and GALILEO. Additional simulation shows that GNSS can potentially support lunar exploration spacecraft at the Earth phasing orbit. This initial assessment of SSV shows the potential of GNSS for space vehicle navigation.
moradi, schuster, feng S, et al., 2014, New stochastic model for carrier multipath in linear combinations, New Navigator Seminar 2014
Wang X, Ji X, Feng S, 2014, A scheme for weak GPS signal acquisition aided by SINS information, GPS Solutions, Vol: 18, Pages: 243-252, ISSN: 1080-5370
In order to enhance the acquisition performance of global positioning system (GPS) receivers in weak signal conditions, a high-sensitivity acquisition scheme aided by strapdown inertial navigation system (SINS) information is proposed. The carrier Doppler shift and Doppler rate are pre-estimated with SINS aiding and GPS ephemeris, so that the frequency search space is reduced, and the dynamic effect on the acquisition sensitivity is mitigated effectively. Meanwhile, to eliminate the signal-to-noise ratio gain attenuation caused by data bit transitions, an optimal estimation of the unknown data bits is implemented with the Viterbi algorithm. A differential correction method is then utilized to improve the acquisition accuracy of Doppler shift and therefore to meet the requirement of carrier-tracking loop initialization. Finally, the reacquisition experiments of weak GPS signals are implemented in short signal blockage situations. The simulation results show that the proposed scheme can significantly improve the acquisition accuracy and sensitivity and shorten the reacquisition time. © 2013 Springer-Verlag Berlin Heidelberg.
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Moradi R, Schuster W, Feng S, et al., 2014, The carrier-multipath observable: a new carrier-phase multipath mitigation technique, GPS Solutions, Vol: 19, Pages: 73-82, ISSN: 1080-5370
Modeling and mitigating carrier-phase multi-path errors continue to be a significant challenge for high-accuracy positioning using global navigation satellite sys-tems. The multipath error is dependent on the operationalenvironment and therefore cannot be mitigated by differ-encing techniques. The effect of multipath is accentuatedwhen observables based on linear combinations of mea-surements from two or more frequencies are formulated.We develop a new carrier-phase multipath error observablethat isolates the inter-frequency carrier-phase multipatherror for linear combinations of observables, such as wide-lane (WL). Real-time kinematic positioning results fromvarying baseline lengths show that a significant reductionin between 14 and 47 % in the time to initial ambiguityresolution are achieved by correcting the WL observableusing the new carrier-phase multipath error observable.
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