Publications
339 results found
Moradi R, Schuster W, Feng S, et al., 2014, A new carrier phase multipath mitigation technique for ionosphere-free combinations, ION ITM (2014)
Zis T, North RJ, Angeloudis P, et al., 2014, Evaluation of cold ironing and speed reduction policies to reduce ship emissions near and at ports, Maritime Economics & Logistics, Vol: 16, Pages: 371-398
Zhang X, Zhan X, Feng S, et al., 2014, An Open-Source Real-Time L1/L2 Dual Frequency Software Receiver with an Open Source GPS-Disciplined Clock - Design, Implementation and Test, 27th International Technical Meeting of the Satellite-Division of the Institute-of-Navigation (ION GNSS), Publisher: INST NAVIGATION, Pages: 1376-1382, ISSN: 2331-5911
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- Citations: 2
Zis T, North RJ, Angeloudis P, et al., 2014, Effects of speed reduction policies near ports
Anvari B, Bell MGH, Angeloudis P, et al., 2014, Long-range collision avoidance for shared space simulation based on social forces, Publisher: Elsevier
Araghi BN, Hu S, Krishnan R, et al., 2014, A comparative study of k-NN and hazard-based models for incident duration prediction, Pages: 1608-1613
Schuster W, Ochieng W, Crook I, 2013, Future Long-Term ATM concept, Infrastructure, Technologies and operational Environment – FLITE, SESAR Innovation Days
Schuster W, Ochieng W, 2013, Aviation Environment Research Update Symposium, Waterside, Aviation Environment Research Update Symposium
Moradi R, Schuster W, Feng S, et al., 2013, Reducing GPS wide lane ambiguity resolution time: A novel carrier phase multipath mitigation technique, Pages: 343-350
Modeling and mitigating carrier multipath errors continues to be a significant challenge for high accuracy positioning using Global Navigation Satellite Systems (GNSS), because the level of multipath is dependent on the operational environment and cannot be mitigated by differencing techniques. Despite significant research in the domain, multipath remains a major problem in high accuracy positioning. The effect of carrier multipath is even more significant when observables are formed by linear combination of measurements from two or more frequencies. Yet, such combinations are commonly in use. For example, in order to facilitate ambiguity fixing for GPS L1, the wide lane observable formed from GPS L1 and L2 measurements is often used to constrain the L1 ambiguity space. Multipath error causes a bias in the estimation of the float solution making it difficult to resolve the integer ambiguities. In this paper, a novel method is developed to mitigate carrier multipath errors for linear combinations, focusing on the wide lane observable. This consists in two stages. In the first stage an observable is derived from combined use of measurements in the same and different frequencies (i.e. GPS L1 and L2), and in the second the observable is applied to mitigate wide lane carrier multipath errors. The proposed method reduces the carrier multipath error in wide lane observables to the level of carrier multipath in the L1 observable, which is significantly smaller. Three test scenarios with different baselines were conducted using real data sets collected in static mode, and post processed in Real-Time Kinematic (RTK) mode. After applying the multipath mitigation method, the time duration to ambiguity resolution were reduced by 25, 48 and 129 seconds, compared to 47, 535 and 427 without the proposed method, for different test scenarios. It means about 53% improvement was achieved in scenario 1, 9% in scenario 2 and 30% in scenario 3.
Nascimento FAC, Majumdar A, Ochieng WY, 2013, Helicopter accident analysis, The Journal of Navigation, Vol: 67, Pages: 145-161
Tobaruela G, Majumdar A, Ochieng WY, et al., 2013, Enhancing Cost-Efficiency and Reducing Capacity Shortages: Strategic Planning and Dynamic Shift Management, Tenth USA/Europe Air Traffic Management Research and Development Seminar
This paper analyses the relationship between capacity and cost-efficiency at an en-route Air Traffic Control Centre level. It develops a set of cost-efficiency metrics to describe the centre planning process, and compares these results to cost- efficiency values. In order to understand the effect of the new tools and procedures implemented at the centre on its cost- efficiency, statistical analysis of the operational data before and after implementation is undertaken. The results show that the introduction of a dynamic shift management enabled by staff planning automation tools, along with a flexible roster and an appropriate planning process can simultaneously enhance capacity and cost-efficiency. These improvements are mapped to the SESAR Operational Improvements, to assess the feasibility of the programme to achieve its capacity and cost-efficiency improvement targets. A set of recommendations is developed.
Moradi R, Schuster W, Feng S, et al., 2013, Carrier Multipath observable: a new carrier phase multipath mitigation technique, New Navigator Seminar
Syd Ali B, Majumdar A, Ochieng W, et al., 2013, ADS-B: The Case for London Terminal Manoeuvring Area (LTMA), ATM Seminar 2013
Nascimento FAC, Majumdar A, Ochieng WY, 2013, A 15-year multivariate analysis of worldwide offshore helicopter accidents, AHS 69th Annual Forum and Technology Display, Publisher: AHS
Jokinen A, Feng S, Schuster W, et al., 2013, GLONASS Aided GPS Ambiguity Fixed Precise Point Positioning, JOURNAL OF NAVIGATION, Vol: 66, Pages: 399-416, ISSN: 0373-4633
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- Citations: 30
Jokinen A, Feng S, Schuster W, et al., 2013, Fixed ambiguity Precise Point Positioning (PPP) using tropospheric corrections based on Numeric Weather Modeling (NWM), ION 2013 Pacific PNT
Panagiotakopoulos D, Majumdar A, Ochieng WY, 2013, Extreme Value Theory based Integrity Monitoring of Global Navigation Satellite Systems, GPS Solutions, ISSN: 1080-5370
Measurements consistency based Receiver Autonomous Integrity Monitoring (RAIM) is the main technique for monitoring the integrity of Global Satellite Navigation Systems (GNSS) at the user level. Existing RAIM algorithms utilize two tests, in the position domain, for RAIM availability and measurement domain, for failure detection. These tests involve the computation of three parameters: test statistic, decision threshold and protection level. The test statistic is based on the actual measurements in the form of the Sum of the Squared Errors (SSE). The decision threshold is chosen on the basis of the statistical characteristics of the SSE including the assumption that the errors are normally distributed. However, in practice residual error distributions exhibit heavier tails than predicted by the Gaussian model. Therefore, this paper challenges the normality assumption of the residual navigation errors in three ways. Firstly, it uses real data to assess its impact on the traditional RAIM algorithm. Secondly, it applies Extreme Value Theory (EVT) to the tails and derives the Generalised Extreme Value (GEV) distribution to capture residual navigation errors. Thirdly, it compares the performance of the traditional RAIM approach with that employing the GEV distribution. The results demonstrate that the GEV distribution has an important role to play in integrity monitoring and therefore, should be considered in the development of future integrity algorithms.
Nascimento FAC, Majumdar A, Ochieng WY, 2013, Investigating the truth of Heinrich's pyramid in offshore helicopter transportation, Transportation Research Board 92nd Annual Meeting, Publisher: TRB
Nur K, Feng S, Ling C, et al., 2013, Integration of GPS with a WiFi high accuracy ranging functionality, Geo-Spatial Information Science, Vol: 16, Pages: 155-168, ISSN: 1009-5020
High accuracy seamless positioning is required to support a vast number of applications in varying operational environments. Over the last few years, the global positioning system (GPS) has become the de facto technology for positioning applications. However, its performance is limited in indoor and dense urban environments due to multipath as well as signal attenuation and blockage. A number of techniques integrating GPS with other positioning technologies have been developed to address the limitations of standalone GPS in these difficult environments. While most of the developed techniques cover the outages of GPS in such environments, they do not provide acceptable performance, in terms of positioning accuracy, especially for some mission-critical (e.g. safety) applications. This paper proposes a tightly coupled (i.e. in the measurement domain) GPS/WiFi integration method which, in addition to addressing GPS outages, improves the overall positioning accuracy to the meter-level, thus satisfying the requirements of a number of location based services and intelligent transport systems applications. The performance of the proposed GPS/WiFi integration method is assessed for a number of scenarios in a simulation environment for an identified dense urban area in London, UK. © 2013 © 2013 Wuhan University.
Feng S, Jokinen A, Milner C, et al., 2013, New methods for dual constellation single receiver positioning and integrity monitoring, Geo-Spatial Information Science, Vol: 16, Pages: 201-209, ISSN: 1009-5020
Navigation system integrity monitoring is crucial for mission (e.g. safety) critical applications. Receiver autonomous integrity monitoring (RAIM) based on consistency checking of redundant measurements is widely used for many applications. However, there are many challenges to the use of RAIM associated with multiple constellations and applications with very stringent requirements. This paper discusses two positioning techniques and corresponding integrity monitoring methods. The first is the use of single frequency pseudorange-based dual constellations. It employs a new cross constellation single difference scheme to benefit from the similarities while addressing the differences between the constellations. The second technique uses dual frequency carrier phase measurements from GLONASS and the global positioning system for precise point positioning. The results show significant improvements both in positioning accuracy and integrity monitoring as a result of the use of two constellations. The dual constellation positioning and integrity monitoring algorithms have the potential to be extended to multiple constellations. © 2013 © 2013 Wuhan University.
Jokinen A, Feng S, Schuster W, et al., 2013, Integrity monitoring of fixed ambiguity Precise Point Positioning (PPP) solutions, Geo-Spatial Information Science, Vol: 16, Pages: 141-148, ISSN: 1009-5020
Traditional positioning methods, such as conventional Real Time Kinematic (cRTK) rely upon local reference networks to enable users to achieve high-accuracy positioning. The need for such relatively dense networks has significant cost implications. Precise Point Positioning (PPP) on the other hand is a positioning method capable of centimeter-level positioning without the need for such local networks, hence providing significant cost benefits especially in remote areas. This paper presents the state-of-the-art PPP method using both GPS and GLONASS measurements to estimate the float position solution before attempting to resolve GPS integer ambiguities. Integrity monitoring is carried out using the Imperial College Carrier-phase Receiver Autonomous Integrity Monitoring method. A new method to detect and exclude GPS base-satellite failures is developed. A base-satellite is a satellite whose measurements are differenced from other satellite's measurements when using between-satellite-differenced measurements to estimate position. The failure detection and exclusion methods are tested using static GNSS data recorded by International GNSS Service stations both in static and dynamic processing modes. The results show that failure detection can be achieved in all cases tested and failure exclusion can be achieved for static cases. In the kinematic processing cases, failure exclusion is more difficult because the higher noise in the measurement residuals increases the difficulty to distinguish between failures associated with the base-satellite and other satellites. © 2013 Wuhan University.
Smith P, Kyriakidis M, Majumdar A, et al., 2013, Impact of European Railway Traffic Management System on Human Performance in Railway Operations European Findings, TRANSPORTATION RESEARCH RECORD, Pages: 83-92, ISSN: 0361-1981
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- Citations: 12
Ali BS, Schuster W, Ochieng W, et al., 2013, A Study of ADS-B Data Evaluation and Related Problems, International Technical Meeting of the Institute-of-Navigation, Publisher: INST NAVIGATION, Pages: 444-455, ISSN: 2330-3646
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- Citations: 1
Wilke S, Majumdar A, Ochieng W, 2013, The impact of airport characteristics on airport surface accidents and incidents, Submitted for review
Schuster W, Ochieng W, 2013, Performance Requirements of Future Trajectory Prediction and Conflict Detection and Resolution Tools within SESAR and NextGen: Framework for the Derivation and Discussion, Journal of Air Transport Management
Jokinen A, Feng S, Schuster W, et al., 2013, Improving ambiguity validation and integrity monitoring of Precise Point Positioning (PPP), PROCEEDINGS OF THE 26TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS 2013), Pages: 1224-1233, ISSN: 2331-5911
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- Citations: 1
Smith P, Majumdar A, Ochieng WY, 2012, An overview of lessons learnt from ERTMS implementation in European railways, Journal of Rail Transport Planning and Management, Vol: 2, Pages: 79-87, ISSN: 2210-9706
The European Union's aspiration for railway systems that are interoperable across Europe is driven by the need to service a market that is open within and across industrial sectors and national boundaries. This in turn requires that the technologies and operational procedures that underpin the railway systems facilitate not only interoperability but also enhancement of safety, capacity and efficiency. The European Railway Traffic Management System (ERTMS) is designed to enable interoperability through use of one unique signalling system as opposed to conventional signalling systems. However, the introduction of ERTMS must be undertaken to facilitate the European wide ambition to reduce risk on the railways.This paper addresses the issues relevant to the safe introduction of ERTMS into European railway systems, with a focus on the technical and procedural challenges of moving from conventional signalling to a new traffic management system. Existing literature, augmented with a targeted survey of subject matter experts, is used for a critical appraisal of safety considerations across Europe. Differences and variations across networks and countries are identified, and used to determine the significant issues that need to be addressed to enable the safe introduction of ERTMS. Finally, generic observations are made on the factors that impact safety and human factors as a result of the introduction of new technologies and procedures into existing railway environments. © 2013 Elsevier Ltd.
Feng S, Jokinen A, Ochieng W, et al., 2012, Multi-constellation RAIM in the presence of multiple faults-a bottom up approach, Pages: 2858-2868
Receiver Autonomous Integrity Monitoring (RAIM) was originally proposed to identify potential faults by consistency checking of redundant measurements in one constellation (i.e. GPS). The limited number of visible satellites imposes constraints on the specification of RAIM algorithms, for example, assuming a single fault. As faults induced by local environments could be present in multiple measurements, the limited number of visible satellites from a single constellation makes it impossible to exclude multiple faults where the requirement for availability is the dominant factor. The availability of multiple constellations including GLONASS and in the future Compass and Galileo offer the opportunity to consider the detection and exclusion of multiple faults. The probability of multiple faults originating from the space and control segments is low. However, it is higher in the case of multiple faults that originate from the user segment due to local environment induced error sources including signal shadowing, Non-Line Of Sight (NLOS), multipath and radio interference. A Top-Down Approach (TDA) is currently employed to deal with multiple faults in multiple constellations. All the measurements are used together or grouped by constellation. In the first approach, if any faults are detected, a data snooping method is used for exclusion. In the presence of multiple faults, this method is time consuming and is therefore, not suitable for real time applications. The second approach is effective if one constellation has multiple faults while the other has only single fault. The availability of this approach is subject to RAIM availability in each constellation. This paper analyses multiple failures modes originating from the user segment and their impact on signal quality. A signal quality model is derived and characterized with the data from an IGS (International GNSS Service) station. On the basis of this model, a group separation approach is applied to exclude a group of
Jokinen A, Feng S, Milner C, et al., 2012, Improving fixed-ambiguity Precise Point Positioning (PPP) convergence time and accuracy by using GLONASS, ION GNSS 2012
Nascimento FAC, Majumdar A, Ochieng WY, 2012, Incident reporting in offshore helicopter transportation, 38th European Rotorcraft Forum 2012
This paper builds on the lessons from accident investigations to analyse helicopter incidents in the British Mandatory Occurrence Reporting (MOR) scheme. From the results of the analysis, the paper highlights potentially severe shortcomings in a number of critical areas, and informs stakeholders in industry of specific initiatives to ensure that the right lessons are learned from past occurrences and how these could be used to inform future interventions.
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