Publications
339 results found
Bhatti UI, Ochieng WY, 2007, Failure modes and models for integrated GPS/INS systems, Journal of Navigation, Vol: 60, Pages: 327-348, ISSN: 0373-4633
GPS is the most widely used global navigation satellite system. By design, there is no provision for real time integrity information within the Standard Positioning Service (SPS). However, in safety critical sectors like aviation, stringent integrity performance requirements must be met. This can be achieved externally or at the receiver level through receiver autonomous integrity monitoring (RAIM). The latter is a cost effective method that relies on data consistency, and therefore requires redundant measurements. An external aid to provide this redundancy can be in the form of an Inertial Navigation System (INS). This should enable continued performance even during RAIM holes (when no redundant satellite measurements are available). However, due to the inclusion of an additional system and the coupling mechanism, integrity issues become more challenging. To develop an effective integrity monitoring capability, a good understanding of the potential failure modes of the integrated system is vital. In this paper potential failure modes of integrated GPS/INS systems are identified. This is followed by the specification of corresponding models that would be required to investigate the capability of existing integrity algorithms and to develop enhancements or new algorithms. © The Royal Institute of Navigation.
Bhatti UI, Ochieng WY, 2007, Failure modes and models for integrated GPS/INS systems, JOURNAL OF NAVIGATION, Vol: 60, Pages: 327-348, ISSN: 0373-4633
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- Citations: 56
Ochieng WY, Feng S, Moore T, et al., 2007, User level integrity monitoring and quality control for seamless positioning in all conditions and environments, Pages: 2573-2583
This paper presents the research undertaken to date to develop sensor level autonomous integrity monitoring and quality control to support centimetre level positioning in all conditions and environments as conceived under the SPACE (Seamless Positioning in All Conditions and Environments) project. The basic philosophy for integrity monitoring and quality control is early detection of anomalies which requires monitoring of the entire processing chain. A number of novel concepts and algorithms are developed including algorithms to deal with special issues associated with carrier phase based integrity monitoring (including integration with inertial navigation systems), a new "difference test" integrity monitoring algorithm for detection of slowly growing errors, and a new group separation method for simultaneous multiple failure exclusion.Both real and simulated data are used to test the new algorithms. The results show that the new algorithms, when used together with selected existing ones, provide effective integrity monitoring and quality control for centimetre level seamless positioning in all conditions and environments.
Moore T, Hill C, Ince S, et al., 2007, End-to-end testing of an integrated centimetric positioning test-bed, Pages: 1128-1138
SPACE (Seamless Positioning in All Conditions and Environments) is a collaborative project with the objective to support centimeter-level positioning everywhere, particularly in difficult environments. To achieve this goal, a number of different positioning technologies have to be integrated together including GNSS, INS, pseudolites and other technologies such as Ultra-Wideband (UWB) and Bluetooth ranging. The integration of these sensors is achieved by the development a 'plug and play' filter that will optimally combine measurements from each sensor to form an accurate position solution. The SPACE project is investigating various factors which degrade positioning performance in difficult environments. A particular focus for the purposes of the research is the difficult environment in the shadow of a building, during the transition from outdoor GNSS-based positioning to indoor positioning based on other sensors. Techniques to mitigate the effects of multipath, at both the receiver measurement and data processing stages, to aid the integrity of the integrated solution, and to improve the performance of the GNSS receiver have all been addressed. This paper describes an end-to-end test of the SPACE concepts. A test-bed has been developed which allows for the different positioning technologies to be used simultaneously, and several trials have been conducted. To date the trials have concentrated on a test site which offers a suitable outdoor-indoor transition area, and which is straightforward to model for purposes such as multipath simulation. The testing addressed by the paper includes a GPS/INS integrated solution, migrating to a UWB/INS solution indoors. The paper describes the field trials themselves, the instruments that were carried on the test-bed during the trials, and some preliminary results from some of the sensors. universities, who will all gain an awareness of industry's needs and real-world experience in addressing those needs as a distributed team. This
Feng S, Ochieng W, 2007, Integrity of navigation system for road transport, Pages: 4351-4361
The integrity of navigation systems has attracted the attention of not only safety critical applications (e.g. aviation) but also increasingly liability critical and other value added applications. This paper proposes the required navigation performance and develops vehicle autonomous integrity monitoring algorithms for road transport including the derivation of protection level in dead reckoning mode. The results of a trial carried out near London show that the proposed algorithms can effectively detect potential failures and generate appropriate protection levels taking into account the availability requirement. The proposed algorithms should be used to improve the quality and safety of location based management and services.
Mautz R, Ochieng W, Brodin G, et al., 2007, 3D Wireless Network Localization from Inconsistent Distance Observations, AD HOC & SENSOR WIRELESS NETWORKS, Vol: 3, Pages: 141-170, ISSN: 1551-9899
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- Citations: 20
Majumdar A, Ochieng WY, 2007, Air traffic control complexity and safety - Framework for sector design based on controller interviews of complexity factors, TRANSPORTATION RESEARCH RECORD, Pages: 70-80, ISSN: 0361-1981
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- Citations: 7
Mautz R, Feng S, Ochieng W, et al., 2006, A high integrity positioning method for ad-hoc networks, Pages: 134-144
The aim of this paper is to present the current status of the positioning algorithm for iPLOT (intelligent Pervasive Location Tracking) as an automatic, low-cost system that exploits current or near future wireless communications based on Bluetooth to enable continuous tracking of the location of devices in all environments. The proposed adhoc method has a full 3D positioning capability and set up for sensor networks. It is based on a lateration strategy to achieve high integrity positioning in wireless ranging networks. The local positioning method has the potential to complement GNSS (Global Navigation Satellite Systems) in terms of coverage. The novel positioning strategy proposed has three phases: (I) Creation of a rigid structure: The smallest redundant and rigid graph consists of 5 network nodes with distance constraints to each other. If such an initial cluster passes statistical tests, it is released for further expansion. Additional nodes are added consecutively using a novel multilateration technique which is based on a surplus of observations and carefully avoids flip ambiguities. (II) Merging of clusters: Experiments show that only a fraction of nodes can become a member of one single cluster. The remaining nodes are likely to make up their own clusters which may or may not be connected with neighbouring clusters. In case two clusters share an adequate number of nodes and/or range observations between them, they can be merged using an over -determinant 3 dimensional 6-parameter transformation. (Ill) Transformation of the cluster(s) into a reference coordinate system. The outcome of these three steps is a cluster of nodes with their coordinate positions and their error variances in a targeted reference system. Nodes with insufficient integrity or positional accuracy are strictly separated by delivering the corresponding integrity flag. Our simulations with large networks (e.g. 100 nodes) demonstrate the importance of carefully making decisions on folding
Subotic B, Ochieng WY, Straeter O, 2006, Recovery from equipment failures in air traffic control: A probabilistic assessment of context
The insights on human performance gained from the area of human reliability assessment are increasingly being employed in the various safety-critical domains, such as air traffic control (ATC). Research over the years has confirmed the important role of context in which human performance takes place. As a result, research on recovery from equipment failures in ATC requires the precise definition of the context surrounding any failure type. This paper defines context through a set of recovery influencing factors (RIFs). It moves away from the common qualitative approach and proposes a generic probabilistic method to analyze both the context and the ensuing air traffic controller performance. The proposed method provides an assessment of the quality of recovery and thus provides a better understanding of controller recovery overall. The method can be tailored to the specific characteristics of any ATC Centre and the airspace within which it provides its service and is therefore, a valuable tool for the management of safety in Air Traffic Management. © 2006 by ASME.
North RJ, Noland RB, Ochieng WY, et al., 2006, Modelling of particulate matter mass emissions from a light-duty diesel vehicle, TRANSPORTATION RESEARCH PART D-TRANSPORT AND ENVIRONMENT, Vol: 11, Pages: 344-357, ISSN: 1361-9209
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- Citations: 20
Feng S, Ochieng WY, 2006, An efficient worst user location algorithm for the generation of the Galileo integrity flag, JOURNAL OF NAVIGATION, Vol: 59, Pages: 381-394, ISSN: 0373-4633
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- Citations: 6
Quddus MA, Ochieng WY, Noland RB, 2006, Integrity of map-matching algorithms, TRANSPORTATION RESEARCH PART C-EMERGING TECHNOLOGIES, Vol: 14, Pages: 283-302, ISSN: 0968-090X
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- Citations: 66
Feng S, Ochieng WY, Walsh D, et al., 2006, A measurement domain receiver autonomous integrity monitoring algorithm, GPS SOLUTIONS, Vol: 10, Pages: 85-96, ISSN: 1080-5370
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- Citations: 61
Mautz R, Ochieng W, Walsh D, et al., 2006, Low cost intelligent pervasive location tracking (iPLOT) in all environments for the management of crime, JOURNAL OF NAVIGATION, Vol: 59, Pages: 263-279, ISSN: 0373-4633
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- Citations: 3
Feng S, Ochieng W, Walsh D, et al., 2006, A dynamic sampling scheme for GPS integrity assessment, AERONAUTICAL JOURNAL, Vol: 110, Pages: 129-143, ISSN: 0001-9240
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- Citations: 4
Peng B, Kemp G, Brodin, et al., 2006, SIP for wireless positioning: System and architecture, Pages: 32-35
The recent boom in wireless communications has led to a wide range of new applications. Wireless positioning is an emerging technology which can provide accurate locations for indoor environments when satellite based positioning systems are not available. In this paper, a Session Initiation Protocol (SIP) based system architecture for wireless positioning is described and an overview of how this can be used in overall system architecture has been provided. The proposed system architecture has shown that SIP is competent as a network signaling protocol for wireless positioning. © 2006 IEEE.
Quddus MA, Ochieng WY, Noland RB, 2006, Map matching algorithms for intelligent transport systems applications
Map matching algorithms play a key role in providing the navigation solution for many Intelligent Transport Systems (ITS) and Location Based Services (LBS). It is essential that the map matching algorithm used in the navigation module meets the specified requirements set for a particular service. Although the performance of a map matching algorithm depends on the characteristics of data inputs, the technique used in the algorithm can enhance the overall performance. This paper sets out to report on map matching algorithms developed by the authors in earlier work, and whether these can satisfy the required navigation performance (RNP) of various ITS services and LBS applications. This is achieved by testing the algorithms using real-world field data. The results suggest that these algorithms are capable of supporting the navigation function of many services including route guidance, bus priority at junctions, fleet management, etc.
Feng SJ, Ochieng WY, Walsh D, et al., 2006, A highly accurate and computationally efficient method for predicting RAIM holes, JOURNAL OF NAVIGATION, Vol: 59, Pages: 105-117, ISSN: 0373-4633
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- Citations: 6
Mautz R, Ochieng WY, Brodin G, et al., 2006, Low-cost intelligent pervasive location and tracking (iPLOT) for the management of crime, Journal of Navigation, Vol: 59, ISSN: 0373-4633
Majumdar A, Dupuy M-D, Ochieng WY, et al., 2006, Developing safety indicators for New Zealand airspace - Analysis of loss-of-separation incidents, 85th Annual Meeting of the Transportation-Research-Board, Publisher: TRANSPORTATION RESEARCH BOARD NATL RESEARCH COUNCIL, Pages: 86-97, ISSN: 0361-1981
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- Citations: 2
Quddus MA, Noland RB, Ochieng WY, 2006, A high accuracy fuzzy logic based map matching algorithm for road transport, JOURNAL OF INTELLIGENT TRANSPORTATION SYSTEMS, Vol: 10, Pages: 103-115, ISSN: 1547-2450
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- Citations: 156
Schuster W, Ochieng W, 2006, Gate-to-Gate with Modernised GPS, Galileo and GBAS – Harmonisation of Precision Approach Performance Requirements, ION GNSS
Feng S, Ochieng WY, 2006, A General Method for Accurate Assessment of GNSS FD/FDE Holes, 19th International Technical Meeting of the Satellite Division of the Institute-of-Navigation, Publisher: INST NAVIGATION, Pages: 2658-2665, ISSN: 2331-5911
Moore T, Hill C, Hide C, et al., 2005, Development of a test bed facility for high accuracy positioning in difficult environments, Pages: 2066-2075
The SPACE project is a joint project undertaken by four of the UK's leading academic GNSS universities and support from eight of the UK's leading companies in the field of GNSS. The project aim is to develop a test bed facility that gives centimeter level positioning in all conditions and environments. The test bed can be used to evaluate positioning accuracy of other sensors, or to test new algorithms via an open interface. In order to achieve this aim, a number of activities are underway. Firstly a reference environment has been established in order to provide an area in which all signal obstructions are known. The environment contains a range of conditions including open areas, partial obstructions of GPS signals close to a building, and inside a building. The environment can then be used to collect data in which all parameters are known which can be used to develop and validate simulation models, help to understand error characteristics, and provide an environment in which the test bed itself can be tested. This paper presents the methodology for establishing a reference environment for the test bed. The environment is then used to validate a multipath simulation of a static GPS receiver close to a wall. The paper then extends this approach to the dynamic case where the performance of a navigation grade INS is assessed to identify if it is suitable to provide a reference trajectory in dynamic conditions.
Majumdar A, Sharma K, Pant R, et al., 2005, Development of air traffic complexity metric for Indian en-route airspace, Pages: 1509-1523
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- Citations: 1
Ziebart M, Cross P, Sibthorpe A, et al., 2005, Every nano-second counts: Estimating the Galileo integrity chain clock offsets globally in a single epoch, Pages: 1381-1390
The information content of the Galileo integrity chain depends on a number of key factors, one of which is contamination of the Signal-In-Space Errors with residual errors other than imperfect modelling of satellite orbits and clocks. A potential consequence of this is that the user protection limit is driven not by the errors associated with the imperfect orbit and clock modelling (i.e. the accuracy of the Signal In Space Accuracy), but by the level of noise in the integrity chain. This noise increases the minimum bias the integrity chain can guarantee to detect, which is reflected in the user protection limit. One contributor to the noise in the integrity chain is the inaccuracy associated with the estimation of the offset between the Galileo Sensor Station (GSS) receiver clocks and the Galileo System Time (GST), termed the receiver clock synchronization error (CSE). This paper describes research carried out to determine both the CSE and its associated error using GPS data as captured with the Galileo System Test Bed Version 1 (GSTB-V1). The CSE is the difference between a receiver clock and system time (in this case GPS time) - whilst it is common to refer to it as an error, in fact, as long as it is perfectly known, it does not lead to any degradation of the system performance. What is important is the error in the CSE, that is, it is vital to determine the CSE as accurately as possible as any error in the CSE leads directly to equivalent range error. The aim of this research was to compare two methods for determining GSS CSE and the corresponding uncertainty (noise) across a global network of tracking stations. The two techniques are: 1: Single station-satellite pair method - an 'averaging' technique using a single epoch of data and carried out at individual sensor stations, without recourse to the data from other stations. 2: Global network solution method - also single epoch based, but using the inversion of one simultaneous linearised model of the system to
Ioannides R, Walsh D, Ochieng W, et al., 2005, Towards a complete FMEA method to assess the performance of GPS system for GPS based applications, Pages: 1826-1840
Failure mode effect analysis (FMEA) methods attempt to analyse the effects of failures on GPS performance by characterising the GPS failure modes and assess their impact on GPS based applications. There are a number of limitations, arising from the complexity of the system, that have to be overcome for validating GPS-based applications, in the presence of the GPS failure modes. To the best knowledge of the author there is no complete FMEA process that can be followed to assess the performance of the system specifically for GPS based flight operations. The intention of this paper is to present a new complete FMEA process for validating GPS based flight operations that can be used to accurately determine the performance of the system for any GPS based application. Geometry is one of the three factors, the other two being biases and nominal range errors, that are key to the assessment of the performance of a satellite based navigation system, like GPS or Galileo. For overcoming the limitations imposed by the complexity of the GPS on FMEA processes used to assess the performance of the system in the presence of these failures, the effect of the geometry had to be analysed and link its effects with the GPS failure modes which has been a major task of this work. In order to identify the geometry parameters that can be used to accurately predict the impact of geometry on the performance of the system required the investigation of several geometry factors starting from the concept of slope. In this paper we also present two new geometry parameters, PB and BT that can be directly calculated from the equation of the slope. PB is defined as the ratio of the position error over the bias applied to the faulty satellite, while BT is defined as the ratio of the bias applied to the faulty satellite over the test statistic contribution due to that bias. These geometry parameters have been tested for evaluating their consistency in predicting the performance of the system linking the
Subotic B, Ochieng WY, 2005, Recovery from equipment failures in air traffic control, Pages: 69-73
This paper gives an overview of equipment failures in Air Traffic Control (ATC). It presents data to show that equipment failures exist in spite of designed technical defences. A preliminary analysis of operational data from two countries has been carried out to determine the average annual number of failures and to highlight the major subsystems affected. The paper concludes with a discussion on the process of recovery from failures and proposes the methods for its improvement.
Majumdar A, Ochieng WY, Bentham J, et al., 2005, En-route sector capacity estimation methodologies: An international survey, JOURNAL OF AIR TRANSPORT MANAGEMENT, Vol: 11, Pages: 375-387, ISSN: 0969-6997
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- Citations: 36
North RJ, Ochieng WY, Quddus MA, et al., 2005, Development of a vehicle emissions monitoring system, PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-TRANSPORT, Vol: 158, Pages: 167-177, ISSN: 0965-092X
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- Citations: 8
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