Publications
83 results found
Feng S, Ochieng W, Samson J, et al., 2010, Integrity Monitoring for Carrier Phase Ambiguities, 23rd International Technical Meeting of the Satellite Division of the Institute-of-Navigation (ION GNSS-2010), Publisher: INST NAVIGATION, Pages: 2148-2159, ISSN: 2331-5911
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- Citations: 1
Feng S, Ochieng W, Moore T, et al., 2009, Carrier phase-based integrity monitoring for high-accuracy positioning, GPS SOLUTIONS, Vol: 13, Pages: 13-22, ISSN: 1080-5370
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- Citations: 65
Feng S, Ochieng W, North R, 2008, Quantitative Measures for GPS Based Road User Charging, 11th IEEE International Conference on Intelligent Transportation Systems (ITSC 2008), Publisher: IEEE, Pages: 495-500
Schuster W, Bai J, Feng S, et al., 2008, Airport Surface Movement – Performance Requirements, Architecture Considerations & Integrity Algorithms, International Civil Aviation Organisation (ICAO)
Ziebart M, Cross P, Sibthorpe A, et al., 2007, Single epoch estimation of the Galileo integrity chain sensor station clock offsets, GPS SOLUTIONS, Vol: 11, Pages: 227-237, ISSN: 1080-5370
Feng S, Ochieng W, 2007, A difference test method for early detection of slowly growing errors in GNSS positioning, JOURNAL OF NAVIGATION, Vol: 60, Pages: 427-442, ISSN: 0373-4633
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- Citations: 7
Bhatti UI, Ochieng WY, Feng S, 2007, Integrity of an integrated GPS/INS system in the presence of slowly growing errors. Part II: analysis, GPS SOLUTIONS, Vol: 11, Pages: 183-192, ISSN: 1080-5370
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- Citations: 29
Bhatti UI, Ochieng WY, Feng S, 2007, Integrity of an integrated GPS/INS system in the presence of slowly growing errors. Part I: A critical review, GPS SOLUTIONS, Vol: 11, Pages: 173-181, ISSN: 1080-5370
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- Citations: 42
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.
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
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.
Schuster W, Bai J, Feng S, et al., 2007, Airport Surface Movement – Performance Requirements, Architecture Considerations & Integrity Algorithms, ION GNSS
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
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
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
Feng S, Ochieng W Y, Walsh D, et al., 2006, A Dynamic Sampling Scheme for GPS Integrity Assessment, The Aeronautical Journal, Vol: 110, Pages: 129-143
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
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
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
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
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.
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
Feng S, Ochieng W, Schuster W, 2005, Determination of the Worst User Location for the Generation of the Galileo Integrity Flag, Proceedings of the National Navigation Conference
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