The last few years have seen a rapid growth of applications based on positioning information provided by satellite positioning systems. In transport management and control, satellite positioning has proven to be the most promising means for spatial location data collection. With the GPS modernisation programme well underway, and the recent developments of the Galileo project, even more GNSS-based applications are to be expected in the future. One such GNSS-based application is the use of position and velocity information as the prime input to a road user charging (RUC) scheme. However, navigation in urban environments raises a number of problems. Most important are the difficulties related to signal obstruction by features such as tall buildings, urban canyons, bridges and trees, as well as the effects of multipath caused by signal reflections from buildings and other vehicles. Given the inevitable limitations of road trials, the use of simulation modelling to assess the present and future satellite positioning systems' performance to support urban RUC seems indispensable. The main objective of the research undertaken at the University of Nottingham Institute of Engineering Surveying and Space Geodesy (IESSG), and the Nottingham Centre for Infrastructure (NCI), was to develop a tool to simulate GPS for Satellite Positioning-based Road User Charging (SPRUC). In this regard, an existing GPS simulator was modified to rectify one of its major weaknesses, namely the inability to address properly the change in non-static GPS measurements with respect to changes in built environment. For this purpose, state-of-the-art Geographic Information Systems (GIS) software was used to complement the simulator, and consequently a seamless interface between the two software has been developed. Finally, in order to provide a prime input to the simulator, field tests have been undertaken and significant amounts of GPS data were collected. Statistics were also derived for positioning accuracy and signal availability so that the results from the simulation modelling can be validated against those from the undertaken road trials.

Separation schemes together with Vessel Traffic Services improve existing standards. Since their role has proved to be rather passive it is assumed that the introduction of active measures could be beneficial and improvement in terms of collision or accident risk reduction is expected. The concept raises a wide variety of problems that are to be discussed, defined and solved.

Air traffic controllers use a radar separation minimum when keeping aircraft safely apart. The choice of minimum needs to ensure, to a very high degree of confidence, that radar inaccuracies are not putting the aircraft into a risk of collision – controllers can of course be required to use larger minima for operational reasons. A particular separation minimum necessarily feeds back into requirements on radar design criteria, data processing and performance. The estimation of the radar separation minimum is significantly improved by the use of a new methodology. Previous derivations were a major step forward, but were ‘static’, in that they did not attempt to take properly into account how controllers use separation minima dynamically. An analysis on the use of separation minima in en route airspace by controllers concludes that they are generally likely to use the radar minimum to pass aircraft, rather than to use the minimum in a ‘strategic’ sense (e.g. ‘in trail’ separation). The new ‘Event Model’ methodology recognises that collisions cannot happen instantly: the aircraft pair concerned must move from a safe configuration to a hazardous one. Collisions are therefore events caused by flawed flight paths, dependent on both the initial positions of aircraft and their subsequent movements and velocities.

A review of safety targets for en route ATC radar separation suggests that the existing target level of safety (TLS) is over-cautious. If risk budgeting principles are followed consistently, a ‘radar TLS’ of 1·0×10−9 fatal aircraft accidents per flying hour is appropriate. This rate is consistent with Joint Aviation Authorities (JAA) guidance on system failure conditions leading to catastrophic accidents. Dynamic and static calculations using published data are compared. The new methodology shows where there are problems with the traditional static calculations, and how to improve the estimation. A further improvement introduces a simple robust model of the controller's decision processes. The focus is not on describing what controllers would generally do, but on setting criteria based on what they could not reasonably be expected to do. This additional ingredient into the calculation adds realism and ensures that attention is focused on hazardous correlated errors. Focused data collection would be an essential component of new risk estimates. The key information required would be on radar performance and the nature and frequency of use of radar separation, including the relative velocities for proximate events at closest point of approach and the frequency of correlated gross errors (through a conditional probability factor). If this factor is not properly taken into account, then the data collection and analysis could be inefficient.

This paper outlines the design of a Vessel Traffic Management and Information System (VTMIS) for the Turkish Straits and taking this as an example shows how modelling and simulation may aid safe and efficient navigation of vessels through waterways which are narrow and winding with changing currents and are therefore difficult to navigate and prone to accidents. Ship Handling and Vessel Traffic Flow simulation models and Hyrographic Prediction model are described and the simulation trials conducted under different traffic and environment conditions are discussed to show the role that these prediction and simulation programmes can play in preventing marine casualities in different waterways, which may result in loss of human lifes and property and contamination of the environment.

The issues in this paper are a continuation of those presented previously by the authors in The Journal. In this paper we discuss the changes in maritime navigation and their consequences. We show the changes taking place in the ship's navigation process and in development of Maritime Navigation Safety and Efficiency System (MNSES). The relations between these two processes are examined. As the result, a probable scope of the competencies required by future navigators is proposed.

The use of low-cost GPS receivers and antennas for attitude determination can significantly reduce the overall hardware system cost. Compared to the use of high performance GPS receivers, the carrier phase measurements from low-cost equipment are subject to additional carrier phase measurement errors, such as multipath, antenna phase centre variation and noise. These error sources, together with more frequent cycle slip occurrences, severely deteriorate attitude determination availability, reliability and accuracy performance. This paper presents the investigation of a low-cost GPS/gyro integration system for attitude determination. By employing the dead reckoning sensor type, the ambiguity search region can be specifically defined as a small cube to enhance the ambiguity resolution process. A Kalman filter is implemented to fuse the rate gyro data with GPS carrier phase measurements. The quality control system based on innovation sequences is used to identify cycle slip occurrences and incorrect inter-antenna vector solutions. The availability of the integrated system also improves with respect to the GPS standalone system since the attitude parameters can be estimated using the angular rate measurements from rate gyros during GPS outages. The low-cost hardware used to design and test the integrated system consists of CMC Allstar receivers with the OEM AT575-70 antennas and Murata ENV-05D-52 piezoelectric vibrating rate gyroscopes. Tests in the urban area demonstrated that the introduction of rate gyros in a GPS-based attitude determination system not only effectively decreased the noise level in the estimated attitude parameters but coasted the attitude output during GPS outages and also significantly improved the system reliability.

We propose a robust trajectory planning method for vision-based autonomous land vehicle (ALV) guidance by target following using a visual field model. The proposed trajectory planning method aims to guide the ALV to achieve the goal that the targeted person will always appear in the image. It is found in this study that the goal can be achieved if three visual contact constraints in the visual field model are satisfied. The first constraint postulates that the target has appeared in the image. The second constraint asks that the vehicle head at the next position points straight towards to the target's current position. The third constraint sets bounds between the next position of the ALV and the current position of the target. A formula for the trajectory of the vehicle that satisfies the second visual contact constraint is derived. The steps for generating a speed and a turn angle of the ALV for real-time navigation are described as a trajectory-planning algorithm. Finally, the approach is tested on a real ALV and successful navigation sessions confirm the feasibility and the robustness of the approach.

The Global Positioning System (GPS) can be employed as a free attitude determination interferometer when carrier phase measurements are utilized. Conventional approaches for the baseline vectors are essentially based on the least-squares or Kalman filtering methods. The raw attitude solutions are inherently noisy if the solutions of baseline vectors are obtained based on the least-squares method. The Kalman filter attempts to minimize the error variance of the estimation errors and will provide the optimal result while it is required that the complete a priori knowledge of both the process noise and measurement noise covariance matrices are available. In this article, a neural network state estimator, which replaces the Kalman filter, will be incorporated into the attitude determination mechanism for estimating the attitude angles from the noisy raw attitude solutions. Employing the neural network estimator improves robustness compared to the Kalman filtering method when uncertainty in noise statistical knowledge exists. Simulation is conducted and a comparative evaluation based on the neural network estimator and Kalman filter is provided.

The accuracy that can be achieved by a single GPS receiver in stand-alone mode is around 10 metres with SA switched off; this is not adequate for most hydrographic studies. This study aims to improve this level of accuracy using a single geodetic receiver in stand-alone mode by applying a phase smoothing algorithm. The algorithm described in this study requires that the measurements be started from a known point for initialisation. The test site selected for the study is Halic bay, Istanbul. After GPS data were collected on a geodetic point for initialisation, the receiver was moved to a hydrographic vessel and trial measurements were performed along several survey profiles. The position of the vessel was calculated at every epoch using the carrier phase smoothing algorithm. In order to analyse the accuracy of the results, a second receiver collected data on another known point on the seashore during the whole session. The position of the vessel was accurately determined using a kinematic positioning method considering the data collected by both receivers. The results produced show that an accuracy of less than a metre can be achieved using the approach considered in this study.

Clod Shannon's fundamental works in the field of Theory of Information are well known and used in many different fields of science and practice. The Theory provides good criteria to evaluate equipment, systems, different effects and situations from the point of view of the necessary information. This article uses the Theory to attempt to create an information model for a “Ship-Danger to Navigation” system, which can evaluate an Integrated Bridge System in critical situations.

GMDSS alerting was introduced in order to automate the call for search and rescue of a ship in distress, through the utilization of the most modern terrestrial and celestial communication systems. However, the GMDSS suffers from the inefficiencies associated with equipment design, operator competence and, most importantly, with those relevant to the equipment–operator interface. The GMDSS inefficiencies are frequently manifested in the form of false alerts, which apart from using resources, degrade the overall effectiveness of the SAR operation. In this paper, the GMDSS post-full-implementation record of false alerts received by the Greek MRCC is presented and analyzed. The observed persistence of high incidence of false alerts dictates the need for the proposal of further measures to combat false alerts, to promote the intended mission of the system and to generally improve the safety of navigation at sea.