Because of increasing traffic in urban areas, public transport has to become more attractive and efficient by introducing computer-aided dynamic passenger information and on-line vehicle location. The tram location pilot system described makes vehicle scheduling and control systems independent of expensive location infrastructure (e.g. beacons). It uses on-board autonomous DGPS positioning with dead reckoning and a radio link to the control centre. The evaluation of the measured vehicle positions clearly demonstrates that operational accuracy requirements for public transport applications are met. The whole Tramway Location System (TLS) is structured into the 3 segments: on-board equipment, components of the operation centre and roadside equipment. The trial set-up for dynamic real-time measurements of the positioning accuracy is described, and the results of the evaluation of more than 7300 position fixes at 15 geodetically measured reference points along the tramway are presented. The conclusions indicate that, during runs in city environments, DGPS combined with dead reckoning achieves vehicle positioning precise enough to enable a reliable, improved and up-to-date passenger information service at the stops.

In this paper, we shall outline the reasons why the installation of shipborne equipment, which enables vessels to be positively identified from the shore and from other vessels, is so important and necessary. We shall also describe the latest innovations in this field and propose minimum standards for a transponder system.

A simulator experiment was conducted to determine the potential benefits of path prediction on the navigational performance of channel-bound vessels. Channel pilots had to sail an approach channel under critical conditions in a deep-draught vessel. For the navigation task, basic radar information was used, supplemented by three different path predictors. Predictor (a) was based on an accurate fast-time hydrodynamic model of the vessel and showed the exact future path of the vessel. Both other path predictors were less accurate, relatively simple extrapolators; predictor (b) was based on a speed and rate of turn extrapolator and showed a curved representation of the future path; predictor (c) was based on a linear speed and course extrapolator and showed the ground velocity vector. Navigational performance was determined in terms of deviation from the planned route. The results indicate that the relatively simple extrapolator (b) supported the navigational task as effectively as the highly accurate path predictor (a). In comparison with the linear extrapolator (c), the navigational accuracy increased by a factor of two. It is concluded that support in anticipating the vessel's rate of turn is essential for accurate navigation. Implications of the use of path prediction for ship control are discussed.

Accurate charts of tidal streams are needed in many fields of science and industry. The Proudman Oceanographic Laboratory's numerically modelled hydrodynamic data sets provide a suitable source for the production of such charts. Different methods of producing data in ‘tidal diamond’ format were investigated and the most suitable was selected for implementation over the UK continental shelf.

The latest statistics on maritime accident alerts are again demonstrating a high percentage of false alarms from Emergency Position Indicating Beacons (EPIRBS) in Spanish waters. Of a total number of 243 received distress alarms, only three were real and 123 were never identified; a very similar situation exists in the rest of Europe. To address this problem, as well as IMO Resolution A.814(19)/23.11.95, there is a Spanish proposal to install a receiver (121-5/243/406 MHz) on board ships, so that the seafarer can detect accidental activation of an EPIRB. The installation of EPIRBS, which had seemed to be sufficient to solve the problem of locating vessels in distress, apparently needs the help of other tools. One such tool could be the very high frequency radio direction finder (VHF/DF) proposed in this paper. Recent experiments using VHF/DF carried on board the ships Salvamar Tenerife and Punta Salinas, in conjunction with the traffic control tower of the Rescue Coordination Centre (RCC) of Santa Cruz de Tenerife (Canary Islands), demonstrated a number of advantages which are described in this paper.

This paper deals with the development of a location database compatible for use with the proposed Radio Data System – Traffic Messaging Channel for Great Britain. It looks at the needs for such a database and the technical difficulties that have been overcome in developing a cost-effective, automatic, production system that provides the most detailed roads location database in Great Britain.

In recent years, both the offshore industry and the navies of the world have become increasingly interested in the potential operational usage of unmanned underwater vehicles. This paper provides a comprehensive review of a number of modern control approaches and artificial intelligence techniques which have been applied to the autopilot design problem for such craft.

This paper looks at the stimulus given by the practice and theory of navigation to certain problems in mathematical astronomy. The need for more accurate techniques of finding latitude and longitude, brought about largely by the great voyages of discovery and exploration as well as an increase in sea trade, gave rise to navigational instrument makers who produced devices of increasing accuracy. These craftsmen also made better measuring devices for the new observatories. Improvements in measurements led not only to new discoveries, but also made greater demands of theories underlying the practice of navigation. This gave impetus to the search for solutions to related problems in mathematical astronomy. Methods and special functions developed in this context were eventually to find application in a much wider range of problems in theoretical physics and engineering.

This paper discusses the necessity and feasibility of the application of Pulse Doppler Radar in vts through analysing the limitations of the non-coherent, single frequency, radar and the advantages of PD radar.

Performance enhancement and cost reduction are driving forces in today's airline industry. In a world of cost pressures and escalating charges, research was conducted into better use of jet streams as a means of reducing costs. When operating on international airline routes, specific features of flight mechanics were adapted and tailored to fit a B747-200 aircraft, major emphasis being placed on intercepting, or avoiding where necessary, the high energy jet stream winds of the global weather system, adjusting flight profiles and modifying route structures. Operations were conducted both into wind and down wind, over a period of five years. Techniques employed show fuel may be saved regardless of the wind being a tailwind or headwind. Both fuel and time have a significant bearing on airline direct operating costs: savings of more than 1·1 percent being made on fuel and 0·786 percent on time. Limitations on using the techniques to gain maximum benefit are related to the high volume of aircraft blocking all major airways, and better quality, real time weather forecasts. The discussion looks at ways of improving the use of jet streams, as the world's airline traffic continues to grow. Forecasting upper winds, particularly in oceanic areas, needs to improve if airlines are to derive maximum benefits from these winds. There is need for further study utilising other aircraft types to ascertain what savings can result. Initial results were encouraging, using a Tristar L1011 aircraft.

In this paper, two algorithms of Global Positioning System based attitude determination are proposed. The first algorithm extends the Kalman filter approach to determine the integer ambiguity and the orientation that is needed in a typical gps-based attitude determination problem. The second algorithm explores the mean field annealing neural network approach, which is a combination of the competitive Hopfield neural network and the stochastic simulated annealing technique, to resolve the optimal attitude problems. A test platform is set up for verifying these algorithms. The two algorithms are further compared in terms of computation speed and convergence rate.

After a brief overview of Loran-C system operation and performance, the present situation of the system in Europe is described. Loran-C is now in operation under the NELS agreement in north-western Europe in newly established chain configurations with old and new transmitter positions. Parallel to Loran-C the Russian equivalent, Chayka, is also operating, with three chains in Europe. There is an agreement between Norway and Russia concerning cooperation and possibly joint chain operations between the two system providers in the north; similar agreements in the Baltic and Mediterranean/Black Sea areas are being worked on. The situation around the Iberian peninsula has not yet been clarified. Being the only long/medium-range terrestrial system in Europe in the 2000+ time frame, Loran-C could be seen as a supplement to satellite systems. Due to the good penetration properties of its low-frequency signals, it can be used in many circumstances where satellite systems fail because of limited satellite visibility. Integration of Loran-C and (differential) satellite receivers, where Loran-C is calibrated by the satellite system as long as there are enough visible satellites, could in fact give the best of both worlds. For this reason, Loran-C is being considered in the perspective of a future international, civil satellite navigation system, initiated in Europe.

Safety is a crucial issue in densely sailed waterways. Traffic guidance systems (VTS) have proven to be valuable in this respect. The effectiveness of current systems and the benefits for improvements in navigation are addressed in this paper. Relevant incidents are analysed with a risk assessment tool (Accident Sequence Precursor method) developed for complex system analyses. The method is capable of drawing conclusions on a high level: strategic and tactic events and the human errors associated with the navigator's task cycle. Changes in current VTS systems will not likely improve safety records in dense areas. Improvements might best be achieved by reducing or eliminating the human factor in incident sequences.

This paper presents results from a doctoral dissertation (reference 12), on the problem of scheduling with Maximum Position Shift (MPS) constraints. The problem typically arises in a queueing system, when the service rate depends on the sequence in which customers are handled by the server. Such a queueing system is the airport runway system, where it has been shown (references 3, 10, 12) that rearranging the sequence of landings and takeoffs affects the runway capacity – that is, the rate of runway operations. An optimal Dynamic Programming (DP) scheduling algorithm is developed that takes as input the set of currently known flights, their desired time of operation, basis of the First Come First Served (FCFS) sequence, and a matrix of Air Traffic Control (ATC) minimum time separations, in order to produce an optimal schedule defined as runway and threshold time assignments maximizing runway capacity.

The increasing volume of traffic in urban areas has resulted in steady growth of the mean driving time on fixed routes. Longer driving times lead to significantly higher transportation costs, particularly for vehicle fleets, where efficiency in the distribution of their transport tasks is important in staying competitive in the market. For bus fleets, the optimal control and command of the vehicles is, as well as the economic requirements, a basic function of their general mission. The Global Positioning System (GPS) allows reliable and accurate positioning of public transport vehicles except within the physical limitations imposed by built-up city ‘urban canyons’. With a view to the next generation of satellite positioning systems for public transport fleet management, this paper highlights the limitations imposed on current GPS systems operating in the urban canyon. The capabilities of a future positioning system operating in this type of environment are discussed. It is suggested that such a system could comprise receivers capable of integrating the Global Positioning System (GPS) and the Russian equivalent, the Global Navigation Satellite System (GLONASS), and relatively cheap dead-reckoning sensors.

I read Captain Gyldeń's account of failure of his GPS set (Vol. 50, 328, May 1997) with some interest. A few days earlier we had had a few thunderstorms while I had my personal hand-held GPS running, using its own built-in antenna and a 12 volt battery. It was lying on a bench inside a wooden hut where I keep some of my amateur radio equipment. After one particularly close flash and bang, which produced a one-inch spark from my transceiver antenna, the transceiver locked up and stopped responding to keyboard commands. Then I noticed the GPS set had also stopped working, showing only random symbols on its readout. I feared the worst but, after switching them both off, leaving them for a few minutes, and then back on again, they worked perfectly.

Microprocessors locking up in strong local electrostatic fields, perhaps? Maybe if I had simply left them alone they would have started working again after the charge had leaked away. Next time I nearly get hit by lightning I'll try it.

Civil Marine Radar (CMR) is now a mature instrument of some 50 years steady development. Following a short history, more to provide benchmarks of achievement than to satisfy historians, this paper examines what will drive the future development of CMR. The answer may not follow recent developments, but may well be the result of a fresh maritime modus operandi to fulfil the navigation, collision avoidance and safe passage needs of all types of craft operating in all types of water with different pressures and Operational Requirements (ORS). Having postulated fresh ORS, suggestions are made on how best to fulfil them in a logical and cost-effective manner.

Most reference books or monographs about the history of the gyrocompass portray individual inventors, each as an inventive genius, respected as a national hero and probably depicted creating novelties in ‘brooding meditation’. This seems to be an accepted, rather comfortable point of view, as the subject covers the invention of a ‘black-box’-type too. But the invention, development and the adaption of this gyro instrument in a complex technological and social system was not achieved on the basis of a ‘single-handed’ venture.

If emerging technologies are not only scientific, but also involve social or cultural requirements, then communication along the networks of knowledge between inventor, mechanic and mathematician, the code of patent lawyers and financiers and – last but not least – navigation officers and the red tape of a navy must play an influential role. I would thus like to sketch out the subject of invention as communication and present the inventor as a navigator, someone who leads his crew through all currents, shallows and drifts and, while keeping ahead of other competitors, arrives at some still uncertain location.

It was with the greatest interest that I read the two important papers by Dr N. Ward, published in the May edition of the Journal of Navigation.