1. INTRODUCTION. In his Presidential address last year J. E. D. Williams treated us to a most absorbing, largely philosophical review of the development of the science of navigation over the last five centuries. In discussing the profound and enduring influence of radio waves on air navigation over the last century he commended as of ‘transcending importance’ the ‘homing quality’ of the radio beam in which the accuracy increases as distance from the transmitter decreases. He illustrated this ‘homing quality’ with references to the radio range for en-route navigation and the instrument landing system (ILS) for guidance to the runway. But he went further and remarked ‘Automatic landings in regular airline service are an example of how a perceived potential of the homing quality of radio has drawn to navigation a whole range of diverse applied sciences including, in this case, information theory, the properties of semi-conductors and the theory of servomechanisms and control, among many others.’

1. INTRODUCTION. The object of open-ocean navigation is basically to find a ship's position. In coastal and confined waters, another dimension is added – the margins for errors are smaller, and actual ship handling must be integrated with the pure navigational disciplines. In restricted waters, the traditional philosophy of position fixing at intervals in terms of a point, e.g. cross-bearings, bearing and distance off a reference object, or latitude/longitude, is no longer a prime objective.

1. INTRODUCTION. The American Global Positioning System (GPS/Navstar) and the USSR's Glonass are superb demonstrations of high technology but we should not forget that they were designed and implemented for a very different set of circumstances from that of the civil surveyor and navigator. Many of their features are not required for civil purposes and it is perfectly possible to get excellent results for many civil applications without the vast expenditure that went into those systems. This paper describes some of the ways in which it is proposed that satellites, not necessarily launched for the purpose, might be, and are being, exploited for civil navigation and location.

On 15 July 1988 in position 39° 08′ N., 58° 43′ W., some 470 miles south-east of Halifax, Nova Scotia, Jester was abandoned and her skipper taken off by the M/V Nilam, a 60000-ton bulk carrier bound for New York.

The boat was engaged in the single-handed transatlantic race from Plymouth to Newport, Rhode Island. The race, which started on 5 June, was Jester's eighth and her fourteenth transatlantic passage. The incident, a knockdown, occurred some 40 days out.

1. INTRODUCTION. Very-low-frequency radio waves were used to implement the Omega navigation system because of their low attenuation (2–4 dB/1000 km) when propagating globally in the waveguide formed between the Earth and the ionosphere. However, it became apparent in the early seventies, throughout the period when the majority of the stations of the Omega network were commissioned, that VLF signals propagating over permafrost or glacial ice could suffer anomalously large attenuations, of greater than 20 dB/1000 km, especially during the daytime. In the Northern Hemisphere problems have arisen with the heavy attenuation of Omega signals propagating over the Greenland ice sheet. In particular a very bad region for Omega coverage occurs around Winnipeg in Canada (the ‘Winnipeg Hole’). In this area Omega North Dakota suffers from ‘near field’ effects, Omega Liberia is contaminated by trans-equatorial modal effects and Omega Norway is removed by the attenuation of its signals when crossing the Greenland ice-cap. There have even been discussions on the feasibility of constructing extra VLF transmitters in Canada to alleviate this problem.

John Habberley is Research Leader at the College of Maritime Studies, Warsash, Hampshire, UK, to which the study was contracted by the Marine Directorate of the Department of Transport. Don Taylor is consultant to the project.

This paper puts forward a case for more precise navigation at sea. It commences by briefly outlining existing and forthcoming navigation aids. The integration of marine navigation systems, and in particular the use of Kalman filtering is then discussed. After outlining the developments in the aerospace industries, the authors suggest why marine developments have not been so rapid as those in the air. The idea of automatic collision avoidance is also raised and a method for tracking radar targets discussed. Finally, the authors survey marine applications of Kalman filtering techniques, including some references to their own work, and assess the need for further research and development.

This paper is concerned with potential improvements in the way man interacts with machines, maps and charts. Particular motivation comes from the new navigational challenges provided by the increasingly widespread use of electronic position-fixing aids in the marine field. Whilst automatic plotting tables and moving light spots have provided part of the solution in larger ships, much recent investment has been witnessed in the development of ‘electronic chart’-based systems.

For a number of practical reasons, among which are the lack of available data bases for these systems and little updating and distribution infrastructure for them, it is believed that there is unlikely to be a wide acceptance of such equipment as the primary or sole plotting aid for a considerable number of years to come.

Yeoman, a navigation plotting system which uses existing conventional charts, was conceived and developed to provide a simple and effective man–chart interface with few drawbacks. This paper provides the background for the development, the product and potential future evolution.

Instrument landing systems (ILS) and the upcoming microwave landing systems (MLS) are (or are planned to be) very important navigational aids at most major airports of the world. However, their performance is directly affected by the features of the site in which they are located. Currently, validation of the ILS performance is through costly and time-consuming experimental methods. This paper outlines a powerful and versatile analytical approach for performing the site evaluation, as an alternative to the experimental methods. The approach combines a multi-plate model for the terrain with a powerful and exhaustive ray-tracing technique and a versatile and accurate formulation for estimating the electromagnetic fields due to the array antenna in the presence of the terrain. It can model the effects of the undulation, the roughness and the impedance (depending on the soil type) of the terrain at the site. The results computed from the analytical method are compared with the actual measurements and good agreement is shown. Considerations for site effects on MLS are also outlined.

In this paper two devices as applied to a marine sextant are presented. A night viewer replaces the usual telescope to allow observation of the horizon in darkness. In addition an automatic reading of altitude is made practicable by a ten-bit encoder mounted on the index arm. In this way the proposed Celestial Navigation Automated Global System may be included within an integrated navigation system.

An account of the calculation of the geometry of collision zones surrounding vessels engaged in overtaking and meeting encounters is given. The zones are calculated for a range of mariners' decision times corresponding to clear and restricted visibility. The determination of encounter risk from the size of the zones is discussed.