Whatever the word ‘navigation’ is taken to mean, it must, etymologically, be something one does to a ship. What a pity that the name ‘airship’ was given so early in the evolution of aviation to its dinosaurs! The modern airliner is truly a ship of the air. There was a move, half a century ago, to coin the word ‘avigation’ but, apart from the obvious retort that, if ‘navigation’ is of ships, ‘avigation’ is strictly for the birds, the term ‘air navigation’ had already been established by the International Convention on Air Navigation and the Air Navigation Acts by which Parliament legislates on aviation in general and its commercial application in particular.

The next issue of the Journal, which starts the fortieth volume, will have a new Editor, Professor J. F. Kemp, and a new publisher, Oxford University Press.

The shape, size and orientation of the protected volume of airspace generated by the airborne collision avoidance system currently known as TCAS II are derived. While based on constant-velocity aircraft flight paths the results are shown to have more general application. It is also shown how the essential features of the protected volume may be used to calculate alarm rates for some simple traffic patterns.

This paper was presented at a seminar entitled a European Concerted Approach to Vessel Traffic Services for Safe Navigation – EEC Project COST-301, sponsored jointly by the Institute's Netherlands branch and the Royal Institute of Engineers, Delft University of Technology and the Netherlands Directorate General for Shipping and Maritime Affairs held in Delft on 20 January 1986. It was published under the auspices of the European Environmental Bureau, an independent coalition body of leading environmental organizations in all the European Economic Community countries (with a total membership of over 10 million). The paper, of which the following is a condensed version, seeks to comment on the implications for environmental protection of the various COST-301 research programmes, and to assess the contribution which the findings resulting from them may make to future European coastal state policy and international measures.

Aline De Bièvre is with the European Environmental Bureau and John Kemp is Professor Emeritus at the City of London Polytechnic.

The United Kingdom's interest in the Joint Tactical Information Distribution System (JTIDS) and its Relative Navigation (relnav) capability began in 1979 with studies into an Electronic Counter-measures (ECM) Resistant Communications System (ERCS). The Singer Kearfott Division (SKD) Time Division Multiple Access (TDMA) JTIDS system, which includes a relnav and position reporting capability, was selected to fulfill this requirement. Early in 1985, approval was also granted to the Royal Navy to procure an ERCS.

Technical studies on JTIDS for airborne applications are being directed by RAE Farnborough and by ARE Portsdown for maritime use. Systems Designers Scientific (SD Scientific) is providing technical support in a number of areas including relnav.

This paper, which was presented at an Ordinary Meeting of the Institute held in London on 15 January, gives a very brief overview of JTIDS and describes the principles of relnav before outlining the structured approach to JTIDS relnav evaluation which has been adopted.

1. ENVIRONMENTAL FACTORS. Since 1975 the inadequacy of knowledge of the depth and shape of the seabed on the continental shelves has become increasingly apparent, as navigational safety has been pushed to further limits in response to economic factors. Less than half of the British continental shelf, defined approximately by the 200 m depth contour, has been surveyed by echo-sounder and only a small proportion to full modern standards. There are inevitably many natural hazards still to be discovered. Inadequate knowledge can have particularly serious effects in heavily trafficked shallow areas, where patches of the seabed may show instability in the form of mobile sandwaves. Seabed wrecks and obstructions, some of them wartime relics, are another problem; thanks to the use of modern sidescan sonar, in 10 years the number of wrecks in the UK area databank has risen from 14000 to 22000.

Knowledge of surface currents is of fundamental importance in many diverse marine activities; for example in navigation, offshore engineering and operations, and in the prediction and monitoring of the movement of pollutants. In those areas of scientific research directed towards improved understanding of climate, and towards the modelling and prediction of currents, studies of exchanges of heat and momentum between atmosphere and ocean also require detailed knowledge of mean and fluctuating components of near-surface flow.

There can be little doubt that the overall standards of safety at sea are high, particularly with the traditional maritime nations. Cockcroft states that of a total of 22600 ships over 1000 g.r.t trading in 1979, 9400 were from the traditional maritime nations. He goes on to say that during the period 1977–9 these countries lost 16 ships out of a total of 189 worldwide losses. Thus the traditional maritime nations ran 41·59 per cent of the ships and incurred only 8·4 per cent of the losses. This does suggest that high standards are not universal and there may be considerable resentment among operators of high standard ships when casualties to sub-standard vessels result in the implementation of measures, such as marine traffic management systems, which give rise to increased operating costs.

1. INTRODUCTION. Interest in the use of video displays for nautical chart presentation has increased rapidly during the last two years. Eaton et al. at the Second International Hydrographic Technical Conference provided a list of ten different systems already in production. Oshima speaking at a Workshop on the subject in Canada, early in 1985, mentioned that some 4000 Japanese fishing boats and 150 merchant vessels now carry electronic charts of varying degrees of complexity.

There is an increasing interest in crossing situations. This has been stimulated by the success of traffic separation schemes to generally reduce the level of risk of collision from ships approaching in opposing directions. There have recently been crossing collisions in the Dover Strait which have occurred during conditions of poor visibility. These might have been avoided if the officers in charge of the vessels had allowed more time to manoeuvre. They bear witness to the fact that, in fog, a vessel can travel a considerable distance before its course alteration is detected on another ship's radar and appropriate collision-avoidance action taken by that other vessel.

1. INTRODUCTION. The Collision Regulations are designed to assist navigators to avoid collisions at sea. However, because of their qualitative nature it has been proposed that the Regulations should be supplemented by quantitative references to give practical meaning to concepts like ‘safe’ passing distance, ‘early’ action, etc. (Cockcroft and Lameijer, 1982). The problem of interpretation and quantification of the Regulations has been analysed in a recent paper by Wu (1984), considering in particular the concepts of ‘substantial’ action to avoid a collision, and the distance of ‘last-minute’ action in turning to avoid a collision. These analyses, along with many others, are concerned with developing prescriptive guidelines for mariners, in accordance with the Regulations.

Until 1950 the largest ships of the merchant fleet and the major warships had the same draught, about 12 m. Hydrographic offices concentrated their efforts on those areas likely to contain hazards to such vessels, that is to say the areas extending from the shallow waters to the 20 m contour line. The maximum draught of warships has been stable whereas the draught of merchant vessels increased considerably up to 30 m in recent years. A VLCC may risk grounding after having crossed the 30 m line or even the 40 m line. Nowadays, the part of the continental shelf which is best known is the part in which the largest vessels are unable to operate.

In this paper the role of the helmsman in terms of man–machine systems theory, such as is frequently used in aerospace work is considered and the literature of the subject surveyed in so far as it relates to the control of seagoing vessels. Lieutenant-Commander Sutton is in the Control Engineering Department at the Royal Naval Engineering College, Plymouth, and Professor Towill is head of the Department of Mechanical Engineering at UWIST, Cardiff.

For many practical purposes it is desirable to have a yard-stick with which safety can be measured. A criterion for the estimation of the safety of ships against collisions is outlined in this paper. The method is based on mathematical simulation and embodies all relevant factors. Numerical results are given for the English Channel and the German Bight showing the effect of parameter variations.

This paper describes modern autopilots for ships. The development of modern optimal and adaptive control theories, together with the availability of inexpensive and fast digital computer systems, makes possible the design of more sophisticated controllers, which achieve better steering and save fuel. Autopilots which simultaneously control the yaw and roll motions are now being developed. In the near future it is to be expected that advanced track-prediction and track-keeping systems will facilitate the navigation and further contribute to fuel savings. The paper was presented at a Workshop held by the Netherlands branch of the Institute on 21 February 1986.

1. INTRODUCTION. The controlled deceleration of a ship in the final approaches to the berthing area is of crucial importance to ensure that the ship is stopped in time and can be manoeuvred to the berth by assistant tugs. Shipborne instrumentation cannot be relied upon entirely to assist the ship handler in this aspect because, with very few exceptions, it does not give sufficiently accurate information at very low speeds and minimum underkeel clearances. Traditionally of course, it is part of the ship handler's skill to judge the ship speed and deceleration by eye and it is important that this skill is finely developed to arrive correctly at the manoeuvring area. It is however the case that the judgment of very low speeds becomes increasingly difficult with the larger ships, yet it is with such ships that this judgment is the most critical.

One aspect of marine navigation which has particular application to the protection of the environment is the establishment of traffic separation schemes and other routing measures in coastal waters. Extensive pollution may be caused by marine casualties. The use of routing to reduce the risk of strandings and of collisions between ships or with offshore structures will be considered in this paper.

A number of studies have been carried out by consultants on behalf of the General Lighthouse Authorities (GLA) to assess the effectiveness of aids to navigation systems and to study the effects of changes to these systems. The usefulness of graphical representation of aids to navigation systems was appreciated and a program was developed for a desktop computer, combining graphics with numerical analysis of effectiveness. The program has been used in two studies for the GLAS, the results of which are used here to illustrate the techniques involved.

An application of the model to manoeuvre ships based on the range to domain over range rate (RDRR) concept is described. A simulation of a training simulator has been set up on which the target ships manoeuvre by the RDRR model in response to mariner controlled ships. Results of experiments show that the RDRR model manoeuvres targets realistically. The applications are reduced instructor work load and increased simulator reality. The method has the potential for development to manoeuvre ships at sea.

B. A. Colley is now with Plessey Marine, R. G. Curtis is with the Department of Trade and Industry and C. T. Stockel is at Plymouth Polytechnic.

The annual total losses of trading ships as a result of collision and wreck were considered in a previous paper for the purposes of comparing the safety records of different flag groups. Losses up to the year 1979 were included in the tables. In order to assess whether there has been an improvement, the losses for the 5-year period 1980–4 will now be considered and compared with losses in previous years.