In an earlier paper I suggested that ATC could be depicted as a hierarchy of processes which differ from each other in the distance ahead in time at which they attempt to solve their problems. When the look-ahead time is very long (several weeks, say) we are usually concerned with the problems of traffic en-masse. These problems are here regarded as the province of Air Traffic Management (ATM) rather than of ATC, which is concerned in general with issuing commands to individual aircraft. It is possible that ATC may attempt to plan say, one hour ahead, but there will be a residue of problems, some of which may require action within seconds. The relatively long-term (or upstream) process is often called ‘strategic’ ATC and the short-term (or downstream) process ‘tactical’ ATC. The present paper is concerned with the problem of distributing the control effort between upstream and downstream activity. Other things being equal, upstream planning can offer a more efficient flight and a more orderly process, with less immediate pressures on pilot and controller. One drawback is that, in Western Europe at least where there are a multiplicity of agencies, the ATC authority may not have adequate data to attempt to plan more than about 15 minutes ahead.

The Royal Institute of Navigation, with its counterparts in France and Germany, played a fundamental role in the introduction of traffic separation at sea, a role that is freely acknowledged in Imco's publications on the subject. J. H. Beattie, who was a member of the successive international working groups whose reports led to the introduction of routing, first of all in the Dover Strait and later throughout North West Europe, recounts the history of routing at sea, whose origins lay perhaps in the Great Lakes. A condensed version of this paper was presented at an Ordinary Meeting of the Institute on 14 December 1977, followed by Captain Emden's paper which is printed at page 203 with the ensuing discussion. Captain Maybourn was in the chair.

In his Presidential Address, presented at the Annual General Meeting of the Institute held in London on 19 October 1977, Sir Edward Fennessy, until recently Managing Director Telecommunications at the Post Office, traces the role of navigation in the development of ocean cable laying from the earliest days. Today, telephone cables capable of bearing several thousand telephone conversations link the continents; plans are now well advanced for the laying of a cable between Cornwall and the United States which will provide some four thousand circuits. To lay and maintain these cables calls for all the precision obtainable from the most modern electronic aids to navigation and position fixing, including the satellites.

It is now generally agreed that the principles of traffic separation, in formulation of which this Institute has played an important part, are proving themselves a success and now that Imco traffic separation schemes have acquired a legal status, specifically under Rule 10 of the International Regulations for Preventing Collisions at Sea (1972), it is appropriate to take stock of the situation and to look ahead.

As far as the Dover Strait is concerned it can be surely said that the number of ships contravening the Regulations continues to decrease and, more important, that the number of collisions has been reduced. Nevertheless apparent infringements continue to occur at the rate of nearly one. every hour and there have already been three collisions this year. In the Dover Strait we have a daily throughput of 300 ships and an average crossing population of about 200 passages each day. Nevertheless the average tonnage of all ships is only about 2000; it may well be a small ship which will precipitate a disaster, and it is mainly with the problems of the small ship that I am now concerned. The aim of this paper is to suggest possible steps which may be taken to improve the safety of navigation and by promoting discussion it may be possible to obtain a clearer view of the mariner's needs, what is practical in the way of meeting these needs, and what new ideas may have to be introduced if there should be a demand for further action. These include passive measures, which must be handled administratively and ashore, and active measures, which directly concern the master's navigation of his ship.

Marine traffic can be defined as the combination of individual ship movements in a specified area and the ‘quality’ of marine traffic depends in the first place on the human and technical quality of the vessels participating. The second important situation is in the rules and regulations by which the individual vessels are bound. In some areas these two conditions seem inadequate to guarantee an acceptable level of marine traffic safety. An adequate yardstick by which to measure this level of safety is however still lacking.

The Home Office in January 1977 invited submissions for inclusion in the United Kingdom proposals to the World Administrative Radio Conference 1979 (WARC 1979.) Prior to that, in August 1976 in Boston, U.S.A., the member Institutes of the International Association of Institutes of Navigation had agreed to exchange views on matters of concern to the world's navigational community which in particular might be considered by WARC. It was envisaged that any approach by the various national Institutes would be through their own administrations.

The reckoning of a ship is the up-to-date record of the courses and distances made through the water since the ship's position was last fixed by observation. The importance of keeping a careful reckoning was paramount in circumstances when observational methods of fixing were not available. In the early days of sea voyaging, even before astronomical methods for checking position had become available, the mariner who would know his ship's position (essentially to estimate his arrival time at his destination) was forced to rely on his reckoning—no other way was at hand when out of sight of land.

One of the major topics of discussion at the moment is the subject of control in marine traffic systems. For many years the principle of the freedom of the sea and in particular the freedom of navigation was recognized universally, but recent advances in many directions have led people to question it closely. The increasing size of ships, and especially those used to transport cargoes such as oil, chemicals and liquid natural gas, is one factor, since various incidents have led to a growing awareness of the human and ecological consequences of even a minor incident at sea. Another factor has been the expansion of oildrilling operations and explorations for other resources, usually in areas such as the North Sea where the available navigable sea room was already restricted, especially for the modern deeper-draught ships. Purely economic factors have also been contributory; modern ships spend less and less time in port with more time at sea and the commercial world demands that the sea voyages should be completed as efficiently as possible, usually with respect to time. For these and other local reasons there is a growing demand for some form of marine traffic control system. Most of the world's major ports have traffic control to some extent and attention is now being paid to restricted seaways such as the Dover Strait.

It has been the Government's policy to maintain an occasional British naval presence in the Antarctic, deploying the Royal Navy's Ice Patrol Ship south each year during the southern summer, when the ice and weather are slightly more clement. Ten years ago one of the authors was navigating officer in the Ice Patrol Ship H.M.S. Protector, the last remaining wartime netlayer, and extensively modified for her new role. A flight deck and hangar had been built over the net deck, special deck level tanks were added for the aviation fuel and eventually a new bow added, similar to the bow of the Blackwood class frigate. It was most effective and made the bridge area much less prone to spray, improving her performance in rough seas. Her original construction was flat bottomed with twin screws in tunnels separated by a skeg; the hangar made her act like a weather vane and when altering course it was usually necessary to apply opposite wheel 300 before the new course in order to steady her. She would roll on a wet sponge in dry dock but I became very attached to her, after all we celebrated our thirtieth birthdays within a fortnight of each other one glorious Antarctic day, and that is long service for a warship by modern standards. John Draper was navigating the present Ice Patrol Ship H.M.S. Endurance ten years later and it is interesting to compare navigational techniques and equipment then and now.

FOR traffic proceeding in random directions on a plane surface the frequency of collisions, if no avoiding action is taken, is approximately proportional to the square of the traffic density and directly proportional to the size and speed of the craft. Avoiding action is normally taken and the rate of collisions is therefore also governed by additional factors such as the visibility, the effectiveness of the collision-avoidance rules, the competence of personnel, the manoeuvrability of the craft and the efficiency of radar and other equipment.

In the post-war years there has been a considerable increase in the number of merchant ships. The number of vessels of ioo tons gross and upwards increased from less than 30,000 in 1948 to over 65,000 in 1976. When considering the population of ships at risk it is necessary to deduct special types of non-trading vessels and ships laid up. The number of trading ships in service has increased by approximately 100 per cent since 1950 (Fig. 1) and the greatest increase has been for large ships. The average length of trading ships has increased by approximately 40 per cent in the same period and there has also been an appreciable increase in the mean speed of ships.

Mr. Collins, Senior Scientific Officer at A & AEE, describes the testing of a modern strike aircraft navigation system. A brief description of such systems together with an outline of a typical flight profile leads to a discussion of the problems of evaluation and the techniques adopted. The paper was read by Mr. T. O. Coldwell, also of A & AEE, at a meeting of the Institute in London on 18 May 1977 with the President in the Chair.

Until its nationalization in 1956, the physical limitations of the Canal had greatly influenced world shipowners with regard to the sizes of ships built, particularly oil tankers. Following nationalization, in an era of cheap oil and transport costs, shipowners took the initiative and began to build large tankers. Mindful of the effect that such changes would have on the tonnage of oil transported through the Canal, the Suez Canal Authority began a programme of expansion in 1958 which was to be executed in two stages. The first stage was completed by February 1964 and consisted of widening and deepening the Canal so that ships with draughts of 38 ft could be accommodated, thus allowing vessels of 60,000 d.w.t. to transit fully loaded. The second stage of development was intended to deepen the Canal to accept vessels of draughts up to 40 ft, corresponding to ships of 70,000 d.w.t. This work was scheduled to be completed by the end of 1967, but the project was not finished due to the start of the Arab–Israeli war.

A number of numerical models of various sections of the North Sea have been developed, primarily for flood prediction; these simulate both the propagation of the astronomical tide and the generation and propagation of storm surges. The tides effectively originate in the deep ocean and their propagation into shallow seas can be simulated for an almost infinite period ahead. Surges are generated by the action of wind and pressure gradients, particularly over the shallow sea regions in the northern and central North Sea.

Captain Brett Hilder first published in 1973 his controversial theory that Torres used Endeavour Strait on his famous and perilous voyage through the intricate waters of the strait that now bears his name. This was the subject of his Macquarie University thesis of 1976, The voyage of Torres along the southern coast of New Guinea in 1606 and he has summarised his findings in a paper published in the September 1977 issue of this Journal. It now seems essential to question the validity of some of his assertions.

An area of sea in which there are several traffic streams may be characterized by the number of potential encounters between two ships that would be expected to take place. The traffic flow in an area of 300 sq. n.m. of the Dover Strait over a nine-year period has been analysed to give the numbers of such potential encounters of head-on, crossing, and overtaking ships in three conditions of visibility. The number of collisions occurring has been similarly broken down and hence the risk of each different type of encounter leading to a collision has been determined. It is shown that decreasing visibility makes collision very much more likely, whereas the direction of encounter makes a comparatively minor difference to the probability.

The author of this paper, which was presented at a meeting of the Institute in London on 16 March 1977 with Captain B. J. Calvert in the Chafr, is the President of Jeppesen Sanderson Inc. He traces the history of the Jeppesen Company's charts from their early beginnings when map reading and dead reckoning were the only aids to air navigation to their adaptation to modern automated airborne systems.

Aerial photography has revolutionized the art of map making over land and if the depth of water could be measured from an aircraft a similar revolution might be expected in hydrography. In 1971 an airborne laser land profiler, designed and constructed at the Weapons Research Establishment, Adelaide, was put into service. At the suggestion of Captain J. H. S. Osborn, then the Hydrographer, R.A.N., this was modified to profile the sea bed and flight tested in June 1975. It was found that, in the vicinity of Adelaide, reflections from the sea bed could be obtained down to 30 m and in places down to 40 m. With an airborne device it becomes possible to survey an area instead of a line and work since has been concentrated on developing a system which will scan at right angles to the aircraft's track.

This account of a recent simulator experiment at the City of London Polytechnic on encounter reaction times at sea will also be published as an internal National Maritime Institute report.

Two ships are said to have an encounter when they pass within a certain distance of one another, say half a mile. The encounter rate bears a relation to the collision rate in a given area of sea and consequently it is desirable to minimize the encounter rate. The effect of routing in sea areas with a high density of shipping has been to reduce the total number of encounters but to increase the number of overtakings. Thus the introduction of a routing scheme greatly increases the proportion of overtaking encounters in the main lanes. For example, the routing scheme in the Dover Strait (with I per cent of through rogues) has increased the proportion of potential overtaking encounters from 27 to 95 per cent.