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.

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.

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.

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.

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.

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.

As on previous occasions this Institute meeting was held to discuss different aspects of the Admiralty Chart as described by the Hydrographer of the Navy and his assistants. Earlier meetings had led to the formation of a Chart Users’ Panel, drawn largely from the Merchant Navy, and members of the panel were present on this occasion. The meeting described below, the fifth of this series, was held in London on 15 March 1978 with the Hydrographer, Rear Admiral D. W. Haslam, O.B.E., in the Chair.

The new-look Admiralty chart is no longer novel; the first metric chart was in fact published ten years ago and there are now over 700 metric charts in our standard series, representing over 20 per cent of the total currently in publication. Their impact is disproportionate to their numbers however, since many metric charts figure among those most used, and there is now about a one-in-three chance that any Admiralty chart being employed is a metric one. Popular charts tend to be much-corrected charts and in fact a third of the new editions and a third of the paste-on blocks that we issued last year were to metric charts. Moreover, we now publish a hundred new charts a year and hope that this figure will be maintained.

In the January 1977 issue of this Journal an article ‘The new buoyage system’ by the Hydrographer of the Navy was one of the many steps taken during the past two years to explain to chart users what IALA System A is all about. Newspapers, magazines, schools of navigation, yachting clubs and commercial printers have all helped to spread the gospel. There are on the market a variety of booklets, wall charts, plastic models, cassette teaching aids and films. The new symbols used to portray the details on the charts can be found in Navigation Publication NP735, available from Admiralty chart agents.

It is seven years since the Hydrographic Department published charts for yachtsmen only. Our policy since then, dictated by the pressure on our resources, has been to suit Admiralty charts and publications as far as possible to the needs of all sorts of user; but we hope that we will be able in a few years to re-enter the field of yachtsmen's publications. It is interesting to see how other hydrographic offices have tackled the problem. In April 1977 members of the International Hydrographic Organization discussed special charts for small craft use; a summary of the prepared statements appeared in the International Hydrographic Bulletin in September. The charts concerned are mainly large-scale inshore ones rather than passage charts.

The 1967 Conference of the International Hydrographic Organization (IHO) set up a six-nation Commission to obtain an agreed specification for a series of small-scale international charts, with a view to sharing production among a number of hydrographic offices on a regional basis. The intention was that any office could reprint any or all of the sheets, and make modifications for language or to obtain conformity with its own national series.

Commander R. A. G. Nesbitt, Superintendent of Notices to Mariners, described a number of proposed future changes in the style and format of Admiralty Notices to Mariners, illustrating his remarks with a series of Vugraph projections of the relevant pages.

Last year this Journal contained two articles by the writer in which he suggested the potential of fully automated radar plotting systems (FARP) in aiding collision avoidance. This was done by considering a number of past collisions and showing how different the behaviour of the ships involved might have been had they been using FARPs. This was an operational study and not a statistical analysis. He followed the line taken in previous articles starting as far back as 1965 and continuing in 1970 with some details of earlier automatic plotters and in 1972 with a comparison of manual and automatic plotting capabilities. In 1974 and 1975 there was a comparison of the different philosophies embodied in the later FARPs leading up to the studies of past collisions in 1977.

The term marine pilot is applied to the man with local knowledge who acts as a guide to mariners in his own specific and limited district, but it is difficult to confine the work of a pilot to anything so specific. Over eight centuries Cinque Ports' pilots have conducted snipping from the Dungeness-Dover sector of the English Channel both into the Cinque Ports and into the ports of the Thames. They have also taken ships to the more northerly waters of the British Isles and were often asked to pilot ships along the European coast as far as the Baltic. They do this today and for the purposes of this paper they are pilots who work in a defined district but who are not necessarily confined to that district.

Prior to the introduction of three Ocean Surveying Ships in the years 1965–66, the Hydrographer's surveys were generally concerned with the recording of depth against a geographical position obtained from manually reading and plotting sextant angles, radar ranges or, more recently, electronic navigational aid data. The new ships were however the first Royal Naval ships to be designed with combined oceanographic, geophysical and hydrographic roles and to have no supplementary naval function. They contained instruments for measuring the Earth's gravitational and magnetic fields as well as depth; as a consequence the number of men required to read, record and plot this data increased. With the use of an electronic positioning system to provide the horizontal control for the surveys it became possible to carry out surveys throughout the full 24 hours each day.

For the past few years it has been technically possible to produce digital versions of charts and maps but the manual digitizing of very large amounts of irregular line and point data is both slow and prone to error; the benefits of automation in this field are less clear-cut than in the production of computed linework such as borders and lattices. Semi-automatic line digitizing equipment is just coming on to the market and this will undoubtedly speed up data acquisition rates, particularly where good-quality line work is being digitized. Nevertheless some mapping authorities (e.g. the United Kingdom Ordnance Survey) have already made considerable progress in the digitizing of maps, both to provide input for the automated fair-drawing of these maps on one or more scales and to supply digital versions of selected features (e.g. road and boundary patterns, frontings of buildings) to prospective customers, such as the public utility group—gas, electricity, telephone and drainage authorities.

The introduction of digital computers in hydrographic surveying has led to a decrease in routine work and an increase in time for decision making. In merchant ships there are likely to be similar benefits, but there are many facets to the introduction of digital computers. The main criterion, if the introduction is to be a success, must be a considerable improvement in the performance of men and equipment when compared with the additional cost of a revised system, including training in its use. There are two main decision-making phases in navigation—voyage planning and watchkeeping; we must therefore consider the assistance that electronic data processing could give to the navigator in providing data on which plans can be evaluated, progress monitored and decisions made.

Decca have undertaken a study for the Department of Industry of possible integrated navigation systems for use in merchant ships, particularly VLCCs, and also the development and supply of an advanced navigation information system for offshore patrol vessels which uses many of the techniques proposed in the earlier civil study. This computer system provides for the integration of various data sources including radar, the processing of the data and display; a prominent item is the Admiralty chart.

At an open meeting of the Technical Committee held in London on 26 April 1978, with Dr. J. F. KEMP in the Chair, the broad question was discussed of the relative benefits of carrying navigational devices in an aircraft as against installing them on the ground. Introducing the discussion Captain B. J. CALVERT of British Airways suggested that for landing in very poor visibility there was no either-or choice; any system must be cooperative and involve the combination of air and ground components. The question was where to strike the balance. With the redevelopment of a fog-dispersal device (for one was used in World War II) it seemed possible to re-examine the question. The fact that there were now many years of airline experience of low visibility landings made the discussion even more appropriate.