When flying at high latitudes the rapid convergence of Earth meridians makes it difficult to establish true heading at any particular instant. Magnetic compass stabilizing forces are weak and steering must normally be carried out using a directional gyro. The navigation problem is normally solved on the chart by using a ‘grid’ technique.

In discussing certain aspects of the manœuvring of large tankers it is necessary to consider the navigational circumstances, and especially the hydrographic and meteorological conditions that obtain in the Europoort-area which can be divided into three zones (Fig. 1):

(i) the approach route through the English Channel and the southern part of the North Sea to the outer approach channel;

(ii) the approach channels—the outer channel (bearing 82° 30′) and inner channel (bearing 112°)—to the harbour mouth near the Hook of Holland;

(iii) from the harbour moles through the temporary mouth to the Europoort basin, ending in the berthing manœuvres alongside the jetty.

The Collision Regulations were long considered as sacrosanct and the question posed by this paper never arose. How to prevent collisions? Simply by applying the Regulations established for that purpose. Nevertheless a revision of the Regulations has been decided upon, to be undertaken by an international conference to be convened in 1972, and meanwhile many public and private bodies have applied themselves to the preliminary studies. As the author is not familiar with all the work now being done in this way a general review will not be attempted, but some thoughts on the subject arise from Commandant Robichon's paper ‘Reflections sur une enqu^tersquo; in the January 1970 issue of the Journal de la Marine Marchande and from the proceedings of the Working Party set up in the spring of 1970 by the Institute of Navigation, of which the author was a member.

In the existing Steering and Sailing Rules there are seven classifications of vessels for assignment of responsibility in the open sea. Three of these classifications (Rules 18, 19 and 24) are based on the bearing criterion, two (Rule 17) on the wind bearing criterion and two (Rules 20 and 26) on the hampered vessel criterion. The only classification of vessels implied in the present writer's collision system is based on the bearing criterion. The object of this paper is to show that it is also possible to establish a single classification based on a turning criterion which offers some advantages over that based on the bearing criterion.

Mr. Wilkinson's paper, which was presented at a joint meeting of the Institute and the Royal Institution of Naval Architects in London on 7 January 1971, with the President, Rear-Admiral G. S. Ritchie, C.B., D.S.C. in the chair, will be published in full in the Journal of the Institution, illustrated with diagrams and inventories tracing the evolution of the ship's bridge and wheelhouse in relation to advances in technology, ergonomic factors and manning policy. A comparison is made with the design of aircraft flight decks and the cabs of diesel-electric locomotives. The value to the naval architect of manœuvring and handling simulators is emphasized. The paper and the ensuing discussion are summarized below.

The problem of avoiding collisions at sea, particularly in restricted visibility, is not likely to have one simple solution. Indeed there are three main areas which need separate consideration because of their different requirements. First, in rivers and estuaries, port approaches and narrow passages traffic is rigidly confined. Second, in waters adjacent to coastlines and in some other areas dense traffic has limited space in which to manœuvre. Third, in the open sea there are fewer encounters and unlimited manœuvring space. It seems probable that the best solution to the first of these problems will be found in shore surveillance of the traffic and regulation of the traffic flow by a licensed authority. Prescribed routes with perhaps speed limits and policing may solve the second, but only ratification of an internationally accepted rule of behaviour will satisfy the third requirement. This paper proposes to develop a set of manœuvres which may be applied as a rule which will be accepted as a possible solution to the third requirement.

Judging from what is written in early Sailing Directions and navigation manuals it would appear that seamen of North-west Europe laid great store in their knowledge of the nature of the bottom in the seas in which they traded. And indeed, even at the present time, mariners are provided (although they may seldom use it) with fairly detailed information about the sea-bed, designedly to assist them in pilotage. A navigator may read, for example, that:

‘The bottom in the Western Approaches appears to consist, mainly of fine or coarse sand, a great deal of broken shell, occasional patches of pebble, gravel, small stones, and, now and then, mud. The sand is mostly white, but in numerous places yellow sand and also black specks are met with…. The greater proportion of yellow sand is found to lie southwards of 49°30′ N and the far larger portion of black specks northwards of that line. This peculiarity is so marked, especially between 9°40′ and 7°30′ W that the mariner running eastwards, and supposing his vessel to be to the southwards of this parallel, should certainly suspect his having been set northwards of his reckoning if the soundings disclose this mixture of black specks to any great extent and with any frequency.’

The possibilities of using the measurement of the ranges to a pair of satellites to give an observer his position have been extensively studied, and expressions giving latitude and longitude have been derived. These since they involve powers of the fourth order are somewhat cumbersome, but given the appropriate computer on his craft an observer at a known distance from the centre of the Earth can obtain track data by measuring the ranges and continuously calculating his position. Alternatively, he may measure the incremental changes in these quantities from their value at the starting point which avoids (if a synchronous time or frequency technique is used) the necessity for continual two-way exchange of signals between the craft and the satellite, but the real-time solution of relatively complicated equations still has to be done.

In the design and analysis of air traffic control systems the considerations which lead to the adoption of a particular route and control structure in a given airspace are partially governed by the traffic demands between given points within the area concerned. When air traffic control plans are being developed for use in a particular area, it is of prime importance to know where the main A.T.C. problems lie and to concentrate planning effort in these parts of the system. The development of routing and control procedures should take into account the degree of risk associated with any particular route structure. In the case of near mid-air collisions (NMAC's) or collisions, quantitative prediction of the risk involved is difficult. In this paper a simple theoretical method for predicting the number of NMAC's for a particular route structure is given. Such a method has been used practically for determining the amount of control required for a particular off-airways area and to help determine the optimum control procedures for air traffic planning in that area.

At the end of February 1971 an exploratory survey of marine traffic on the English side of the Dover Strait was organized and conducted by the National Physical Laboratory of the Department of Trade and Industry. The aim of this first short-term study was to examine possible methods for the long term, and the basic radar ship count was carried out by Decca Radar on behalf of the N.P.L. This trial took place over 72 hours between 12.00 hours on Friday, 26 February and 12.00 hours on Monday, 1 March 1971, all times G.M.T.; it showed that further flow data in other areas of the Strait would be of value and Decca Radar decided to gather additional limited data on traffic flow. The most urgent appeared to be at the narrowest part of the Strait between Cap Gris Nez and Folkestone where the Greek M.V. Niki sank off the Varne during the trial at 20.00 G.M.T. on Saturday, 27 February.

Instances of merchant ships beset in times of ice pressure in the Gulf of St. Lawrence were investigated to study the observed relationship between winds and ice pressure generation. The relative power of the ships reported beset was calculated in an attempt to relate ice pressure severity with ship performance. Most pressure episodes occurred during onshore winds or near the time of major wind shifts. Ice pressure intensity during onshore winds appeared to be related to wind strength and duration and distance from shore. The ‘Mouth of the Gaspé Passage’ area was anomalous.

The recent spate of collisions and groundings in the Dover Strait and its approaches lend some urgency to Admiral Van Hooff's paper in which he calls for the introduction of traffic information in regions at sea where the traffic may be controlled by local authority after the fashion of air traffic control. The author was until recently Director-General of Pilotage and Aids to Navigation in the Netherlands Ministry of Defence.

The number of voices that maintain that the conduct of ships about the sea, particularly when approaching ports or other focal areas, should be regimented in a similar way to aircraft when under Air Traffic Control, has been steadily on the increase.

In this paper the basic principles of avoidance action are developed. It is shown that a unique set of rules exists which will guarantee the safe passage of converging aircraft; when two are involved, if either, or both simultaneously, act according to these rules, it is impossible to have an accident whatever the situation. (This assumes inerrant assessments on the part of Controllers, and it also assumes that the uncontrolled aircraft continues on course.) The rules are consistent with the Rules of the Air. Past attempts to formulate rules are compared.

The action taken by an aircraft in flight to avoid coming dangerously close to some other nearby aircraft we call ‘avoidance action’. This action may be made by the pilot should the other aircraft come within his field of view, or if ground controlled, it will be initiated by the Radar Controller. The pilot works to the Rules of the Air and the Radar Controller works to them whenever it is possible for him to do so. The Rules of the Air do not always help the Radar Controller because, in every case, except for two aircraft approaching each other head-on, one or other has the right-of-way and ‘an aircraft which has the right-of-way shall maintain its course and speed.’ This means that an aircraft which has the right-of-way must not take avoiding action. The object of this paper, therefore, is to attempt to propose a set of avoidance action rules which will assist Radar Controllers in their task.

In 1260 Brunetto Latini, a native of Florence, was exiled and went to live in France. While there he followed the example of others of his period and compiled a kind of encyclopaedia which he called Li Livres dou Tresor.

In 1802 a young man called Dupré informed the editor of the Monthly Magazine or British Register that Latini had come from France to England as tutor to the son of Richard, Earl of Cornwall, brother of Henry III. While here he had written a series of letters to Guido Cavalcanti, a Florentine poet, describing what he saw in England and that the letters had come into Dupre's possession. During 1802 several free translations from these letters ran through the magazine and no suspicion of their authenticity seems to have been aroused, though when a description of an elephant, said to have been seen in the Tower of London, appeared a correspondent pointed out that it seemed to have been derived from a contemporary Bestiarium.

For marine traffic engineering, traffic surveys are most important and provide the fundamental materials necessary for harbour and fairway design, traffic control planning, &c. Such surveys cover numerous items, the main subjects being traffic volume, speed, distribution of ships' tracks, origin and destination and type of cargo. Since we have to deal with many vessels, handled by people with varying temperaments, knowledge and ability, observations usually show a wide scatter; the object is often to find some formula or rule to explain the phenomena, and traffic surveys are therefore apt to prove both expensive and time consuming. When, for example, Yamaguchi and others conducted a year long observation on traffic in the Akashi Channel in 1963 at least two members of the team stood watch for 24 × 365 hours in a hillside cottage making both visual and radar observations. Since then the survey has been extended to more than ten other straits well known for difficulties in manœuvring.

In this paper, which was originally published in Navigation, Paris, July 1970, the distinguished General Secretary of the French Institute of Navigation, Professor Pierre Hugon, a Gold Medallist of this Institute, examines some of the premises adopted by M. W. Richey in his paper on the Institutes of Navigation presented to the Australian Institute of Navigation in October 1969 (this Journal, 23, 99). It is interesting to note the extent to which the conclusions in these two papers differ in emphasis.

Following in the footsteps of my friend Mr. M. W. Richey who, at the twentieth anniversary meeting of the Australian Institute of Navigation in Sydney on 10 October 1969, presented a remarkable address on ‘The Institutes of Navigation in the 70's’, I am impelled to state the position of the sister Institute in France by examining once again the very principles of such an undertaking and discussing its future character. This unpremeditated essay concerns a duty and a faith which, though they must not give way to doubt, are nevertheless open to question.

Traffic separation at sea is barely five years old and inevitably most attention has so far been devoted to the delineation of routes and separation zones rather than the conduct of ships within them. Routing, however, is not a panacea; if it is to reduce collisions it must be observed intelligently and responsibly. And at the same time the routes themselves must be made safe and easy to navigate.

The twenty-third session of the Maritime Safety Committee of Imco instructed its Sub-Committee on Safety of Navigation to ‘give urgent consideration to matters concerning the safety of navigation in the English Channel and to suggestions of how to improve it …‘. This paper has been prepared under the authority of the Council with this directive in mind and was submitted to the Department of Trade and Industry's Safety of Navigation Committee at its meeting on 26 May 1971.

A marine traffic accident may be defined in the wider sense as a collision or stranding and in a narrow sense as a collision. Several reports are available on the causes of collisions and on the relation of collision frequency to such factors as location, weather and time; S. Fujii continuing Asai's work has shown that the ratio, R, between the number of vessels in collision and the number of vessels registered increases with the length of the vessel between perpendiculars. Shiobara gives a linear correlation between log R and log G with a slope of 0·5 and a correlation factor of 0·95, where G is the gross tonnage. In other words the collision frequency is proportional to L1.4. He further shows that R is almost proportional to L.

There is no doubt that the increasing size and speed of aircraft, and in particular the continuing growth in air traffic movements, pose unique problems for the development and use of efficient and safe methods of air navigation and control. The scientific, technological and operational difficulties involved are, of course, quite fundamental. This paper, however, is based on the propositions that such technological opportunities and regulatory systems as may be developed necessarily affect directly or indirectly the use of real resources; and insofar as these resources have a value in alternative uses, they incur costs on the community (as well as prospectively providing benefits). Situations involving economic choice, therefore, necessarily are involved. Air navigation and control systems are not immune from the general objective of achieving an efficient overall distribution of national resources.