This paper, which was presented at an Institute meeting held in London on 21 January 1970, suggests a range of philosophical implications which result from the interaction of guidance and control systems in the context of all-weather landing of fixed-wing aircraft. It then attempts to deduce the considerations which must be applied to the approach to the engineering solution to the guidance and control problem.

In the context of this paper the terms guidance and control have specialized connotations which have achieved the status of common usage.

As they are used in the all-weather operations (AWO) jargon they are easier to define as adjectives than as nouns; the ‘guidance system’ is the system which defines the flight-path which the landing aircraft must follow and the ‘control system’ is that part of the aircraft equipment which enables the aircraft to follow the flight-path which has been defined by the guidance system.

A ship's log is described which works on the principle of electromagnetic induction. The measuring head contains a coil with a vertical axis and is arranged so that voltages are picked up proportional to the two components of water flow past it. The electronic circuits are designed to give a true and stable zero by using a low-frequency squarewave energizing current. Laboratory tests show the output to be linearly related to water velocity. Because of the complicated flow patterns round a ship, the log must be calibrated in situ at sea. Calibration of the forward component meter follows the usual procedure and this meter is accurate to about ±0·1 knot or ± 1 per cent, whichever is greater. However, calibration of the athwartship component meter is difficult and time-consuming, and the sensitivity is dependent on forward speed. With care, it seems that an accuracy of ±0·2 knot or ± 10 per cent, whichever is greater, should be possible with this meter, but more experience of such calibrations is required. The paper is discussed on p. 319.

Dr. Bulman's paper (which is Crown copyright) was presented at an Institute meeting held in London on 19 February 1970 with the Hydrographer of the Navy, Rear Admiral G. S. Ritchie, C.B., D.S.C., in the Chair. The paper, which describes work undertaken by the Royal Radar Establishment on the measurement of ship movement for berthing very large vessels, was presented at the same time as the paper read by Mr. M. J. Tucker, National Institute of Oceanography, and the discussion relates to both.

When a 200,000-ton tanker hits a jetty at more than about 24 ft./min., that is, nearly a quarter of a knot, some damage is likely to be caused. However, the problem of measuring the speed of the ship starts much sooner than that. One could say that from the moment the log is retracted on entry to the estuary some other form of assistance ought to be made available. Traditionally pilots and masters have relied on visual estimation—on the appearance of the passing land and passing landmarks in order to judge the speed over the ground while travelling up an estuary. This has been adequate for smaller ships where the height of eye, length of ship, width of ship were all considerably less than they are now on the largest tankers, and where the critical velocities were higher. Now, however, it has proved very difficult to judge by eye the speed of a very large ship from a station some 80 ft.above the water to the accuracy required, the accuracy being of the order of ± 3 ft./min. It is in this spirit that the Esso Petroleum Company approached the Royal Radar Establishment (R.R.E.) some two years ago or so to tackle the problem.

The objective of navigation is to ensure safe and economic operation of the craft and new trends and developments in navigation have to be judged against the return that they might be expected to bring in operating economics and reduction in accidents. Modern technology offers a wide range of fascinating possibilities, many of which will be discussed at this quadripartite meeting. The potential of these new trends and developments, however, cannot be judged just on the basis of the improvement they bring to the reckoning of position and course. This is but the starting point (Fig. 1) to a complex interaction between navigation, operator and the world at large. The operational navigation performance is determined by the interaction between the means of reckoning position and course, the operational situation and the human operator's interpretation of the operational situation in relation to such regulations, rules and procedures as have been established.

During the morning of 27 January 1968 the submarine Minerve was on exercise south of Cape Sicie. She was due to return to her base, Toulon, in the evening. Her last-known position was that fixed by a Breguet Atlantic aircraft on the same day at 0735. The last communication between this aircraft (then returning to base) and the submarine was at 0755.

The rapidly growing demand for more information on the manœuvrability of ships is distinctly recognizable nowadays, especially by an industrial service institute in the field of ships’ hydrodynamics like the Netherlands Ship Model Basin. At this moment, means like manœuvring basins, rotating arms and towing banks with planar motion systems are available at many places. The information obtained from ship-model tests in such facilities is still insufficient to satisfy all questions. There is a growing interest in training people under the circumstances which will confront them on ships in the near future. Governments, harbour authorities and shipowners like to know the criteria by which a decision to enter a harbour with a large ship can be taken. The human aspects of manœuvring very large ships have raised an interest in designing semi-automatic pilots. A clear explanation of the role of the human operator was presented by Segel at the ‘First Symposium on Ship Manoeuvrability’ in Washington in 1960. That paper discusses the many items that influence the path of the ship, which the pilot, captain or helmsman desires to follow. The block diagram presented in Fig. 1 illustrates the complexity of the phenomenon.

When we look at the sea today we find a new world being unfolded. We find oceanology, the art of living on and using the sea-bed, no longer the sole domain of Jules Verne. Whole areas are devoted to the production of oil and gas from the seabed, with their rigs bringing literally new horizons as well as new hazards. Whole areas of the sea required for mankind's subsistence will be set aside in the eyes of civilization for purposes other than navigation. The sea will no longer be sacrosanct to ships and seamen alone.

Captain F. J. Wylie is, of course, the complete master of the cumulative turn in all its aspects, not for a moment omitting the mathematical. And Commandant L. Oudet has greatly contributed to the study of this important and interesting subject in collision theory. He has provided detailed and lucid information on actual cases, brilliantly researched and reconstructed in a manner that would do credit even to the immortal analyst the Chevalier C. Auguste Dupin. There is indeed little that can be added to what these two and other distinguished authors have already recorded in the pages of this Journal, most notably in Wylie's 1963 article, Collision at Sea in Fog: The Commonsense Approach (16, 100), Oudet's 1965 article, Collision and the Courts (18, 188), and Wylie's article, Legal Aspects of Radar and Collision (18, 203). It also turns out that Wing Commander E. W. Anderson has made a most important contribution to this subject.

Some publicity has recently been given to a new plan proposed by Trinity House and the Honourable Company of Master Mariners for the separation of traffic in the Dover Strait. This would reverse the direction of flow established by Imco in 1967 according to which the main streams of traffic between the Channel and the North Sea keep to the right.

The authors of the scheme suggest that the number of collisions in the Sandettié-West Hinder area has increased dangerously since 1967 because of an unforeseen increase in the size, draught and speed of ships. Their aim is to prevent, in this area, crossings between traffic coming out of the Scheldt and traffic bound for Rotterdam, Germany, Scandinavia and the Baltic.

It is generally accepted nowadays that, to obtain full value for anti-collision purposes from the use of radar by a ship proceeding in poor visibility, it is necessary to plot, or to compute in some other way, the raw data which may be obtained from the radar. It is also usually conceded that, for this to be done effectively in frequented areas, without the aid of mechano/electronic devices, a great deal of time and expertise is demanded from the radar observer and a great deal of responsibility thereby rests upon his shoulders.

To reduce the load of work and the possibility of human error and to give the observer more time to use his intelligence in appraising the situation and keeping it under review, radar engineers are already pressing forward the development of automatic devices which, in one way or another, produce computed informatioa in the form ultimately needed.

In certain esoteric mathematical and computing circles there is, or used to be before the advent of the electronic computer, an interest in near-integral solutions of incommensurable problems. Apart from aesthetic considerations such solutions can have valuable applications in the checking of methods of computation; this is the excuse for the following note.

The investigation from which it arises was itself a by-product. As part of the British contribution to the new Sight Reduction Tables for Marine Navigation (H.O. 229 in U.S.A.; H.D. 605, in the United Kingdom) it was necessary to examine carefully each of the approximately 20 million figures in the six volumes; although the setting was computer-controlled and numerically checked, only visual examination could detect indistinct or broken figures. Such examination is extremely arduous and calls for great powers of concentration if its purpose is not to be wasted.

The Admiralty Tide Tables give the utmost accuracy in tidal calculations, but at the cost of a number of tedious interpolations. Many seamen, particularly those in small vessels, would be willing to sacrifice some of this accuracy if they could have a simpler form of calculation. In any case meteorological effects, and the uncertainty of the time and height corrections for some of die smaller ports impose uncertainties which upset the apparent accuracy. In fact many yachtsmen do not use the Admiralty Tide Tables, but use tables in commercial almanacs, usually giving the times and heights of high water only.

Captain P. A. Thompson's paper, Revised Rules for Preventing Collisions at Sea, in the January issue of the Journal should be discussed. I agree with him that ‘rules (the ones which are mainly based on the operational aspect of the collision problem, i.e. manœuvring rules) to cover every conceivable circumstance would be of such length as to be impracticable.’ However, in my opinion, rules based on the principles—the organic aspects—can cope practically because then the object of the rules is to define the collision problem and its solution so that use of the rules can be immediate, easy and effective. For example, by establishing a safety distance the passing operation would have to be carried out such that the miss distance would always be greater than the safety distance. Furthermore, by keeping the ship's range above the safety distance, one ensures that the entire operation is correctly carried out.

When the danger of collision between vessels occurs, the proper interpretation of radar information will indicate that, with respect to the manœuvring rules, any avoiding action should always be positive. However, it is well known that radar information is not always properly interpreted. Misinterpretation may cause a situation to be assessed as ambiguous. This, in turn, may produce disagreement, on both vessels, about how the rules should be correctly applied. To solve this difficulty, some authors propose communication between the vessels. Others think the avoiding action of any vessel should automatically be such that the sight line rotates in the anti-clockwise direction. (The latter suggestion results in a port-to-port passing whilst the vessels cross with a port bearing from the aspect of the overtaking ship.) Complications may arise from either proposal.

This country, and the marine industry in particular, is in the throes of a change that it has been decided shall be called metrication. It is evident from what is both written and spoken that not everyone is aware of what metrication means, that many people assume that it is simply a change from imperial units to metric units. However, what is really intended is the adoption of the S.I. system of units and this implies much more than just the use of metric dimensions. The two main points of the S.I. system are (i) that every dimension is measured in decimal multiples of a basic unit and (ii) that the system of units is a coherent one. The educational advantages of such a system are too well known to require restating here. Antagonists of change usually point out that time does not conform to condition (i) and while this is true, nevertheless the S.I. system will be a great improvement on our present one and the non-conformity of time should not be used as an excuse for other non-conformities.

A conference was held in Rome at the Hall of Congresses of the National Council of Research between 11 May and 14 May 1970, under the general theme, Trends and development in the Reckoning of Position and Course at Sea, Beneath the Sea, in the Air and in Space. The conference was sponsored jointly by the Italian, British, French and German Institutes of Navigation with the cooperation of the American Institute. A list of papers presented, with a summary of most of them, appears below. A selection of these papers will be published in this and subsequent numbers of the Journal. The papers have been arranged in an order that corresponds loosely with their subject.