Perhaps the most surprising thing about sea waves is that they come in a vast range of shapes and sizes. The casual observer on a ship in waters not exposed to an ocean, for example the southern North Sea, may rightly think that the waves he can see have all been generated by the same wind blowing over some particular stretch of water for a fixed length of time. It then seems almost logical to deduce that all the waves ought to be of the same height, length and shape. Unfortunately this is not the case, the energy of sea waves is locked in wave components spread over a wide range of wave periods, each of which travels at a speed dictated by its period. Considering the very simple case of a sea with only wave components, when a crest of one component overtakes the other, a higher wave will ensue. As a result of this process, high waves come in groups; during the time in which the components gradually get into phase the wave height builds up giving a train of waves of increasing, which then decreases as the faster component travels away, until when they are out of phase the sea is temporarily fairly calm. This is the reason why it is commonly said that every seventh wave is the highest, although whether it is every fourth or every fourteenth depends on the relative speeds of the components.

Before turning attention to the problems of heavy weather sailing in yachts it is useful to attempt to define what a yachtsman considers to be a gale.

When I first took up ‘going foreign’ in my own boats cones were hoisted at signal stations when winds of Force 7 or above were anticipated. Thus it may be said that gales started at Force 7, but skippers of commercial craft such as Brixham trawlers (in which I occasionally sailed), barges and other coasters did their own forecasting and used their own judgment of what constituted a gale without bothering too much about the Beaufort notation. Amateurs followed suit in this matter and when wind or sea rose too high for their own particular yachts they would describe the conditions as a gale. It was not until the radio became a commonplace in yachts that a more scientific approach came to be made. Of recent years few yachtsmen will make even a cross-Channel passage without first receiving a weather forecast and the tendency is to rely entirely on forecasts. In passing, I would comment that the vagaries of the weather are such that some of the severest gales have occurred with only very short warning.

M.V. Geestport of the Geestline left the island of Dominica on 1 February 1970. She arrived at Barry on 10 February 1970. Between these dates the ship underwent a considerable ordeal, seldom experiencing a wind-force less than 7, while all the time she was pitching heavily, thereby shipping great amounts of water owing to the heavy swell and rough seas. From the 2 February the barometer pressure dropped about 1 millibar per hour and then, from 04.00 G.M.T. on the 3rd until 12.00 G.M.T. on 5 February, a slow rise was observed, finally steadying at 1034.6 mb. From the latter date the pressure began to fall at a slow rate and on arrival at Barry the barometer reading was 1002.8 mb. During these ten difficult days the speed of the vessel was varied continuously between 120 r.p.m. (about 20 knots) and 50 r.p.m. depending on the circumstances.

The description by Captain Evans and Captain Burger of the damage sustained by the MV. Geestport suggests that at the time of the impact it was night and that therefore it was difficult for the officers to suit the ship speed to the waves. In general a decrease of ship speed in given sea conditions will have little effect upon pitch motion, but vertical motion, or heave, will be lessened, and because of changed phase relationships, the relative vertical motion between ship bow and wave will be markedly reduced. The choice of a prudent speed for a particular situation at present depends upon the judgment of individual Masters. Some are too cautious, and waste time at sea, while others are too daring, so that their ship suffers damage. It should be possible to select a speed which cuts the risk of damage to a relatively small one while the minimum possible time is lost. A particular Master might be able to judge his speed well, but how can such wisdom be transmitted to others?

This paper describes the application of an IBM 1800 computer installed in R.R.S. Discovery to the processing of oceanographical data, and in particular the navigational aspects of the system.

It is beyond the scope of this paper to discuss the development of computer applications in oceanographical research, for which a number of quite advanced systems have been projected or are already in operation. Factors affecting the choice of the computer system adopted for use by the National Institute of Oceanography may be listed as follows:

(i) Data logging, typically to punched tape, was becoming more complex with every cruise of the R.R.S. Discovery

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.

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.

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.

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.

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.

The main concern of this paper is with the limitations of techniques already commonly applied, and in the more promising points of application for new technology in navigation, surveillance and traffic control. In seeking the latter, some of the current trends in other fields, particularly aircraft design, are taken into account. Considerable emphasis is placed on the efficient use of land at airports, in view of the strength of feelings aroused in ‘the community’ by the questions of apportionment and exploitation of land resources.

The air traffic controller provides a service and can do so effectively only with the cooperation of his customers, namely the pilots of many different types of aircraft. For the purpose of this paper it is assumed that pilots do not wittingly take avoidable risks and are fully capable of finding their way from one place to another by the shortest available route. According to I.C.A.O., A.T.C. exists to provide ‘safety and expedition’, but, left to his own devices, the pilot can take care of his own ‘expedition’ so that the main function of A.T.C. is to provide a safety service. When A.T.C. has to regulate flights for safety reasons, however, it may have to ask a pilot to deviate from his chosen flight path. It then has to assume a measure of responsibility for expedition, but safety is still the prime consideration.

The following discussion took place at an open meeting of the Technical Committee, held at the Royal Aeronautical Society in London on 20 January 1971 with Mr. H. E. Smith in the Chair, the introductory discussion paper being presented by Mr. W. P. Robinson, Senior Navigation Superintendent of B.O.A.C.

The interest in area navigation has been stimulated by the knowledge that in many areas of the world air traffic density is expected to exceed the capacity of the existing A.T.C. system in the foreseeable future. Nevertheless, it is important to realize that air traffic delays often result from a lack of airport capacity rather than deficiencies in the air traffic services. Airport capacity is a subject in itself; it is our task to examine how we can improve the present A.T.C. system by the use of area navigation.

This paper covers aircraft navigation with emphasis upon self-contained systems, although a survey of the scene cannot avoid reference to external aids. It traces briefly the evolution of self-contained systems since World War II to the present time and then attempts to forecast the way development appears likely to go in the future. The paper deals with both military and civil aviation because, in spite of the increasing importance of the latter, military navigation, as ever, leads the way to improvements for the future.

In the Interim Report of the Institute's Collision Regulations Working Party (Journal, 23, 448), it was stated in the preliminary that Dr. Calvert was not able to subscribe entirely to propositions (1)to (19). Dr. Calvert here states his views.

My disagreement with the interim report is concerned only with the propositions and principles at the end. The body of the report I regard as masterly in the circumstances.

The following proposed system of rules was presented to the Collision Regulations Working Party of the Institute by Admiral García-Frías and is referred to in the January issue of the Journal (24, 56–9).

IT is evident that the revision of the Collision Regulations would only be effective with a system of Rules able to cope with all situations that may arise at sea. The system must include all that it is necessary and sufficient to solve the collision problem in the easiest and most effective way and consequently it must apply both in clear weather and in restricted visibility using radar; differences between these situations being defined, if necessary, in every Rule.

Since the appearance of the note by Sayers in 1968, followed by the publication of the table by Thompson in 1969, and having myself described the method which was the subject of Sayers' and Thompson's communications, in a work on seamanship in 1962, I have searched for the origin of the method whereby an observer may find his distance off a ship or floating mark by means of a sextant observation of the vertical angle between the visible or sea horizon and the waterline of the ship or mark whose distance off is required.

Lately there have been a number of articles and discussions in the Journal involving the use of computer programs to solve navigational problems. As one often involved in complex programming systems, I have some strong views on the subject. We are not an institution of programmers, and the few of us who have some programming knowledge, a very useful asset, are usually limited to one or possibly two languages. I would doubt if many people who could follow B. J. Moss's ALGOL could also follow R. J. Turner's FORTRAN. Thus it seems strange that authors should go to the trouble of publishing the routines by which they do their calculations. After all, most of us are only interested in the method of attack and the answers rather than computer techniques.