This paper summarizes recent measures to improve the safety of navigation in the Channel, particularly in the Dover Strait area, and gives the point of view of one administrator involved in these efforts. Much of the material in the paper is already well known and indeed the paper relies heavily on work published by the National Physical Laboratory. The views and opinions in this paper are of course the author's and not necessarily those of the Department of Trade and Industry.

In the matter of marine traffic in confluence and approach waters we are, it seems, in a state of modest confusion. Society and the ecologists demand protection from pollution and coastal catastrophe. Operators of ships do not want to be put to inconvenience and expense, which in their view may not be justified. Their Masters, on the other hand, are largely in favour of some changes, even approaching compulsion, in areas where they know from long experience that something needs to be done to improve the safety factor. The underwriter does not seem to involve himself directly in safety. His business is, after all, in the accurate prediction of total risk, not its elimination. The statistician cries out for facts which nobody seems to want to give him, in response to the plea that his art may throw up some unseen lead. Governments and the shipping industries in so many countries seem loath to step in any positive direction, being so sensitive to the lobbies and interests that support them.

This paper examines the problem of those ship collisions which are associated with infringements of the International Regulations for Preventing Collisions at Sea. Experimental evidence indicates that there are classes of encounters which lead to indecision and uncertainty on the part of ship's officers. It is suggested that the identification of these classes of encounters is the first step towards eliminating the difficulties associated with them.

This paper is a report on some early findings of a long-term study which has the ambitious objective of suggesting better alternative solutions to the general problem of controlling a collection of aircraft. The study aims to answer questions about the optimum division of responsibility between the aircrew and ground A.T.C., about the way in which the A.T.C. tasks are shared between a number of controllers and A.T.C. computers, and about the fundamental principles on which traffic flow is organized.

To judge from literature and verbal statements made in recent years, it is probable that among those who read the title of this paper, a substantial proportion will already hold strong views on the relative merits of the two types of system, that these views will reflect a wide range of incompatible conclusions and that they will not all agree on the precise definitions of the two terms themselves. The terms have not been formally defined which has, of course, contributed to the confusion and this is unfortunate because, in the opinion of the author, the terms do lend themselves to logical definition. Furthermore many of the attributes of the two types of concept do confer obvious penalties or advantages which are not seriously in dispute among the contending parties.

A discussion on current progress in the development of Omega as a world-wide navigation aid, on technical problems that still await satisfactory solutions, and on the probable magnitude of the resulting errors in position, took place at an open session of the Technical Committee held in London on 24 January 1973 with Mr. H. E. Smith, o.b.e., in the Chair. The discussion was opened by the President.

In studying the behaviour of marine traffic in the Strait of Dover observations have been made of vessels contravening the recommendations of the Imco Traffic Separation Scheme. This report, originally published by the National Physical Laboratory (Crown Copyright), considers the risks attached to the courses of these vessels in terms of the number of encounters to be expected and in the light of the recommended routing principles.

The discussion printed below took place at an open session of the Institute's Technical Committee held at the Royal Aeronautical Society in London on 2 May 1973 with Claud Powell in the Chair.

During my days of ‘tramping’ across the Pacific Ocean as an apprentice, I had heard vague references to the effect that the Polynesians used coconut shells as an aid to navigation. Intrigued as I was, the opportunity never presented itself for me to pursue the matter further until years later, by which time I knew that I was in search of the ‘Sacred Calabash’.

This paper describes a method of constructing accuracy contours for a position line obtained by observing the horizontal angle between two stations. An example is given using an estimate made, from experimental evidence, of the observational errors that are likely to occur when such angles are measured by sextant. A recent paper by Cotter described the historical development of this method of obtaining a position line.

Captain S. T. L. Lecky, in his famous Wrinkles, wrote with derision in his reference to so-called ‘short-methods’. He warned his readers to ‘beware’ of these:

They generally only look short [wrote Lecky] because good care is taken to apply the various corrections beforehand, and the unsuspecting reader is deceived of this device.

As a case in point Lecky considered the ‘small but expensive pamphlet by Mr. Martelli’, to support his derogatory remarks:

When his so-called ‘short-method’ is overhauled and compared with Raper, we get the following startling result:—Martelli, 56 figures and five logarithms, against Raper's 59 figures and five logarithms, required to produce the same result. So that by the first method we have the enormous (!!!) gain of three figures. Furthermore Mr. Martelli's pamphlet contains several glaring errors which makes one rather dubious about the general correctness of the tables, although (for all the writer (Lecky) knows to the contrary) the mathematical principle of his method may be correct enough.

Readers of Captain Cotter's very interesting article ‘A Brief History of the Method of Fixing by Horizontal Angles’, may be interested to know that the possible use of the resection or three-point problem was appreciated by English mathematical practitioners of the seventeenth century.

Explanations have been given by John Collins, F.R.S. (1625–83), and Edmond Halley, F.R.S., Master and Commander, later Captain, Royal Navy and Astronomer Royal. It seems probable that Halley actually made some use of the principle when he charted the English Channel.

Dr. Angus Armitage and Dr. A. H. W. Robinson have explained Halley's method.