A deeper understanding and love for the creatures with whom we share this planet must develop as we read the works of animal specialists. These great men and women will surely forgive a navigator who suggests alternative methods by which creatures may find their ways, methods which do not seem to conflict with the remarkable facts they have brought to light but which happen to conform to modern navigational principles.

In a notable series of articles, Hsu advances theoretical models which are used to graduate 7582 observations of aircraft lateral deviations. The goodness of fit of these models, as judged by the χ2 test, is satisfactory. Hsu's main theoretical model is the Double Double Exponential distribution (DDE), a three parameter model whose probability density function is given by

Other model types are also considered, such as the family of exponential power distributions whose probability density is cited by Hsu insection 9. This leads to a four-parameter model, and the fit is (not surprisingly) better even than that of the DDE.

In an earlier contribution to this Journal the Author described some striking characteristics of the casualty statistics for the airline operations of the western world and proposed a model for the generation of a perceived risk by an individual living in a dangerous environment. It was hoped that a simulation including a population of such risk observers in the feedback loop of a control system might help with the understanding of what was happening in the real world of operations. Since then he has published an account of the development of the model, including some results from the simulation.

This paper, which was presented at a meeting of the Institute in London on 2o May 1981, with Captain R. Maybourn in the Chair, describes some studies of the conflicts arising between a multiplicity of aircraft in straight-line flight through a volume of airspace. Topics include the effect of coercing traffic to fly fixed routes, the direction from which a threat can be expected and the choice of alerting criterion for a groundbased advisory service or an airborne collision-warning system. There are some analogies, perhaps, with marine traffic problems.

There exists, worldwide, a complex scheme for the segregation and control of various classes of air traffic. To fit into this scheme aircraft must make detours, horizontally and/or vertically, the cost of which in Europe alone must be at least £50M per annum. The cost of the rare failures in traffic management is higher still. To authors trained in electronic engineering it is therefore rather surprising that the published theory of air traffic management and control is still in a rather rudimentary form.

On the whole global surface of land and sea it falls to the lot of some few places to emerge through time to be of immense importance. Lizard Point is just one such place. Who were the first mariners to realize that it was the most southerly point of the English mainland or to use it for landfall and for caping, we shall probably never know. What is clear, however, is that, by the time Claudius Ptolemy was compiling his Guide to Geography, C. AD 160, it was sufficiently well known to the Roman world for the name by which it was then called, Damnonium or Ocrinum Promontorium, to be included, with its geographical coordinates, in his famous gazetteer. It is of academic interest only for us to query whether those coordinate values were right or wrong, whether they were a good approximation or not: what is important for us, with the benefit of very long hindsight, is to marvel at the sheer brilliance of the conception of a spherical coordinate system, and at the industry and far-sightedness of one or more men who set about compiling lists of known places with assigned coordinates. What, in so doing, they handed down to posterity is of inestimable value.

The number of ships involved in collisions in Japanese waters, excluding collisions with fixed or floating objects, increased rapidly in the 1960s, as can be seen in the statistics of the Marine Accidents Inquiry Commission: 1578 in 1955, 3604 in 1960, 6043 in 1965 and 7642 in 1970, while the increase in average tonnage resulted in numerous serious accidents. To cope with this situation, the Maritime Traffic Safety Law (MTSL) was enacted in 1973, defining eleven traffic routes in congested waters. The Tokyo Bay Traffic Advisory Centre was established in 1975 and started operation in 1977. The trend in the number of traffic accidents requiring assistance shows the effect of traffic management in reducing the number of accidents.

This paper, which was originally presented at the Fourth International Symposium on Vessel Traffic Services held in Bremen from 28 to 30 April 1981, here summarizes the results of an investigation into collisions world-wide, with particular emphasis on the circumstances of collisions associated with different types of encounter for conditions of both clear and restricted visibility.

Information relating to the circumstances of collisions is available from various sources but analysis of casualty information has usually been restricted to ships under one flag and been mainly applicable to accidents in restricted waters.

Commander Paton's paper, here slightly condensed, was presented at the Fourth International Symposium on Vessel Traffic Services held in Bremen from 28 to 30 April 1981. The author is Hydrographic Adviser to the Department of Trade, but the views expressed here should not be taken to represent those of the Department. Commander Paton has also for some years been Chairman of IMCO's Working Group on routing matters.

Apart from some wartime measures, modern ship routing really dates from the early sixties, when the Institutes of Navigation in Britain, France and Germany set up a joint Working Group on traffic separation. The principal result of their labours was the Dover Strait traffic separation scheme, jointly submitted to IMCO by the British, French and German Governments and implemented in 1967. This was followed by various proposals for the North Sea, Baltic and elsewhere, considerable impetus being given by the Torrey Canyon disaster off the Scilly Isles in 1967.

In this paper Captain I. D. Irving, master of a cross-channel ferry, discusses some of the problems which arise from the operation of the 1972 Collision Regulations within the Dover Strait Traffic Separation Scheme. The paper is a revised version of one presented at the Fourth International Symposium on Vessel Traffic Services.

The Dover Strait and its approaches form one of the world's busiest waterways. Perhaps inevitably therefore it has been the scene of a large proportion of the world's collisions and strandings, and for this very reason became the site of the first offshore Traffic Separation Scheme. At first the scheme was only voluntary, but with the introduction ten years later of the 1972 International Regulations for Preventing Collisions at Sea, compliance with the IMCO-approved scheme became mandatory for all vessels.

This paper by the Harbour Master of Marseilles and his adviser on radio aids describes the system of traffic surveillance developed by the Port of Marseilles. The paper was originally presented at the Fourth International Symposium on Vessel Traffic Services held in Bremen from 28 to 30 April 1981.

The creation of an Integrated Traffic Regulation Centre (ITRC) was the solution chosen by the Port of Marseilles Authority to deal with the numerous traffic problems that had arisen in recent years in the Gulf of Fos due to the extremely rapid growth of the maritime traffic, especially oil tankers, converging on the Gulf which now totals over 80 million tonnes per year and the general tendency towards the construction and operation of very large ships, conspicuous in the development of oil tankers but now to a lesser extent in other categories of ship also.

For hundreds of years ships have roamed the oceans at random, serving the trades according to the prevailing supply and demand; each vessel taking care of itself, none caring about the whole transport and traffic pattern, but each one willing to assist and save unfortunate brothers in distress. This historic and very individualistic pattern of maritime transport operations, with as little interference, regulation and control as possible, is called by some ‘freedom of the sea’. In the minds of generations of seafarers there is instilled the idea that this utter freedom of operation was in essence the proper interpretation of being master under God. Away from the home port nobody could interfere in the way the ship was managed or the voyage proceeded. Even selling the ship abroad was a possibility on which the master could decide.

What constitutes a minimum safe distance of approach in an overtaking or meeting situation is a problem that has engaged the interest of seamen since steam began to supplant sail. Prior to that time vessels were often obliged to steer zig-zag courses in tacking against the wind, and though they were probably no less concerned with avoiding a collision the problem was of a different order.

In recent years acoustic logs have begun to replace mechanical and electromagnetic logs as a technique for measuring the speed of ships at sea. The acoustic Doppler log has become well established and, although its performance is usually far from ideal, there are many models available commercially, including those from Krupp Atlas, Thomson CSF, Simrad, Magnavox, Edo Western, Marquardt, Sperry and Amatek Straza. The acoustic correlation log has only made its appearance relatively recently.

To what extent, if at all, were globes used for practical navigation during the sixteenth and early seventeenth centuries? Globes were discussed by several writers of the period, but, with the exception of John Davis, these were not practical seamen. What evidence is there that globes were ever actually used by navigators at sea?

The first recorded globe was made by Martin Behaim in 1490. The most celebrated makers who followed were Gemma Frisius in 1530, Gerhard Mercator in 1541 and Emery Molyneux in 1592.

D. H. Sadler has pointed out that the method I proposed in my paper (34, 247) can be improved, in his view, by the use of the formula

(1 + f) × distance = D.lat × sec(Co)

where the tabulation of Jean be found in his earlier paper (9, 371).