In 1960 Dr. Calvert published a paper in the Journal (13, 127) which proposed a fundamentally new conception of how to avoid collision between single craft at sea or in the air, based on work carried out by the Mathematics Department of the Royal Aircraft Establishment. Later Hollingdale (14, 243) published a rigorously mathematical explanation of Calvert's ideas. The following paper to some extent draws together the arguments that have ranged so widely over this subject during the last ten years or so.

The chief criticism which has always been made against the existing Collision Regulations and is now being made against the revised ones, is that, except for the end-on encounter, no directives are given as to how a vessel should manœuvre to ‘keep out of the way’. Their role, it has been said, is not so much to prevent collisions as to enable lawyers to apportion blame after collision has occurred. The explanation usually given is that ‘the infinite variety of encounters which may arise at sea does not yield to a uniform treatment’.

The present deadlock between Western Europe and U.S.A. reflects a difference in emphasis on motivation largely traceable to the space technology gap. The problem is to establish institutional and work sharing arrangements bridging U.S. desire for early commercial space exploitation and European desire to promote its industrial space techology. The European approach is compatible with I.C.A.O. and I.A.T.A. preference for a non-operational experimental first phase Aerosat programme, and unless a compromise with U.S.A. is reached the best solution may be a European E.S.R.O. programme able to cater for the experimental mobile satellite communication system requirements of both aviation and shipping. The paper was presented at the Conference on Aeronautical and Maritime Satellite Systems held in London on 13–15 March and sponsored jointly by the Institution of Electrical Engineers with this Institute, the Institution of Electronic and Radio Engineers and the European Space Research Organization.

The Royal Institute of Navigation has in its possession a remarkable set of works by its late Honorary Member Vice-Admiral Francisco Radler de Aquino. An interesting feature of many of the items of this set is the large number of annotations, made by Aquino, which throw light on the development of his short-method tables—a development which continued throughout Aquino's long career as a distinguished navigator.

It is generally felt that by causing aircraft to follow accurate climb and descent paths the flow of traffic in terminal areas can be improved. This paper, which was presented at a meeting of the Institute held in London on 29 November 1972, with the President, G. E. Beck, in the Chair, discusses the special constraints involved in vertical plane navigation. These arise from difficulties in the accurate measurement of position, and the limitations of aircraft response. The need to fly at differing speeds and in various configurations, while minimizing passenger discomfort and external noise, is also considered.

The system of winds and currents in the North Atlantic rotates in a clockwise direction so that, crossing from east to west in the northern part of the ocean, the winds and currents will be predominantly foul. This means that a sailing vessel making her way, for example, from the Channel to New York will be likely to cover a distance something nearer 4000 than the nominal 3000 n. miles—more or less according to her windward ability. Alternatives to the direct route have thus grown up over the years from considerations as to which 4000 miles or so is likely to prove the most advantageous and swift. An earlier paper gave an account of the generally accepted routes and the principal sources from which they have been derived.

Dr. J. P. Hooft who is a Vice-President of the Netherlands Ship Model Basin at Wageningen, discusses the hydrodynamic forces which act upon a large ship sailing in shallow water. Their effects on the manœuvrability and control of the ship include a smaller response to a given rudder angle, a shift of the pivoting point aft towards the centre of gravity, a larger turning circle and less reduction in speed when turning. In general a ship becomes more sluggish in shallow water.

Since manœuvres with large ships are usually only performed in the proximity of harbours while in deep water the ship is kept on course by means of an autopilot, it will be difficult to compare the manœuvrability of large ships in shallow water with their manœuvrability in deep water. The influence of water depth on the hydrodynamic characteristics of the ship will therefore be the main subject of the present paper; the consequences of these ship characteristics on manœuvrability will then be considered. This term ‘manœuvrability’ is often replaced by ‘controllability’. In this respect a ship is said to be controllable when the navigator is able to manœuvre the ship with ease in such a way that departures from the anticipated manœuvre remain within acceptable limits.

In clear-weather conditions well trained mariners experience little difficulty in dealing with multi-ship encounters in all circumstances. In restricted visibility they do not display the same confidence in manœuvring even in the open sea, and the problem is amplified as the waters narrow and the traffic density increases. The plea of the mariner would be to find an anti-collision system that would make manœuvring in fog at least as straightforward as in clear weather. To satisfy such a request it might seem that there would need to be two systems, one for fog and another for clear, but it seems probable that a system evolved to work safely in fog would also be acceptable in the less demanding conditions of clear weather; this would in time be the only system adopted.

Captain Jones has indicated that the navigator needs improved technical assistance in avoiding collisions during conditions of inadequate visibility. When the aided eye fails to distinguish the aspect of a vessel until it is much closer than the optimum distance at which a risk of collision ought to be recognized, then visibility is inadequate. For large ships a warning can be required before the distance closes to three miles, for example, whereas a visibility limited to three miles is commonly experienced. However, more guidance on this point is still needed from navigators.

This paper describes a new radar system which aims to give the Master of a vessel, on a television screen, the kind of information which could be obtained visually from a wheelhouse window in daylight in clear weather. The system was described by Mr. P.O. Prior at a meeting of the Institute held on 17 January and an account of the discussion will be given in the next number of the Journal. S. R. Parsons is Chief Engineer of Kelvin Hughes and Captain J. P. Stewart a Marine Consultant.

The early history of marine radar when the phrase ‘radar assisted collision’ was coined, the setting up of radar simulator schools to assist in teaching the interpretation of the radar picture, and more recently the increased number of collisions at sea, particularly in congested areas like the English Channel and the approaches to major harbours, all call into question the adequacy of the presentation of radar data on conventional relative and true-motion radar sets.

Reduce speed, stop engines, navigate with caution. There can be little doubt that there will be very few legal obligations that are so consistently ignored as Rule 16 of the Collision Regulations at Sea. Yet the circumstance to which Rule 16 applies, reduced visibility, is only one of the causes for reducing speed and the factors involved in the decision to accept delay may prove interesting and revealing. It is the purpose of this paper to stimulate further investigation into the subject, an investigation that will certainly require the cooperation of ship owners associations and master mariner organizations and which could well be carried out by the Marine Science Departments of such advanced educational institutions as for example University of Wales Institute of Science and Technology in Cardiff.

W. Palmer's note on Standard Time (this Journal, Vol. 25, page 535) may mislead some readers. He tends to confuse ‘Time’, as an abstract philosophical concept, with the measures of time, or time-scales, used in practice by astronomers, navigators, surveyors, physicists, electronic engineers and the general public. Such measures of time may be based on any recurrent phenomenon, whether uniform or not, ranging from the growth of coral to atomic transitions; and, for this reason, those professionally concerned use precise terminology to distinguish the many time-scales in current use. Unlike Mr. Palmer, they do not use ‘Time’ for a particular time-scale; and, for example, they restrict ‘standard’ to its generally understood application to the meridian to which the legal time of a country is referred. There are a number of factual errors arising from this confusion (e.g. G.H.A. Aries is equivalent to sidereal time) which need not be elaborated here.

As a passenger on the Queen Elizabeth 2 on a westward crossing of the Atlantic in late May 1972, I took sextant sights with my standard marine Plath sextant and also with the ‘bubble’ attachment for this instrument. Inspired by Francis Rogers' discussion of the development of bubble sextants, my project was to compare the accuracy of the bubble sights with that of the conventional marine sextant sights, which require the horizon.

Details have been given in this Journal (Vol. 25, pages 3 2–42) of the new system of Coordinated Universal Time (U.T.C.) introduced on 1 January 1972. In accord with the agreed recommendations a positive leap-second was introduced at midnight on 30 June 1972 when the value of U.T.1–U.T.C. (DUT1) changed from −0s.64 to + 0s.36. However, the Bureau International de l'Heure has now announced that another positive leap-second is to be introduced at midnight on 31 December 1972, when (according to current estimates) U.T.1–U.T.C. will be about −0s.2; on 1 January 1973 DUT1 will thus be +0s.8, in excess of the maximum permitted value of of 0s.7.

Henry Raper (1799–1859) the eldest son of Admiral Henry Raper (1767—1845) retired from active service in 1825, from which time he devoted himself to nautical science. He served repeatedly on the Councils of the Royal Geographical and Royal Astronomical Societies and for many years was Secretary of the Royal Astronomical Society. His Practice of Navigation and Nautical Astronomy earned him the award of the Gold Medal of the Royal Geographical Society.

Dense fog prevailed over the whole of the Thames area for three days from 1518 on 18th through to 1900 on 21st December 1972, with no real clearances of significant extent or duration throughout this period. Such prolonged fog had not occurred there since December, 1962.

I Suppose this incident might be entitled ‘How not to find a lightship’. It took place in the 1930s while I was serving in the M.S. Potter, one of the United States Line's long-haul cargo motorships of the period. She was a three-island, fivehatch ship which could lift eight-thousand tons and move it at eleven knots. She was my home for five years and wound up as part of a breakwater at the Normandy beachhead.

Marine and air navigation can still learn from each other. Mariners are following aviation in adopting some routing and control but aviation could follow mariners in their refusal to accept routing and control unless it is cost effective. However it may be easier in the marine case to measure the cost and probability of a collision than it is in the aerial case. But many states have established mandatory airways and routes; originally their navigational aids were very useful and in the event of forced landing the search and rescue people knew where to look. But many airliners now have self-contained navaids like the inertial navigation system (INS) or doppler so that they can navigate off airways, and also forced landings are rare. In the history of air traffic control at first it applied only around airports; when it spread to routes many aircraft were quite happy to fly off airways. But now airways have proliferated and have become customary and respectable to airline pilots so that few complain when some states force aircraft to follow lengthy and costly routes. The only virtue of airways is their freedom, theoretically, from uncontrolled traffic and from military dangers. If A.T.C. were confined to those situations where the risk of collision without A.T.C. would be worse than, say 1 in 10,000,000, flying would be a little more expeditious, but everyone feels secure within the system and insecure, guilty and uncomfortable outside it, so A.T.C. is used universally by airliners.