The Royal Air Force has no operational aircraft fitted with Omega but the author was closely associated with two assessments of the system planned and flown by R.A.F. navigators. Both series of flights used the Marconi Elliott AD 1800 equipment. The first flights were from Boscombe Down in mid-1973; the second series, arranged by the Department of Air Warfare at the R.A.F. College, Cranwell consisted of two flights over the North Pole in September 1976.

This paper reflects nearly three years experience of flying with Omega and suggests that in an Omega with doppler fit the necessity for the continuous compass feed can be turned to advantage by using Omega to measure and display the accuracy of the feed, which can then be applied as a system tracking correction to the doppler. The equipment we have been evaluating is a prototype Marconi Elliott AD 1800 comprising a receiver and computer in a 1 ATR black box in the avionics bay, a control display unit on the navigator's desk and an aerial input from the ADF 2 sense aerial, via a pre-amplifier and splitter that allows Omega continual use of the aerial; the ADF 2 shared access to it as required. In three years we have effectively had one hardware failure per year. These were a timing card fault, a 10 V power supply failure and a sticking ‘INSERT’ button. All these faults were detectable pre-flight; we have had no inflight equipment failures.

As a replacement for the Loran A systems installed on approximately fifty B-707/300 aircraft and to have this replacement fully operational by the end of 1977 only two options were available: the very well proven but relatively costly inertial systems and the almost totally unproven but potentially much less costly Omega. Economic considerations played a major role in this choice in view of the limited remaining useful life of the aircraft involved. The general object of the programme was to assess the acceptability of Omega as a pilot-operated substitute for Loran A in aircraft also equipped with dual doppler/computer navigation systems. Critical aspects of the use of Omega which were to be investigated were:

(i) the availability of adequate Omega signal coverage on a reasonably worldwide basis,

(ii) the normal in-lane accuracy of the Omega position output,

(iii) the in-lane stability of the Omega position output, i.e. susceptibility to ‘lane-slip’,

(iv) the reliability of the airborne Omega hardware,

(v) the operational suitability of the control/display units.

At first sight, it may seem inappropriate for an equipment manufacturer to present a resume of operation experience in the use of Omega at sea. The manufacturer is however a natural collection point for user experience and bad news travels fast while good news rarely travels at all!

The Omega transmitter network has improved considerably during the last year and with the exception of Australia all transmitters are now usable for navigation, with a typical reliability exceeding 99 per cent. This has only occurred in recent months, as previously coverage was only available in the northern hemisphere and it is users who frequently operate in this area who have become familiar with the system and gained confidence in its use.

The Japanese Maritime Safety Agency has established a Tokyo Bay Traffic Advisory Service Center at Kannon Saki at the entrance to the bay in order to promote the safe navigation of vessels. The Center is equipped with radar linked to a computer. The information and control service has been operational from 25 February 1977.

Information will be broadcast to all vessels concerning the traffic schedules of very large vessels, the movement of fishing craft and of other vessels on the traffic route or in neighbouring waters. Transmissions are also made by v.h.f. individually to any vessel requesting information as to her position or the movements of other vessels.

The need to improve and regulate navigation in the Gulf of Suez became urgent when the Suez Canal was reopened in June 1975, and urgency increased with the number and size of ships passing through the Canal. In 1975 the Suez Canal Authority embarked on a three-phase development operation over a period of six years; the first phase, completed in 1976, allowed the passage of vessels having draughts of up to 38 ft, while the final phase, initially due for completion in 1981 but later extended to 1983, will allow the transit of vessels having draughts of up to 68 ft.

Over the past few years several papers have been written based on the results of surveys of marine traffic in different parts of the world. The general knowledge of the overall picture of the behaviour of ships at sea has increased considerably but there are still many aspects which need to be explored. One of the main fields of interest of the Marine Traffic Research Unit at the City of London Polytechnic is the use that mariners make of available sea room. For any particular area the navigational difficulties are going to vary considerably in situations where ships enter the area at different points, travelling indifferent directions, from situations in which the ships tend to keep to a number of defined routes through the area. If ships do tend to adopt a routing structure through an area, the next question of interest is how wide the various routes are, given no physical limitations for their width. The behaviour patterns may vary for different types of ship, and speed is another variable which may affect the situation. Answers to all these questions would be needed if one wanted to analyse the efficiency and safety aspects of marine traffic in an area.

Various surveys have been carried out in narrow waters throughout the world and provide data on the traffic volume, traffic density, velocity distributions of ships, &c. Although these surveys certainly contribute to the safety of local navigation they do not give any information on traffic movements between terminal points in a marine traffic system. There are a few papers on voyage distribution based on traffic surveys, statistical reports or questionnaires to mariners and also a few based on radar observation, including one in Osaka Bay in Japan which was carried out by the traffic research group of the Kobe University of Mercantile Marine and Nautical Technical College.

In this paper, which was presented at a meeting of the Institute in London on 26 January 1977 with Group Captain H. L. Sheppard in the Chair, Mr. Attwooll, Head of the Air Traffic Studies Division at the Royal Aircraft Establishment, discusses the application of the theory of queues to air traffic control. He shows the importance of random perturbations due to late arrival of aircraft, and how traffic schedules in an airway network can best be adjusted to minimize delays due to congestion on certain routes. Much of this study was carried out on behalf of the Civil Aviation Authority but the opinions expressed do not necessarily reflect the policy either of the CAA or the Ministry of Defence

The prime purpose of the navigation system in a combat aircraft is to determine the relative positions of aircraft and target with sufficient accuracy to enable a weapon to be released. In practice the actual system installed in the aircraft is a compromise solution, which depends on three factors, namely, the mission to be flown, the type of aircraft and the navigation phases through which the aircraft flies while performing the mission. Broadly speaking there are two types of navigation phase; these will be termed macronavigation and micronavigation. Macronavigation is concerned with the navigation of an aircraft to some pre-determined point on the Earth's surface while micronavigation is the final, highly accurate navigation phase required for weapon release. Micronavigation can be further sub-divided into static and dynamic micronavigation; static when the target and the coordinate system within which it exists are fixed, and dynamic when the target moves within a coordinate system which is defined by the attacking aircraft.

The dissemination of navigational information is capable of several different interpretations and this paper will be concerned mainly with the display of information to the navigator of a modern merchant ship. It will not be concerned with the need for more navigational information in certain parts of the world, or the need for new sensors for critical areas of operation.

Most research papers on modern navigational systems launch into technical details without mention of the fundamental partner to the equipment—the man. Three quotations seem, however to be relevant. J. B. Carr says: ‘A frightening aspect of some of is he new problems is that they frequently defy solution by even the most skilled officers as the data available is in some cases changing with a speed and complexity that taxes the human mind beyond its limits.’

In this paper the ship is treated as an information handling and processing system with a variety of information sources, sinks and processing areas both internal and external. Information flows and is processed in a variety of patterns depending on a number of variables. These include the proximity of other ships, the shore or the sea bed, the state of the weather, whether it is day or night and whether the ship is at sea or in port.

The author wishes to thank the Science Research Council for help in funding this study and also many industries and organizations for their assistance.

The Southampton School of Navigation and the National Maritime Institute, in association with the Royal Institution of Naval Architects, the Nautical Institute and the Royal Institute of Navigation, are organizing a Conference to be held at the Southampton School of Navigation, Warsash on 5, 6 and 7 September 1978. The theme of the Conference is the use of simulators for training and research in the shipping industry and papers are invited on the following, topics: the assessment of training needs, the design and construction of simulators, their use and effectiveness for training and research, the qualifications and training of simulator staff. Although the main emphasis will be on navigational and bridge simulators it is hoped that material on other marine simulators will be offered, e.g. engine room or cargo control simulators.

Captain Wylie reviews a further selection of collision cases in which more information might have been available on the bridge had the vessels concerned been equipped with modern automatic radar plotting equipment. The first five cases and introduction were published in the May 1977 issue of the Journal.

Case 6: Sitala and Niceto de Larrinaga, in fog in the English Channel at 19·32 on 23 September 1961. Admiralty Court, London, 1963; Mr. Justice Hewson found Niceto de Larrinaga 60 per cent to blame and Sitala 40 per cent (1963) 1 LR 205.

The cause of an increasing number of ‘radar-assisted collisions’ is the inadequate link between the radar receiver and the human operator. In contrast to all other traffic situations, the seaborne radar display forces the navigator to assess an imminent danger of collision from a ‘bird's-eye view’. When navigating in reduced visibility those vessels are most dangerous which are detected on the radar screen as being on a reciprocal or nearly reciprocal course.

It is normally no problem for the navigator to assess the collision threat from a vessel he detects optically as being near his own course line; the heading of the opponent clearly indicates the situation. A head-on situation indicates the necessity to take evasive action and the aspect of the opponent's port (or starboard) bow is left (right) indication for a left (right) change of bearing. The collision danger arising from any other target located in good visibility, and not near one's own heading line, can be assessed by repeatedly measuring or judging the target's bearing. Thus two different principles are applied to determine the threat of collision:

(i) With direct vision, by assessing the movements of approaching vessels in a horizontal direction,

(ii) With radar, by assessing the future passing distances from the plan view of the traffic situation.

The voyage of Luis Baez de Torres in 1606 resulted in the discovery of the whole southern coast of New Guinea, and of the existence of a strait between Australia and New Guinea. These great geographical results were hidden from the world, and even from the Spanish realms, so completely that sufficient data on the voyage for general study has not been available until recently. The very brief report by Torres to the King was not found, copied, translated and published until 1806, exactly 200 years after the voyage; the four charts made during the voyage were published in 1878, and the long narrative by Prado was found by chance in London, translated, and published in 1929. Hundreds of documents of secondary importance were collated and published in 1965, but owing to the habit of historical writers of using older ‘authorities’ instead of original sources, many fallacies regarding the voyage have been perpetuated to the present day, and no doubt will be in the future. The present writer, working from photostat copies of the original reports and charts, has plotted the track of Torres' two vessels from island to island and point to point by interpreting the records, by navigational deduction and from a long experience of navigating ships through the very waters traversed by Torres. He has also made sketch surveys of uncharted areas and has studied the various rare charts, maps and globes compiled by different cartographers between 161 3 and 1700 from the three or four coastal charts drawn by Prado but missing from the archives since soon after the voyage.

The principal conclusion of this study is that Torres used Endeavour Strait to get clear of the innumerable islands and reefs which blocked his course to the west and was therefore in sight of the Australian coast for many days, a finding contested by several previous writers.

There has been an enormous increase over the last few years in the number of yachts at sea and it seemed worthwhile for the Institute, which has been so closely concerned with collision, traffic separation and navigation safety generally, to discuss some of the problems that arise with members of the Royal Ocean Racing Club which is responsible for so much offshore sailing in home waters. A meeting at which the following papers were presented was held in London on 15 February 1977 with Mrs. Mary Pera, Secretary of the Royal Ocean Racing Club and a Vice-President of the Institute, in the Chair.

In discussing the navigational requirements for any vessel (including yachts) it must be remembered that there are two co-related areas for discussion: equipment and knowledge. Of these two the requirement for knowledge is of greater importance. Knowledge implies the ability to use the apparatus at one's disposal to the maximum efficiency in order to obtain the information one requires and, of equal importance, the ability to assess the validity of the information so obtained, and thereafter to use it in the most beneficial manner in the prevailing circumstances.

Radio aids are making a substantial contribution to the safety of yacht navigation, mainly by enabling off-lying dangers to be avoided when making landfall in conditions of poor visibility or overcast sky. The ability to obtain fixes of sufficient accuracy to keep clear of shipping lanes in fog is another important safety factor.

The use of hyperbolic aids, of which Loran is one, is expressly banned in ocean racing both in the U.S.A. (except in the Bermuda race) and the U.K., on account of the high price of the receivers and the advantage they might confer on those who can afford to buy or hire them. Table I shows the systems which are available in British waters, the types of error to which they are prone and some typical accuracy figures obtainable at sea. It is of particular interest to note that the accuracy of the hyperbolic aids, VOR and Consol is unaffected by the motion or attitude of the vessel, or by its metallic structures and rigging; d.f. is subject to errors from all three of these causes and all the systems except VOR are subject to the night-time sky-wave error.

From a weather forecasting viewpoint the situation of the sailing yacht at sea is unique. The yacht is small and entirely dependent on one meteorological element, wind, for its motive power. It is a device where an increase in that power increases the safety factor of speed by a very small margin while at the same time it increases the danger factor to a much larger degree. This is mainly because the increase in wind speed is accompanied by wave building and the latter increases with wind speed, time and, very dangerously, with approach to the shallow water that must often be traversed before safety is gained. It is not only wind speed that puts yachts in danger, but the combination of wind speed and attendant seaway. However seaway is not an element predicted in weather forecasts; it is a branch of seamanship left entirely to the skipper on the spot.