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.

In this paper the author sketches the historical development of radar beacons: the different types are classified in relation to code and frequency employed and the benefits and drawbacks of more recently proposed types of beacon are discussed.

The paper was presented at a Marine Electronics Symposium sponsored by the Society of Electronic and Radio Technicians at the University of Southampton in July 1976.

The military use of responder beacons before 1945 led to secondary radar systems, such as Rebecca-Eureka, Oboe, and IFF, giving facilities for target location at long range with an accuracy and identification not available from a primary radar system. The desirability of these advantages in civilian systems was recognized but the absence of military urgency and considerations of cost led to delay. Although responder beacons became an essential part of the Air Traffic Control System, extension into the marine field did not succeed until the U.K. Ministry of Transport Safety of Navigation Committee set up a Technical Committee and Working Party in 1962 to investigate the conditions governing the marine installation of responder beacons as a navigational aid. This committee recommended that responder beacons (alternatively called racons) should be set up to an agreed specification at selected sites around the UK coast, to become the first civil marine navigational racon system. The co-operation of the Admiralty Surface Weapons Establishment, Trinity House, and Kelvin Hughes made possible the installation and operation of three racons—on the Liverpool Bar LV, the Kish LV, and St. Abb's Head LH—to provide operational experience on which the committee's recommendations were based, followed by the setting up of the complete system.

Throughout history man has navigated himself or his vehicle; while some of the methods he has used have remained unchanged through the centuries, other methods have been developed, and when superseded by later developments often lost. The stone age cave dweller used navigation, after chasing his quarry, to find his way back to his cave and this particular form of the art of navigation is little changed today. On the other hand the arts and the techniques which enabled early Polynesian navigators to sail the South Seas, and the crews of Arabian dhows to return to their home ports unerringly, may well be lost for all time. We do not propose to regret this; it is part of the evolutionary process that as each skill is lost it is replaced by a greater skill. The modern marine sextant can trace its ancestry back to the practice of measuring the height of a star in finger breadths used by those Arab navigators. Aerial navigation entirely, and from our limited knowledge we suggest ship navigation also, is at a point in its development where the man is being replaced by the machine, and it may be that we should assess the best way to ensure that we, as navigators, remain master of that machine.

Anyone concerned with navigation, be he practising navigator, design or development engineer, teacher, or amateur yachtsman, will be aware that the great majority of developments took place prior to Captain Cook's epic voyages (1768–1779) or after 1904 when the first radio time signals were transmitted. During the first period the science of astro-navigation had been developed and such aids as log, chronometer, sextant and Nautical Almanac were available. The methods developed during that period differ very little from the traditional methods which are still in use today.

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.

Early in 1976 the Navigation Research Centre of the Netherlands Maritime Institute started research to develop a ‘maritime risk criterion number’ for a specific sea area. The need was urgent as the Navigation Research Centre (NRC) became more involved in marine traffic studies in the North Sea and the approaches to Dutch harbours. The main purpose is to calculate the criteria for traffic patterns in a given area as an element in the information needed to find the best regulatory solution for the overall traffic situation. The criterion should give due recognition to such elements as the traffic density, the course and speed distribution of the traffic, and the danger classes of the ships participating in the traffic.

To fulfill any specific task a certain navigation accuracy is in general required. If this requirement can be achieved by different systems the cost effectiveness will be decisive. Apart from missions which allow large position errors, medium or high navigation accuracies will normally be desired, obtained either by high technological standards or by an unsophisticated system with an updating procedure. The cost of highly sophisticated systems increases exponentially with increasing accuracy, so that our object was to find an appropriate updating system.

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.

The first reference to western techniques of navigation in Japan is in the Genna-Kohkaisho or The Navigation Arts in the Age of Genna by Koh-un-Ikeda, written in 1618 just sixty-three years after the first Portuguese visit to Japan. During these sixty-three years the Japanese had built some western-style sailing vessels and actually used western techniques for navigation to south-east Asia. The author shows a good grasp of western navigation. For instance Ikeda had asked his teacher, the Portuguese captain Gonsaro (Japanese pronunciation) ‘Is there any method of obtaining the latitude when the sky is clouded for a short time just as the Sun or the star transits the meridian?’ Captain Gonsaro answers ‘It is of course impossible, no one in the world can ever do it.’ Ikeda suggests the possibility of estimating the altitude of the Sun or star on the meridian and one can see now that this foreshadows the famous ex-meridian method that was developed much later.

Fragments of documents and instruments identifiable as almanacs, together with the comments of ancient writers and the circumstances surrounding historical deeds indicate that almanacs have existed from the earliest attempts at the organization of time into units larger than the day. The value of such works to navigation was slight when voyages beyond sight of land were few and of short duration; nor were they readily available when books had to be hand copied. Yet the contents of almanacs had an influence on sailing; the average mariner, being neither more ignorant nor less superstitious than the merchant or farmer, was likewise subject to occult predictions when almanacs were in the hands of the astrologers.

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.

John Hamilton Moore (1738–1807), a well-known teacher of navigation, was born in Edinburgh, educated in Ireland, and subsequently joined the Royal Navy at Plymouth. In about 1770 Moore established a Nautical Academy in Brentford, Middlesex, and in 1772 he published his popular epitome of navigation under the title The New Practical Navigator and Daily Assistant. Later he established himself at 127, Minories, near Tower Hill, where he not only taught navigation to ‘Gentlemen designed for, or belonging to the sea‘ but carried on the business, aided by his sons and son-in-law Robert Blachford, of chart-seller and purveyor of nautical instruments. In the preface to the twelfth (1796) edition of his Practical Navigator, Moore presumed that he had been enabled to have made gradual but progressive improvements in navigation as his ‘knowledge became extended through investigation’ and as his ‘judgement matured by experience’. In this edition of his work Moore styled himself as ‘Teacher of Navigation, Hydrographer and Chart-seller to His Royal Highness the Duke of Clarence’. There can be no doubt that Moore's Practical Navigator was favourably received; and, indeed, a twentieth edition was brought out by Joseph F. Dessiou (1790–1842), a master in the Royal Navy who, on retiring from sea-service, was employed in the Admiralty Hydrographic Office where he specialized in the study of tides. Dessiou's twentieth edition of Moore appeared in 1828, some 21 years after the death of its original author.

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.