The Chief Marine Superintendent of BP Tanker Co. and his Electronics Superintendent examine cost–benefit analyses of expenditure on improved navigational aids as part of a broader study which includes a technical appreciation of individual items of hardware and their contribution to the navigational package. It is suggested that the range of modern, and in many cases complex, aids now available needs careful scrutiny before the optimum outfit for a given vessel may be selected. This paper was read at a meeting of the Institute in London on 19 December 1973 with the President in the Chair.

During the last decade virtually every merchant vessel of any consequence has been equipped with v.h.f. radio-telephony equipment. It had been hoped by many that the emergence of this remarkable and widely available communication facility would have been recognized in the recently (1972) agreed International Regulations for Preventing Collisions at Sea, as a means of helping to ensure that no cancelling actions would be taken by two vessels trying to avoid each other. However, for a variety of reasons, this opportunity was not grasped by the Imco working party on the Collision Regulations and consequently was lost at the International Conference held in October 1972.

The use of shipborne computer-controlled navigation systems has increased considerably during recent years. The expected advantages depend on the type of vessel; in cargo ships the safety aspect is predominant, whereas in research vessels the accuracy and reliability of position fixing are of primary importance.

Generally, computer-controlled navigation systems include a collision avoidance facility operating in conjunction with the radar. This basic equipment is usually extended by a position fixing system, calculating the latitude and longitude from the signals of position fixing transmitters and achieving optimum accuracy by sophisticated weighing techniques (Integrated Navigation). A further step in automation is the automatic guidance of the ship on preselected tracks.

It is likely that in the future aircraft designs will be increasingly tailored to optimize the traffic system rather than the economics of the aircraft considered in isolation. In this paper Mr. Attwooll, of the Mathematics Department at the Royal Aircraft Establishment, discusses the effect on the properties of air traffic systems of the individual characteristics of aircraft. This paper (published by permission of the Ministry of Defence), which reflects Mr. Attwooll's personal views rather than any official policy, was read at a meeting of the Institute in London on 28 November 1973 with the President in the Chair.

The Vinland Map, published with considerable publicity as ‘the most exciting cartographic discovery of the century’ by Yale University Press in 1965, has now, on the evidence of spectographic analysis by Walter McCrone Associates of Chicago, been virtually proved to be a modern forgery. The details, which have appeared widely in the press and were the subject of a meeting at the Royal Geographical Society on 4 February 1974, need not concern us here. The interest in Professor Taylor's paper written in 1963 well before the map's publication, is that working from measurements on a facsimile reproduction and with her own unrivalled knowledge of early cartography she was able to establish, at any rate to her own satisfaction, that the Old Map, as she calls it throughout, was a fake. She was the first scholar to cast serious doubt on the map's authenticity, and needless to say her views were hotly contested.

There have been many new developments in the North Sea during the last seven years since gas was first discovered in the B.P. West Sole field. First, half a dozen other gas-fields have been found and a large quantity of methane has already been piped to Britain. Secondly, oil has been discovered in the northern part of the North Sea between Scotland and Scandinavia. One may well ask why this large source of energy was not discovered many years ago. The reasons are much the same as applied to the gas discovery; the North Sea 10 years ago was not a very good prospect from a geological point of view, and in any case the techniques of exploration and production in offshore areas were not adequate until recently, especially in a place such as the North Sea wher severe storms and tidal streams make operations difficult and hazardous.

Means for position fixing in the North Sea using Decca have expanded greatly over the past 10 years, since the first rig was positioned in 1964, and without precise knowledge of position much of the work observed at sea is valueless. Some offshore problems have therefore changed or have been solved, others remain.

The problems associated with marine traffic engineering in the Baltic area are difficult to solve, and casualty statistics are extremely important as a basis for safety and anti-pollution activities. A statistical analysis has been made of the data relating to a total of 283 ship casualties in 1971–72; the results are presented and the discussion covers local and seasonal distribution, distribution by other time-dependent variables, and weather, visibility and the use of navigation equipment at the time concerned. The statistics further cover the type of ship involved, its nationality, loading condition, age, speed, and the damage arising. This paper was presented at the November meeting of a Navigation Group in Helsinki.

The traffic capacity of a crossing of two fairways is one of the most important problems in marine traffic engineering and a few papers published in Japan deal with this subject, either by theoretical analysis or mathematical simulation. However little is yet known on the size of domain or diameter of evasion, without which any quantitative estimation of capacity is almost impossible. Partly for this purpose a year-long observation was performed in the eastern part of Bisanseto, a strait in the Seto Inland Sea, where the number of crossing encounters is the largest in Japan.

Fujii shows that the collision diameter is about 1/10,000 of the ship length; this figure is to be interpreted as meaning that skilful manœuvres decrease the collision frequency to about 1/10,000 and, since the geometrical collision diameter is of the same order as the ship length L, attention has to be paid to ‘collisions’ which include even slight contact. The probability of a mismanœuvre which leads to stranding is studied using the marine traffic accident ‘library’ of the Japanese Association for Preventing Sea Casualties and the Report on the Marine Traffic Survey of the same Association. The library includes records of casualties in the original cards both of Marine Casualty Statistics and Statistics of Marine Accidents Requiring Rescue. The authors were members of the working group which prepared both the library and the Report. In this paper stranding includes any kind of grounding unless intentional, e.g. after collision or fire, and includes groundings with slight damage such as bottom contact.

There is no doubt that visibility influences the probability of collision and stranding and even a full moon, which gives a brightness of only 0·2 lux, seems to reduce the probability compared with a dark night; there is a much greater difference in the brightness by day (several thousand lux even with cloud) and at night. However the number of accidents in a seaway is influenced by many factors, such as traffic density, average speed, encounter condition, visibility, the helmsman's skill, availability of information &c. Of these factors, traffic density has most influence on the probability and this influence must be removed in order to study the influence of brightness. The present writer has shown that the danger of collision is roughly proportional to the square of the traffic density, and therefore proportional to the square of the traffic volume. Diurnal changes in the number of accidents and in traffic volume are therefore used to estimate the ratio of the danger by day and by night.

The visual sense supplies a major part of the information necessary for avoiding traffic accidents and fog impedes this channel of information, even though the invention of radar has removed the limitation to a considerable extent. The closure of airports is caused mainly by reduced visual range and partly by low cloud, or by typhoons in Japan. The length of signal sections on the Japan National Railway (600 m) was determined from a study of the frequency of visual ranges. Nishikura and others have studied the influence of visibility on the probability of marine traffic accidents and conclude that the ratio of the collision danger with a visibility less than 1 km and more than 1 km is in the range of from 30 to 100. Wheatley et al. have also shown the risk of traffic accidents to be high in bad visibility in the Dover Strait.

The prudence of determining the best windward and running courses for sailing yachts can be seen from Fig. 1 in which the heart shaped curve represents a polar diagram of yacht performance with respect to the true wind direction. It is a diagram of yacht velocity V and the angle α between the yacht's track and the true wind direction. The gap in the curve dead to windward is an area over which no performance is possible, whereas any destination lying outside this zone can be reached directly; there is only one sailing angle at which a destination lying between X and Y can be reached the quickest. A similar situation occurs on the running point of sailing where the curve may have an inflexion, i.e. there is profit in tacking a course downwind.

As part of their navigational outfit many of the ships in service today are equipped with Sight Reduction Tables (A.P. 3270 = H.O. 249), and many navigating officers include amongst their personal kit a Rude Star Identifier (H.O. 2102), or some similar device according to individual preference, for the purpose of obtaining the approximate altitude and azimuth of a selected body as a preliminary to making observations, particularly for star sights. However, for the benefit of those without such means at their disposal and as a matter of interest for others, the use of ABC tables for this purpose is suggested. The origin and author of this method are not known and it does not appear to be included in any of the navigational manuals which have been in circulation in recent years, but there was reference to it by Capt. S. T. Lecky in his General Utility Tables first published in 1897, a reference for which I am indebted to Capt. C. H. Cotter.

It is some considerable time since the questions associated with irradiation were considered in the pages of the Journal. Indeed the interesting and practical paper by Captain Brett Hilder is the latest considerable contribution to the Journal and this appeared no less than twenty years ago. It is only in comparatively recent times that nautical astronomers have been provided with an authoritative irradiation correction of any sort. This, which applies only to observations of the Sun's upper limb, was incorporated in the altitude correction table for the Sun and appeared annually in the Nautical Almanac after 1953, the year of Hilder's paper, but was discontinued after 1969.

A few hours after reading the above article in the October Journal an incident occurred which highlighted the dangers indicated by Captain Kemp. At night, but in clear weather and deep water, and with no navigational hazards, a ship was reported at Green 30, 3 miles, with a C.P.A. of 2 cables to starboard. This was unnecessarily and dangerously close and the officer-of-the-watch (a relatively inexperienced watchkeeper) proposed standing on to 1 mile and then altering 10 degrees to port to open the range.

There are occasions when it can be useful to plot bearings from objects not shown on the chart, for example a radiobeacon or a lighthouse outside the coverage of the chart in use. The traverse table may be used for this purpose in the following manner:

1. Establish the latitude and longitude of the object (radiobeacon, lighthouse, &c).

2. Choose a convenient latitude from which to plot the bearing and calculate the difference of latitude between it and the object.

3. With the bearing as course extract from the tables the departure corresponding to this d. lat.

4. For the middle (or mean) latitude derive the corresponding d. long. and apply it to the longitude of the bearing object.

5. Plot the bearing, as a position line, through the chosen latitude and the longitude thus derived.

As the hitherto anonymous reviser who prepared the current G.H.A. edition of Martelli's Tables, was interested, instructed and surprised by Captain Cotter's article in the Forum on this subject. I was surprised that he should write of them as if they were things of the past. In fact they are available off the shelf at my local chart agents, and no doubt elsewhere, so a demand presumably exists today, and they are in current use. From some of the comments which he makes, and the extract from Table 5 which he reproduces, it appears that he has not seen the current edition.

Much of Captain Wylie's note (this Journal, 27, 111) is undoubtedly correct, particularly the part headed ‘automatic versus manual’, which restates the strong operational requirement for automatic plotting. The earlier part, however, contains some truth, some error, and shows a notable omission. A detailed analysis would take far too much space, so I will deal with three points only.