The statistical relation between wind and temperature in the lower stratosphere is not only of theoretical interest but is of practical concern for the operation of supersonic aircraft since for example the incidence of abnormally high temperature together with strong head-winds could substantially increase the time of flight and reduce the pay-load. Temperature and tail-wind component have been correlated on the great-circle route between London and New York at 50 mb. The route was divided into six legs of approximately 500 nautical miles; at the mid-point of each leg, temperature and tail-wind component for an eastbound flight were obtained from daily charts for the period of the International Geophysical Year and its extension, July 1957 to June 1959 (U.S. Weather Bureau, 1960–63). Seasonal correlation coefficients were evaluated for each leg and for the route as a whole. The seasons in the lower stratosphere in middle latitudes differ from the conventional seasons except in summer (June–August). Although autumn has been taken as September–November, it appears that the transition to the winter type of circulation is usually completed by late October so that November should strictly be included in winter. However, the period December to March has been taken for winter; conditions in March are very variable from one year to another but on balance this month is probably more appropriate to winter than to spring.

The Regulations for Preventing Collisions at Sea were formulated before the invention of radar, and radar has invalidated one of the principles upon which the Rules are based. This principle is that when two vessels are in risk of collision one shall get out of the way, and the other shall stand-on (except in the cases where two vessels are meeting end-on, and where the stand-on vessel finds herself so close that collision cannot be avoided by action of the giving-way vessel alone). This assumes that if one vessel can see another she also can be seen, and this is of course likely to be the case where visual sighting is concerned. From radar observations one cannot know if the other ship has observed you, and it is unlikely that we shall know this with certainty, for radar and other aids may fail. Providing there is sufficient sea-room and not too much traffic, this drawback can usually be overcome by taking early and substantial avoiding action (as recommended in the Annex to the Rules). If one ship makes a manœuvre which cancels the avoiding action taken by the other there is still time for second thoughts; but in crowded waters there may not be so. Even when both vessels are navigated correctly, the imprecision of radar predictions may lead to dangerously close passings.

The wide range of interests of members of the Institute, combining as it does all aspects of marine and air navigation from the basic concepts through research, development, design, manufacture and marketing to practical operation, presents a most interesting challenge to the president in his address. This challenge is increased by the knowledge that this address will appear in the twenty-first birthday issue of the Journal in company with articles by eminent members of the Institute on developments in their own fields.

Since the last Institute meeting on the Admiralty chart in 1967 the compilation office, formerly at Cricklewood, has been moved to a new building at Taunton, alongside our printing works established there in 1940. Thus, except for a small office in Whitehall, which keeps in touch with the ever changing defence scene, the whole of our organization is now concentrated at Taunton, from where every week between 30,000 and 40,000 Admiralty charts are despatched, through our agents, to navigators in every part of the world.

As readers of the Institute's Journal will know, to mark the 21st anniversary of the Institute a special edition, entitled The Navigation Explosion was published. Papers published in this edition highlight the very rapid advances which have been made during those 21 years as a result of a happy marriage between the ancient art of navigation and modern science and technology.

Traditionally ‘Freedom of the Seas’ has meant that the ‘Master under God’ has been answerable to no one for his ship handling and manœuvring, except in the case of collision, when he has been answerable to the Courts. Congestion of certain sea areas and waterways has created situations where some restriction to this freedom has become acceptable in the interests of general safety; harbour radar procedures, the Dover Strait and other traffic separation schemes are the most well-known examples. Such areas will increase in number and size as the volume of trade increases.

By 1966 it was obvious, the Government having announced its intention for the country to go metric, that we had to think seriously of the metrication of Admiralty charts. With some 3500 navigational charts, many additional special charts, plotting sheets and other publications the task was unquestionably a formidable one, but it was decided that it could be done and a start should be made as early as possible.

It could be tackled in two ways, either by a gradual process, whereby charts would be converted as they came up for correction or where it was necessary to produce a new chart; this would mean slow progress and result in a haphazard geographical distribution. Alternatively such resources as were available could be concentrated in one area at a time and blocks of charts produced in metric units. This would avoid, to some extent, the difficulty to the mariner of having to jump about from fathoms and feet to metres and back again as he changed charts, and we eventually decided on this method—but in true British fashion are doing a bit of both.

On the one hand, there is the inevitable reluctance to change Rules that have stood the test of time but I think this reluctance comes mainly from the older officers in their last few years of service, who, very understandably, do not wish to have to learn new Rules and find that their instinctive and almost automatic reaction to any situation gained through years of practical experience has now all to be changed.

On the other hand there is a very strong body of opinion which feels that the old Rules, designed for quite different circumstances and unable by their basic concepts to be suitably amended to meet modern conditions, must be completely re-written—amendment to the existing Rules just will not do.

“Through art to science” was the theme of the second “Off the Beaten Track” programme of lectures for nautical schools and colleges. In the last twenty years navigation has changed in precisely that fashion. At the end of World War II, in spite of equipment developments, navigation remained an art, and this shines through the pages of our early Journals. Today the Journal proclaims that the art has become a science. “Sic transit gloria Astro!”

There are three main reasons why the rules for preventing collisions at sea need revising:

Rule 21 is unsatisfactory. This is particularly the case in encounters between vessels of widely different speeds and manœuvring capabilities when Rule 19 may require an unreasonable manœuvre from the slower and more ponderous craft and Rule 21 at the same time prohibits manœuvre by the more easily handled craft.

If in an encounter the giving-way vessel does not take action in good time, Rule 21 requires that the other vessel must maintain a collision course until the situation becomes so dangerous that action by one vessel is insufficient to prevent collision. For a rule which is intended to prevent collision this seems hardly credible, but in fact Rule 21 does legislate to maintain a risk situation from a time where disengagement might be comparatively easy to a point where it is almost impossible.

It is often suggested that moderate speed in fog should be a function of the performance of the ship in question, but if Rule 21 is to be observed when vessels sight one another, then it ought to be a function of the performance of the vessel required to give way. This of course may not be known until the sighting.

Because it is unnatural to maintain course and speed into a dangerous situation, Rule 21 is frequently disregarded, particularly by navigators of fast and highly manœuvrable craft.

An accuracy contour can be defined either in terms of a locus of constant radial error or a locus of constant probability density. A short comparison of the two concepts is given in reference 3.

The object of this note is to define contours of constant probability density in the case of a two-position-line running fix; the outcome is of interest in that it enables the navigator to plan his observations so that the accuracy is optimized. In Fig. 1 the object observed is S. The transferred position line corresponding to the first observation is drawn from the point S′, where SS′ is the vector corresponding to the ship's run during the time between the two observations. The fix is at O.

In July 1963 the Hydrographic Department published a Notice to Mariners announcing the integration of charting arrangements between Great Britain, Australia and New Zealand.

Because of the historical associations, the Hydrographer of the Navy was the primary charting authority in Australian and New Zealand waters until comparatively recently. Local Hydrographic Offices were set up, and these, not unnaturally, began to turn out products strongly resembling British Admiralty charts, to such an extent in fact that we were clearly wasting effort in recompiling British charts which virtually duplicated the originals. Facsimile reproduction seemed an attractive proposition. Unfortunately the normal arrangements for use of another authority's charts, as laid down by the International Hydrographic Bureau, do not allow for facsimile reproduction but special agreements can get round this difficulty.

At the 9th International Hydrographic Conference in 1967 it was agreed to set up a Commission to study the constitution of an international set of charts, confining the study initially to charts on scale smaller than 1 in 1 million. This set should eventually enable all the members of the International Hydrographic Bureau (I.H.B.) to print in facsimile all such small-scale charts required for world-wide navigation in international waters. Among the factors which influenced this decision were:

(1) The duplication of charting which exists at present; as an example, six nations compile and publish a general chart of the Mediterranean, all with almost the same scale and limits.

(2) The large degree of standardization of chart symbols achieved by the work of the Bureau.

(3) The great and continuing increase in the work load of all the national hydrographic offices.

In January 1967 the Centre National d'Etudes Spatiales and the Secrétariat Général à l'Aviation Civile agreed on the definition of the main characteristics of the Project Dioscures, a system for telecommunications, air traffic control and navigation by means of satellites. Since then, technical studies have been carried out and the main equipment is being developed. The proposed system will enable air traffic control centres to provide continuous position determination for aircraft in the common visibility zone of two geostationary satellites. Furthermore, it will establish dependable and good-quality communication links between aircraft, control centres and other users (airlines and shipping companies, meteorological services, &c.). The system will initially be implemented over the Atlantic, mainly to serve the North Atlantic region, to be progressively expanded to cover the whole world.

Since the introduction of the present (1960) Regulations for Preventing Collisions at Sea, we at Cardiff have noticed that the actions taken by Masters and senior officers, during simulator exercises, have been bolder and, perhaps, taken somewhat earlier than they were previously. Unfortunately, however, the actions taken by two ships approaching each other often cancel out. This is not always dangerous because the initial actions have generally been taken early enough for further action to be taken but, it does lead to unnecessary delays and frustration. We think, therefore, that it is desirable that any new Regulations should contain a set of rules of action for a vessel detecting another, on a collision course, by radar only.

The twenty-first birthday of the Institute coincides very closely with that of commercial marine radar. Many merchant ships were fitted with naval radars between 1942 and 1945 but these bore little resemblance to the sets which would be needed for peaceful purposes.

Even before the war had ended, the United Kingdom Conference on Radio for Marine Transport (U.K.R.M.T.) was set up under the auspices of the Radio Board of the War Cabinet, to discuss the peacetime applications of the war developments. This conference led to the establishment of an Application Committee (R.A.M.N.A.C.) which kept the administration, the user and the manufacturer in touch. Immediately after the war, the Admiralty was in collaboration with the Ministry of Transport (M.O.T.) and the shipowners to arrange the supply of surplus 3-cm (Type 268) radar to the merchant navy, pending the design and production of commercial sets. At the same time the Admiralty Signal and Radar Establishment (A.S.R.E., now A.S.W.E.) was drawing up a specification1 to meet the needs of navigation and anti-collision. A prototype to this specification was demonstrated to all concerned in 1946.

Everyone now knows that radar has not fulfilled expectations as a means of preventing collision at sea, and that, because of this, its legal status is merely that of an aid to navigation. Nevertheless, everyone seems to feel that such a good technical instrument should enable ships to proceed safely in fog without reducing speed, and the fact that the collisions per fog day have increased by about thirty times in the fifteen years since radar became operational, shows that many mariners are in fact relying on it for collision avoidance. During these fifteen years, many papers have been published pointing out the dangers and giving advice, but in spite of this, the number of vessels involved in collision every year seems to have settled down to a constant figure of about 1700, or 7 per cent of the world fleet.

Some 7 years ago the North Sea Hydrographic Commission took up the question of deep draught routes in the North Sea and a basic pattern was selected and examined against existing hydrographic materials by the members of this Commission. In 1966 Shell International Marine produced a publication entitled The Channel and North Sea Routeing Folder. These more detailed routes together with the basic ones proposed by the Hydrographic Commission (although they are in no way official or necessarily accepted) form the basis of our present thinking on routes and planning of surveys in this area.

It was only a few years ago that a draught of 50 ft. was exceptional and it was generally considered that draughts were unlikely ever to exceed 60 ft. In fact draughts have increased rapidly ever since and for this reason, last year, we extended the limit to which we show soundings in fathoms and feet from 11 to 15 fin. in areas where deep-draught vessels could be expected to operate.

The transport of cargo is not of itself a navigational subject; it is however the purpose of nearly all marine navigation and a development such as ‘containerization’ which is having such a profound effect on the nature of shipping cannot fail to be of interest to navigators at sea. In this paper, a version of which appears on the U.S. North Atlantic Pilot Chart for May 1969, Mr. Van de Ree of the Ship Analysis Division of the U.S. Navy Oceanographic Office describes the background to the development of unitized cargo handling and transportation, its economic advantages and its significance for the pattern of trade at sea.

The definition of the word ‘navigation’ has been discussed frequently in meetings of this Institute and a very flexible thing it appears to be, varying its scope to suit the lecturer. This is not really surprising however, since whatever we think of as ‘navigation’ is only part of the wider business of living. In aviation for instance, the business of ‘conducting a craft as it moves about its ways’ can legitimately include seeing that the fuel tanks are full as well as pulling back on the stick to avoid hitting the top of the hill.