I remember that on V-J Day in 1945 a heroic band of Common-wealth delegates, greatly reinforced by the cooperative presence of colleagues from the United States, decided that they would not rise in celebration of victory but would continue their work, which included an estimate of the probable air-traffic density at the world's great airports in or about this year 1950. We made the best estimate we could of the numbers in which aircraft would in this present year be likely to be moving in and out of Heathrow (as it was then called), of Amsterdam, Brussels and Paris. Looking back through the mist of five years I detect a band of enthusiastic and starry-eyed optimists.

In this year of 1950 the British aircraft industry has an absolute and undisputed lead in the design and manufacture of civil turbo-jet and turbo-propeller aircraft. This time again I look forward, but I warn myself that we are another group of starry-eyed optimists if we think that another five years hence Britain will hold that undisputed lead, or will be comfortably established in a position of monopoly in the sale of jet-propelled civil aircraft.

The seaman requires of radio aids to navigation that they should be effective substitutes for astronomical and terrestrial methods of fixing when these fail him, either wholly or in part. For normal peacetime voyaging there has been no firm demand for a radio system that will improve on the performance of the other methods at their best. The requirements for radio aids can therefore be related to the facilities which these other systems afford. This does not, of course, imply that circumstances do not exist in which radio aids can provide a degree of assurance that the other methods might not.

The position of a point on the surface will then be expressed by two spherical coordinates: namely, ist, the distance of the point from the primitive circle measured on a secondary; 2nd, the distance intercepted on the primitive circle between this secondary and some given point of the primitive circle assumed as the origin of coordinates.—William Chauvenet, Manual of Spherical and Practical Astronomy (1896).

On 16 May 1870, exactly eighty years before this paper was written, Lord Kelvin, then Sir William Thomson, worked out an epoch-making example of how to find the hour angle and azimuth of a heavenly body by inspection, in order to facilitate the use of Captain Thomas Sumner's method at sea. His work was published one year later in the Proceedings of the Royal Society, and in it he describes a page of his new Tables for Facilitating Sumner's Method at Sea. These tables, comprising nine pages, were made public on 11 November 1875 and were published in London in May of the following year; from them have been derived all modern navigation tables based on right-angled spherical triangles. Kelvin then used, for the first time, Greenwich hour angle in arc and assumed latitudes and longitudes. (The writer has himself used G.H.A. in arc since 1902 and assumed positions since 1908.)

In May 1948 the Radio Technical Commission for Aeronautics, a cooperative association of United States government and industrial air telecommunication agencies, issued a report outlining a comprehensive scheme for the development of air traffic control facilities in U.S.A. for the next fifteen years. This report was prepared by a committee set up by the R.T.C.A., Special Committee 31, and it is generally known as the SC31 Report. It was the result of a study undertaken at the request of the Technical Division of the Air Coordinating Committee, an inter-departmental committee established by the Secretaries of State, War, Navy and Commerce, and directed by the President to examine aviation problems of mutual concern and to develop and recommend integrated policies and actions to be taken for their solution.

This paper discusses the possibilities of using diagrammatic solutions for accurate astronomical navigation and gives a detailed description of two methods of doing so that have been put into effect in Germany. These methods, the ARG1 and the Astronomischer Rechenatlas, have previously been described in German publications and referred to in numerous reports and memoranda written in this country and the United States. So far as is known no authoritative description of these two aids to navigation has yet been published in English, and it is appropriate that this, the first, should have been written by Dr. Freiesleben, who played a prominent part in their development.—Ed.

The development of radio aids to navigation has not made astronomical navigation redundant, but it has given more force to earlier demands for the simplification of methods of reduction. No longer is it acceptable to have a large variety of alternative methods, and it is probable that attempts will be made to select a single method that is both simple and universally applicable.

Presented at a meeting of the Institute held at the Royal Geographical Society on 15 June 1951.

Shore-based radar stations to supervise or assist the navigation of ships have now been employed for at least a decade. Such stations were more extensively used during the war than they have been since, principally because there had to be large convoy movements along heavily mined coastlines under conditions when, because of wartime limitations, many of the more conventional navigational aids were not available. The most important wartime development in the use of radar in this direction was undoubtedly the introduction of high power centimetric equipment and the plan position indicator. Since the war the use of shore-based radar to assist navigation of merchant shipping has been extremely limited and the only outstanding installation of this type is the Liverpool Harbour Supervision System, which was brought into service in 1948. This system has now been in operation for three years and has provided a great deal of information and has created a world-wide interest.

Recently an electromagnetic method for measuring the velocities of ocean currents for oceanographic purposes has been shown to be reliable enough for the observed velocity of the surface current to be taken into account in dead reckoning navigation in the open ocean. A preliminary test of the electromagnetic method as a navigational aid was made in 1949 on one cruise covering a distance of 1000 miles across the Gulf Stream and back. A total of 52 miles of lateral drift was corrected to produce a straight line of travel through the observed currents, and this correction enabled the ship to return to within 2 miles of the starting point. Seven less formal experiments performed in 1950 indicate that ordinarily, on straight-away courses, the lateral drift component caused by currents can be measured and corrected with the expectation that the undetected drift will be less than 1 percent of the distance travelled.

A common feature of all systems of hyperbolic navigation (such as Gee, Loran and Decca) is the necessity of interpreting the instrumental readings of lattice coordinates and of transforming them into position—either directly into latitude and longitude or relative to neighbouring geographical features. Several methods are in use: elaborate tables giving latitude and longitude in terms of the lattice coordinates are published for use with Loran; chartlets, on a special projection, are available for certain routes on the Decca system; but the most generally useful form of interpretation, combining both presentations, is the latticed chart. This paper is concerned solely with the construction of such charts. Although formulae and examples are given, details of the computing techniques are deliberately omitted; it is hoped to issue a fuller account with the tables that have been prepared for the use of this method.

This paper describes two methods by which lines of position may be obtained by observation of stars (in pairs) without the use of instrumental scale readings either for altitude or for azimuth. These lines of position represent arcs of great circles of the Earth. An instantaneous observation is proposed.

Great circles determined by star positions form, on the celestial sphere, a lattice which is not deformed by precession. Whether or not he be at rest relative to the rotating Earth, the observer's zenith traverses this lattice, which thus may serve in celestial navigation precisely as does a well-marked terrain in contact flying over land, or as do ranges and markers in coastal and harbour navigation. Observation of the zenith-transit of an element of this lattice is akin to the process of noting the moment when an aircraft crosses a coastal line or other visible terrestrial mark or to the recognition of when a vessel near shore is on a certain range. Observation of this type is as rapid as the navigator may be able to make it since it is the observation of the occurrence of an instantaneous situation.

Sailors as a class may fairly claim to have been the earliest technicians; they were the first, that is to say, to graduate from the stage of simple craftsmanship, involving only the use of tools and rules of thumb, to the employment of instruments and mathematics for solving their problems. For the nautical chart and magnetic compass are instruments of precision while sailing directions, if they are to be useful, must be couched in mathematical language. All these three aids to navigation go back at least seven hundred years, and an Italian ship inventory of 1294 has been quoted which included two charts, a pair of compasses and two lodestones with their accompaniments.

The basic procedures used by most airlines to compile their flight plans are very similar, and are by no means as simple as they could be. When a choice of routes exists it is the normal practice to compile a series of flight plans from which the one giving the most advantageous route in the prevailing weather conditions is selected. In the absence of a direct approach to the problem of selecting the best route, the method of comparing different flight plans is improved by increasing the number of plans; it is therefore desirable that a method of speeding up the process of compilation should be evolved so that a greater number of plans can be prepared. Also the increased aircraft speeds which are to be expected in the future, and the requirement to reduce fuel loads, especially fuel reserves, to a minimum call for some rapid method of modifying the flight plan on receipt of in-flight forecasts and observations.

The three basic problems of navigation are determination of position, definition of direction, and steering the direction required. In polar regions, all these problems are affected either by the high latitude, or by the polar climate, or by both. In this paper the various problems which arise are reviewed, possible solutions are discussed, and it is indicated where further research and experiment might be desirable.

The Earth's magnetic field can evidently be divided into its horizontal and vertical components, the horizontal component being of more immediate interest to the navigator since it directs the compass needle in the horizontal plane. Whereas on the magnetic equator the full field is horizontal (about 0·400 c.g.s. units), in high latitudes, with the angle of dip between 60° and 70°, H, the horizontal force, maybe about 0·180 c.g.s. units. At the magnetic pole H is negligible and, given the opportunity, the compass needle would point vertically downwards, the instrument then having no directional properties in the horizontal plane.

Reference to a chart of the Thames Estuary will show that the dominant feature of the submarine morphology is the series of elongated banks, of which the Barrow, Sunk and Long Sand are the most important. Between these banks, and with the same north-east to south-west trend, are the navigable channels of the Swin, Barrow and Black Deep (Fig. 1).

The alignment of the channels suggests that they originated as a result of tidal-stream scour of a fairly uniform sheet of fine silt and sand. In each tidal period, streams enter the estuary from the north and flow on the flood in a south-westerly direction parallel to the Essex coast. After about six hours they slacken, turn and flow out of the estuary in the reverse direction. This continuous flood and ebb stream action, with a maximum velocity varying from 2·3 to 2·9 knots depending on whether the tide is neap or spring, has apparently scoured out channels to depths which exceed 10 fathoms in places. If the channels largely arose in this way, the banks represent the modified remnants of the initial surface. These banks are constantly being extended seaward as more riverine silt is emptied into the estuary by the Thames, Medway and the rivers of Essex. The distal end of Long Sand alone has grown almost ½ mile in the past 100 years (see Figs. 1 and 4).

The problem of how birds find their way can be examined by studying natural migration movements and also by forcing birds to undertake long journeys more or less under conditions which can be decided by the experimenter. The racing pigeon is an ideal subject for these homing experiments, but they have also been conducted with many species of wild bird and Fig. i shows some of the more remarkable flights that have been achieved with these. The use for these experiments of birds breeding in colonies has many advantages as large numbers can be caught and transported together, and their return watched for in a small area. Conspicuous birds such as gulls can be made individually recognizable by a code of plumage marks or by putting coloured leg rings on them.

Nature has provided few bright stars and these are unevenly distributed in the sky. Even for air navigation it is necessary to use stars fainter than the first magnitude. There is then a choice which rapidly widens as the limiting magnitude is decreased. Brightness is not the sole criterion; distributipn is also of importance. In choosing a number of stars for use in astronomical navigation, no two people can be expected to give precisely the same weight to small variations of brightness and distribution; there thus arise different selections for similar purposes. The navigator, however, expects that the star he knows and observes will be catered for in such lists; he cannot be expected to remember that a particular star (no fainter and perhaps even brighter than neighbouring stars) is in one list but not in others. Any rule which seeks to include all stars brighter than a given limiting magnitude results in too long a list and an uneven distribution. There is thus a strong case for the selection of a list of stars, to which permanent names and numbers can be attached, which can be used for all purposes of astronomical navigation.

Over thirty-seven years have passed since the writer published his ‘Wrinkles in Plane Chart Methods’, explaining the value and use of his then new ‘Protractor Diagram’ and ‘Graduated Triangle’ for plotting lines of position on squared paper. A figure showed the simplicity of the solution, overcoming the difficulty of the use of different units for the differences of latitude and longitude.

It is now proposed to present a further ‘wrinkle’ to facilitate the use in navigation of six prominent equatorial stars, particularly Mintaka (δ Orionis) which is only 2o′ south of the equator, and practically a fixed star since its annual (precessional) variation in declination is only 2″·67. It is one of the three stars of Orion's belt and its magnitude is 2·5, slightly fainter than Polaris.

Oceanography is concerned with the applications of all sciences to the study of the sea, and navigation, in its widest sense, with the application of any science and systematic knowledge to the purpose of maintaining safe and efficient communications across the oceans. They have something in common, but oceanographical work, whatever its future promise, is primarily academic, and navigation the application of well-tried conclusions. It would be wrong to suggest that basic studies of sea conditions are followed by systematic attempts to use them to improve navigation. Progress is sporadic, depending on individual enthusiasms and commercial enterprise as well as the efforts of government departments and professional associations. There is no sharp division between the basic work and its applications, or, after allowing for some extremes, between the scientist and the authority on navigation.

It is now generally recognized that, under instrument conditions, traffic congestion at busy airports is already bad and any further increase in traffic density would be unmanageable without improvements in methods of air traffic control. A study of the problems of air traffic control by full-scale tests is prohibitively expensive and a practical alternative is required. This paper describes a series of investigations into air traffic control problems by simulation methods.

Laboratory equipment suitable for such experiments is described briefly and has been shown to give a reliable quantitative assessment of the effect of changes in a control system. A number of possible control systems were studied in detail.

The use of radar in relation to the Rule of the Road at sea is a subject over which there is still a great deal of controversy. An examination of the main problems involved was made in this Journal (Vol. 3, No. 1, January 1950) by Captain F. J. Wylie who concluded in his paper that the use of radar might justify a more liberal interpretation of the term ‘moderate speed’ than has hitherto been countenanced; and a recent amendment to the King's Regulations and Admiralty Instructions clearly accepts the use of radar as an existing circumstance within the meaning of Article 16.

No attempt, however, has so far been made to arrive at a precise definition of ‘moderate speed’, and it may well be that the reasons which prevented a definition being made in the non-radar case are in fact given more force when radar, with its added variables, is used. On the other hand it is unlikely that any progress in the matter can be made without a full discussion of the factors involved, and Captain Robb's paper, though it may be possible to dispute some of his conclusions, is presented here as an interesting attempt to achieve a definition which can serve as a guide to shipmasters.—Ed.