In recent years the problem of preventing collision in the air has become urgent because of increased speeds and traffic densities. Some operators now install what have come to be known, perhaps optimistically, as ‘anti-collision’ lights, and at the meeting of the third Air Navigation Conference of I.C.A.O., it was suggested that one or other of these systems, or some new system, should be adopted internationally. Agreement was not reached at that meeting, and the question was discussed again by the Airworthiness Committee as an ‘exchange of views’ item in July 1958. The present memorandum was prepared mainly for the use of the representative of the United Kingdom at that discussion.

During the period prior to the formation of an independent surveying service as part of the Royal Navy, the making of hydrographic surveys was a haphazard affair often dictated by circumstances rather than as part of a well ordered and integrated scheme. Ordinary serving officers of the Navy were encouraged as part of their duties to obtain information relating to depths, sea-marks, time of tides, setting of the currents, &c.; especially when on a foreign station. In home waters, although the same directive applied, the Admiralty authorities also sought to improve the standard of charting by helping, and in some cases commissioning, private individuals to carry out hydrographic surveys of various parts of the coast. The valuable contribution made by these ‘amateurs’ is shown by the number of charts they produced, particularly during the first half of the eighteenth century. Although the printed charts have survived as a tangible record of their labours, little is known of the methods they employed and the difficulties that confronted them. In the case of Lewis Morris, however, the fact that he was an antiquary, literary scholar, philologist and mineralogist and attained greater fame in fields other than surveying, has meant that a considerable amount of his manuscript material has survived.1 From a surveying standpoint this material includes a number of letters and memoranda sent by Morris to the Admiralty and other interested persons, the original manuscript plans of his survey of the Welsh Coast and a rough survey notebook in which he jotted down his observations while out in the field. The latter is probably unique as, for obvious reasons, field notebooks are inevitably destroyed as the finished product emerges. It is thus possible to obtain a well documented and comprehensive picture of the way in which a zealous individual like Morris set about the stupendous task of surveying hundreds of miles of coastline and inshore waters in the interests of safer navigation.

In 1952 the first transpolar flight by a commercial aircraft was carried out. During the six years that have since passed, S.A.S. aircraft have made 1635 flights across the arctic region representing approximately 26,000 flying hours. Our experience in polar navigation has been built up first on a large number of charter flights, then on regular flights on the sub-polar route to Los Angeles, and finally on regular flights across the Arctic Ocean to Japan.

The R.C.A.F. Meridian Convergency Computer is designed to help the navigator get the best performance out of a precision gyro which can be compensated for Earth rate, such as the N-I, the C-8, the LDG-I and the polar-path. These gyros are characterized by a low drift rate and provision is made for the effects of Earth rotation to be compensated for at the observer's latitude. Any heading set on the gyro will remain on the gyro provided the gyro remains at the same place. The only drift observed will be the random drift of the gyro itself.

Synthetic training aids in use in the Royal Air Force today range from a sectioned miniature valve used in teaching basic electronics through a wide range of devices of increasing complexity until we reach the Victor Flight Simulator linked with an N.B.S. (Navigation and Bombing System) trainer, which rivals in complexity, and probably surpasses in cost, the famous ERNIE.

The Ministry of Transport and Civil Aviation makes extensive use of radar for the protection of aircraft en route and also in helping to bring them in on approach for a final visual landing. Since we really became interested in radar we have trained 470 PPI directors and 150 precision controllers; the latter use special equipment and cathode-ray tubes which accurately show the glidepath being followed.

Many of the problems arising out of the use of radar in poor visibility can be laid at the door of ‘incorrect appreciation’ of the information available on the PPI, coupled with the lack of timely action to avoid, if possible, a close-quarter situation. To this must be added the over-confident ship handler who has never yet been faced with a collision situation in poor visibility and who may be complacent until too late.

The purpose of this note is to indicate how the design of radar simulators can be adapted to meet the requirements of navigational radar uses. The simulator can be roughly divided into four sections:

1. (1) Control Units, which determine the initial parameters of the target and afford a means of adjusting the rate of change of these parameters.

2. (2) Computers, which determine the range, bearing and elevation of the target from the base.

3. (3) Pulse production and video shaping circuits.

4. (4) Aerial rotation simulation.

Dectra is a long-range radio navigation system designed to give accurate position fixing coverage over specific areas, and in particular over long trans-oceanic crossings. The position of an aircraft or ship equipped with a Dectra receiver is continuously available in the form of dial indications relating to coordinates of a Dectra lattice, and in addition this information can be presented pictorially on a normal Decca flight log. The system is at present functioning over the North Atlantic, and flight trials have been in progress since May 1957. This paper discusses the experience gained and the results obtained in the trials.

The introduction of the Mark 10 Decca promised certain advantages over existing types and it was therefore deemed expedient to examine the potentialities of the equipment, its operational accuracy and general suitability for airline operation. The Ministry of Transport and Civil Aviation in conjunction with British European Airways were subsequently involved in two series of tests which began in early 1957 and continued into 1958. These tests were designed to determine the operational suitability of the Mark 10 Decca receiver and, in addition, provide a direct comparison between the performance of Mark 10 and Mark 7 equipment. All the flights were made, by day and night, on B.E.A. routes within the cover of the English chain. Ample opportunity was afforded to study the equipment under typical service conditions.

‘There are no charts of any part of the world so accurate and no directions so perfect as not to furnish frequent occasion for revision and amendment.’ (From the title page of the Nautical Magazine, 1832.)

In March 1832 a new monthly was published, the Nautical Magazine. Subsidized at first by the Admiralty and the Mercantile Marine Fund, it was edited by Beecher who was the right-hand man to Admiral Beaufort in the Hydrographic Department. Part of the introduction to this first volume read as follows: ‘The principal feature of the work will consist of the particulars of those hidden maritime dangers which are too often fatal to ships. … Much information, of a nature highly valuable to mariners, is scattered about, destitute of any systematic arrangement by which it can be made available to them; but the pages of the Nautical Magazine will hereafter become the receptacle, in which it will be preserved for their reference.’

The following contributions are selected from contributions to the discussion on Wing Commander E. J. Dickie's paper ‘The Effective Use of Airspace’. The paper was presented at an Institute meeting held in the Royal Geographical Society's house on 21 March, and is printed in the last number of the Journal.

I remember on many occasions in my Service experience undertaking cross-country flights with a large number of other aircraft flying along exactly the same route at almost precisely the same time. These were usually navigation training flights and, therefore, to some extent the errors which arose might not be held to be representative of what one would expect to happen to seasoned airline operators. Nevertheless, it was a commonplace to find on such occasions, very shortly after taking off, that all aircraft became so scattered as often to disappear from each other's view completely. And yet, at each turning point and again at the destination they all arrived at the same time. I am sure that there is something to learn from this particular aspect of flight along identical or parallel tracks. I do not think a simple fore-and-aft radar indicator would provide the safety in flight which we are anxious to establish. I believe that a secondary radar, giving an all-round horizontal view, would probably go a long way to meet the stated requirement; although, of course, only one giving a spherical view could give 100 per cent safety. Even with pilots who can see exactly where they are going, along clearly defined tracks over country abounding in natural navigational aids, it is true to say that the really effective variable is the track and not the timing. This lateral scatter is due to inaccurate steering data and to the many other inaccuracies affecting the actual path of an aircraft through the air, quite apart from wind-finding errors. Even with the best primary navigational aids, tracks cannot be flown with absolute precision. It follows that collisions are at least as likely to arise from errors of track as from errors of timing. So I would suggest that what we really need is a secondary radar which will give us an all-round horizontal view and I think that we must not delude ourselves into thinking that even the finest primary navigation aid will provide an accuracy in the air by which all aircraft proceeding along one route will remain only fore-and-aft of each other.

Despite increasing use of radar, marine collisions have continued to occur in significant number. The principal reason advanced for this development has been the ‘human element’ and many new electronic innovations have been suggested or built to minimize this factor. This note is written not for the purpose of providing an absolute answer to the problem, but rather to suggest there may be another angle from which it may be approached.

It may not be humanly possible to draw up a code of rules for international use which are completely comprehensive and clear in every particular. The Rules for Preventing Collisions at Sea are not, and it would be useful to know the accepted interpretation of doubtful points. Criticism of the Rules is not here intended, and all references to the impact of radar upon their interpretation is omitted, as this question is now being studied by a Working Party. Suggested correct interpretations are added in brackets.

I Have read Professor Taylor's article with great enjoyment. There are, however, two matters of fact on which, though they do not affect her main thesis, the record should, I think, be set right, (a) The earliest experimental proof of the Earth's revolution round the Sun was neither Bessel's detection of the relative parallax of 61 Cygni, nor Henderson's determination of the absolute parallax of α Centauri (both of which occurred in 1838) but Bradley's very beautiful discovery of aberration in 1725, together with his slightly later explanation. The discovery was made in a deliberate search for parallaxes; and although that particular proof of the Earth's movement was not then achieved, it was at once recognized that aberration provided a different and equally cogent one. Bradley's work was indeed resisted, in some quarters and for a short while, for reasons which Professor Taylor will by no means find unexpected. His later discovery of one term in the nutation was also a discovery of something which would have embarrassed Ptolemy, and delighted Newton; it certainly tended to confirm the picture, if that were needed. By the time parallaxes actually were discovered, though there still were individuals, sometimes of high rank, whose prejudices were stronger than their intellects, the only point of genuine doubt was the question how far away the nearest stars really were.