In navigating an aircraft visually over terrain the chance of successfully reaching the destination greatly depends upon the human element together with the visual aids provided. Some visual factors are studied in detail in this paper, particularly the detection and identification of ground features from the air. The suitability of various identification points for use as visual fixes is assessed quantitatively and the interaction between navigational accuracy and feature detection is discussed. The effects of visibility, speed and search are also studied. Visual aids considered include different scale maps, heading information, and fixed, zoom and search optics on television. A number of navigational tasks are covered, from following line features to direct cross-country tracks. Successive visual up-dating of a mixed manual and automatic navigation system is then assessed theoretically.

Soon after the middle of the eighteenth century, improvements in the design and construction of astronomical and nautical instruments, coupled with the increased accuracy of tables of the Moon's motion, at last made the accurate determination of longitude at sea by lunar distance a practical possibility. The Astronomer Royal, Nevil Maskelyne, was quick to appreciate the importance of publishing the calculated solar and lunar ephemerides, together with other relevant tables and explanations, in the form of a Nautical Almanac, which was first printed under his supervision in 1766 and immediately distributed to mariners in different parts of the world. The present article is concerned with the circumstances relating to the origin and development of this publication during the first fifty years of its existence.

This paper, which was presented at an Ordinary Meeting of the Institute held in London on 20 November, 1964, presents the results of a study on the interrelation of cruise fuel consumption, temperature and track selection in supersonic transport operations on the New York–London/Paris route. The range of temperature variations at S.S.T. altitudes over the North Atlantic for 26 months is illustrated and from this data period 24 cases are chosen to reflect extreme departures from standard and to give a seasonal distribution of such variation. The results of the application of a computerized nasa programme to these 24 cases to determine whether diversion from the great circle is warranted, in terms of economy of cruise fuel consumption due to existing temperature gradients over the area, are then discussed and illustrated.

The results of a general solution, taking into account all these considerations, applied to an additional 117 cases are also discussed and illustrated. Finally the influence of climb fuel consumption upon cruise fuel consumption and data requirements for temperature forecasts in climb and cruise are discussed.

One of the most general topics mentioned in discussion at the Institute's lectures, in its Technical Committee, and during meetings with other Institutes, is the extent to which automation can help in navigation; and it seems rather unfortunate that the question should so often be examined purely from the viewpoint of whether it will reduce the cost of performing a certain function, perhaps by saving a man or two. It would surely be more profitable to see whether it will, even at considerable expense, enable somewhat better performance and lead to further advances: not by supplanting human enthusiasm and endeavour, but by supplementing them with new and powerful tools. The advantage will be marginal at first though probably significant in keen competition, and soon amounting to the difference between success and failure.

Every collision situation implies the existence of a sector within which any course steered will lead to a dangerously close approach and a sector within which the danger of collision will be avoided. The definition of these sectors may be said to constitute the structural aspect of the collision problem. The appropriate manœuvre in a given situation constitutes the operational aspect. The structural aspect is fundamental to the problem itself, the operational aspect offers possible solutions. The Steering and Sailing Rules involve the structural aspect because this is the only basis for legal rules.

In proposing a Sector Rule for use with radar in conditions of bad visibility, it is intended to establish a structural basis for legislation. In its most general terms, the Sector Rule is based on the principle that if the radar echo of another ship is always at an angle to one's own course determined by the speeds of the two vessels, their distance apart and the safe passing distance, then one's course lies within the safe sector for collision avoidance.

A discussion on the extent to which automation can usefully be introduced into navigational procedures took place at a technical session of the Institute in London on 25 April 1964. Automation in the sense intended may be defined as the use of machines which derive or accept navigational information, and operate on it to provide a function for the control of the vessels or aircraft. Automatic devices which are parts of individual machines (such as the time averager on a bubble sextant, or the true motion facility for radar) may be excluded.

This article may be regarded as a continuation of the previous article in this Journal (18, 203) and it has the same basis and purpose. It deals first with an unusual case of collision, while overtaking in the presence of a second threat, and secondly with an Appeal case.

The lessons of the Nassau–Brott collision relate to the duties of the overtaking and overtaken vessels, poor look-out, and too short a range-scale.

The Crystal Jewel–British Aviator case relates to excesssive speed, failure to stop, failure to avoid close quarters and the cumulative turn.

The Nassau–Brott case was an extremely interesting one in which one ship, Brott, was being overtaken in open waters by another, Nassau, and, at the same time, having a third ship, Haminella, coming down from ahead. The latter presented the more immediate threat.

When studying the influence of navigational accuracy on collision risk, operating economy, or traffic organization it is necessary to distinguish between monitored and unmonitored traffic. With the monitored traffic the relative separation between aircraft is detected by the monitor and can be controlled by it. This is a closed-loop concept. With unmonitored traffic the separation is provided by procedural clearance of the flight plan. This is an open-loop concept.

In this paper, which is a revised and up-dated version of an article which appeared on the back of the United States Pilot Chart of the North Pacific Ocean for May 1964, Mr. Fricker, a member of the Maritime Safety Division of the United States Naval Oceanographic Office, first of all analyses world-wide statistics of collision at sea on a geographical basis. He highlights the results of an investigation conducted by the U.S. Coast Guard into the conditions surrounding marine collisions; taking into account the results of this enquiry the author then goes into the common causes of collision. The paper then reviews the whole subject of radar and collision and the interpretation of the Collision Regulations in relation to the use of that aid. Certain collision counter-measures such as particular radar displays, improved lights and sound signals, bridge to bridge communication, &c. are then discussed.

These two notes are the first of a series which will suggest to mariners the causes of collision at sea when radar is in use, by showing against each apparent cause an accumulation of court evidence and judgment, by isolating certain kinds of action which seem to have led to collision but have not been so regarded in every judgment and by examining certain judgments against a technically informed background.

In the articles which follow, a particular judgment is examined in the light of a more precise study of true motion as a direct source of intelligence at slow speeds, of plotting when courses and speeds are changing and of the suggestion that the Crossing Rules may be applied in fog after ‘ascertainment’.

The 16th Technical Conference of the International Air Transport Association was held in Miami, U.S.A., from 22-30 April, 1965. The theme of the meeting was Air Navigation. Some 450 delegates attended, representing the world's airlines, aircraft manufacturers, national state agencies of one kind and another, and manufacturers of navigational equipment. The Institute was represented by the Executive Secretary.

The following discussion on the design of ships' bridges took place at a technical session of the Institute held in London on 6 January 1965. Captain Wacher illustrated the layout he proposed with a diagram.

Captain J. F. Wacher, P. & O.—Orient Lines. Existing general arrangements of the bridge, wheelhouse and chart room are inadequate for the needs of fast modern ships; the disposition of navigation, control, communication and safety instrumentation also leaves much to be desired. In recent years this has been recognized, prompted by an alarming increase in the number of ship collisions, particularly those which have occurred in restricted visibility.

The question of training pilots in the use of radar on a marine radar simulator was first brought up by pilots of the Swansea Pilotage Service. Their service is privately administered by the Swansea Pilotage Authority and, besides their ordinary pilot duties, each of the pilots has his own additional responsibilities, such as administrative and supervisory duties as members of the Pilotage Authority, the disbursement of pilotage earnings, the management of the Pilot Cutter Service, liaison with the dock authorities and towing companies in matters concerning the navigation of ships, pilot cutter crew training, navigational techniques, Swansea Bay surveys, &c. (There is even one pilot whose task it is to collect all the particulars of the latest navigational aids and so introduce them to his colleagues.) Altogether one is struck with a progressively-minded service consisting of members who want to make the best use of the modern aids which are being provided on board ships these days. Before pilots can enter the service they must be in possession of a Master Mariner's certificate F.G. (about one half of the pilots in the service have held command and candidates with Extra Master's certificates are on the waiting list).

Wing Commander Anderson has drawn attention to the fact that the distribution of the larger navigational errors is frequently observed to be non-gaussian in character. He raises the point whether this can be accounted for by the generation of such errors in succession, rather than simultaneously. The successive generation of navigation errors arises through the error incurred on a particular leg being distributed about a mean which is dependent on the error up to the end of the previous leg.

Since January 1962, waves have been recorded by a shipborne wave recorder (Tucker, 1956) on the Sevenstones light-vessel which is stationed about 20 miles south-west of Land's End in about 200 ft. of water. Records were taken at three-hourly intervals and were mostly of 12 minutes’ duration. The analysis presented here is based on 2920 records taken in the first year of operation; the method of analysis which has been used is that described by Tucker (1961). This gives for each record:

(a) H1 = The sum of the distances of the highest crest and the lowest trough from the mean water level.

(b) Tz = The mean zero-crossing period.

(c) Tc = The mean crest period.

This paper discusses a method for determining the collision risk implicit in horizontal and vertical separation standards which has been developed in the U.K. in accordance with Recommendation 7/1 of the RAC/OPS Divisional meeting. The acceptable collision risk for the North Atlantic is assessed; this must be related to airworthiness criteria and an accident rate of one in ten million is adopted. It is concluded that no immediate change in separation standards can safely be made but that the standard of navigation should be improved to allow a 90 n.m. standard; that with more data a 1000- or 500-ft. vertical separation may prove to be safe; and that longitudinal separation standards require further study. The improvement in traffic capacity which would result from changes in separation standards is also considered.

This and the following nine papers were presented at the 16th I.A.T.A. Technical Conference, of which a report appears opposite. An analysis of long-range air traffic systems made by the Mathematics Department of the Royal Aircraft Establishment for the Ministry of Aviation was presented in several preliminary papers at the Conference. These studies will be described in a series of papers specially prepared for the Journal.

The paper proposes highly stable moored ocean platforms and a transatlantic submarine telephone cable to provide a reliable v.h.f. communication service and other A.T.C. facilities to civil aircraft on the main air routes across the North Atlantic. The main features of the platform and cable system are discussed and some idea of the time scale and costs is given.

The planning of facilities needed to enable future operations over the North Atlantic to accommodate reduced separation standards and to satisfy the specialized requirements associated with operating S.S.T. aircraft has emphasized the present unsatisfactory standard of communication services in the area.

Loran C, a long-range hyperbolic navigation system, is currently used in transoceanic aircraft only to provide periodic position up-dating of primary self-contained navigation systems. The successful development and flight testing of an automatic coordinate converter has recently shown that the potential of the Loran system of navigation is vastly greater than past utilization has indicated. This paper briefly discusses the advantages of combining an increased capability Loran sub-system and an unsophisticated inertial sub-system within the framework provided by a heavy logistics support aircraft.

Radar was introduced as a navigational aid at the end of the last war. In spite of its introduction collisions soon began to occur again and even to increase in frequency with the increase in the number of radar sets in use. Evidence accumulated, and its examination and correlation revealed a systematic pattern of accident. This led gradually to the formulation of a code, officially promulgated in 1960 by the International Conference on Safety of Life at Sea.

It may be surprising that so long should have elapsed and so many accidents occurred before this was achieved, but the fact remains and should never be forgotten: even more so as things are still continuing the same way. Collisions still take place, and though it is difficult to determine the exact nature of the general trend, it certainly shows no sign of producing the spectacular drop we all hope for. Recently Captain Weekes, in this Journal, regretted the complete ignorance among the majority of seamen of papers and discussions on collision risks and the means of avoiding them, and hoped that steps would be taken to make them more widely known.

It is never easy to convert theory into practice.

In this paper air traffic control capacities at Sydney Kingsford Smith (Mascot) Airport are determined for the three most heavily loaded air traffic sections of the A.T.C. organization. Controller saturation levels are then found and maximum desirable traffic volumes estimated. The influence of various airspace restrictions is shown.