This paper, which was presented at an Institute meeting held in London on 21 January 1970, suggests a range of philosophical implications which result from the interaction of guidance and control systems in the context of all-weather landing of fixed-wing aircraft. It then attempts to deduce the considerations which must be applied to the approach to the engineering solution to the guidance and control problem.

In the context of this paper the terms guidance and control have specialized connotations which have achieved the status of common usage.

As they are used in the all-weather operations (AWO) jargon they are easier to define as adjectives than as nouns; the ‘guidance system’ is the system which defines the flight-path which the landing aircraft must follow and the ‘control system’ is that part of the aircraft equipment which enables the aircraft to follow the flight-path which has been defined by the guidance system.

Before the war it would have been comparatively easy for anyone interested to quote the names of all the really large ships afloat, if not some of their vital statistics. To do so today would require a considerable feat of memory as the number of vessels in the 50,000 ton and upwards class has reached almost 200 with, in recent years, a growing emphasis on those of over 100,000 tons. In the last few years no less than 51 of these monsters of over 100,000 tons have appeared at sea representing about 1/10th of the total world tonnage completed during that period. There are several 326,000 tonners ploughing the seas; 350–375,000 tonners are on the slips, with 750,000 tonners on the drawing boards and the possibility of topping the 1 million mark in the future.

Whatever else may be said about man's first landing on the Moon, it was surely the most spectacular navigational achievement of all time.

In the following paper Dr. Mayer, Chief of the Mission Planning and Analysis Division at the Manned Space Flight Center, Houston, and Mr Osburn give a general outline of the operational use of the space navigation systems which contributed to the success of the first manned lunar exploration mission. The ground and onboard navigation systems, their interfaces with the Apollo guidance system, and their uses in various phases of lunar landing are reviewed. The navigation procedures are then discussed, with particular emphasis on the Apollo 11 mission, the first manned Moon landing. Post-flight analyses and actual mission results from Apollo 11 are examined to give an accurate assessment of the overall performance of the navigation system.

The paper was presented by Dr. Mayer at a joint meeting of the Institute and the Royal Astronomical Society held in London at the Royal Geographical Society on 1 October 1969 with Professor Sir Bernard Lovell, F.R.S., in the Chair.

A list of the terms and abbreviations used in the paper is given on page 148.

The Apollo navigation problem may be divided into two general areas. The position and velocity of the vehicle must be determined at some specified time, present or immediate past. (This will be referred to as orbit determination.) This information must then be utilized to determine the future course of the spacecraft. (This is referred to as trajectory prediction.) Ground orbit determination may be performed in either a low-speed or a high-speed mode. Low-speed computations require 5 to 10 minutes for processing, while high-speed solutions are available virtually instantaneously. The ground system utilizes both types of processors. Low-speed solutions are used for trajectory prediction and, in a few cases, for processing astronaut observations. The high-speed processor is used to monitor manœuvres such as the descent to the lunar surface and for special situations where near real-time orbit solutions are necessary. The spacecraft system uses only a high-speed processor, modified slightly to facilitate manual use by the astronaut in some cases.

This year, the subject for the Duke of Edinburgh Lecture was chosen by the President and the Council as a result of recommendations made by the Educational Sub-Committee. Although the lecture was to be an individual contribution it was to have the full help and support of the Institute. Without this, the lecture would have been impossible, and therefore it seemed necessary to make acknowledgments at the outset.

Help has been given most freely and generously by many Fellows and Members, and in particular by the President, Professor A. Stratton, by Dr. G. E. R. Deacon, F.R.S., the Chairman of the Educational Sub-Committee, and its members, Captain C. H. Cotter and H. E. Smith, by D. H. Sadler, the Chairman of the Membership and Fellowship Committee, by Captain F. L. Main, a member of the Council, and by M. W. Richey, the Executive Secretary. Further invaluable suggestions came from many sources outside the Institute, notably from Dr. A. Clow of the B.B.C., J. A. Edgar of the Department of Education and Science, Dr. H. F. Huddleston of R.A.E., Farnborough, and Professor S. Sutherland of Sussex University. Finally, a very special word of thanks to B. W. Lucke, Schools Inspector, Liverpool. This paper owes a great deal to his ideas and to his inspiration.

Although it has been technologically possible for some years to give warning of ground collision hazards, the specialized radars for this purpose have been limited to military aircraft. Because of complex cost and installation problems, radar of this type have not been installed in civil aircraft.

This paper discusses possible developments in civil weather radar to enable it to give a warning of ground collision hazards. The paper was presented at an Ordinary Meeting of the Institute held in London on 19 November 1969 with the President in the Chair.

For the purpose of this paper, ground collision is defined as an error of navigation or height management, which results in a zero ground clearance. The error can, of course, be human or instrumental but the assumption is made that the aircraft was basically capable of avoiding the hazard. There has been a tendency to associate ground collisions, particularly hill and mountain collisions, with the older piston-engined aircraft. Its importance in terms of airlines operating modern jet aircraft is not always well appreciated. It is true that the normal operating altitude of jet aircraft almost eliminates ground collision hazards in the cruise phase, but in general they suffer from a longer response time and a higher approach speed, which makes them more vulnerable in the let-down and approach phase. Since in any event the let-down and approach phase accounted for about two-thirds of the accidents with piston-engined aircraft, ground collision hazards remain a serious problem with pure jet aircraft.

Because tankers are increasing in size some thought has lately been given to reducing the underkeel clearance in order to make more economic use of available water. But the problem is being stated in unnecessarily narrow terms by placing too much emphasis on tanker draught. A lot more cargo is still being carried in moderate tonnage vessels, which would show a sizeable economic benefit from a reduction in their under-keel clearance in many areas where tankers would not venture.

A ship's log is described which works on the principle of electromagnetic induction. The measuring head contains a coil with a vertical axis and is arranged so that voltages are picked up proportional to the two components of water flow past it. The electronic circuits are designed to give a true and stable zero by using a low-frequency squarewave energizing current. Laboratory tests show the output to be linearly related to water velocity. Because of the complicated flow patterns round a ship, the log must be calibrated in situ at sea. Calibration of the forward component meter follows the usual procedure and this meter is accurate to about ±0·1 knot or ± 1 per cent, whichever is greater. However, calibration of the athwartship component meter is difficult and time-consuming, and the sensitivity is dependent on forward speed. With care, it seems that an accuracy of ±0·2 knot or ± 10 per cent, whichever is greater, should be possible with this meter, but more experience of such calibrations is required. The paper is discussed on p. 319.

I propose to discuss the problem of long-range navigation from the point of view of the A.T.C. system planner and to describe in outline the work that has been done in the North Atlantic Systems Planning Group (N.A.T.S.P.G.). In this area there are tidal flows of traffic of relatively high density and there is inevitably a need to reduce separations as much as possible, consistent with safety, to ensure operating costs are reduced, or at least kept in bounds with anticipated increases in traffic. This requires a much more precise definition of an acceptable separation standard, and for future planning the establishment of a relationship between separation standards and navigational capability.

S.S.T. flight operations are likely to commence early in 1970 and meteorological briefing for all flight levels must therefore be established, especially for temperature, wind and clear-air turbulence. This paper, which was presented to the S.S.T. Working Group, outlines the accuracy of temperature prediction over 24-hour periods and suggests forecast rules. Finally the resultant requirements are stated.

Several conceptions of possible and desirable temperature forecasting accuracy have been expressed in relation to S.S.T. performance by different panels. For example, the Fausst WP 529 (Franco-Anglo-U.S.-S.S.T. Working Paper 529), revised 3 March 1967, recommends a maximum standard error of 3°C for temperature forecasts at the S.S.T. level, which means the accuracy of temperature forecasting must be within a range of ± 3°C in 68 per cent of all cases. After other recommendations, such as the I.C.A.O. S.S.T. panel, July/August 1968, the subsonic requirements may be adopted for the S.S.T. too; these recommendations allow a standard error of 1°·8C, i.e. the accuracy of temperature forecasts must be within a range of 1°·8C in 68 per cent, or 3°C in 90 per cent, of all cases.

Dr. Bulman's paper (which is Crown copyright) was presented at an Institute meeting held in London on 19 February 1970 with the Hydrographer of the Navy, Rear Admiral G. S. Ritchie, C.B., D.S.C., in the Chair. The paper, which describes work undertaken by the Royal Radar Establishment on the measurement of ship movement for berthing very large vessels, was presented at the same time as the paper read by Mr. M. J. Tucker, National Institute of Oceanography, and the discussion relates to both.

When a 200,000-ton tanker hits a jetty at more than about 24 ft./min., that is, nearly a quarter of a knot, some damage is likely to be caused. However, the problem of measuring the speed of the ship starts much sooner than that. One could say that from the moment the log is retracted on entry to the estuary some other form of assistance ought to be made available. Traditionally pilots and masters have relied on visual estimation—on the appearance of the passing land and passing landmarks in order to judge the speed over the ground while travelling up an estuary. This has been adequate for smaller ships where the height of eye, length of ship, width of ship were all considerably less than they are now on the largest tankers, and where the critical velocities were higher. Now, however, it has proved very difficult to judge by eye the speed of a very large ship from a station some 80 ft.above the water to the accuracy required, the accuracy being of the order of ± 3 ft./min. It is in this spirit that the Esso Petroleum Company approached the Royal Radar Establishment (R.R.E.) some two years ago or so to tackle the problem.

Mr. Blake has given us an outline of what is needed in the context of Navigation of Long-Range Subsonic Transports in the 1970's. I now intend to pursue the theme by saying what I think v.l.f. navigation techniques can contribute to the solution of the navigation problem. In particular, I want to talk very briefly about the contributions that we feel v.l.f. might make towards the particular problem of limiting the numbers of aircraft which creep beyond Mr. Blake's navigation tolerance ‘fringe’ in addition to, possibly, by adding navigational information, increasing the effective M.T.B.F. of the total navigation system.

Clearly, addition of equipment cannot reduce M.T.B.F. in the narrow sense of the term—more equipment must have more faults—but if one interprets ‘fault’ as the incidence of a navigation error beyond the specified limit rather than narrowly as an electronic malfunction, I do think that v.l.f. navigation has its contribution to make to effective M.T.B.F.

Dr. David Lewis has contributed two earlier papers to the Journal on Polynesian navigation: ‘Ara Moana’ in 1964, a theoretical examination of navigation methods, and ‘An experiment in Polynesian navigation’ in 1966, an account of his own voyage in the catamaran Rehu-Moana from Tahiti to New Zealand. The present paper presents the result of further research which included voyages between the islands with Polynesian navigators. A version of this paper, which was presented at the Annual General Meeting of the Australian Institute of Navigation in Sydney on 10 and 11 October 1969, has been published in Navigation (Sydney).

The Collision Regulations are due for revision by Imco in 1972 and already governments and other agencies are formulating proposals for consideration by its Maritime Safety Committee. The Institute's working party on the subject, which was formed initially to try to lessen the area of disagreement between people who had put forward positive proposals over the last few years, has now formed a cohesive view and formulated a set of recommendations. These are given in the interim report which follows. In the normal course of events things would have been allowed to run their course and the final report published only after further meetings of the working party which has still to reach firm conclusions on a number of points (for example on the precise form of the manœuvring diagram referred to at the end of Section 2 and in proposition (14), and on the whole question of lights). However, time is short and it seems probable that if the views of the working party are to have any effect on the deliberations of Imco, they must be made known straight away. The report (of which M. W. Richey is the author), therefore, which embodies the whole area of agreement between the members of the working party, is published here in interim form.

Dr. Calvert has expressed some unease from his own point of view about propositions (1) to (19) and it is hoped in the final report to publish an appendix by him suggesting a totally new approach to the whole problem of collision avoidance by manœuvre. It is hoped also to publish an appendix by Admiral García Frías describing the system he proposes. Both these contributions are perhaps likely to be of long-term rather than immediate significance.

For the integration of different navigational aids of an aircraft by a general purpose computer the following way is proposed: The basic navigational system is a doppler or inertial dead reckoning system (D.R.S.). The other navigational aids serve for control measurements, with the help of which the error of the D.R.-position and the most important systematic error sources of the D.R.S. are determined by least square adjustment during flight. These error quantities are then used for a corresponding correction of the D.R.S. The supplementary navigational aids are consequently used both for the correction of the D.R. position and for the calibration of the D.R.S. The method is described for the example of the integration of a doppler D.R.S. with Tacan.

From the great number of different navigational aids, which are today available or in development, we can draw the conclusion that none of these navigational systems can satisfy all requirements. Therefore, for many years it has been the custom to combine several navigational aids, and thus the human navigator has the task of evaluating the different navigational information. This evaluation is, however, often disturbed by unfavourable conditions. In a high-speed aircraft for example the navigator is overburdened by a lack of time and space, errors in the navigational sensors, &c. This necessarily means that the evaluation of the data is reduced to a minimum, and that a great deal of the available information is lost.

In 1963, in addition to examining the characteristics of the Omega system, we were also very concerned with a comprehensive navigation system study which was designed to examine all aspects of a world-wide navigation system operating in a B.O.A.C. type environment. This concerned a study of dead reckoning as well as externally referenced sources of information. You have the choice of an all dead reckoning system probably employing multiple sensors of the same type, triple IN is typical, or you could have a mixture of externally referenced and self-contained, in other words dead reckoning sensors. Occasional reference could be made to short-range aids or even a satellite system if available to increase the integrity of the position-fixing information. The inertial and computer aspects have been examined by the Avionics Department at R.A.E. whereas the radio sensors, which are externally referenced, and the relevant software have been the responsibility of the Radio Department.

The objective of navigation is to ensure safe and economic operation of the craft and new trends and developments in navigation have to be judged against the return that they might be expected to bring in operating economics and reduction in accidents. Modern technology offers a wide range of fascinating possibilities, many of which will be discussed at this quadripartite meeting. The potential of these new trends and developments, however, cannot be judged just on the basis of the improvement they bring to the reckoning of position and course. This is but the starting point (Fig. 1) to a complex interaction between navigation, operator and the world at large. The operational navigation performance is determined by the interaction between the means of reckoning position and course, the operational situation and the human operator's interpretation of the operational situation in relation to such regulations, rules and procedures as have been established.

The equipment fitted in Queen Elizabeth II was supplied by Aerospace through the International Marine Company. It consists of three units: an aerial, a two-channel receiver and a data processor. The receiver and data processor are housed in a single rack, the print-out machine stands beside the rack on its own pedestal. The aerial reposes on the truck; how-ever, as a result of experiments carried out on board, we are convinced that satisfactory reception of signals is obtained with the aerial sited directly on to the wheelhouse top. The rack and pedestal are located in a corner of the chartroom. Since fitting (Dec. 1968) the receiver has operated continuously, though we must own up to an occasional spot of bother with the processor. Nevertheless the vessel has only on one occasion entered port with the equipment out of use.

During the morning of 27 January 1968 the submarine Minerve was on exercise south of Cape Sicie. She was due to return to her base, Toulon, in the evening. Her last-known position was that fixed by a Breguet Atlantic aircraft on the same day at 0735. The last communication between this aircraft (then returning to base) and the submarine was at 0755.

The name log, to denote a device for measuring a ship's speed or the distance she has made through the water, appears to have come down to us from the Saxon log—‘a hewn trunk or branch of a tree’. Harboard amplifies this by remarking that the log is so named from the word ligen (Dutch liggen=to lie down) because it lies, as it were, immovable. It therefore seemed appropriate that the primitive contrivance for measuring a ship's speed—a wooden board attached to a line—should be called a log. The principle of this—the so-called common log to distinguish it from more sophisticated contrivances—is simple: a floating object cast from a ship tends to remain stationary after entering the sea. The line attached to the log-ship is allowed to render freely as the vessel sails away after the log is hove from the vessel's stern into the sea. A specified length of line which runs out in a measured interval of time or, what became more common practice, a measured length of line which runs out in a specified interval of time, is equivalent—at least approximately—to the distance travelled by the vessel in that interval.

The ability to map terrain by means of an airborne radar raises many possibilities. Some few years ago it was recognized that a mapping radar which scanned to the side of an aircraft (rather than ahead) might, additionally, have important military potential. The research described here concerns the early operator evaluation of a prototype sidescan equipment which promised, among other things, to permit accurate fix-point navigation at lower flight altitudes.

By recent standards our aircraft was to progress at a fairly gentlemanly rate, somewhat below the speed of sound. Hence the radar map, produced as a moving strip by a rapid photo-development technique, did not threaten to flash past the navigator's eyes at an impossible speed. Nor, in general, did we expect the operator to be provided with anything unsatisfactory in the way of briefing. What is more, the navigator would be able to devote his undivided attention to the radar material whenever a fix-point was due.