The following Address, by the retiring Director of the Institute, was presented at the thirty-fifth Annual General Meeting held in London on 27 October 1982 at the Royal Geographical Society with the President, Captain B. J. Calvert, in the Chair. The President said that Mr Richey's pending departure (although he would continue to edit the Journal) was an event of considerable importance in the Institute's history and he felt it appropriate to have invited him on this occasion to present an Address in place of the Presidential Address normally delivered at the Annual General Meeting. Calling the Meeting to order, the President drew attention to a gavel, around which the names of past Presidents and Directors were to be inscribed, made from wood, for the anvil, from HMS Victory and, for the striker, from the yacht Jester. After the Address Wing Commander Anderson gave a reply reminding the Institute of Mr Richey's achievements during his long period in office. The audience then broke all traditions by giving the Director a standing ovation. His successor as Director, Rear Admiral R. M. Burgoyne, was then introduced to the Meeting.

Automated aids, computer assistance and other forms of advancing technology are gradually changing the human involvement in many tasks, so that the primary roles of man are to monitor, verify, manage resources and respond to emergencies, rather than to participate actively and continuously in the control loop. Many of the terms traditionally employed to designate or describe jobs are retained throughout this process although they are no longer apposite, and they can give a misleading impression of the nature of the residual human roles and of the skills required to fulfil them. In many respects an aircraft pilot may no longer actually fly his aircraft for much of the time, but monitor equipment that flies it automatically. A nominal supervisor may remain in many environments where revised human roles and facilities mean that effective supervision is impracticable. An assistant may not in fact be able to offer true assistance because he has no facilities to share any of the tasks, do parts of them, or assume temporary responsibility for them. The future navigator may not need to be able to navigate in the traditional sense.

One of the major concerns in the operation of an air traffic system is the maintenance of adequate separation between aircraft. The assurance of an ‘acceptably low’ risk of collision is a crucial element in the system design. A number of factors need to be assessed in this process. What is the navigational performance of the aircraft in the system ? What are the possibilities for radar surveillance ? Are procedural arrangements together with position reporting a suitable mechanism? What difference would be made by collision avoidance or warning systems? Given that any combination of these or other factors has an implication on the minimum separation between aircraft, the level of safety ‘assured’ has to be balanced against the costs of the various alternatives which may present themselves.

In planning for change the implications of new operating practices or devices have to be assessed carefully. For most changes the process is one of evolution rather than revolution, although collision avoidance devices may have more of the latter's characteristics. Even for ‘revolutionary’ changes it may be possible to model the new system. Thus the existing situation is studied and its characteristics observed, then there are hypotheses of the ways in which the change alters the mechanisms in the system and finally the likely effects on system performance through mathematical and computer (often fast-time simulation) modelling.

Over the last decade there has been considerable development of the applications of modern technology to the avionics of new aircraft. Examples of this have been the provision of area navigation and flight management systems, and now with the advent of cathode ray tube displays there is the opportunity to provide a greater range of information to the pilot in a more readily assimilable form than is at present possible. There have been similar developments in computer assistance to air traffic control (ATC) to aid the ground controller. There has, however, been a tendency for these and other parts of the operational system to be improved without fully evaluating their interaction with each other, especially the interaction between ATC and the flight deck. Unless this aspect is studied it is probable that the full capability of the system with its potential for improving the safety and economy of operation will not be fully realized.

The Civil Avionics Section of Operational Systems Division at RAE Bedford, in collaboration with UK avionics manufacturers and funded by the Department of Industry, has been concerned for a number of years with the development and integration of these systems in the flight deck of the future and with the way in which they can be used to develop, in conjunction with ATC, an improved system of air traffic management.

Based on a survey of its members in Europe and the Middle East, IATA expects that by 1985 almost half their aircraft will be equipped with Flight Management Systems (FMSs) incorporating 2-D, 3-D or 4-D navigational capabilities. The prime aim of this very significant investment is to increase airline operating efficiency, in particular through fuel saving. Flight Management Systems can perform a wide range of tasks, including flight planning and performance management, for which inputs of meteorological data are required. The more sophisticated systems can accept a number of wind and temperature inputs for the climb and descent profiles plus a wind input at each way-point of the cruise phase. Any estimate of flight progress and fuel requirements based on the use of the most economical aircraft speeds, whether made by the pilot or by an FMS, can only be as good as the knowledge of the wind-vector data pertinent to the flight. Whereas FMS-equipped aircraft in level cruise can often ‘update’ or correct the forecast data relating to the next flight leg, this is not feasible when major changes of altitude are necessary, e.g. during the descent phase. Accurate meteorological data are essential to ensure the optimum results from the FMS.

During the early 1970s, before the fuel crisis began, some thought was being given to the problem of handling the rapidly increasing number of aircraft movements in Europe.

The traditional non-adaptive Kalman filter includes models of the error characteristics of the navigation aids in use and such filters are very successful, so long as their model assumptions approximate to the true error characteristics sufficiently closely. However, for any filter there will be times when the environment changes and one or several aids will have errors which are not consistent with the assumed error models. It is necessary to consider carefully the sensitivity of the filter to such changes and, where a significant reduction in performance ensues, modifications to the filter are necessary.

This paper introduces a Kalman filter which monitors the behaviour of internal variables to detect and characterize any model imperfections. The filter will then adapt its internal model of the environment accordingly. The discussion is restricted to the development of a navigation filter for integrating dead reckoning (EM log and gyrocompass) and Omega data. The principles are the same for any filter and details regarding similar analysis involving the use of other aids, for example Satnav and Decca, have been developed in a similar way.

Before implementing any filter it is necessary to understand the behaviour of the measurement errors. For the dead reckoning and Omega aids this behaviour is described in section 2, while section 3 outlines a filter for integrating these aids and introduces the problems of model imperfections.

Estimation methods and filtering techniques are nowadays an integral part of any computer-based navigation system. The purpose of these techniques is to provide an estimate of required variables which is sufficiently accurate for real-time command and control purposes. Repeatability, which is important for so many applications, is deemed to be a by-product of the estimation process. For this requirement it is not strictly necessary for the process to be accurate, it is sufficient if it is only consistent; these are closely linked but one does not imply the other. The modern approach is to minimize the variance of the noisy observations or the sum of the squares of the residuals, and the methods available for doing this are increasingly refined. The impression given in the literature (and it is extensive) is that data processing can somehow compensate for the shortcomings of the basic sensors with respect to the operation being considered. Within certain limits this is true, but the real reason for the sudden surge of Kalman filtering for real-time on-line applications was the relative simplicity of the computational process. In a way, Kalman filtering has done for estimation theory what the Fast Fourier Transform has done for spectral analysis.

The concept is simple enough to state. It consists of combining two independent estimates of a variable to form a weighted mean. One of these estimates is a forecast and the other is the current measurement.

The history of manav goes back fourteen years to 1967 when Esso placed a contract with the Ministry of Technology (mintech) to carry out work to develop a system to assist in ensuring the safe operation of its Very Large Crude Carriers, which were then coming into service. The 1967 era saw much public, governmental and company concern about the stopping and manoeuvring ability of large tankers, particularly when close to shore in estuaries or when berthing.

manav was therefore one of a number of developments or studies initiated by the introduction of VLCCs. Some years were to pass before coordination of the various study results proved possible.

The Racal-Decca (or Decca as it then was) involvement began in 1969 when Esso and mintech decided that an industrial partner should be sought. From the firms approached, the Decca Navigator Company was contracted to undertake a design study. The cost of this study, which started in January 1971, was equally shared between Decca and mintech. This said, it is remarkable how even with a wealth of supporting data having been collected in the intervening fourteen years, the objectives for manav, as set by Decca and mintech, have not radically changed.

The present Department of Industry involvement in funding the sea trial evaluation of manav has its roots in yet a different study; namely the Bridge and Wheelhouse Ergonomics Study, which resulted in the DOI Code of Practice for Ship's Bridge Design.

With the rapid changes taking place in so many countries – new ports, new terminals and anchorages and new buildings of significance to mariners – it is essential that users report back to us whenever they feel that our charting service could be improved. Whilst it is flattering that we seldom do have criticism, this is not always very helpful. At the recent International Hydrographic Conference in Monaco preliminary results of a recent questionnaire issued by the International Chamber of Shipping on the use and availability of navigational charts and Notices to Mariners were made known; it was flattering to hear that over 2000 of the replies stated that they used British Admiralty products as their primary series, but disconcerting that about a quarter of the replies said that arrangements for the supply of both charts and Notices to Mariners were less than adequate. Even for the various national or world-wide series of charts, it has given me food for thought to hear that our own arrangements were considered to be ‘adequate’ in Western Europe (including the Mediterranean) by only 504 out of 1150 ships, by 753 out of 2547 ships in North American waters, and by 457 out of 1507 ships in the Middle and Near East. Many other areas seem to reveal reports just as conflicting as those which we have heard at earlier Chart Users' Panel meetings, when we have repeatedly asked for reports of areas where our service could be improved, but seldom if ever have had any reports of difficult areas.

Figure 1 shows the present state of surveys over the UK continental shelf. Out of an area of some 173 000 square miles contained within the British Fishery limits, 36 per cent has been surveyed by echo sounder, but not necessarily to a scale suitable for modern standards, and only surveys to full modern standards are sufficient to ensure safe navigation within r m of the seabed; a modern standard survey must be carried out using a modern echo-sounder and include a thorough sonar sweep. All hips of the Survey Flotilla are now fitted with a Kelvin Hughes MS48 echo sounder and an OAL side-scan sonar.

New technology, such as the towed side-scan system, has enabled the surveyor to examine the whole of the sea bed between a regular pattern of sounding lines, spaced to ensure that the sonar beam from one line searches at least 50 m beyond the adjacent lines either side. This ensures that all wrecks, rocks and other obstructions on the sea bed which could be a danger to navigation are located, and subsequently closely examined for the least depth over them. Side-scan sonar is best operated at a speed of 5 or 6 knots, which means that the time taken to carry out a survey to full modern standards is far longer than twenty years ago, but during the last five years almost 8 per cent of the UK continental shelf has been fully surveyed to modern standards.

Our Survey Flotilla comprises eleven vessels, four Ocean Survey Ships – Heda, Hecate, Herald and Hydra; four Coastal Survey Vessels – Bulldog, Beagle, Fox and Fawn; and three Inshore Survey Craft – Egeria, Enterprise and Echo.

Users of Admiralty charts will be familiar with the fact that the specifications which are followed in respect of content and design evolve continually; some of the changes are in response to suggestions put forward by users. It is intended, for example, to add the morse identification of racon signals on charts, following a suggestion by Trinity House. The Hydrographer is always anxious to encourage comments from sea and the Chart Users' Advisory Panel is dedicated to that end. Some changes result from new developments in the navigational field: the representation of vhf radio lighthouses, for example, is now being considered so that they may be charted by symbol when they emerge from their present on-test status to become fully operational. Other changes stem from office considerations, such as new cartographic techniques or the requirements of effective maintenance of the published charts. The more important of these changes are announced through Admiralty Notices to Mariners as corrections to the Symbols and Abbreviations booklet, 5011, a document indispensable to chart users since charts do not themselves carry a key to the symbols used; over 40000 copies of 5011 have gone into circulation in the past two years alone. Other innovations, less significant or self-evident, are not normally announced by Notices to Mariners in this way but implemented through office instructions to the cartographic staff of the Department. Recent examples have been the decisions to include notes giving the relationship of charted latitudes and longitudes to WGS-based positions, so that SatNav observations can be reliably plotted on charts; and, on a minor level, to add the label ‘o’ (zero) to the drying line at intervals in the same way that other depth contours on metric charts are labelled with their values, a step deemed to be useful in case copies of charts have to be printed without the superimposed colour tints.

We recognize that in the general line of trade (or, as we have had underlined again recently, of war) there will be places where ships have to go but where, with the best will in the world, we have not been able to provide adequate charting or even to recommend anyone else's chart as fit for use. The master and his owners, or the naval commanding officer and his operational authorities, have got to weigh the advantages of calling at that port, or using that route, against the danger to the ship and decide whether the gain justifies the risk.

In 1973 we were astonished to hear that a foreign coaster on passage from a Bristol Channel port to Penzance had attempted to go between Godrevy Point, the north-eastern head of St Ives Bay, and Godrevy Island, some 2½ cables offshore, at low water. Fortunately for her, she was spotted by the local coastguard before she was irrevocably committed to the passage – and dissuaded. The largest scale chart of the area, Chart 1168, is on a scale of 1: 25000, and shows the passage as some ¾ inch across from high waterline, or less than half an inch between drying rock shelves. Admittedly it did show a narrow gap where the contour lines suggested that more than 5 m of water could be carried through the centre of the passage. The sailing directions state that the channel outside the island, between it and the outer shoals, should not be used without local knowledge. The inner passage is briefly mentioned but no instructions for passing through it are given.

The first edition of the English Channel Passage Planning Guide was published in February 1981, over a year ahead of the July 1982 routing changes, to familiarize navigators with this new type of publication and to gain experience from users. Edition 2 was published on 2 April 1982 to give advance warning of the full details of the new routing measures; it includes many suggestions from those who answered the questionnaire printed at intervals in Admiralty Notices to Mariners. Even before publication of Edition 1 we had had much useful advice from various professional bodies and, throughout, we have tried to meet the known wishes of those who would be using the Guide.

Format is not the most important feature but it is one on which strong views were expressed. Edition 1 was plainly over-large and unwieldy. We have now reduced the width to standard chart size and completely redesigned the panels to permit folding to a size of about 10 × 14 inches. This compromise between chart and booklet should combine the virtues of a chart (quick correction and filing with other charts where its existence will not be overlooked) and some of the virtues of a booklet (folded, it will not cover the whole of a standard chart which may be in use at the same time).

In 1970 a review of the Sailing Directions was undertaken to find out if they met the needs of the twentieth-century mariner. This review was based mainly on the response to a questionnaire promulgated by Notices to Mariners, to which some 900 replies were received. The general assessment was that considerable improvement was required in the port and pilotage information; a loose-leaf type of book, for ease in correction, was also suggested.

The outcome of the review was the adoption of a new style, involving a stricter geographic sequence in dealing with the coastal features, more headings to divide up the text and proper names highlighted by the use of bold type at the principal mention. At the same time the international A4 size was adopted to provide a shorter line of print in two columns, and a better page size for graphics. Much pure description of the chart has been removed, but there is still rather too much repetition of detail which can already be seen from the chart.

Real Admiral Ritchie, who retired on 1 September 1982 after ten years as President of the Directing Committee of the International Hydrographic Bureau in Monaco, here looks at the work of the International Hydrographic Organisation, more particularly in those areas which are of direct interest to the navigator.

In 1919 an International Hydrographic Conference was called in London at which representatives from the hydrographic services of twenty-four nations attended. After discussing at length cooperation in the fields of charting, Notices to Mariners, and the international exchange of hydrographic data, it was resolved to set up a permanent Bureau. The Conclusion to the Conference reads as follows:

The International Hydrographic Bureau whose formation is here suggested fulfils, in our opinion, an imperative need. Assuring a close and permanent association between the National Hydrographic Services, it allows of the cooperation of the efforts of all maritime Powers to furnish navigators with more perfect and up-to-date nautical documents. Without limiting in any way the liberty and initiative which should be retained by the Offices of the countries concerned, the new organisation will avoid unnecessary effort and wasteful expenditure; it will create amongst the surveyors of the different countries a fruitful rivalry and personal relations which are frequently of great value. We are convinced that its rôle will constantly increase in the future, and that its establishment will tend greatly to advance the Science of Hydrography.

The italics in the above statement are mine. These words still reflect the most important aim of the International Hydrographic Organisation over sixty years later.

The term ‘portolan chart’ first occurs in Italy in the thirteenth century, not long after this aid to navigation came into general use on board ship. The Italian word portolano, however, can best be translated as ‘pilot book’ or ‘sailing directions’, a different aid to navigation of which one example survives from the fourth century b.c., and pilot books are indeed still published in modern form by all seafaring nations. References by Herodotus in the History make it probable that such documents already existed in his time, and under the name of periplus they continued up to the sixth century a.d.; after which they do not appear again until the golden age of navigation in Italy and Catalonia in the late Middle Ages, apart from some much simpler early medieval types. The portolano or periplus is a description of ports, with information required by the navigator concerning anchorages, dangers threatening landfall and the winds and weather over wider areas. Commercial information was sometimes included, obviously also a matter of interest to the mariner who could read, though it may be doubted if many of them then could.

Italian portolan charts exist from almost the same period as the portolani, both of them denoted by the same word compasso, but while the pilot books have their modern successors the charts were only produced up to the beginning of the seventeenth century and are not really the forerunners of the modern sea chart.

Efforts to determine the mean size of ship ‘domains’ from measurements of the distribution of ships in the vicinity of an individual ship have been made by several workers, particularly by Goodwin, who made extensive observations in the Sunk Lightship area of the North Sea. The work involved plotting the positions of vessels at time intervals of a few minutes to estimate the number of ships in an annulus about a central ship, or alternatively the number per unit area at various distances from a central ship. These figures were used to obtain distribution curves from which the average domain could be estimated. The work of Curtis and Barratt on the validation of simulator studies of passing manoeuvres in fog, in which the nearest point of approach of ship's tracks was determined, serves to illustrate an alternative method based on the distribution of the density of tracks. In both procedures use is made of the point at which the distribution function first returns to the value which would obtain if the distribution were uniform, that is, if ship domains were absent. Some doubts have been expressed as to the validity of using the position of the cross-over point as a measure of the average domain size, and also whether it would be more appropriate to employ the position of the maximum value of the functions.

Wing Commander Anderson, the author of The Principles of Navigation in which he emphasized the essential unity of philosophy which underlies all forms of navigation, has further developed this concept in two papers in this Journal published in 1980, ‘Navigational Measurements’ and ‘The Magic of Animal Navigation’ (Vol. 33, pp. 33 and 444). In the present paper he examines further in non-mathematical terms some of the difficulties met with in the analysis of rotations in navigation, including the effects of the Earth's rotation on its axis.

The ICA system which is now being considered by the Civil Aviation Administrations in the UK and the USA is based on a new height unit, the ‘millica’. Below an arbitrary fixed level (29000 ft) this unit is equal to 0.3 m; above that level it increases gradually, the rate of increase corresponding to the standard deviation of aircraft height from assigned cruising level. At 10 000 m the unit is equal to 0.325 m and 15 000 m to 0.477 m. In this way the ratio between the separation of cruising levels and the standard deviation of the departure from assigned level remains constant; that is to say, the safety margin is constant. At present, cruising levels up to 29 000 ft are separated by 1000 ft and above this level by 2000 ft, so that there are five cruising levels between 29000 and 39000 ft; in the new system there would be nine.

If δh is the height difference, δp the barometric pressure difference and p the mean atmospheric density in this interval, it is clear that δp = pδh and δh(1/p)δp. From this it follows that if δh is constant between adjacent flight levels the δp decreases with altitude and the vertical separation safety factor also decreases.

If, as has sometimes been suggested, δp remains constant between adjacent flight levels, then δh will increase with altitude and the safety factor will increase also.