Early in 1967, a few months before the restored Meridian Building of the Old Royal Observatory was opened to the public by Sir Richard Woolley, the Astronomer Royal, I received a visitor in my office then in the Meridian Building — later, I was to move to the west summer house of Flamsteed House. My visitor was Colonel Humphrey Quill, Royal Marines, Master of the Worshipful Company of Clockmakers that same year and author of the hook John Harrison, the Man who Found Longitude, which has become a standard work. He brought with him some manuscripts written by the subject of this lecture — Nevil Maskelyne, fifth Astronomer Royal, who lived in Flamsteed House for 46 years from 1765, making most of his important astronomical observations in the very building in which Col. Quill and I were sitting.

In order to navigate and thereby survive in a hostile environment the Inuit have developed a sophisticated body of knowledge that makes travel possible even during a blizzard or white-out. This unique skill was developed from a thorough understanding of the properties of snow and local meteorology. Problems of space, time and distance are also taken into account by Inuit navigators but this is done with minimal use of quantification and abstraction. However this highly practical form of navigation in which the Inuit deal directly with their environment is none the less scientific and empirical.

In 1971 the author attempted a single-handed sailing of the North West Passage and in 1973 completed a crossing of Arctic North America by dog team.

The aim of this paper is to summarize the contributions made by the Royal Observatory at Greenwich that led, almost inevitably, to the choice of the Airy transit circle to define the zero meridian for the measurement of longitude and the beginning of the universal day. Although astronomical considerations were not of direct relevance to the deliberations of the 1884 conference, they formed the essential background to the navigational and civil interests which were dominant.

Alexander Dalrymple was not appointed as the first Hydrographer of the Navy until 12 August 1795. Until this time, and indeed for at least twelve years later, individual commanding officers of British warships were expected to buy whatever charts they could find – and could afford. Apart from Greenvile Collins's Coasting Pilot, no official chart was generally available although the East India Company (of which Dalrymple was allowed to remain Hydrographer when taking up his naval appointment) had produced many reliable charts of the Indian Ocean and East Indies.

By the middle of the nineteenth century, there were over a dozen different initial meridians for longitude on navigational charts, and a much greater number in use for time-reckoning. The need for a single internationally agreed meridian was recognised in the resolutions of the first International Geographical Congress held in Antwerp in 1871. They proposed that the meridian through Greenwich should be adopted, recognizing that this was already the choice of the vast majority of users, and linked this with a second resolution recommending the adoption of the metric system. This was partly a recognition of the intrinsic merits of the metric system, and partly as a concession to the French as compensation for the adoption of Greenwich rather than Paris. Although not widely used, the Paris meridian had some claim to consideration since the observatory through which it passed had been in existence several years before that at Greenwich.

During the century since 1884 there have been fundamental changes in the principles on which timekeeping is based; nevertheless, almost all countries now base their civil timekeeping on a time scale which is the standard time of the Greenwich meridian and which remains within 1 second of the time envisaged at the Washington Conference. The system of time zones, in which universally valid hourly markers were given longitude-dependent labels, spread rapidly under the influence of the railway systems, with legislation usually following established practice. Daylight saving time, first introduced in many countries in 1916, is a form of mass self-deception which provides extended summer evenings in the temperate zones but causes inconvenience to the travel industry and confuses its customers.

In this technological age, when an artist of nautical astronomy is fast becoming a figure of history, there is a tendency to regard astro-navigation as something that went out with the dodo. It would be as well to remember, therefore, that despite the widespread use of radio navaids from the early years of World War II, astronomical navigation remained the only world-wide fixing system until the launch of the Transit navigation satellites during the 1960s. The truth is that the first half of the present century saw enormous advances in both its methods and practice and the fact that it is still in wide use can be judged by the large number of Nautical Almanacs sold annually.

New techniques of measurement make it possible in 1984 to determine positions on the surface of the Earth to a much higher precision than was possible in 1884. If we look beyond the requirements of navigation we can see useful applications of global geodetic positioning to centimetric accuracy for such purposes as the control of mapping and the study of crustal movements. These new techniques depend upon observations of external objects, such as satellites or quasars rather than stars, and they require that the positions of these objects and the orientation of the surface of the Earth are both known with respect to an appropriate external reference system that is ‘fixed’ in space. We need networks of observing stations and analysis centres that monitor the motions of the external objects and the rotation of the Earth. Observations of stars by a transit circle are no longer adequate for this purpose.

Methods of generating random air traffic are described for two- and three-dimensional computer models used in a study of the problem of managing off-route traffic. Edge effects which influence the estimation of conflicts taking place near the boundaries of such models are explained and quantified.

The applications of computer models in air traffic management studies are many and varied. References 1 and 2 describe some of these for which the appropriate model required the generation of randomly distributed aircraft following straight-line flight paths at constant speeds. Such behaviour can be a plausible representation of that of off-route air traffic for many purposes and the main objective of this paper is to describe methods for generating random traffic of this nature, that is traffic outside airways, terminal control areas and aerodrome control zones.

The possibility of reducing the current vertical separation minima in order to increase traffic capacity on economical flight levels has been discussed mainly at the RGCSP (Review of the General Concept of Separation Panel) meetings of ICAO. A collision risk model based on the mathematical model developed by Reich (1966) has been adopted for evaluation of safety of air traffic systems under consideration. This collision risk approach requires several parameters which should be estimated from empirical data on navigational errors, traffic dynamics, etc.

The ocean environment within which navigators operate is not only physical in character; it is an economic, political and legal environment as well. One of the most significant factors influencing general environmental development in recent years has been the rapid advance and expansion in the field of ocean and ocean-related technology. Much of this technological evolution, while helping to reduce the restrictions imposed by the physical characteristics of the oceans, has created new challenges of an economic, political and legal nature.

Commercial interests now demand a close awareness of fuel consumption, which is one of the major costs in vessel operation. This paper outlines one shipping operator's attempts to monitor and improve economic performance as indicated by fuel consumption alone. The authors are well aware that some aspects of operation, such as main engine performance variables, are closely and easily monitored whilst others such as environmental effects are not. They have therefore adopted a ‘macro-economic’ approach to the analysis and advice on Fleet operation in this instance, attempting to monitor the vessel operation system as a whole. Thus fuel consumption is used as a yardstick and it is this particular variable which is the subject of management focus. Although many of the inputs to the complete economic equation are necessarily unquantifiable in precise terms, it is considered that a valid determination of performance is attainable from a scientifically based overview.

For more than a century and a quarter ships' crews of the world's voluntary observing fleet have made meteorological and surface current observations. Those observations recorded in the ships' logbooks are the backbone of the Marine Archive now held in the Meteorological Office, Bracknell, UK. Much use is made of computer processing for providing suitable statistical data which form the basis of maps and current roses. This article outlines the method of processing used in the Netherlands, illustrating various situations the observer at sea may encounter. The supposition that the use of modern navigation equipment could hamper the making of current observations is discussed, and situations that could cause the reduction of accuracy and reliability of current mean values are mentioned. In essence: how reliable are surface current observations from ships collected in the past few years, and particularly those that will be collected in the years to come?

Time and space scales are compared for selected speeds of ships in the North Atlantic and North Pacific oceans. Viability of westbound passages on some northern great circle routes is discussed.

There would be no problem in precisely weather routing a vessel across an ocean if it were possible to forecast with total accuracy the actual sea state existing for the duration of a voyage. All mariners are well aware that such an ideal circumstance is not as yet possible. Depending upon the general synoptic situation existing for the period, it is fair to make the assumption that the actual accuracy of a weather forecast deteriorates as time progresses.

At the International Boat Show in London this year, the former Director was presented with a special Yachtsman of the Year award for ‘services to yachting taking into account his achievements in offshore racing and distinguished service to the art of small craft navigation’. The following account of his single handed transatlantic voyage last year may thus be of some interest to Members even though its strictly navigational content is limited.

The purpose of this note is to outline a system of celestial navigation which is both decimal and coherent. In a decimal system there can only be one unit, with its decimal multiples and submultiples, for measuring any quantity. It follows that a decimal system of celestial navigation requires one unit for measuring time and one unit for measuring arc. In a coherent system these units must be related by a factor of one.

This paper discusses some of the implications of speed control in the vessel traffic picture, emphasizing how speed relates to other safety factors so that control can be utilized with understanding and sensitivity. Speed control can seldom if ever be examined in isolation. The structuring of vessel traffic schemes implies a need for some form of speed control as an integral part of almost all those schemes. One technique reinforces the other. Speed limits become extremely critical at the lower end of the speed scale, the higher the traffic density, the more critical the limits. Again, the requirement for enforcement becomes clear. No over-emphasis of these operational limitations should be allowed to cloud the indisputable fact that — for the individual ship as well as for traffic management — speed control can be a most useful tool. At least three papers have been published in recent years pointing out that speed reduction by ships for safety purposes, either by individual ships themselves or through general imposition by a shore-based vessel traffic system (VTS), needs in all cases to be used with great care, reluctance even. Their warnings can easily be turned into a negative approach to such control. A number of points would therefore seem to demand looking at again.