Nowadays it is as an astronomer that Halley is best known. While still an undergraduate at Oxford, he travelled to St Helena and there observed the positions of the southern stars and compiled a catalogue of them similar to those Hevelius and Flamsteed were making of the northern stars. In the last decades of his long life, when he was now the second Astronomer Royal, he began and finished a series of observations of the Moon for a complete saronic cycle of eighteen years. In the middle years of his life he made those observations and calculations of comets that we shall shortly recall with the return of the comet bearing his name. To many of us his outstanding contributions to knowledge and natural philosophy lie in his instigating Newton to undertake the studies that led to the Principia and in ensuring that it was written and published.

In September 1931 Sir Hubert Wilkins and Harald Sverdrup made the first attempt to explore the Arctic Ocean by submarine in Wilkins's Nautilus. The Nautilus was the ex-Navy submarine O-12 modified with topside runners to slide against the underside of the sea ice. Seventeen years later the US Navy developed the sonar system necessary for safely piloting a diesel-battery submarine underneath the ice pack and began exploration of ice covered areas.

In 1957, with the nuclear-powered Nautilus, the US Navy began exploration far into the Arctic Ocean. Problems were found concerning determination of ship's position, ice avoidance manoeuvres, and surfacing up through ice. Sonar and inertial navigation equipments and operating techniques were developed to solve these problems. Submarines have since sailed to all parts of the Arctic Ocean during all seasons — more than twenty explorations since 1957. The history, problems and interrelationships of the many explorations are described.

Dr Lyon's paper was presented at a colloquium on the conquest of the North Pole held in Paris, 7–1 1 November 1983, and organized by the Centre d'Etudes Arctiques by whose permission it is here published. (Throughout the paper miles means nautical miles.)

The United States is in the process of determining what the future mix of radio-navigation should be for its users. Air, marine and land navigation requirements are being closely re-examined and the ability of future or existing systems to meet these requirements is being investigated. Events such as the destruction of Korean Airline Flight 007 have focused new attention on the Navstar Global Positioning System (GPS), both by the President and Congress. Behind the selection of a future systems mix is a planning process that has been under way for some time. The first Federal Radio-navigation Plan, published in 1980, listed two key decision points in the planning process; a joint preliminary recommendation to be made by the Departments of Defense (DOD) and Transportation (DOT) in 1983 and a national level decision in 1986 (Fig. 1). A national decision will not be made without an opportunity for user comment and international consultations.

The commercial viability of wind propulsion is of itself not strictly a navigational problem. However, the implications for navigation of a return to commercial sail in some form are clearly considerable. Mr Bradbury's summary of the various proposals put forward in the last few years and the extensive bibliography will interest many navigators.

In 1980 The Times printed an article on its front page under the headline ‘Oil prices put sails back on the horizon’ (Baily, 1980). This article must have surprised many people. It reflected a growing awareness and interest in the idea of wind propulsion for commercial ships. A better indication of this interest may be the number of related symposia held since the oil crisis. The symposia have been held by The Royal Institution of Naval Architects (1975 and 1980), Liverpool Polytechnic (1976), this Institute (1977), and the Department of Industry (1979). Some interesting papers by Mudie (1977a, b and 1980) have particularly brought the subject to the attention of this Institute.

At the end of World War II civil aviation inherited an infrastructure in which the state of the art had necessarily been accelerated beyond normal commercial pressures and for which the research and development costs had been funded by military resources and requirements. Within the UK a patchwork quilt of military aerodromes were progressively run-down as military activities decreased and were either adopted by the state, the municipal authorities or private ownership. The possibilities for civil aviation development seemed boundless and to many communities the availability of airline services were deemed sufficiently desirable, because of ancillary benefits, to justify the subsidization of the airport and navigation facilities inherited.

This paper, with Dr Lyon's was presented in Paris in November 1983 at an international colloquium organized by the Centre d'Etudes Arctiques of the Centre National de la Recherche Scientifique, by whose kind permission they are here reproduced. The theme of the conference, at which some 35 papers were presented, was the Conquest of the North Pole; the subjects covered included both the history of Arctic exploration and contemporary problems and the future of polar transport, sea and air. Mr Kerr is Director of the Canadian Hydrographic Service's Atlantic Region; both he and his co-author are at the Bedford Institute of Oceanography in Dartmouth.

In the course of a summary of established views about the still unknown origins of portolan charts (this Journal, 36, 124, 1983) the hypothesis was advanced that they originated as a result of the maritime interests of Frederick II of Hohenstaufen. It should perhaps be made clear straight away that this is no mere attempt by a German author to further German pretensions in this matter. In fact, of course, Frederick II (1194–1250) was the last emperor of the Holy Roman Empire and, according to the excellent biography by Kantorowicz, felt himself more and more the spokesman for cosmopolitan thought as his years advanced. He spent his youth in Sicily and was known as ‘The Sicilian’, and learned to speak German only during the third decade of his life during his first visit to Germany; by then he was fluent in half a dozen other languages. Sicily of course, where he spent most of his life, meant not simply the island but the kingdom of the two Sicilies which, since the Norse conquests, comprised extensive parts of southern Italy and notably Apulia, where Frederick had his court at Foggia. His dominions bordered papal territory, which accounts for the hostility to him of several popes.

If an operational requirement for an oceanic application of global civil satellite navigational systems is to emerge it is almost certain to appear first in the North Atlantic airspace. Other areas of application, their time-scales or relative time-scales and their possible accuracy requirements are more difficult to anticipate. Perhaps the Central East Pacific routes or the North Pacific routes could be next in line for justification of an operational requirement in the foreseeable future. For this reason the remainder of this paper draws entirely upon the North Atlantic, but the potential application in other areas cannot be overlooked. The views expressed are those of the author and do not necessarily reflect the views of the Civil Aviation Authority.

Det Norske Veritas is a Norwegian ship classification society with a large classified fleet registered in 94 countries. The paper printed below was presented by Mr Cuming at an Ordinary Meeting of the Institute held in London on 18 May 1983 with Dr J. F. Kemp in the Chair.

Risk analysis is a method of evaluating potential risks which has been used for the past ten years by Det Norske Veritas, in both the shipping and the offshore fields of operations. The method is based on the systematic identification of hazards, the estimation of probability of occurrence and the evaluation of consequences.

This paper presents a description of a general method for the evaluation of marine collision risk. The approach differs considerably from existing methods in this area, in that it combines analytical modelling in a special way to analyse historical data. The method makes it possible to find the collision probability of a specific ship in any particular location, taking into account such location factors as area geometry, ship movements and speeds. It also constitutes a basis for worldwide data collection.

In view of the growth of marine traffic and the increase in the transportation of hazardous materials over the past two decades, considerable efforts are being made towards the development of maritime risk evaluation methods, the main objective being the quantification of ship collision probability. The methods developed to date can roughly be subdivided into the following two groups: (a) kinematic models (see for instance refs. 1–6); (b) historical data analysis (see for instance refs. 7–17). It is a well-established fact that most collisions are due to human failures, and it is widely accepted that human behaviour cannot be described well by mathematical formulae. Kinematic models are therefore not recognized as suitable for estimating this probability. Historical data analysis estimates the collision probability as the ratio of the number of observed collisions to the number of ship movements. Probabilities estimated in this way are only correct in a probabilistic sense when the assumption is satisfied that every ship movement has the same probability of collision. This assumption is rarely fulfilled since most ships often pass each other without collision danger. In addition, this approach is often hampered by lack of data for a specific traffic area, while the application of worldwide data cannot be considered realistic. As far as we know, there does not exist a method which can transfer, in a statistically justifiable manner, marine traffic data from one area to another. Moreover, neither of the above-mentioned approaches is appropriate to analyse alternative routes in the same area, or under changing circumstances.

Navsat is a civil satellite-navigation system which was presented by the European Space Agency. It is still at the system definition phase as distinct from the pre-operational stage, but since the original presentation it has been the subject of studies which have included analysis and synthesis of the main parameters.

The underlying principles of the concept as initially described by Rosetti remain unchanged but sufficient progress has now been made to predict the capability of the system in satisfying a number of objectives in the civil fields of navigation, position fixing and survey.

Recent years have seen a number of proposals for the use of satellites by aviation, either for navigation or for air/ground communications and the question is often asked why commercial aviation, one of the most technologically advanced industries in the world, is so reluctant to utilize satellite techniques. So far, these proposals have not succeeded because they failed to satisfy a genuine operational requirement and were not, by any standard, cost effective. Up to the present time the systems which have evolved over the years have performed the required tasks reasonably adequately and would appear, given the normal process of development, to be able to continue to do so for some years to come.

A mathematical collision risk model can be used for evaluating air traffic control (ATC) separation standards. As one of the parameters required for calculating the expected number of collisions by this model, the probability of overlap in the vertical dimension based on height-keeping errors of aircraft must be estimated.

However, there are few examples of empirical data on height-keeping errors because data collection is expensive and time-consuming. In order to collect these data, the author et al. started data collection using a newly developed simple height-finding radar, the navigation accuracy measurement system (NAMS) which has been installed under a trunk airway in Japan.

Retrospective analysis of the Total Loss and Serious Casualty Rate (TL/SC Rate) for UK registered deep-sea and inshore fishing vessels over a twenty-year period (1961–80) revealed a gradual and sustained increase.

The mean TL/SC rate for 1971–80 (6·041/1 000 vessels at risk) was almost 70 percent higher than the corresponding mean for the previous decade (3·79/1000 vessels at risk) and this difference was statistically significant (p < 0·05).

Subsequent examination of vessel losses and casualties by cause indicate that 64 per cent of this detected increase was due to a concomitant increase in vessels lost or damaged due to foundering (particularly inshore vessels) and that the mean vessel age at loss from this cause was 24 years old. Synthesis of available evidence relating to the onset of this increase (1971); mean age at loss due to foundering (24 years); and the current age structure of the fleet, supports the hypothesis that the increase in founderings in the early 1970s may be explained partly by a cohort effect resulting from the uncontrolled fleet rebuilding programme almost a quarter of a century earlier in the immediate post-war period.

Current combined risks of fishing vessel loss and casualty are about twice as great overall as those with which the Committee of Inquiry into Trawler Safety (1969) was concerned and over which it expressed deep concern.

Since the end of the second world war hyperbolic position-fixing systems have been available for use by merchant vessels. These systems originated in military requirements. Today for the navigation of merchant ships a number of existing systems can be used, such as Decca, Loran C, Omega, Transit and Cikada, the two latter being satellite navigation systems. Transit became operational in 1964 for military use and in 1967 the system was made available for use by merchant shipping.

In this review of the evolution of displays and controls in military and civil fixed-wing aircraft, the author traces the development of flight instruments, largely in this country, from their rudimentary beginning before the first World War to the present high degree of automation and suggests certain pitfalls from the pilot's point of view in high-technology solutions.

The Wright Brothers' aeroplane flew with only a stopwatch, a tachometer to measure engine speed, and an anemometer, all for measuring performance; the pilot had no instrumentation to help him fly the aircraft. There was little change up to the beginning of the first world war in 1914. The cockpit hardly existed as such: controls varied in design; some were levers, and often there was a wheel which, in the early days, controlled wing warping to change the lift of each wing to allow the aircraft to bank.

Everyone needs a knowledge of ‘the time’, even if the accuracy required is only sufficient to keep an appointment, catch a train or watch a particular TV programme. An isolated clock, started at random and ticking at an unknown rate, can only be used to compare intervals of time. Although this is often useful – for example, in cookery or athletics – the full value of a clock can be realized only if its reading provides a model of the status of a continuing process (such as the rotation of the Earth) or if the clock is a member of a group of clocks, all of which show the same time and may be expected to continue to do so. Particular applications may demand that some members of the group must be kept in closer agreement than others, or must all reliably remain within a stated tolerance for a longer period, but specifications of this kind arise only from economic necessity; in principle all clocks should agree at all times – subject, of course to the unavoidable restrictions imposed by the laws of physics and perhaps the complexities of daylight-saving time.

Collision statistics indicate that many collisions at sea occur after one or both vessels take action to avoid collision. It is worth considering why this should be so. Is the action taken contrary to the requirements of the Regulations for Preventing Collisions at Sea or are the Rules unsatisfactory in not stating clear and effective requirements? It is necessary to consider the principles of collision avoidance to determine whether a more effective solution can be obtained. This investigation relates to all types of craft, not necessarily only marine craft.

In a previous paper a model was outlined for an encounter between two vessels using the ‘range to domain over range rate’ (RDRR) criterion. This paper shows how the model has been developed to simulate traffic flow and collision avoidance through the main south-west bound lane of the Dover Strait traffic separation scheme. B. A. Colley and C. T. Stockel are at Plymouth Polytechnic, R. G. Curtis with the Department of Trade and Industry. The paper was presented at an ordinary meeting held in London on 16 November 1983.

Granas (Global RAdio NAvigation System) is a satellite-based radio navigation system with global coverage, high accuracy and continuous availability for civil users on land, sea and air. Its performance, thus, is superior to existing ground-based radio navigation systems as Omega, Loran, Decca, and so on.

The principle of Granas user-position determination is similar to that of Navstar GPS or Navsat in that a user makes pseudo-range measurements to a number of satellites visible above a 5° elevation angle. These ranging operations are performed using time-of-arrival (TOA) measurements of navigation signals transmitted by satellites. Knowing the discrete positions of four or more satellites and their pseudo-ranges, a user may compute its own clock bias and its position in three dimensions (longitude, latitude and altitude).