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.

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.

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.

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.

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.

The Swedish National Administration of Shipping and Navigation together with the Port of Gothenburg Authority decided in 1980 that in order to increase the safety level by providing shipping with improved navigational information, a new Vessel Traffic Centre should be introduced. The decision was based upon a number of considerations. The Port of Gothenburg handles 30000 vessels each year, the total volume of cargo being of the order of 22 million tonnes. Taken individually, fully loaded vessels entering the port can exceed 225000 tonnes deadweight with a length overall in excess of 325 metres. The crude oil discharged at Torshamnen, within the Gothenburg port area, supplies over 30 per cent of the oil requirements of the Swedish nation. In addition to the tanker trade, Gothenburg has a large ro-ro/container capacity and the ferries calling at the port carry three and a half million people per annum.

This second Matthew Flinders Memorial Lecture, in a series sponsored jointly by the Royal Institute of Navigation and the Hydrographic Society with the cooperation of Lincolnshire and Humberside Arts was presented at the University of Hull on 11 May 1983 with Sir John Dudding, Chairman of Lincolnshire and Humberside Arts in the Chair. The first lecture, presented by Rear-Admiral G. S. Ritchie in April 1974 (Journal27, 3) on the bicentenary of the birth of Matthew Flinders, described the hydrographic work of this exploring navigator. Miss Ferrar concentrates on the graphical records of Flinders's Australian voyages.

When Marco Polo made his journey to China, overland from Venice in the thirteenth century, the lands around the Pacific Ocean were wholly unknown to Europeans. But the silks and spices with which he returned sowed the seeds of the quest for a sea route to the ‘Spice Islands’ which was to be one of the mainsprings of exploration for nearly 500 years. The Spaniards crossed the Atlantic. But instead of finding themselves on the coast of Asia as they had expected they discovered the lands (and the wealth) of the Aztecs and Incas, and their explorations extended along the Pacific coasts of Central and South America from Mexico to Peru. The Portuguese found their way around southern Africa and across the Indian Ocean to South-east Asia, where they attained their objective and established a lucrative trade with the Spice Islands. Sailing ship routes depend upon the direction of prevailing winds, so the outward voyage took them eastwards from the Cape of Good Hope and then northwards to their destination. The homeward crossing of the Indian Ocean was in more northerly latitudes.

In this last communication to the Journal, the late Wing Commander Anderson, whose book Animals as Navigators is reviewed on p. 146, discusses the natural sensors by means of which man may control his (purposeful) motion from place to place.

The qualification ‘human’ can convey many things. It could cover the impact of human characteristics on various systems, including the most sophisticated, but we shall use the word to mean that navigation information is garnered by the human senses without the aid of anything that has been manufactured. We shall exclude artificial sensors to provide control and not even accept a marching compass to guide the motion. There will be no printed map to give position and no watch to register time.

The mathematical collision risk model developed by Reich can be used for evaluating the current air traffic control (ATC) separation minima. This model requires such parameters as volume of traffic, navigational errors of aircraft and the structure of routes. The navigational errors are closely related to the probability of overlap, which is one of the most important parameters for the model.

Distributions of navigational errors have been studied by many researchers since the advent of the collision risk model. Because data collection on the navigational errors in the vertical dimension is expensive and time-consuming, there are few examples of observed data. Thus, at present, data on the probability of overlap in the vertical dimension are not available in a large enough sample to derive any conclusions.

A symposium was held in London on 6 December 1982 under aegis of the Institute with the traffic management fuel conservation working group to discuss meteorological forecasting and its application in terms of fuel saving. The chairman was J. C. Morrall, Chief Scientist of the Civil Aviation working group. In the United States, the work of Dr R. Steinberg of NASA on the penalties of imperfect forecasts and possible benefits from an improvement was of considerable interest. V. W. Attwooll and L. Bennett of the CAA had also studied penalties from North Atlantic forecasts. Part of the UK civil avionics programme was concerned with the forecast of winds applied in particular to 4-D time-slot following; this was. described by R. C. Rawlings of RAE Bedford. Mr C. Flood, of the Meteorological Office, finally presented prospects for improved forecasts.

A large percentage of the air traffic flow in the UK is associated with movement to or from other European countries. It would therefore be unrealistic to consider further development of the UK air traffic control network other than on an inter-European basis, although this would necessarily raise many problems.

Throughout Europe, during the period since the Second World War, the various nation states have developed their individual air traffic control systems based on national centres and extending to the boundaries of their own Flight Information Regions (FIR). The movement of aircraft across the FIR boundaries of neighbouring states is at present governed by a series of bilateral agreements, whilst attempts to reach international agreement on integration of the European ATC system have not as yet met with much success.

It is always reassuring to find a kindred spirit thinking along the same lines as oneself. R. Williams's proposal for a table of latitude parts (34, 247) is a reiteration of my paper of twelve years ago (23, 233).

The equations of a rhumb-line track were established by Sadler (9, 371) and it always seemed to me to be a more elegant solution to solve the equations themselves rather than to apply corrections to inaccurate equations, hence the approach suggested in my paper.

Lenart derives boundaries of a Collision Threat Parameters Area (CTPA), which defines the range of velocity and heading which own vessels must not adopt if it wishes to maintain a specified minimum spacing from a given threat. Lenart's treatment of the problem is algebraic, and a geometric demonstration of the validity of the CTPA boundaries may be of interest.

In Fig. 1, O is the position of own vessel. OX and OY are Cartesian axes, fixed in direction as own vessel manoeuvres. T is the position of a threat, whose velocity is represented on the diagram by a line TT´ whose length gives the distance the threat will travel, relative to own vessel's present position, in some time τ, 0·2 hours, say.

When computers were first used for navigation — mostly air navigation — there were debates as to whether all the computing should be done centrally or implemented by a series of smaller computers, each doing certain limited tasks. The debate was largely academic, since the technology for distributed processing did not really exist. Consequently, the development of navigation systems was centred on single processors and special-purpose input and out-put devices.

A technical session on the above subject was held in London on 13 April 1983. The topic was introduced by Mr M. St Erme Cardew, who first stressed the distinction between navigational data and positional data. The former, unlike the latter, are referenced by time so that there is a sense of urgency in processing navigational data. Inherently these are always out of date, possibly only slightly, due to the finite processing time required. Some extrapolation is always required. He recognized the importance of errors, possibly gross ones, and distinguished these as due either to the assumptions made by the navigator being incorrect or to errors in the data. He advised checking the calculational methods, possibly by undertaking, via a computer, two or more independent analyses. Checking that incoming data were both stable and within specification was imperative. In an emergency it was necessary that human intervention into computer-produced information be accepted.