This paper is based on the Eva G. R. Taylor lecture given by the author at the Royal Geographical Society on 28 November 1990. The precise landfall of Columbus in the New World has been the subject of discussion for many years owing to various interpretations of the information given by copies of his log and his own statement that his San Salvador lay about 28° north. The twofold aims of the author's 1989 voyage were: first, to experiment with fifteenth-century methods and instruments to find out by practical experimentation how accurate the navigation at the time might have been and so cast light on this 4° error in latitude; and secondly, to follow the navigation information given by Columbus as closely as possible to assess the effect of the currents on his dead reckoning as clues as to his landfall.

This is a synopsis of a paper that formed the 1991 Anderson Memorial Lecture. It was presented at a combined meeting of the Bristol Channel and Boscombe Down branches on 21 February 1991

In 1989 the International Maritime Organization (IMO) published its Provisional Performance Standards (PPS) for ECDIS (Electronic Chart Display and Information Systems) and asked member governments to assess these standards and submit their findings to the Sub-Committee on Safety of Navigation. IMO intends to finalize the standards in 1993.

Improved radar surveillance for air traffic control can be obtained by the integration of radar systems. Integration, however, might cause the delay of radar information, which would hamper the air traffic controllers in their work. To estimate the delay, a mathematical equation to assess the amount of radar information causing this delay has been deduced from the properties of the behaviour of air traffic. The mathematical equation has been tested using results obtained from operational secondary surveillance radar in the Netherlands.

The proposal to develop an extensive North-West European Loran-C system, replacing many existing chains of the Decca Navigator System (DNS), has led to an intensive debate on the merits of the two navigation aids, especially in the United Kingdom. The paper reviews the principal sources of random and systematic position errors in the two systems. The wide range of DNS random errors, predominantly due to skywave interference, are compared with the Loran-C random errors, and typical coverage limits of acceptable repeatable accuracy are presented. The paper also identifies the factors which control the magnitudes of Loran-C and DNS systematic effects due to land paths. It demonstrates that differences between the two systems are substantially less than are predicted by simple models. Loran-C and DNS techniques for dealing with land paths are compared and the errors experienced by Loran users are shown to be reduced by modelling and publishing ASF values.

This paper is based on a presentation made by the author at a technical symposium of the Wild Goose Association.

The collision avoidance of a pair of uniformly moving bodies is considered in three dimensions. The relative motion of the bodies yields an expression relating the time to closest approach, the minimum range, the current range and its rate of change, other variables being unobservable. A Boolean relation is then proposed that is satisfied whenever the minimum range and time to closest approach simultaneously fall below given thresholds. The relation is further studied, in particular with regard to the issue of false and premature alarms. An airborne collision avoidance system is a possible application.

This paper, and the following one, were originally presented at an Institute afternoon meeting held at the RAF Museum, Hendon, on 5 June 1991. This first paper gives a personal view of the development and use of radionavigation techniques in the UK in World War II. The second paper gives some technical background to the systems discussed in the first one.

During the 1939–1945 conflict, the development of navigational aids, particularly for the purpose of bombing the opposing nation, took place at an unprecedented rate. The life of any system was only the period of time it took scientists of the opposing nation to determine the nature of the aid and devise an appropriate countermeasure. So much so that in several cases, the time from conception to operational service could be measured in months.

The present-day emphasis on the need to analyse and identify risk situations in ports is hardly a new phenomenon. In fact, port managements have, as a matter of course, been very conscious of this need but over the years, with the ever-increasing transport by sea of hazardous hydrocarbon, chemical as well as nuclear-related products, this need has simply become much more pronounced. Moreover, present-day public awareness and concern about the possible incident impact on the environment in the form of pollution or personal injury has even further increased the awareness of the corporate responsibility and the need to assess the operational risk levels of ports. Of equal importance, of course, is the need and the capability to predict operational risk levels for new port developments or modification projects or of the possible risks associated with the introduction of hazardous cargo-handling facilities at existing or new port terminals.

This paper is the second of a series of three papers, documenting the European studies into the feasibility of 1000 ft vertical separation minima above FL290. The paper discusses the vertical collision risk estimation methodology and an assessment of the collision risk against a target level of safety.

The analysis indicates the technical feasibility of a reduced vertical separation minima in the North Atlantic Region. However, for current operations and technical performance within European continental airspace, the risk estimation indicates that a 1000 ft minima is not technically feasible.

The contents of this paper reflect the views of the authors concerned; they do not necessarily reflect the official views or policy of the CAA or NLR.

This paper reviews the history and the evolution of international ship collision avoidance research. The direction which research should take in the Chinese People's Republic is discussed and the authors recognize that new ideas may be needed to take account of the conditions in their country.

Lambert, in his paper entitled The distance between two widely separated points on the surface of the Earth, published in 1942, having given a solution which was applicable in most cases, stated that there was a particular problem in determining the shortest distance between two nearly antipodean points on the surface of the spheroidal Earth but this was not fully analysed in that paper.

This paper concerns the estimate of a ship's position from a sequence of measurements of 3, 4 or 5 altitudes of stars or planets. The measurement errors are assumed to be mutually correlated. This correlation is mainly caused by the appearance of so-called systematic errors. It is the main intention of this paper to dispense with the policy of pre-separation of these systematic errors. Instead, the equal contribution of some partial errors to the total measuring errors is fully accounted for by the formation of the covariance matrix, which corresponds with the vector of measurement errors. The algorithm produces a position estimate with a bias-free estimation error, meaning that the estimate and the error are stochastically independent. The resulting covariance matrix of the position error has a minimal trace.