This paper formed the 1992 Anderson Memorial Lecture. It was presented by Air Commodore Grocott at a meeting of the Solent Branch at the Warsash Campus of Southampton Institute of Higher Education on 12 March.

Zheng He was the greatest navigator in China's history and he conducted major oceanic voyages, before the western ‘Age of Discovery’, at a time when the Portuguese under Prince Henry were just beginning to feel their way down the coast of Africa. Under the orders of Emperor Yongle and then Emperor Xuande in the Ming Dynasty, Zheng He led a fleet which was the greatest in the world in the fifteenth century and made, in all, seven expeditions to the Western Ocean from 1405 to 1433. His fleet sailed across most of the sea areas of the Western Pacific Ocean and the Indian Ocean, and visited more than thirty Asian and African countries and regions. This paper will mainly discuss the extraordinary achievements of Zheng He's expeditions and their navigational technology, and will also briefly evaluate their role in navigational history.

The historical development of positioning in relation to the nautical chart is very briefly described. Present nautical charts are largely based on geodetic surveys which date from the 19th and early 20th century. This gave rise to the use of many local datums and there has been a need to provide the mariner with information to enable him to transfer his position from one chart to an adjacent one on a different datum. The sizes of discrepancies in position between various datums are given. The availability of the Global Positioning System (GPS) and the World Geodetic System 1984 (WGS 84) datum enables positioning on a single worldwide datum to become a reality. The important factors affecting the adoption of WGS 84 as the datum for nautical charts, namely data availability and the practical and political considerations, are discussed. The importance of the proper consideration of datum in relation to new developments in the use of nautical charts is also mentioned.

Whilst unmanned aircraft (UMA) can be said to encompass missiles, targets for weapon training, preprogrammed reconnaissance drones and civilian systems such as radio-controlled models used to carry cameras, for the purpose of this paper we will restrict ourselves to aircraft which are capable of sustaining autonomous flight and accepting navigation commands whilst airborne. The terms applied to unmanned aircraft are variously UMA, remotely piloted vehicle (RPV), Drone and Unmanned Aerial Vehicle (UAV).

This paper was presented at the SASMEX 92 Conference in London, April 7–9 1992. Permission to reproduce it is gratefully acknowledged.

In planning routes between well-defined points of departure and arrival, both aircraft and ships can take into account forecast values of certain geophysical parameters so that the route chosen is in some sense optimized. For aircraft flying the North Atlantic, the methods used are described in the papers by Attwooll, Bennett, and Monk (all 1982). There have been a number of papers on ship-routeing; they were reviewed by Motte and Calvert (1988). It should be noted that whereas for aircraft the dominant consideration is the wind (for which the maritime equivalent is the current), ship-routeing on the trans-oceanic scale is dominated by considerations of waves. However, on smaller scales, currents can be the dominant consideration: for example, see the paper by Fales (1991). That paper does not make use of the basic theory that was applied to the aeronautical problem in the 1940s. Although the work reported here is orientated to aeronautical applications, it clearly has ramifications for certain maritime problems.

1. Introduction. This paper is concerned with collision risk reduction through the identification, measurement and analysis of contributing factors and the evaluation of risk control measures appropriate to the approaches to the Strait of Juan de Fuca. Risk factors were identified through a traffic survey and collision probabilities were estimated and modified by a simulated modification to traffic routeing. Marine collision risk analyses have tended to describe the circumstances of collisions without comparison to the conditions encountered by marine traffic. In the absence of any test of significance, such an analysis is revealing yet provides an incomplete basis for traffic management decisions. This study examines the importance of contributing factors through such a comparison.

Navigating officers at sea have duties other than watchkeeping and navigation. This paper considers the problems associated with a seagoing career in the context of social and technical developments. The worldwide pool of skilled maritime labour is rapidly diminishing and steadily ageing. Seafaring as a career is becoming progressively less attractive. Worldwide shortages of qualified staff are predicted to get far worse with serious commercial consequences, but it may be that further reductions in crewing levels will merely exacerbate the problem. The psychological difficulties of present-day seafaring are considered and a sociotechnical re-design of the shipboard system discussed as an option.

1. Introduction. Active MTC (Marine Traffic Control), in its various forms, is at present mainly confined to port areas and canals and their approaches, whereas all other areas are mainly subject to passive MTC measures; that is, the Collision Regulations, including traffic separation schemes, areas to be avoided by certain classes of vessels, deep water routes, etc. The Collision Regulations, however, despite many attempts to improve them, are fundamentally flawed by specious logic sanctioned, unfortunately, by legislation which is supported in turn by the well-meaning connivance of the courts. This paper highlights some of the insoluble problems of the Collision Regulations and looks at the planning of ocean passages, weather routeing, search and rescue, and fishery protection; and shows that there is already a measure of active MTC in these areas of activity. The future possibility of a comprehensive global active MTC system to deal with avoidance of collisions and strandings, in addition to those other activities, is considered with respect to technical feasibility and to social and political impediments.

(1) In the paper ‘The Avoidance of Collisions for Newtonian Bodies with Hidden Variables’, by B. D. Bramson (vol. 45, p. 55), equation (4.4) should read:

(2) In the paper ‘Quantitative Estimation of Secondary Surveillance Radar Information, by D. J. A. Weeda, L. P. Ligthart, L. R. Nieuwkerk and B. C. M. van der Klein (vol. 45, pp. 26–35), the first initial of the last-named author was given as D instead of B.

On p. 27 line 22, the phrase ‘scans of 32 plots’ should be replaced by ‘scans of 32 numbers of plots’.

On p. 34, the denominator on the right-hand side of equation (12) should be v(v ± Δv) instead of v(vδv).

On p. 35 line 16, ‘air traffic route 1’ should be replaced by ‘air traffic route i’.