The paper is mainly concerned with the principles used by TCAS (Traffic alert and Collision Avoidance System) to resolve conflicts between airborne aircraft. It leans heavily on an earlier paper which describes the threat-detection process. The simulation results given were obtained using a fast-time computer model for random traffic and comprise statistics on miss distance, warning time, etc., for a simple traffic pattern.

The twelfth Duke of Edinburgh Lecture was presented in London on 15 October 1986 at the Royal Geographical Society to the thirty-ninth Annual General Meeting of the Institute, the President in the Chair. The lecturer, the President said in his introductory remarks, was a geographical scholar who had devoted much of his time to the verification of early voyages by following the paths described in the often legendary accounts:the travels of Marco Polo in 1961 and later the voyages on which the present paper is based, of St Brendan, Sindbad and Jason. In 1976–7 in the medieval leather boat Brendan he followed a route from Ireland across the Atlantic described in the 8/9th century Navigatio. In 1980–81 in the Arabian boom Sohar he sailed over 6000 miles from Oman to Canton in a reconstruction of Sindbad's seven voyages described in One Thousand and One Nights, and finally in 1984 in Argo, a reconstructed Greek vessel of the 13th century B.C., his voyage took him from Greece through the Bosphorus to Georgia in the USSR, following the legendary path of Jason in search of the Golden Fleece. No-one could be better fitted to reflect on the human factor in early navigation.

In Heavy Weather Sailing, Adlard Coles defines a survival storm, as distinct from a full gale, as those conditions in which, the wind at Force 10 or above and perhaps gusting at hurricane strength, wind and sea become the masters; there is little the unfortunate mariner can do. It is impossible for anyone in a small boat in the middle of an ocean storm to judge wind-speed or sea-state accurately, if only because the height of eye will be too low to see enough of the sea surface. However, an experienced observer will be able to distinguish between storm-force and gale-force winds and if he knows his craft well enough he will sense when she has become at the mercy of the seas. In precisely these terms I believe Jester to have experienced a survival storm in the vicinity of 48° 30′ N., 12° 30′ W. on 1 August 1986. She was on her way back from Nova Scotia to Plymouth, some 25 days out, 250 miles from her destination. It was her thirteent transatlantic crossing.

This is an abridged version of a paper which was presented at the NAVIGOS Seminar held in Cairo in October 1986. It describes the development of ship routeing in the Gulf of Suez since 197J. Dr Mokhtar is Director General of the Arab Maritime Transport Academy and Commodore Hussein is a consultant at the same Academy.

The navigation and control of commercial aircraft has developed in an almost random fashion during the past forty years. Now circumstances have produced an opportunity, through the ICAO Special Committee on Future Air Navigation Systems, for the industry to put time aside from more immediate problems to plan ahead for the future. Although our current methods and procedures are immeasurably better than those of forty years ago there is now little scope for further refinement and it is very apparent that by the end of the century present systems will be unable to cope efficiently with the traffic in the world's high-density areas. In addition our current methods do not permit us to operate our aircraft as efficiently as we would wish.

Spacecraft which are sent on deep space missions to the planets must be accurately navigated in order to achieve the correct flight path. Navigation analysts use precise measurements and large computational software systems to determine a spacecraft's position throughout the mission and compute the velocity corrections for its guidance through space. When the spacecraft is launched into deep space on its voyage, it is impossible to know with great precision where it is headed. Imperfections in both the launch vehicle's terminal velocity and the uncertainty in the knowledge of the parameters which will affect the spacecraft trajectory contribute to errors in the predictions of the total flight path. Continuous navigation of the spacecraft achieves an ever-evolving prediction of its orbit from the reduction of radiometric and astrometric observations of the craft. Control of the spacecraft is achieved by computing and signalling to the craft a series of propulsive, velocity correction commands, which manoeuvre the craft to its desired course.

Practical navigation is far from an exact science because the navigator in his daily routine uses too many approximations which would be unacceptable in careful scientific work. These approximations will not be referred to in detail, or elaborated upon, since the matter is adequately dealt with in standard navigation manuals and textbooks. The laws that govern the distribution of random errors, however, their occurrence and frequency, will be discussed in this paper in terms of the theory of probability and mathematical statistics. The main objective will be the quantitative error analysis of random structures. We shall also formulate mathematical models and use them for computer simulations of practical navigation problems.

Omega is one of a wide range of navigational aids that have been developed and are in everyday use by ships and aircraft. By contrast, outside the military field as yet there has been no significant application of these aids to mobile land vehicles. The reason has been a mismatch between the perceived accuracy requirements of the potential user, what he is prepared to pay, and what technology could provide.

Mobile satellite communications and navigation are, historically and technically, intertwined. This paper offers a historical perspective on this interrelationship to see if the past provides some guidance to the future.

In the past, air traffic services (ATS) have been compared with vessel traffic services (VTS) in numerous articles, in particular from a technical and operational point of view. Generally emphasis has been laid on existing technical differences between air navigation and shipping, which in brief are related to the speed of aircraft and ships and the medium in which these craft move.

This paper formed the 1987 Anderson Memorial Lecture, and was presented to the Bristol Channel branch on 24 March.

The Global Positioning System (GPS) is a military positioning and navigation system that, like all radio navigation systems, will also be used by the civil community. The system has just completed a transition from the development phase into production. In order to speculate on how the GPS will look in the year 2000 and beyond, a determination must first be made on how the system will look in the 1990s after it has become fully operational and has gained some maturity. As the system is being fielded and after it is operational, certain pressures will be exerted to change the system. These pressures will tend to make it change, and various types of change could occur. These potential changes will be examined primarily from the point of view of the civil use of GPS. The pressures come from at least four sources: the military needs of GPS, money, technological innovation and user requirements. These pressures could also cause changes to occur in the various GPS plans and policies associated with civil use. The pressures and/or new policies and plans could affect the GPS hardware and software. In addition to system or policy changes, new applications of GPS will surface and new ways of installing and integrating GPS on various platforms will emerge.

Significant developments have taken place in navigation and positioning techniques at sea. These include radio, acoustic and inertial methods, and satellite based techniques. The latter consist of the Transit Doppler system, which has now been in operation for over 20 years, and the Global Positioning System which is due to be inaugurated in the early 1990s. These various systems are described in the paper, and their marine engineering, geodetic and geophysical applications discussed. The paper is based on a lecture presented at the Oceanology International Conference held at Brighton in March 1986.

Mean relative collision risks for marine crossing encounters are derived from calculated encounter rates by the use of a two-part weighting function. The relative importance of the two parts is determined from data concerning the collisions which have taken place during the last few years. The method is applied to the crossing traffic in the English Channel to obtain the optimum crossing angles in both clear and restricted visibility.

A decade ago the opinion was expressed in that authoritative work The Use of Radar at Sea that:

In its peaceful application marine radar is hardly out of its adolescence. In twenty years it may have grown out of recognition. Whether it does so or not depends upon a number of factors of which, perhaps, the most important is progressive thought on the part of the user and his employers (p. 258).

In any maritime emergency where time elapses from the start of the incident to the arrival of rescue units it is necessary to establish the most probable survivor area. The procedure for establishing a most probable area is known as search area determination and requires the calculation of one position from another, known respectively as the datum point (DP) – the most probable position of survivors – and the last known position (LKP) – the incident position with recourse to the effects of tide and wind. Under the present manual methodology of the search and rescue planning system (USCG 1973), the DP is given an error treatment comprising drift initial position and search and rescue unit navigational (SRU) errors. Error calculations produce a search area radius (R) which is ‘boxed’ and referenced by four corner coordinates given in latitude and longitude.

In the past, various authors have published ideas aiming at the functional integration of communication, navigation and surveillance (COM/NAV/SURV) subsystems with the advantage that the same subsystems and components like transmitters, receivers and antennas can be used more efficiently.

There are now radar installations which track ships automatically, and these radars can provide the researcher with statistics on collision-avoidance manoeuvres. The extraction, by hand, is laborious and time consuming. This paper describes a mathematical model which automatically detects collision-avoidance manoeuvres. The model operates on an adaption of the Range to Domain Over Range Rate (RDRR) principle, which enables ships to be identified for analysis shortly before they are expected to initiate a collision-avoidance manoeuvre. The model has been computerized and results presented.

A system which yields the automatic positioning of a ship from computer analysis of marine radar images of nearby coastlines has been tested on data from the survey vessel Maxwell while proceeding in and out of Halifax harbour. Differences between radar-determined position fixes and those obtained by a microwave navigation system with an error of the order i o m show little evidence of additional error when the origin of the radar images used as ‘reference map’ is within 500 m of the actual position. As the distance increases the accuracy slowly decreases.

Airport visual aids are examined for failure of transfer from chromatic (i.e. normal) to achromatic viewing situations which would suggest a non-redundant use of colour, and for their information value during VFR (visual flight rule) operations as a function of the airport operating classification for which they were designed. From photographs taken under visual meteorological conditions at night, slide sequences representing the visual presentations associated with aircraft movements during taxi-out, take-off, approach and landing operations were prepared and shown to experienced pilots in a time-stressed forced-choice procedure. The results suggest that among displays in current use only the signal light from the control tower is completely colour-dependent. Also, the information value of some taxi-way and approach lighting components might be questioned. An argument is presented for a ‘building-blocks’ review of the airport visual-aids system that could in some cases result in improved relationships between economy of display content and information value.