This paper commences by outlining the developments expected in en-route navigation capabilities in Western Europe and describes the current provision of surveillance employing monopulse SSRS. Following a brief review of GPS characteristics, it then considers the use of ADS, in conjunction with GPS, as an alternative and/or supplement to these ground-based systems. In the light of a simple cost comparison, it suggests that the space-based system could be very advantageous, particularly where new routes are to be established in areas with little or no ATS infrastructure. A final section discusses the possibility of using GPS for height-monitoring purposes as will be necessary when a reduced vertical separation minimum of iooo ft, is employed above FL290 in Europe, and elsewhere.

Recently, there has been wide-spread interest in the use of the Global Positioning System (GPS) for precision approaches in a civil aviation environment. However, most of the work to date in Europe and North America has treated a GPS/inertial reference system (IRS) combination as the source of guidance for this phase of flight. Since the US has a very large general aviation population, the FAA is very interested in determining the role of a stand-alone implementation of differential GPS (DGPS) as a navigation sensor for precision approaches. This paper has two parts: a summary of the analysis of this application of DGPS; and a discussion of the navigation satellite test bed that is under development at the FAA's Technical Center.

The first part contains proposed accuracy, integrity and availability operational requirements, and their air traffic implications. A stand-alone DGPS concept is developed, and analysed. The major results of the analysis indicate that stand-alone DGPS may not fully meet Category I (CAT I) accuracy requirements. The results of the analysis are then used to provide the rationale for the major recommendation: that FAA pursue an implementation of a wide-area DGPS (WADGPS) to achieve a Near CAT I precision approach capability. The second part of the paper discusses the three-phase navigation satellite experimental programme that is being developed to acquire the data to validate the enhancements to GPS, including a GPS Integrity Channel (GIC) and WADGPS. The objectives of each of the experimental phases are presented and discussed. Then the experiments of Phase I that address GIC/WADGPS are discussed.

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.

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.

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.

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.

Over 20 years ago, collision with high ground was identified as being the single most significant cause of fatalities among air travellers worldwide (Smith, 1968), and some human factors responsible were highlighted. The three factors most commonly found to be present during major civil aviation accidents were: (i) pilot's visual flight in instrument meterological conditions (IMC); (ii) navigational error by the crew and'; (iii) pilot's failure to react correctly to new circumstances resulting from air traffic control (ATC) instructions or advice – sometimes made in a language foreign to that of the aircrew. The latter factor will be tested here to see if it still applies to recent cases in the UK.

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, and the following two papers, were presented at a joint meeting sponsored by the Institute in association with the Honourable Company of Master Mariners and the London Branch of the Nautical Institute. The meeting was held at Trinity House on 20 November 1991. This first paper was read by Captain Houghton.

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.

The weather is rarely out of the news. Weather can be hazardous at times almost anywhere on Earth, and the media are always keen to report dramatic events. On the global scene, weather, climate and the environment are issues of great international public concern at present because of the likely implications of increases of greenhouse gases in the atmosphere. The contributions of the meteorologist to the understanding of this global problem are increasingly recognized, as is the progress which has been made in the accuracy of day-to-day forecasts. This paper provides a brief résumé of our present ability to model and forecast the behaviour of the global atmosphere and the ocean surface, and also demonstrates how these models are applied to the practical problems of operational ship-routeing by the UK Meteorological Office. It is worth remembering that it was the very high incidence of losses at sea in the 1850s which brought about the establishment of the UK's first meteorological service.

British Airways was recently granted permission for its fleet of Boeing 747-400 and 767 aircraft to operate using automatic landing systems in Category IIIB conditions; that is, decision height lower than 50 ft and a runway visual range of less than 200 m. This development might lead some people to think that the weather is no longer a significant factor in aviation operations. However, while these developments are taking place one sees reports such as ‘departure delays are still on the increase’; ‘poor weather slowed airport operations’; ‘BA flight from Singapore delayed by strong winds was five minutes from declaring an emergency’; ‘heavy rain might reduce wing lift when an airliner most needs it’. These reports confirm the realistic state of affairs that the weather, despite the introduction of modern avionics on board the aircraft, and automated instrumentation on the ground assisting aerodrome operations, is still a vital part of aircraft operations decision-making, affecting the safety and efficiency of flying.

(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’.

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.

A research and development programme performed in Sweden over a period of 9 years has created a substantial know-how on the design of satellite navigation user systems. Thus, a basic user system, called the GP & c Total System has been developed and tested over 3 years. This system can serve as a basis for the tailoring of an almost endless number of applications. The system is currently using data from the GPS satellites, but can also be operated with combined GPS/GLONASS receivers. The Swedish GP & c System is an example of how the communication, navigation and surveillance (CNS) concept and the various elements (ADS, ATM, etc.) for a new global Air Navigation System published by the ICAO FANS Committee can be implemented and integrated into a user-friendly operational system. The ICAO 10th Air Navigation Conference (5–20 September 1991) endorsed the FANS concept in which the main elements are based on the implementation of satellite navigation technology.

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.