The annual total losses of trading ships as a result of collision and wreck were considered in a previous paper for the purposes of comparing the safety records of different flag groups. Losses up to the year 1979 were included in the tables. In order to assess whether there has been an improvement, the losses for the 5-year period 1980–4 will now be considered and compared with losses in previous years.

Australia, with its large continental shelf, requires faster and more economic methods of conducting hydrographic survey. Backed by the Royal Australian Navy an experimental programme to investigate airborne laser methods was commenced in the mid 1970s and completed in 1984. This programme demonstrated that airborne laser depth sounding can be used effectively in Australian coastal waters. This paper reviews the achievements of the experimental programme and describes some features of LADS, a ‘Laser Airborne Depth Sounder’ planned for operational use by the RAN Hydrographic Service. The paper was presented at the Congress of the International Association of Institutes of Navigation, Tokyo, 1–5 October 1985.

1. INTRODUCTION. This paper describes the results of a survey carried out to investigate the views and practices of mariners when navigating in the vicinity of offshore installations in the North Sea.

The orbits of navigation satellites have to be determined very precisely. The Transit broadcast (predicted) ephemeris, which is computed by the US Navy Astronautics Group, has an estimated orbital positional accuracy of the order of 25 m in each direction. By contrast, the precise (post-mission) ephemeris, which is determined by the US Defense Mapping Agency, from tracking data collected by the global TRANET network, reaches accuracies of the order of 10 m. These orbital precisions affect the navigation and (static) positioning accuracies which can be achieved by users of the system. The same is true of the GPS system which will become fully operational some time during 1988—89. However, unlike Transit, GPS will allow quasi-instantaneous absolute positioning (i.e. real-time navigation) as well as very high relative positioning accuracies. The latter will be obtained by using special operational and processing techniques (e.g. ‘differential GPS’ and ‘GPS interferometry’).

In a previous paper the writer considered the problems of establishing latitude at sea in the sixteenth century and in part based his conclusions on the results of experiments made with modern replicas of the quadrant, the mariner's astrolabe and in particular the cross-staff, these being the instruments in use at the time. Reference was made to the backstaff or Davis quadrant which, though first described by John Davis in its simplest form in 1595 was not in effective use in its final version until well into the seventeenth century. It remained, together with the cross-staff, the principal altitude-measuring instrument in use at sea until the introduction of instruments of reflection in the eighteenth century and indeed continued in use long after that time, no doubt because it was cheaper than the new instruments, but perhaps also in part because of the ingrained conservatism of seafarers. The name ‘backstaff’ can be used generically to refer to all those instruments with which the observer turns his back on the Sun (e.g. the Gunter's bow), but they all post-dated and derived in concept from the Davis quadrant, which remained the most common in England and elsewhere. (The French knew it as le quartier anglais.) It is in this sense that the term is used here.

Whereas the proper object of all commercial transportation is profit-making, the navigational objectives of taxis and of airliners differ remarkably. In airlines navigation only affects product quality and operating costs but in taxis the revenue (the fare on the meter) is a function of the navigation. Regularity of service is meaningless to taxis whereas regularity of schedule keeping is an imperative of airline navigation because it is only possible to offer air fares a full order lower than taxi fares on aeroplanes costing up to $200,000 a seat by achieving high equipment utilization. Many taxi drivers hire their cabs at a weekly rate which includes maintenance and repair but not fuel. They therefore have a direct interest in the cost of fuel but not in wear and tear of machinery. Finally, taxi drivers are self-employed businessman whose income depends entirely on their navigational skills.

This paper attempts to explain the development of a method to quantify navigational risk within European waters as a part of the COST 301 project. The objective of this project, partly funded by the EEC and partly by the member countries and a few other European countries, is to increase marine safety and to prevent pollution in European (coastal) waters by shore based aids to navigations. The methodology of this study is explained. The analysis of the collected data regarding traffic and casualties is given. The probability of a collision and a stranding is determined.

The authors are all members of working group 2 of COST 301. Ir. Glansdorp and Captain Tresfon are from the Netherlands Maritime Research Institute, Dr Goodwin is Head of the Mathematics Department at the Polytechnic of North London and Professor Kemp is former Head of the School of Navigation at the City of London Polytechnic.

Positioning by navigation satellites is carried out in three-dimensional geocentric cartesian coordinates, X, Y, Z. This applies to both the Transit System, which has now been in operation for over 20 years, and the Global Positioning System which is being tested and is due to become operational in 1988. Traditionally, the cartographer, the seafaring navigator and the geodetic surveyor have always expressed their coordinates in geographical terms, i.e. latitude and longtitude, whereas the land-based civil engineer, surveyor and the foot (or mechanized) soldier preferred theirs in terms of projection grid coordinates, i.e. northings and eastings. Transformations between these various coordinate systems involve not only complex algebraical formulae, but also some very specific numerical parameters, which are appropriate for different countries and continents and which can only be determined empirically. Moreover, the treatment and interpretation of the different systems of coordinates may frequently involve some very basic conceptual misunderstandings. These include confusing astronomical latitudes and longitudes with their geodetic counterparts, treating projection northings and eastings as if they were ordinary plane coordinates and, in the case of positions derived from observations to Transit satellites, applying the wrong set of transformation parameters or using inappropriate geoidal contour maps. These are typical examples of the sort of common misconceptions leading to gross errors and affecting even the most precisely determined absolute positions. Relative positioning, with respect to another point or a framework of points with known coordinates, eliminates some of the worst effects of these systematic sources of error, and is commonly used in geodetic surveying. However, instantaneous navigation (especially by using satellites) is most likely to be based on continuously determined, successive absolute positions and will therefore inevitably be affected by reference system errors. This is particularly important in the case of land navigation where much higher accuracies will be expected. This is a review paper with definitions and descriptions of the various types of coordinate systems and their mutual relationships. Geographical and geodetic coordinates are discussed in section 2, and projection grid coordinates in section 3. This is followed, in section 5, by a description of three-dimensional cartesian coordinates used in conjunction with navigation satellites. A brief discussion on current and proposed navigation satellite systems is given in section 6 and the paper is concluded in section 7.

Inertial navigation systems represent the ideal in automatic navigation. They operate entirely without external assistance, other than information as to their starting conditions, which makes them of great interest to both military and civil operators.

1. INTRODUCTION. At the 30th Session of the International Maritime Organization (IMO) Sub-committee on Safety of Navigation, held in July 1985, agreement was reached on some further amendments to the International Regulations for Preventing Collisions at Sea, including some amendments to the rule relating to navigation in or near traffic-separation schemes (Rule 10). These amendments will subsequently have to be approved by the Maritime Safety Committee and finally, in November 1987, by the IMO Assembly. Provided there are no objections to the proposals the amendments are likely to come into force in 1989.

1. INTRODUCTION. The North Atlantic air traffic system is the busiest and most important long-range system in operation today with a current total of 127 000 flights“annum. The combined effects of the total flight time and the difference in time zones on either side of the Atlantic makes it desirable for most passengers to fly westward in the day-time. Conversely, it is most convenient (or least inconvenient!) to fly eastbound during the hours of darkness. Thus the Atlantic traffic system is strongly tidal with the flow predominantly (though not entirely) westbound during the day and eastbound overnight. Currently the central core of the traffic in the busiest hours is organised into a parallel track structure – the Organized Track Structure (OTS), though nearly half the aircraft operate so-called random routes clear of the OTS.

Mathematical collision risk models, e.g. the Reich (1966) model, may be useful for evaluating the safety of air traffic control systems. The model requires parameters associated with the navigational errors of aircraft. Among navigational errors the distribution of height-keeping errors (HKE) is of great interest for evaluating the feasibility of reducing the current 2000 ft vertical separation standard above flight level 290 (29000 ft). The distribution is closely related to the probability of vertical overlap which is a key parameter of the collision risk model.

Magnetic sensors have been used in navigation for many centuries. During this time the effects of magnetic interference from ferromagnetic materials used in vehicle construction have become an increasing problem, and correction techniques have evolved progressively to allow the continued use of magnetic heading detection. The advent of the microprocessor has made it possible to take a fresh look at the problems of compass operation in vehicles and to devise more accurate processes for the correction of the indicated heading. The compass system described in this paper uses a mathematical representation of the magnetic environment based on fundamental physical principles to supply accurate heading information even in the most magnetically hostile land vehicles.

Large numbers of land vehicles, ranging from complex and expensive military vehicles to private cars, are fitted with, or are considering fitting, navigation systems from the range of systems available. Common requirements for all applications are that the navigation system should contribute to increased operational performance and, at the same time, reduce the crew's workload. A most important element of the system is the operator's display.

It is generally acknowledged that the present terrestrial radio-navigation facilities are in need of updating. Furthermore, satellite navigation offers great potential benefits to all classes of user. One of the factors to be taken into account is cost, and with this in mind it would be useful to establish how much the present spectrum of terrestrial radio-navigation aids itself is costing and what it provides for the money. This is a difficult task which has been attempted before. Each attempt makes a dent in the armour of impenetrability that is inherent in the problem. This paper adopts a fresh approach which it is hoped may make a dent slightly greater than some of the others.

The aircraft referred to in the title are the Airbus Industrie A 310, the Boeing 767 and the Boeing 757. The paper has been written in conjunction with representatives from British Caledonian Airways, Britannia Airways and British Airways, airlines which are currently operating these aircraft. I am indebted to the following for their contributions: Captain Stuart Grieve (Chief Pilot, Britannia Airways), Captain Chris Norman (Britannia Airways), Captain Brian Myers, (Chief Training Captain A 310, British Caledonian Airways), Bill Grice (Chief Development Engineer Avionics, British Airways), Captain Rod Fulton (Flight Training Manager 757, British Airways) and Captain Paul Woodburn (Flight Manager Technical 757, British Airways).