The fact that the de Havilland Comet cruises at nearly double the flying speed and nearly double the flight altitude of comparable piston-engined airliners is a measure of the great leap forward in air transport which the introduction of gas-turbine engines has brought about. It also illustrates an inherent feature of jet aircraft, for only at high speed and high altitude do turbo-jet engines, and to a less critical extent turbo-prop engines, operate at their maximum efficiency, expressed in distance flown per gallon of fuel consumed. With reduction of altitude and speed, however, the fuel consumption does not fall off proportionately and efficiency decreases rapidly. For example, even when taxying on the ground the Comet's fuel consumption is about 70 per cent of that at cruising altitude, and when flying at sea level the still-air distance flown on a given quantity of fuel is less than half of that at cruising altitude. In other words you get the best out of a jet aircraft when you are going somewhere fast, and when the length of the flight is sufficient for the aircraft to climb to its optimum cruising altitude and remain there for a considerable proportion of the flight time.

Anchor work is generally considered to be a question of seamanship rather than navigation; Commander Sharpey-Schafer's paper, which deals with a number of subjects only indirectly allied to navigation, is, however, presented here because what he has written will be of interest to so many navigators.

Even today much time is lost in bringing effective help when an accident with a truck carrying dangerous goods occurs. The location of the accident is often not well described by the people reporting it. Often it is difficult to determine what sort of freight a lorry is carrying, for example when the vehicle is burning, and sometimes the fire brigade does not bring the appropriate extinguishing equipment for the first help approach. Now an emergency location system is under development which will remove all these disadvantages. For immediate help on car accidents, an automatic alert message is transferred from the crashed vehicle via the emergency call centre to the fire brigade, the police station or the headquarters of an ambulance. The alert is initiated by a crash sensor within the car or the truck. The data channel between vehicle and base can be a radio link or, for longer distances, a mobile telephone connection using CNET or GSM. AS help is faster and more effective with this system, environmental damage caused by dangerous goods can be reduced.

In Stuttgart the mobile part of the DGPS-based emergency location system has been integrated in several vehicles. The full system is being tested within a field trial of a pilot project called STORM (Stuttgart Transport Operation by Regional Management), which is part of a programme of the European Community. The results of these tests are summarized in this paper. The integration of the system into fleet management applications is also considered.

A method of measuring wind variations along an aircraft glide path is described. The technique uses a ground-based pulsed doppler radar to measure the line of sight velocity of precipitation particles. At low angles of elevation this velocity is that of die horizontal wind component toward the radar.

Wind variations likely to be encountered by an aircraft as it lands or takes off from an airfield are estimated almost invariably from a nearby anemometer placed 10 m. above the ground. It is obvious that this wind is not fully representative of conditions at higher levels; however, winds other than near the ground are difficult to measure. This note describes a method of measuring the line of sight wind using a pulsed doppler radar and presents some observations of the wind variation along a path at an elevation of 3°, which is typical of the glide path of many aircraft. These winds are compared with those recorded by a nearby anemometer.

The advantages of a standardized avoidance manoeuvre as distinct from a late collision avoidance manoeuvre are discussed with reference to passenger comfort. The general use of plan type displays suggests the possibility of having a standard manoeuvre based upon turning one aircraft on to a new heading.

An analysis of this manœuvre was undertaken in order to obtain data as to the closest permissible approach between pairs of aircraft on various collision courses. Results show that the permissible closure is smallest if the faster of the two aircraft is manœuvred, and that little is gained by changing the heading by more than 30°. The results of this type of analysis can assist also in the programming of the computer in a future automated A.T.C. system.

The work of the Greenwich Observatory throughout the three centuries of its existence has been characterized by the painstaking efforts of its eminent directors to attain an ever-increasing degree of precision in pinpointing the positions of the heavenly bodies, with a view to the improvement of the science of navigation. The pursuit of this purpose, in accordance with the express desire of its founder King Charles II, has been assisted by the steady improvement in the accuracy of the instruments with which it has been equipped, and these have naturally also been applied to investigating problems of a purely theoretical nature. Nevertheless, the tradition pioneered by the first Astronomical Observator (or Astronomer Royal) John Flamsteed (1646–1719) whom the King in 1675 charged with rectifying the coordinates and motions of the heavenly bodies, has remained predominantly practical and utilitarian.

Britain is often thought of as a maritime nation. The history books certainly support this thesis with their chronicles of explorations for trade routes, of the development of overseas commerce, which became rather absentmindedly an empire, of the growth of a navy to defend these interests. As an island race which aspired to global enterprise, maritime affairs have never been far from central policy considerations as our livelihood began to depend increasingly on overseas trade routes for food, raw materials and export markets. And along the way we developed merchant and fighting marines that were supreme in their day. From this global perspective we have been and will, probably, always be a maritime nation.

Captain Emden of H.M. Coastguard's Dover Strait Operations Centre discusses the problems encountered in setting up the experimental Dover Strait Surveillance Scheme and inaugurating the Information Service. The paper, which was presented at a meeting of the Institute in London on 20 November 1974 with the President, G. E. Beck, in the Chair, describes the service today, the results so far achieved and what it hopes to do in the future. A note on the results of surveillance operation between April 1973 and December 1974 will be found at page 244 of this Journal.

The possibility of reducing the current vertical separation minima in order to increase traffic capacity on economical flight levels has been discussed mainly at the RGCSP (Review of the General Concept of Separation Panel) meetings of ICAO. A collision risk model based on the mathematical model developed by Reich (1966) has been adopted for evaluation of safety of air traffic systems under consideration. This collision risk approach requires several parameters which should be estimated from empirical data on navigational errors, traffic dynamics, etc.

The principal purposes of this introductory paper are to identify and describe the main aspects of marine traffic engineering, and to suggest ways in which traffic engineering principles and methods developed for land and air transport systems may be applied to marine problems. Traffic engineering is a relatively new branch of engineering science, but it was quickly and widely recognized as essential in ensuring that all forms of land and air transport operate safely and efficiently. However, although sea transport is a long established activity, it is only during the past few years that marine traffic engineering has begun to emerge as a separate aspect of this broader scientific discipline.

These two notes are the first of a series which will suggest to mariners the causes of collision at sea when radar is in use, by showing against each apparent cause an accumulation of court evidence and judgment, by isolating certain kinds of action which seem to have led to collision but have not been so regarded in every judgment and by examining certain judgments against a technically informed background.

In the articles which follow, a particular judgment is examined in the light of a more precise study of true motion as a direct source of intelligence at slow speeds, of plotting when courses and speeds are changing and of the suggestion that the Crossing Rules may be applied in fog after ‘ascertainment’.

Every collision situation implies the existence of a sector within which any course steered will lead to a dangerously close approach and a sector within which the danger of collision will be avoided. The definition of these sectors may be said to constitute the structural aspect of the collision problem. The appropriate manœuvre in a given situation constitutes the operational aspect. The structural aspect is fundamental to the problem itself, the operational aspect offers possible solutions. The Steering and Sailing Rules involve the structural aspect because this is the only basis for legal rules.

In proposing a Sector Rule for use with radar in conditions of bad visibility, it is intended to establish a structural basis for legislation. In its most general terms, the Sector Rule is based on the principle that if the radar echo of another ship is always at an angle to one's own course determined by the speeds of the two vessels, their distance apart and the safe passing distance, then one's course lies within the safe sector for collision avoidance.

Many nations are debating the implementation of vessel traffic services (VTS) and it is envisaged that some regulation of the movement of marine traffic may soon be imposed. It is highly desirable that prior to any change a rigorous appraisal of the existing traffic be carried out to establish the level of risk in the area; this level can then be used to evaluate any proposed change. The following note describes a research project concerned with establishing a general method of determining the base risk level, developed from earlier research by M. Degré and M. Lefèvre who used a computer simulation of marine traffic in the Dover Strait to assess the impact of various suggested traffic separation schemes. A cost-effective tool has been developed at Liverpool which will enable traffic patterns to be studied in areas remote from the land. This is a computer simulation model which is being used to establish dynamic areas of risk in the Irish Sea, which could easily be transposed to study traffic patterns in any other area.

This paper presents a description of a general method for the evaluation of marine collision risk. The approach differs considerably from existing methods in this area, in that it combines analytical modelling in a special way to analyse historical data. The method makes it possible to find the collision probability of a specific ship in any particular location, taking into account such location factors as area geometry, ship movements and speeds. It also constitutes a basis for worldwide data collection.

In view of the growth of marine traffic and the increase in the transportation of hazardous materials over the past two decades, considerable efforts are being made towards the development of maritime risk evaluation methods, the main objective being the quantification of ship collision probability. The methods developed to date can roughly be subdivided into the following two groups: (a) kinematic models (see for instance refs. 1–6); (b) historical data analysis (see for instance refs. 7–17). It is a well-established fact that most collisions are due to human failures, and it is widely accepted that human behaviour cannot be described well by mathematical formulae. Kinematic models are therefore not recognized as suitable for estimating this probability. Historical data analysis estimates the collision probability as the ratio of the number of observed collisions to the number of ship movements. Probabilities estimated in this way are only correct in a probabilistic sense when the assumption is satisfied that every ship movement has the same probability of collision. This assumption is rarely fulfilled since most ships often pass each other without collision danger. In addition, this approach is often hampered by lack of data for a specific traffic area, while the application of worldwide data cannot be considered realistic. As far as we know, there does not exist a method which can transfer, in a statistically justifiable manner, marine traffic data from one area to another. Moreover, neither of the above-mentioned approaches is appropriate to analyse alternative routes in the same area, or under changing circumstances.

The Navstar Global Positioning System (GPS) is a satellite-based passive radio-navigation system under development by the US Department of Defense (DOD) and due for operational deployment in the late 1980s. Each satellite carries an atomic frequency standard and transmits L-band spread-spectrum signals whose carrier frequencies and code epochs are synchronized with the satellite clocks. A suitably equipped user may measure the arrival time and frequency of the signals from at least four satellites to obtain accurate three-dimensional position and velocity information and, as a by-product, an accurate ‘system’ time.

Although the use of bisectors to select the most probable position determined from astronomical observations is well known, the system seems to have received insufficient recognition in current navigational literature. In what follows an attempt is made to assess the problem practically.

Since 1975 the Royal Netherlands Naval College has operated a bridge manoeuvring simulator for the training of naval officers and petty officers of the deck department. There is a strong relationship between training objectives and performance abilities of a simulator and the way the two match defines the cost effectiveness and the value of simulator training. The training objective being the result aimed at (for a professional watchkeeper) consists partially of a combination of training subjects (things to be learned at the simulator). During 1980 and 1981 R.Nl.N.C. conducted a survey on simulator training subjects by means of an inquiry amongst Royal Netherland's Navy and Merchant Navy officers, marine lecturers (all of Dutch origin) and members of the International Marine Simulator Forum (IMSF). The results form the subject of this note.

Throughout the history of marine navigation it has been recognized by seamen that soundings of the sea bed are a most natural and valuable aid to safe passages. Yet it is probably true to say that the methods of obtaining such soundings and for recording and using the information so obtained remained relatively primitive for longer than any of the other arts or systems used by seamen.

Records can be found which indicate that the earliest navigators used poles or lines and plummets to measure the depths of water on the coasts and in the rivers. An example of the use of soundings by Phoenician seamen is recorded by Strabo, who relates that the captain of a Phoenician ship on a voyage to the Casseterides for tin thought himself too closely followed by a Roman ship and deliberately sought a shoal which he knew of on which to run his vessel to avoid capture and the loss of his precious secrets. Then Hanno, the famous Carthaginian admiral of about 500 B.C., at his furthest point south on the West Coast of Africa, outlined the contours of the River Niger, and the Greek admiral Nearchus at the same time made his voyage from the Indus to the Euphrates by soundings in the rivers and on the coast.