This paper, which was presented at a seminar sponsored jointly by the Institute with the Nautical Institute in London on 9 December 1982, seeks to identify the environmental and political pressures behind the international and regional efforts to regulate the safety of shipping in European waters. It examines the role of Port State control and vessel traffic management in safety and the prevention of pollution.

This paper describes the process of developing a safe access route to the Hook of Holland. The traffic situation in the Roads was tested by means of simulation. Van Riet, Pollen and Valstar are with the Directorate General of Shipping and Maritime Affairs in the Netherlands, Tresfon with the Maritime Research Institute in the Netherlands.

Since its inception in 1972 progress of the Channel Navigation Information Service (CNIS) has twice been described in the Journal. The tenth anniversary of the first broadcast bulletin of information occurred on 31 July 1982, and it is perhaps appropriate to review and bring up to date the major milestones in the history of the Service and to review the safety of navigation in the Dover Strait.

It will be recalled that, following the multiple collision off the Varne in 1971 and bearing in mind previous major disasters – Torrey Canyon, Pacific Glory, etc. – the Department of Trade concluded that a voluntary Traffic Separation Scheme (TSS), without surveillance and without a coordinating information service, was inadequate for the dense and complex maritime traffic problems of the Dover Strait. Thus was born the Dover Strait Information Service, now CNIS, under the aegis of HM Coastguard, and located on the upper floor of an old Port War Signal Station at Leathercote Point, St Margaret's Bay. The Decca Marine Radar Company installed a simple harbour radar and its associated display towards the end of 1971 and Coastguard evolved the essential elements of what remains to this day a half-hourly bulletin, broadcast on vhf/rt Channel 10. In low visibility intermediate broadcasts are given, based on actual visibilities reported from sea.

In August 1973 the French authorities installed a similar system at Cap Gris Nez and a very close co-ordination, vital from the mariner's point of view, developed.

The feasibility of utilizing psychometric tests to investigate accident liability at sea has previously been reported. Analyses of four psychometric tests and ship handling measures, using the statistical techniques of factor analysis and discriminant analysis, investigate the relationship between safety margins and accident liability and support and expand upon earlier conclusions. Evidence is also provided on the validity of a perception-of-risk test for navigators.

This paper reviews the measures commonly used in experiments to evaluate collision avoidance systems. The use of Closest Point of Approach, Time to Closest Point of Approach, and Manoeuvre Magnitude was criticized particularly for multi-ship encounters. However, the data do suggest that two measures, Entropy and the use of experienced judges to give rank scores of performance, seem to be good measures even in multi-ship encounters. The use of a composite measure is not experimentally evaluated in this paper, but it is suggested that if one were used, it would have to be very complicated. Mr Cook is with the Department of Applied Psychology at UWIST, Dr Crawshaw in the Department of Psychology at the University of Hull.

In spite of, or perhaps because of, the almost universal use of some ftym of electronic calculator for the reduction of astronomical sights, there is a growing demand for a simple back-up method for emergency use when a calculator is not available. Presumably the need arises because of the disinclination to carry the material for a standard method in order to provide cover for the small chance of calculator failure. It is a surprising development, enhancing the continued interest in, and use of, astronomical navigation in a field increasingly dominated by instant and continuous position-fixing systems of high precision and universal applicability.

Similar considerations may apply to the ephemeris data, which are being increasingly generated by calculator or computer. However, to a precision adequate for emergency use, near-permanent data for the Sun and stars can be given in a few pages in tables similar to those for G.H. A. Aries (Vol. I) and the Sun (Vols. 2 and 3) in Table 4 of AP 3270 Sight Reduction Tablesfor Air Navigation. In fact the simplest conceptual solution might well be to carry the appropriate latitude pages extracted from the loose-leaf US edition, HO 249.

In 1948 I had occasion to review the existing tables for the reduction of astronomical sights (this Journal, Vol. 1, p. 298, 1948); the review was limited to intercept methods and, mainly, to those based on the use of the DR position.

The two papers which follow, by the late Captain (and Dr) Charles Cotter, are the last of a number of papers he submitted for publication in the Journal, and which have appeared from time to time. Now that he is no longer with us it seems appropriate that they should be published simultaneously.

Sailing Directions nowadays implies ‘Pilots’, with which all mariners are familiar. However, the term in a broader sense embraces a wide range of printed and descriptive material of help to the seaman. In his paper, which was presented at a meeting of the Solent Branch of the Institute in December 1979, Dr Cotter traces the origins of the publications – pilot books, light lists, tide tables, and indeed charts – which are now available to the navigator. The paper has been abridged.

In this paper we investigate the applicability of a second-order differential equation in the physics of mechanical vibration as a model for aircraft lateral position errors obtained from the VOR environment. Navigational interpretations of the parameters in the model are constructed analagous to a vibrating mechanical system. One interesting observation is noted and used to narrow down the potential range of a key parameter. Solutions to the second-order differential equation are described, and the properties and phenomena implied by the model are explained. In extending the theoretical reasoning, we discover phenomena that are embedded in the aggregated data. We also find ways to explain the most salient features of VOR position errors based on the suggested model. Steps required for future empirical confirmation, clarification, and calibration of parameter values are sketched. This paper is only intended as a starting point of a further systematic construction of theory and models useful for the design, evaluation, and regulation of VOR navigation systems.

The standard height rules applied in off-route airspace are examined to assess the degree of intrinsic safety they provide, i.e. the reduction of conflicts without action being taken by pilots or ATC. The yardstick used is the conflict rate which would obtain if the aircraft were uniformly randomly distributed in the height dimension and flying straight and level on uniformly randomly distributed tracks. It is shown that the application of the standard rules can lead to a reduction in intrinsic safety unless significant height-keeping errors are present. An alternative height rule apparently having more desirable characteristics is examined on the same basis.

Among the major problems encountered in the control of air traffic are those concerned with conflict prediction and resolution. An interesting method by which many of the associated difficulties could probably be overcome would be by employment of a suitable type of computer-controlled Airborne Traffic Situation Display (ATSD). This would operate in a manner similar to that described for the Fully Automated Pilot-Monitored ATC, utilizing information derived from an ATC Centre via ground/air data link.

In addition to the ATSD and the associated digital computer the airborne equipment required for this system includes an electronic data display (EDD) and a bulk storage unit for enabling flight plan and map data to be set up on the relevant display. The ground-based ATC subsystem could automatically provide the pilot with information concerning other air traffic in the vicinity, warning him of any potential conflict situations and advising him of an appropriate evasion manoeuvre. The air traffic data could automatically up-date the back-up information for both the ATSD and the EDD, whilst details of any proposed collision-avoidance manoeuvre could appear on the EDD. The pilot would be able to employ his airborne computing and ATSD system for monitoring the situation. He should therefore be able to confirm the likelihood of a collision, to check the time available before a potential impact and to determine the most suitable manoeuvre for collision avoidance. This manoeuvre will generally agree with that selected by the ground system.

The squadrons of the Army Air Corps are intended for deployment with ground troops in the forward battle zone in roles which include reconnaisance, observation, fire direction and, to a limited extent, the movement of men and material. These roles indicate the nature of the navigational requirement.

Conventional survey methods for position and azimuth as practised in the Royal Artillery, although sufficiently accurate, were slow and expensive in manpower, while vehicle-navigation systems based on distance measurement by odometer and directional gyros were not sufficiently accurate. In the early 1970s therefore a General Staff Requirement was issued for an equipment designated PADS (Position and Azimuth Determining System) which would provide the necessary combination of speed and accuracy for gun batteries and observation posts, which may have to move frequently, by day or by night, in poor visibility. Precise knowledge of battery and target location, together with an azimuth reference, can help to achieve the first-salvo hit capability that is essential, not only from the point of view of surprise, but also to reduce risk of detection by shell-locating radar.

Recent articles by R. Williams and others have indicated an interest in ‘loxodromic distances’, and have described methods of calculation on the spheroidal Earth. However, these methods are not directly suitable for simple hand-held calculators. The following, approximate, methods are therefore suggested.

In 1835 Gustave-Gaspard Coriolis proved that, if a ‘body’ travelling unaccelerated at a speed v is made to conform to a medium rotating at a rate w, it will be accelerated sideways at vw. Hence air travelling freely, if subjected to the rotation of the Earth's surface, will be accelerated at – 2vω sin ø, –ω sin ø being the rate at which the local surface rotates, with –ω the speed at which the Earth spins and ø the local latitude. (In the diagrams ω is presented as Ω).

2. Coriolis also proved the converse formula from which, if air travels freely over the surface of the Earth, it will accelerate at + 2ω sin ø relative to the local rotating surface. This reversed Coriolis formula happens to be far more important than the original direct formula. It has been applied to long-range artillery, to aircraft using spirit-level sextants, to inertial navigation systems and to the ground tracking of space craft. It has also been applied to forecasting wind speeds.

3. We can handle the duality of Coriolis by a loop diagram as in Fig. 1. The central link shows the direct Coriolis acceleration produced when air travelling freely is forced to conform to the rotating surface of the Earth, The link to the left depicts the reversed Coriolis acceleration which applies to air travelling freely as seen from the local surface of the rotating Earth.

Two main concepts in mathematical modelling of ship encounters have been proposed by Davis. The first, the ‘domain’, was an adaptation of a concept originally introduced by Goodwin, who defined the domain as the ‘area about own-ship that a navigator wished to keep free with respect to ships and other stationary objects’. The second, the ‘arena’, conceived by Davis, is the area around the domain which when infringed causes the mariner to consider whether to make a collision-avoidance manoeuvre. Thus, in a computer model, when a vessel enters the arena the computer analyses the situation and, depending on the severity of the threat, makes a collision-avoidance manoeuvre.

Goodwin's domain was divided into three sectors corresponding to the ‘giveway’, the ‘stand-on’ and the ‘overtaking’ regions as defined by the relative velocity of approach. The domain was derived from radar films of ship tracks and records of radar simulator experiments. Davis smoothed the sectored domain to a circle with own-ship off-centred astern and to port, and the weighting of each of the sectors retained. Davis's domain had a solid theoretical grounding; the arena, however, was simply a larger version of the smoothed domain. Its size and position were obtained by means of a well-distributed questionnaire. It served its purpose in the model, but lacked any real validation.

One problem with the Davis arena was its inability automatically to take into account different velocities, both of own-ship and of targets.

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.