Ever since the introduction of the Air Almanac and the Astronomical Navigation Tables, requests have been received for information as to the errors that can arise in their use. Estimates of error, for particular combinations, were made on several occasions and, in 1947, the calculation was systematized; but the methods and results were not published. It is now probable that the Sight Reduction Tables for Air Navigation, A.P. 3270 (H.O. 249 in U.S.A.), and possibly the Air Almanac, will increasingly be used for surface navigation and it therefore seems desirable to put on record a precise statement of the errors that can arise through their use. The earlier work has accordingly been modified for the changes in the publications.

This paper gives an account of a study carried out by the Institut Français de Navigation for the Administration de la Marine Marchande. The object of the study was to investigate the possibilities of introducing automation into the navigation of merchant ships. In addition to examining projects already underway in France and other countries, the Institut Français de Navigation sought the cooperation of numerous companies working in the electronics and computer fields and notably the Compagnie Générale d'Automatisme (C.G.A.), Compagnie Européenne d'Automatisme Électronique (C.A.E.) and Compagnie Générale de T.S.F. (C.S.F.).

Only the main features of this study are described here. Professor Hugon is Secretary-General of the French Institute.

However misleading statistics may be, they often make an interesting study and those of marine collisions are no exception. In Volume 13 of this Journal, page 430, some figures were given for collisions in fog with radar, which permitted the conclusion that, in North-west European waters in 1959, each day of fog produced 1·2 collisions. Up to and including 1959 this figure was not rising significantly.

Dr. Ahrens's paper, which was presented in a more extended version at the meeting in Paris, describes a number of ways in which automatic processes may be applied to, or operated from, echo-sounders.

Knowledge of the depth of water is of secondary navigational value to the surface ship since (as compared with the submarine), she has no changes of course to make in the vertical direction. The present state of development of surface navigation systems makes the use of the depth as a method of navigation superfluous in all cases in which sufficient water is available, where there is no danger of grounding. It can, however, when the topography of the sea-bottom is known from accurate charts, be employed for checking and confirming the data determined by other forms of navigation.

We are told by Captain Greenvile Collins that Charles II was ‘A great lover of the noble art of navigation’. I think his brother, James, Duke of York, who became the Lord High Admiral at the happy Restoration in 1660, shared the same enthusiasm. Members of the Royal Society, including distinguished seamen, studied mathematics, mechanics and optics. The time was ripe for improvements to be tried out, under royal patronage, in ship design and construction as well as in the navigation of ships. English methods began to be regarded as not only the best but even as unnecessarily exacting, and we are told that Davis's backstaff was known as the English Quadrant by the French, and the English log and log-line for estimating a ship's speed through the water was better than the simpler methods popular with Spanish, Portuguese and Dutch mariners.

This paper describes selective tests performed in the areas of Gdansk and Gdynia VTS Centres. The main goal of the tests was to determine the accuracy of position, speed and course estimations measured by shore-based radar VTS tracking systems by using measurements of the same parameters available on board a tracked vessel equipped with GPS and GLONASS receivers. Six DGPS/GPS/GLONASS receivers were installed on board a survey vessel, and all of them recorded the vessel's route simultaneously with two different VTS radars – one at Gdansk and one at Gdynia (20 km apart). All DGPS receivers tracked the same reference station. Presented results show that the radar information can be used by VTS operators to provide navigation assistance within certain limits, but these limits must be understood. A more detailed description of the experiment was presented during the IALA Conference in Hamburg in June 1998.

This paper was presented at the Third Electronic Chart Technology Conference, SASMEX International, Brighton, 22–23 April 1998.

Electronic Chart Systems have been used by mariners across the entire user spectrum without official standards or specifications for 10 years. In the last three years, the debate has centred on chart data and the merits of differing cartographic technologies. There is little new that can be said for or against raster or vector technologies except what actual users might say to support the requirements of their day-to-day operations. Today, we approach a new stage as ENCs start to become available but only for limited areas. This in turn means that ENCs are capable of supporting the only approved electronic chart system, ECDIS, in a limited way. There is an urgent need for alternatives to ECDIS to cover those areas where ENCs will continue to be unavailable for the foreseeable future. This paper therefore summarizes a feedback from users of RCDS and ECDIS-type systems to demonstrate the benefits which can be secured from official recognition of RCDS systems as the legal equivalent of paper chart navigation.

Training courses on marine radar simulators are held in this country at the Navigation Schools and Colleges in London, South Shields, Hull, Glasgow, Liverpool and Cardiff, with Southampton starting at some future date. The entry for each five-day course is limited to six members and places on the courses are at present generally restricted to serving masters and chief officers. The purpose of these courses is to give seagoing masters and senior officers realistic practice in manœuvring their vessels by radar in conditions of bad visibility without any of the risk involved in an actual encounter between vessels at sea, as well as risk-free opportunity to try out and test the different methods of radar presentation and plotting.

This paper represents a follow-up of work previously reported at an Ordinary Meeting of the Institute and published in the Journal in May 1986 under the title ‘Navigational Aspects of JTIDS’.

Technical studies on JTIDS for the airborne applications are being directed by the Royal Aircraft Establishment (RAE), Farnborough and by the Admiralty Research Establishment (ARE), Portsdown, for maritime use, for which Systems Designers Scientific is providing technical support in a number of areas. One such field is Relative Navigation (relnav). As part of this MOD-funded work a relnav simulator has been developed at the RAE. This simulator is currently in use for the assessment of the relnav capability and has been used to produce the results presented in following sections.

This report gives a brief description of JTIDS relnav and presents some basic features of relnav performance in simple communities. Then a description of relnav performance in fragmented and loosely coupled communities is presented. Finally a brief summary of the main points and conclusions is given.

When radar is used at sea as an aid to collision avoidance, the necessary information has to be obtained by maintaining a plot, which, however, can only offer the average course and speed over a passed time. It is not a reliable prediction of future actions, so that to make too long an extrapolation from a plot is hazardous. It might in some circumstances be better if a ship could be called up by radio and asked her intentions, though this requires first a knowledge of her identity and call sign.

This paper outlines a system of communication that would make it possible to call a ship (fitted with the necessary receiving equipment) initially located only by range and bearing, to obtain the identity of the ship and establish courses, speed and intended actions, and if necessary, radio call signs and calling frequencies. The messages passed by a ship would be recorded automatically. It is proposed that the system should have an operating range of 15 miles, though this does not represent a limit to the range possible. There are objections perhaps to trying to get out of a mutilateral situation of danger by bilateral agreements, and at least one school of thought would hold that the danger is likely to be increased by relying on communication. Nevertheless the system described here holds considerable interest and might, as the author suggests, serve other purposes at sea.

This paper outlines some of the results being achieved by the UK research programme on civil avionics which is based at RAE Bedford. Acknowledgments are therefore due to members of the civil avionics team and UK industry from whose work these examples are drawn, and not least to the Department of Trade and Industry who fund the programme.

No attempt is made to define ‘flight management systems’. The concept, originating in the complex outer loops of autopilots, has now come to include all the detail involved in managing the flight deck systems as well as planning and controlling the aircraft's progress from ramp to ramp. As this paper will hope to demonstrate, the concept is still growing.

The history of mechanical transport has been one of increasing speeds and there seems to be little doubt that air transport will follow this pattern. To the passenger, increased speeds mean a saving of time, and time is money. To the operator, increased speeds mean more flights per week and therefore greater earning capacity for his aircraft. This year indeed has been marked by the appearance of the four-jet air liner, the forerunner of the four hundred knot air transport.

Traditional receivers for the low-frequency, hyperbolic radio-navigation systems – Loran-C, Decca Navigator and Omega – are expensive and are operated manually. They either display position fixes in hyperbolic coordinates for plotting by hand on navigation charts printed with hyperbolic overlays or they plot tracks automatically, often on distorted charts. Recently, low-cost receivers have been developed for marine navigation which operate wholly or largely automatically and which display position measurements in geographical coordinates – latitude and longitude – or as headings and distances to waypoints which are entered by the navigator in geographical coordinates.

The use of hand-held pocket calculators for navigation was discussed at an open meeting of the Technical Committee held in London on 7 May 1975 with the President; G. E. Beck, in the Chair. A number of those who took part in the discussion have prepared written contributions which are printed below with the account of the meeting.

W. D. Rushworth (Directorate of Overseas Surveys, Ministry of Overseas Development): Land surveyors, unlike navigators, do not have to do instant calculations but before we leave an area we have to carry out sufficient computations to ensure there are no blunders in the observations. Overseas in developing countries this usually means a computing session in camp every evening and until a couple of years ago this was a ponderous business, using hand cranked calculators and massive books of eight figure trig. tables. For the surveyor moving on foot these items were often a real burden so that the advent of battery-operated electronic calculators was a godsend, especially once we got calculators with pushbutton trig. functions.

This paper describes a number of proposals concerning the correction of the errors of magnetic compasses. The first proposal concerns the correction, by means of special soft iron correctors, of the deviating effects of both vertically and horizontally induced magnetization.

A scheme for removing constant error without having to use algebraic addition or even having to record the existing deviations is next described.

A scheme is then suggested whereby, provided no constant deviation is present, a compass may be corrected for the effects of permanent magnetism in four operations, each of which consists of the complete removal of deviation on a particular heading by a particular corrector.

Possibilities of putting compasses below decks without seriously affecting their performance are also discussed; these particular suggestions cannot apply to merchant ships in which magnetic cargo is being transported. Suggestions are also made of correcting the compass by modifying the disposition of the magnetic material in the bridge structure instead of by adding a corrector to the compass binnacle.

Finally, a scheme is introduced to maintain an aeroplane compass mounting parallel to the surface of the Earth during a level turn by using the centrifugal force due to the turn.

This paper puts forward five separate suggestions concerned with the correction and siting of magnetic compasses. The suggestions are unrelated to each other except in the fact that they have all resulted from viewing the problems from a deliberately unconventional standpoint. Some of the solutions proposed may be of interest to those concerned with magnetic compasses in ships, aircraft and vehicles.

Although the economic theory of congestion as applied to road traffic has been known since at least the time of Pigou its application to marine problems has been much slower. It is the purpose of this paper to remedy this somewhat by interpreting the theory in a marine context and to suggest some of the practical implications of taking proper account of congestion effects.

As sea traffic grows, so too does the problem of the acoustic pollution of fishing grounds. This paper describes the measurement and analysis of ship-produced underwater sounds and their effect on the behaviour of certain fishes. It would seem that their influence on marine organisms is a growing problem and should not be ignored by navigators, for the sounds produced by large or high-speed vessels, or even fishing boats, can frighten fish shoals or cause them to change their migration routes.

After a series of tests to measure and analyse the underwater sound, the output of submerged loud-speakers, either at sea or in an aquarium, was adjusted to ensure that the sound intensity near the fish was at the required level and the fish behaviour was carefully observed. For these experiments a hydrophone was connected to a pre-amplifier. A signal amplified by the pre-amplifier is attenuated before being sent to the main amplifier, the sound level being read directly on an indicator using the sound analysing character ‘C’. A tape recorder registers the sound signal in a flat response from 20 to 50 Hz to within 3 dB. A tracing recorder was also sometimes used and the two methods gave almost the same results.

The usual method of using radar for navigation at sea is to transfer the information from the PPI to the chart. In many instances, however, the pilot will con the ship directly from the PPI, using his local knowledge, which is equivalent to using a chart impressed on his mind. In such cases it is necessary to identify immediately and unambiguously the PPI paints, which often bear little resemblance to the shape on the chart of the feature which is producing the echo.