In traditional satellite navigation receivers, the parameters of tracking loop such as loop bandwidth and integration time are usually set in the design of the receivers according to different scenarios. The signal tracking performance is limited in traditional receivers. In addition, when the tracking ability of weak signals is improved by extending the integration time, negative effect of residual frequency error becomes more and more serious with extension of the integration time. To solve these problems, this paper presents out research on receiver tracking algorithms and proposes an optimised tracking algorithm with inertial information. The receiver loop filter is designed based on Kalman filter, reducing the phase jitter caused by thermal noise in the weak signal environment and improving the signal tracking sensitivity. To confirm the feasibility of the proposed algorithm, simulation tests are conducted.

Although the Astrograph has never been formally described in print, the basic principles of the instrument are sufficiently well known to require no further elaboration; so also are its limitations. Over many years, numerous proposals (but mainly unpublished) have been made for the extension of the Astrograph to cater for the Sun, Moon, and planets, as well as for a larger number of stars, but none have been really satisfactory. Without such improvements the Astrograph must have a very limited use, and accordingly a further study was made some time ago of its application to the Sun, Moon, and planets. Methods were developed on familiar lines for shifting (and rotating) the star curves for a standard declination to cater for neighbouring declinations, but these introduced complexities that were clearly unacceptable.

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.

Time and space scales are compared for selected speeds of ships in the North Atlantic and North Pacific oceans. Viability of westbound passages on some northern great circle routes is discussed.

There would be no problem in precisely weather routing a vessel across an ocean if it were possible to forecast with total accuracy the actual sea state existing for the duration of a voyage. All mariners are well aware that such an ideal circumstance is not as yet possible. Depending upon the general synoptic situation existing for the period, it is fair to make the assumption that the actual accuracy of a weather forecast deteriorates as time progresses.

The objects of the International Geophysical Year have been fully described in the Journal. The idea itself was first conceived in 1950 at a social gathering in the home of Professor J. A. van Allen, in Maryland, U.S.A. The small group included Professor Sydney Chapman of Great Britain and Dr. Lloyd Berkner of U.S.A., now respectively the President and Vice-President of the special committee for the International Geophysical Year. They considered that recent advances in geophysical science were such that an interval of fifty years, such as lay between the First and Second Polar years, would be too long. Moreover an interval of twenty-five years from the Second Polar Year would coincide with a period of maximum sunspot activity. Later in the same year the International Council of Scientific Unions adopted the idea and in the following year set up the special committee; at the same time the nations adhering to I.C.S.U. were invited to form national committees, of which there are now more than sixty. Their programmes make up the vast international world-wide effort. A duration of eighteen months, July 1957 to December 1958, for the Year was agreed.

Rule 10 of the new Collision Regulations deals with the conduct of vessels in Imco adopted traffic separation schemes. In this paper, which was presented at a meeting of the Institute in London on 20 April 1977 with Commander R. B. Richardson, R.N. (ret.) in the Chair, Commander Paton, Hydrographic Adviser to the Department of Trade, discusses the traffic situation in the English Channel and Southern North Sea in the light of this Rule with particular emphasis on encounter situations at route junctions and the problems of crossing traffic.

This paper is based on one presented by the author at the Maritime Technology 21st Century Conference held at the University of Melbourne in November 1992.

Many vessels trading on North Atlantic routes are equipped with weather facsimile receiving devices of various types. Ship-masters engaged on regular voyages in this area are thus able to conduct their own passage planning using the information readily available from these intruments. The capital cost in relation to other ship operation costs is negligible; in US dollars (1983) it is likely to be of the order:

There would be no problem in planning a vessel's route across an ocean if it were possible to forecast with total accuracy the actual sea state existing for the duration of a voyage. Such an ideal circumstance does not yet exist and a method must thus be used which incorporates flexibility to modify a voyage plan as actual weather varies from the prognosis. This means that a subjective approach to storm avoidance may, on occasions, be preferable to the stringent demands of a least-time track. The obsession of routing agencies with the latter method may be one reason why weather routing has not achieved the success it perhaps deserves.

A ship may be damaged or delayed by the action of sea waves on her hull or structure. Hull form and ship dimensions are usually selected on the basis of calm-water performance, rather than for sustained sea-speed.

Traffic separation was first introduced on a voluntary basis in the Dover Strait in September 1967, just over fifteen years ago. Compliance with the IMO provisions relating to traffic separation schemes has been mandatory for all ships during the last five years and for some ships for as much as ten years. It may therefore be appropriate to assess the effectiveness of routing off North West Europe by comparing collision statistics for five-year periods since 1957.

The results given in the following tables apply only to collisions involving trading vessels of over 100 g.r.t. under way and not engaged in any special activities. Collisions in harbours, rivers and congested port approaches where special circumstances apply are not included. The figures quoted for the Dover Strait have been checked against the results obtained by the National Maritime Institute but are based on different criteria, and there may be some discrepancies.

The area covered is the coastal region from the south-western approaches to the Ushant TSS to the approaches to the Elbe including all parts of the English Channel and the Dover Strait, but not including waters off the East Coast of England which are well clear of the traffic separation schemes and deep-water routes.

The numbers of collisions are based almost entirely on Lloyd's Weekly Casualty Reports. Information relating to encounter situations is based on voyage data supplemented wherever possible by information received from additional sources relating to the actual courses steered by each vessel. It is not claimed that the figures constitute a precise record but they should provide a good indication of changes in the incidence of collision off North West Europe.

The paper discusses the way in which the accuracy provided by different navigation systems can best be presented diagrammatically, and it is concluded that contours of constant 95% radial error give the best general picture of a system. Where a more detailed picture is required error ellipses can be added at suitable points in the system. The 95% radial error of fixing is calculated for radial, rθ, azimuthal and different hyperbolic systems, and graphical methods are developed for drawing contours along which the 95% error is constant, and also for drawing 95% ellipses. Diagrams show typical results for the different systems.

We recognize that in the general line of trade (or, as we have had underlined again recently, of war) there will be places where ships have to go but where, with the best will in the world, we have not been able to provide adequate charting or even to recommend anyone else's chart as fit for use. The master and his owners, or the naval commanding officer and his operational authorities, have got to weigh the advantages of calling at that port, or using that route, against the danger to the ship and decide whether the gain justifies the risk.

In 1973 we were astonished to hear that a foreign coaster on passage from a Bristol Channel port to Penzance had attempted to go between Godrevy Point, the north-eastern head of St Ives Bay, and Godrevy Island, some 2½ cables offshore, at low water. Fortunately for her, she was spotted by the local coastguard before she was irrevocably committed to the passage – and dissuaded. The largest scale chart of the area, Chart 1168, is on a scale of 1: 25000, and shows the passage as some ¾ inch across from high waterline, or less than half an inch between drying rock shelves. Admittedly it did show a narrow gap where the contour lines suggested that more than 5 m of water could be carried through the centre of the passage. The sailing directions state that the channel outside the island, between it and the outer shoals, should not be used without local knowledge. The inner passage is briefly mentioned but no instructions for passing through it are given.

This is a synopsis of a paper that formed the 1991 Anderson Memorial Lecture. It was presented at a combined meeting of the Bristol Channel and Boscombe Down branches on 21 February 1991

Real Admiral Ritchie, who retired on 1 September 1982 after ten years as President of the Directing Committee of the International Hydrographic Bureau in Monaco, here looks at the work of the International Hydrographic Organisation, more particularly in those areas which are of direct interest to the navigator.

In 1919 an International Hydrographic Conference was called in London at which representatives from the hydrographic services of twenty-four nations attended. After discussing at length cooperation in the fields of charting, Notices to Mariners, and the international exchange of hydrographic data, it was resolved to set up a permanent Bureau. The Conclusion to the Conference reads as follows:

The International Hydrographic Bureau whose formation is here suggested fulfils, in our opinion, an imperative need. Assuring a close and permanent association between the National Hydrographic Services, it allows of the cooperation of the efforts of all maritime Powers to furnish navigators with more perfect and up-to-date nautical documents. Without limiting in any way the liberty and initiative which should be retained by the Offices of the countries concerned, the new organisation will avoid unnecessary effort and wasteful expenditure; it will create amongst the surveyors of the different countries a fruitful rivalry and personal relations which are frequently of great value. We are convinced that its rôle will constantly increase in the future, and that its establishment will tend greatly to advance the Science of Hydrography.

The italics in the above statement are mine. These words still reflect the most important aim of the International Hydrographic Organisation over sixty years later.

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.

Astro-navigation cannot be regarded at present as one of the principal aids to air navigation. It suffers, by comparison with radio aids, in that it is slow in use and much more subject to interruption by bad weather. The average navigator needs at least 15 minutes to take and plot a two-star fix with present methods. This is quite a long time in the air, though not prohibitive with present-day aircraft, and in consequence astro-navigation is now used extensively only on long flights over sea or desert where radio aids are lacking.

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.

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.

The basic principles of Consol have been explained in a previous article; the factors affecting the range and accuracy of the system are here discussed. A summary is given of the results obtained practice, and the article concludes with a brief discussion of developments which will lead to improved performance.

The high concentration of aircraft near aerodromes, with consequent collision risk is well known. It is at present necessary, in poor visibility, to guarantee the indispensable commodity of safety by the sacrifice of schedule regularity and fuel economy. So long as this is the case, the problem of terminal navigation and control must be regarded as one still demanding a satisfactory solution.