This paper, which was presented at an Ordinary Meeting of the Institute held in London on 20 November, 1964, presents the results of a study on the interrelation of cruise fuel consumption, temperature and track selection in supersonic transport operations on the New York–London/Paris route. The range of temperature variations at S.S.T. altitudes over the North Atlantic for 26 months is illustrated and from this data period 24 cases are chosen to reflect extreme departures from standard and to give a seasonal distribution of such variation. The results of the application of a computerized nasa programme to these 24 cases to determine whether diversion from the great circle is warranted, in terms of economy of cruise fuel consumption due to existing temperature gradients over the area, are then discussed and illustrated.

The results of a general solution, taking into account all these considerations, applied to an additional 117 cases are also discussed and illustrated. Finally the influence of climb fuel consumption upon cruise fuel consumption and data requirements for temperature forecasts in climb and cruise are discussed.

The method described provides glide-paths for climbing and descending aircraft by combining in a single instrument information from the barometric altimeter and radar distance measuring equipment. Preliminary flight tests have shown that the method provides a smooth path along which an aircraft can be flown within close limits, and is one that appears sufficiently promising to justify further development.

Height separation has for years been a fundamental concept in the control of air traffic. It is the basic method of preventing collision during en-route navigation and in some holding procedures. The main reason for this is that a suitable instrument already exists in the form of the barometric altimeter, aninstrument which is intrinsically more accurate and reliable than any of the usual navigational aids.

For many years there has been evidence (for instance from pilot balloon ascents and drift of cirrus clouds) of the existence of occasional very strong winds in the upper troposphere. However, it was not until about 1933, that Bjerknes, who had introduced the concept of the polar front during the first world war, produced a map of geostrophic wind deduced from upper-air temperature soundings made at a few scattered stations and showed a core of strong westerly winds at about 12 kilometres in middle latitudes in winter. No further progress was made until during the second world war when a comparatively large number of upper-air stations were set up and it was found that narrow belts of very strong winds were almost always present over some part of the Earth's surface in the 30,000/40,000 ft. altitude band. In 1944–5 American bombers encountered some rather frightening winds over the Japan area and since that time some extensive investigations of jet streams have taken place.

The term jet stream is popularly applied to any strong upper-wind current (of say 80–90 knots) and it is safe to assume that such winds are in fact associated with a jet stream, which may be considered as a narrow tube containing very strong winds embedded in the surrounding atmosphere.

A deeper understanding and love for the creatures with whom we share this planet must develop as we read the works of animal specialists. These great men and women will surely forgive a navigator who suggests alternative methods by which creatures may find their ways, methods which do not seem to conflict with the remarkable facts they have brought to light but which happen to conform to modern navigational principles.

Mr. Wilkinson's paper, which was presented at a joint meeting of the Institute and the Royal Institution of Naval Architects in London on 7 January 1971, with the President, Rear-Admiral G. S. Ritchie, C.B., D.S.C. in the chair, will be published in full in the Journal of the Institution, illustrated with diagrams and inventories tracing the evolution of the ship's bridge and wheelhouse in relation to advances in technology, ergonomic factors and manning policy. A comparison is made with the design of aircraft flight decks and the cabs of diesel-electric locomotives. The value to the naval architect of manœuvring and handling simulators is emphasized. The paper and the ensuing discussion are summarized below.

Oscillator phase noise has a negative effect on the tracking performance of Global Navigation Satellite System (GNSS) receivers. To provide GNSS software receivers with real test environments, this paper proposes a method to simulate the GNSS Intermediate Frequency (IF) signal, taking the oscillator phase noise effect into consideration. The oscillator parameters are first measured via a pseudolite transmitter and receiver system. According to the measured oscillator parameters, an oscillator-induced frequency fluctuation is then generated, and added to the digital IF signal. Further simulation experiments are conducted that attempt to measure the oscillator phase noise effect on a second-order Phase Lock Loop (PLL) performance. Results indicate that the IF signal simulator considering the oscillator phase noise is able to provide software receivers with real signal dynamics, helping to evaluate the performance of signal processing algorithms on a software platform.

I am pleased to see that, in light of my critical evaluation, Arne B. Molander has reevaluated a number of points in his analysis, and has revised his proposals of Columbus's alleged use of the Moon for determining his longitude. However, it is disappointing that these latest proposals again do not seem to have been thoroughly considered.

Since it is clear that Columbus's East–West position fixes are not correlated with visible lunar-planetary conjunctions, Mr Molander's latest hypothesis is that Columbus observed a dark-horizon moonrise or moonset near each conjunction – which usually can be done whether or not the conjunction itself is visible. However, it is entirely unclear how such an observation can be converted into a longitude. Reading attentively, we can glean a few details of this process: only a single observation is required, since some positions are computed within a few hours of the purported observation; and Columbus apparently used the Ephemerides of Johann Miiller, since errors in that ephemeris are alleged to have caused errors in the computed longitude. In his 1992 paper, Mr Molander asserted that timing of the conjunction is not required by this method, because Columbus somehow utilizes the Moon's daily topocentric motion. But how this datum is utilized, and in fact all details of the longitude determination itself, are entirely obscure.

A method of obtaining aircraft altitude to within 50 feet at altitudes of 10,000 to 20,000 feet is described. This accuracy is necessary in a few special cases. The method consists of determining the height of a pressure level at some convenient point by radar or other means, and then calculating from a knowledge of the wind vector the change of height of this pressure level between the check point and the point at which an accurate altitude is required. The limitations of alternative methods of height finding, such as the use of an aneroid altimeter corrected for temperature at the upper level, are discussed.

For most purposes the aircraft type aneroid altimeter gives a sufficiently accurate indication of height, provided corrections are made for the temperature at flight level. In the application of radar to topographical surveying, however, it is necessary to know the altitude of the aircraft used in the measurement to within 50 feet when flying at heights of 10,000 to 20,000 feet. This can be achieved only by special techniques. The method here outlined has been used extensively during investigations into the use of radar for surveying. It is simple and appears to give satisfactory results.

The following discussion took place at an open meeting of the Technical Committee held in London on 8 December 1965. Captain Cotter, Extra-Master, is Senior Lecturer in Navigation at the Welsh College of Advanced Technology. Captain Wepster is Marine Manager of the Holland-America Line. Commander Leathes' contribution was prepared by the navigation section of H.M.S. Dryad and Wing Commander Rayson's contribution was presented on behalf of the Director of Navigation at the Ministry of Defence. Mr. Page is Chief Navigator of British United Airways.

Those familiar with the history of navigation aids may, with good reason, be reluctant to look upon any new aid as a panacea, but there appears to be no doubt that doppler will effect a revolutionary improvement in air navigation as we know it today. We have, for the first time, an aid self-contained in the aeroplane, independent of propagation conditions or weather, capable of giving position information anywhere over the globe with an accuracy certainly adequate to join the approach facilities at the destination aerodrome. Some of us not actively engaged in flying the world's routes tend to be influenced in our outlook by the navigation problems and facilities in high-density areas like western Europe, the United States or even the North Atlantic, and we are inclined to forget that this is only a very small part of the world route structure. The intensity of aviation activity in these high-density areas warrants the establishment of a network of radio beacons, ranges, VOR's and space pattern systems like Loran and Decca to bring order into the traffic flow, besides assisting the navigation of individual aeroplanes. When, however, we consider the immense distances flown by aircraft through Africa and India to the Far East and Australia, to South America and across the Pacific, to say nothing of Communist Asia, we begin to realize what a real dearth of navigation facilities there is over the globe.

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.

This paper by the Vice-President of the Netherlands Ship Model Basin presents the results of a study performed on the N.S.M.B. ship manœuvring simulator aimed at the development of criteria for the manœuvrability of ships sailing in a current. Six pilots navigated four types of 250,000 d.w.t. tankers in sixteen different conditions of current.

Ships have grown so large that it is no longer taken for granted that they can be manoeuvred as required. The problem can be split up in two aspects, the ship's inherent manoeuvring ability, which is mainly a technical problem, and the mariner's ability to manœuvre the ship, which is mainly a psychological problem.

The publication of a new impression of Professor E. G. R. Taylor's first volume of Mathematical Practioners so soon after the appearance of her second volume makes it a particularly appropriate time to take stock and consider the next steps. Despite various criticisms, some of which will be discussed below, all reviewers agree that her volumes mark a great advance in this field and will be of ‘immense service to scholars’. Our debt to the author is all the greater when we realize that these books followed on a whole series of standard works in her own subject of geography, and that she was neither a mathematician nor a bibliographer. The best tribute to Professor Taylor is to continue the work recorded in these two volumes, but there are few who have the detailed knowledge and expertise to follow her in such a wide field. This article will, for example, offer little comment on instrument-makers who form such a large section of her practitioners and who left records of their work in museums and private hands all over the country; here we shall be much more concerned with the written work, with the bibliography of the subject.

Reviewers of her volumes have found it difficult to define the practitioners of whom she wrote and to decide in what sense they differ from mathematicians in the normally accepted sense of this country or overseas.

Captain Brett Hilder first published in 1973 his controversial theory that Torres used Endeavour Strait on his famous and perilous voyage through the intricate waters of the strait that now bears his name. This was the subject of his Macquarie University thesis of 1976, The voyage of Torres along the southern coast of New Guinea in 1606 and he has summarised his findings in a paper published in the September 1977 issue of this Journal. It now seems essential to question the validity of some of his assertions.

This paper was first published in 1960 (Vol. 13, p. 127). It is followed by comments from John Kemp. The paper has been abridged, including the omission of section 5 which described a proposal for a new radar display.

When the problem of collision in the air is discussed, it is usual to start by pointing out the enormous closing speed of two modern aircraft meeting head-on, and to conclude from this that avoidance on the ‘see and be seen’ principle has ceased to be possible. The fact is, however, that the great majority of mid-air collisions (about 85 percent) occur within five miles of an airport and the typical case is not the head-on one, but the case in which the two aircraft crab into one another from a direction which may be anywhere around the whole enclosing sphere. Since the field of view of the aircrew covers only about 20 percent of the enclosing sphere, the aircrew of colliding aircraft seldom see each other. It would seem, therefore, that the ‘see and be seen’ principle never did afford much protection, even when speeds were low. In other words, the fact that the number of mid-air collisions in Europe has hitherto been small is not primarily due to seeing and evading, although this sometimes happens, but to the fact that the airspace is very large compared to the volume of all the aircraft in it at any given time. However, as traffic densities go up, the risk rapidly increases, and in congested airspace, such as that around New York, the problem of avoiding collision has already become acute. In the period 1948–57, there were 159 mid-air collisions in the United States, and many of these made headlines in the world press. One can imagine the public outcry if two large transports were to collide over a housing estate; but unless something effective is done, something like this will presumably happen eventually. At very high altitudes the ‘see and be seen’ principle certainly fails, by day, because the speed will be high, and in addition, the range at which a pilot can see an object the size of an aircraft may be less than 1½ miles due to what is sometimes called ‘high-altitude myopia’.

This paper starts with a brief overview of cross-rate interference (CRI) and methods developed in the past for estimating the CRI between two Group Repetition Intervals (GRIS). It presents an algorithm for fast calculation of the loss of pulses due to blanking in dual-rate stations. These stations broadcast on the GRIS of two chains but, if pulses of both chains overlap, one GRI is not transmitted at that instant. Furthermore, it will discuss the impact of this blanking on the use of Loran-C signals for transmitting data. A strategy is given for selecting GRIS, based on the presented theory. The paper is based on papers presented at the 1993 WGA technical symposium and the 1993 INA conference.

Any comment on arctic navigation must be broadly based since the ability to conduct voyages in ice-infested waters is influenced by many factors. The traditional technique of exploiting open channels in the ice is now no longer adequate and there is an increasing need for vessels to force ice in order to reach places and to carry out activities well inside the boundaries of the permanent ice cover during parts of the year when the sea ice is at its maximum extent.

The standard formulae, assuming a spherical Earth, for converting distance on a rhumb-line track into differences of latitude and longitude are:

where C is the course and α is known as the middle latitude. It is approximately the mean latitude when both points are on the same side of the equator; tables of the correction to be applied to the mean latitude to give the middle latitude are given in most collections of nautical tables.

This paper examines the evolution of the arctic submarine and the ever-increasing scientific and commercial potential which have accompanied this evolution over the past 340 years. It is a sporadic history of arctic submarine ideas, concepts and actual experiences with vessels at sea. It happens to be a history that is largely American, with important additions as a result of the experiences of the Germans, Soviets and the British, particularly during World War II. Finally, it is a history in which five early visionaries in particular stand out: Bishop John Wilkins of England; Jules Verne of France; Professor Anschutz-Kampfe of Germany; the submarine designer Simon Lake, of the United States — whose influence extended over four decades until well into the twentieth century; and Sir Hubert Wilkins of Australia.

Knowledge of the statistics of aircraft vertical speeds is important both for the construction of realistic traffic simulators and for the development of trajectory prediction tools for use in future air traffic control (ATC) systems. This paper reports on the analysis of radar data recordings for nearly 10000 civil flights on airways. Results are presented for the means and spreads of vertical speeds as functions of altitude. Evidence is presented that roughly half of the observed spreads arise from fluctuations within each aircraft's trajectory, as opposed to variation from one aircraft to another. A simple procedure is proposed for simulating vertical speed data which has statistics similar to those obtained from the radar recordings. Some consequences of the results for the development of trajectory prediction tools for use in future ATC systems are discussed. The results suggest that the provision of accurate trajectory prediction tools is not as straightforward as it might at first appear to be.