bluuebunny/crossref_metadata_2025 huggingface dataset:
The Rotterdam Approach Control
Authors: Richardson R. B.
Published: January 2010

Listening to Captain Brandenburg's talk on his ideas about the future navaids in Rotterdam (this Journal, 25, 67) I was left with the conviction that even the most ardent opponents of change will at least be better informed having heard it. Although in his introduction he excluded direct reference to Rotterdam, it is well known that the new Auto Com/Radar Data system when introduced there will be a real milestone for historians of port entrance techniques. I would like to think that it will lead us in this country one step closer to the day when we take the option out of progress on our own coasts and waterways and get on with it as they are doing in Rotterdam. There is of course one great difference—in Holland and Germany the Governments and Municipalities are involved, so that the necessary finances are seen in a clearer light.
Navigational Discipline at Sea
Authors: Thompson P. A.
Published: January 2010

It is doubtful if at any period in the history of seafaring a greater effort has been made to organize the safe conduct of ships about the seas than that which is being made today, and it is equally doubtful if the need was ever more urgent. At the present time a large amount of thought and work is being put into the task of trying to formulate rules and systems aimed at providing for the safer navigation of vessels at sea. Excellent ideas have been proposed for conduct in traffic, such as those put forward by Dr. Calvert, Admiral García-Frías and many others, which, together with the systems of traffic separation which have been established in areas of heavy shipping concentrations, could bring about a decrease in the present rate of marine casualties.
The Continental Drift
Authors: Blackett P. M. S.
Published: January 2010

The fourth Duke of Edinburgh's Lecture was presented by Professor P. M. S. Blackett, C.H., P.R.S., at the nineteenth Annual General Meeting, held in the Royal Geographical Society's house on 27 October 1965, with the President in the Chair. The President introduced the lecturer as one of the most eminent physicists of our time. Over the last thirty years he had held a number of very distinguished appointments, and was until recently Professor of Physics at the Imperial College of Science and Technology. He is now deputy chairman of the Ministry of Technology's Advisory Council. In 1948 Professor Blackett was awarded the Nobel Prize for Physics. A summary of the main points covered is given below.
A Concept for Navigation and Communication using Satellites
Authors: Anderson Roy E.
Published: January 2010

Of all man-made objects, satellites are unique in their ability to ‘see’ large regions of the Earth at one time. Because of this ability, they can serve as relays to provide the advantages of line-of-sight communications between widely separated points on the Earth. They have another useful characteristic also—their locations in space can be determined to high accuracy, hence they can be used as position references for navigation or surveying.
True Motion and Relative Motion
Authors: Wylie F. J.
Published: January 2010

1. Types of presentation. The choice of the method of presentation used by a radar operator is probably the most important of the various alternatives open to him for the most effective keeping of his watch, because they are all different, each has its advantages and limitations and one of them may be best suited to the circumstances and to the mentality of the observer himself. In what follows, the anti-collision use is principally in mind.
Subsurface Navigational Hazards
Authors: Chanslor John W.
Published: January 2010

1. Introduction. Nautical charts of many areas of the world carry notations adjacent to natural marine hazards such as ‘position doubtful’, ‘existence doubtful’, ‘position approximate’ and ‘reported (date)’. In spite of the development of precision survey and navigation systems, many of these notations must continue to be carried until the positions of the hazards are accurately determined or their existence disproved.

The expanse of the oceans obviously precludes costly systematic hydrographic surveys in all areas, particularly in remote offshore areas. Although international cooperation in the exchange of hydrographic information assists in meeting modern charting requirements, the task of charting the seas may never be complete.
II—Inertial Techniques in Height Measurement
Authors: Whalley R.
Published: January 2010

Inertial navigation techniques have been applied as a means of improving the height information in military aircraft for some time. It is almost certain that the supersonic transport will use inertial techniques for plan navigation and it is interesting to see how far it is worth extending this to include height, and also height rate, information.

It is convenient to start by looking at the fundamental principles of inertial navigation as applied to height measurement; Fig. 1 shows the essential features. There will be an accelerometer measuring vertical acceleration; this must be maintained approximately vertical and can be very conveniently mounted on the main inertial platform. The output of the accelerometer contains a number of unwanted terms for which corrections have to be made. The expressions are well known and are explained in the Appendix.
III—Some Aspects of Pressure Measurement Techniques
Authors: Cape B.
Published: January 2010

From an examination of the outline requirements given by Mr. Davies, it is apparent that pressure measuring techniques can be used in all stages of a flight although it must be acknowledged that some of the tolerances he has called for cannot be met. The advantage of the pressure technique is that it uses the Earth's atmosphere which is experienced by all airborne vehicles and so provides a common datum for height or altitude measurement. It should be noted that wrong impressions can be got from the present pattern of accepting altitude or height in feet as a fixed physical measurement. A pressure sensor measures the pressure and, as the millibar is a widely accepted unit of pressure in aeronautics, it would really be more sensible to express aircraft altitude and separation values in millibars.
IV—Radio Altimetry
Authors: Garfield W. L.
Published: January 2010

In the terminal area and for the approach and landing phase, radio provides the most appropriate method of height measurement. That is to say that the altitude reference frame is switched from barometric to terrain clearance measurement. It is at first a little surprising to see from Mr. Davies' requirements for this phase that the accuracies are in line with those currently in use in subsonic jets. But consideration shows that this is because the approach speed and general handling characteristics of the S.S.T. must approximate to those of subsonic jets in the approach and landing phase. Mr. Davies has also stated that automatic landing is essential for the S.S.T., so that the picture of requirements for radio altimetry in the approach and landing phase is fairly clear.
Analysis of Long-Range Air Traffic Systems: Separation Standards—I
Authors: Reich P. G.
Published: January 2010

This and the following paper by Mr. Attwooll are the first of a series which will describe the work of the Royal Aircraft Establishment on various aspects of air collision risk and traffic control. Mr. Reich's paper will be presented in three parts, the last two of which deal with the analytical techniques and how they are applied. Mr. Attwooll deals with methods of costing the effects of air traffic control deviations and shows how these costs are related to the size of separation standards. He discusses systems for both subsonic and supersonic transports.

1. Objectives. The main task of air traffic controllers is to plan traffic flows so that aircraft are allotted sufficient separation to absorb not only systematic differences in speed but also the imperfections of navigation and piloting, which we term flying errors. To this end, they usually work with three separation standards, to be applied in, respectively, the along-track, across-track and vertical dimensions of space. The separation standard for any one dimension is the minimum intended (i.e. planned) separation permitted in that dimension when the intended separations are less than standard in the other two. The problem is to choose standards which are safe enough, but not so large as to lead to unnecessary traffic delays and deviations.
Costing Air Traffic Control Deviations
Authors: Attwooll V. W.
Published: January 2010

1. Introduction. An air traffic control system maintains adequate separation between aircraft by requiring some aircraft to deviate from the paths which they would otherwise follow. In the absence of such deviations it must be assumed that civil transport aircraft would choose to operate at the most economical combination of airspeed, track and altitude (within the limits set by inaccuracies of weather prediction); A.T.C. deviations therefore involve economic penalty to the operator. It is important to assess the magnitude of such penalties for two reasons:

(a) To provide a yardstick by which to compare different A.T.C. systems.

(b) To give a measure of how much might justifiably be spent on new systems and equipment, to enable separation standards (and hence the penalty of deviations) to be reduced without reduction in safety.
Longitude without Time
Authors: Chichester Francis
Published: January 2010

In 1964 during the second single handed transatlantic race Colonel H. G. Hasler in Jester lost the correct time and, having no radio, could not get a time check. Thus he could not obtain the longitude but, being a fine seaman and practical navigator, made a landfall on Nantucket light-vessel by a method used by old sailing ship skippers. This was to position himself on the correct parallel of latitude and sail due east or west to the destination.
A Survey of the use of Astronomical Methods at Sea
Authors: Bissett D. McG. , Evans J. J.
Published: January 2010

This investigation of methods used in Astronomical Navigation has been carried out by means of questionnaires completed by senior students at a few of our Navigation Schools. The data has been classified into fairly broad categories since some of it has been rather difficult to assess, due to incomplete information on such details as trading areas, which watch was being kept, and the actual time spent at sea during the year.
The Science and Technology of Navigation
Authors: Stratton Andrew
Published: January 2010

The wide range of interests of members of the Institute, combining as it does all aspects of marine and air navigation from the basic concepts through research, development, design, manufacture and marketing to practical operation, presents a most interesting challenge to the president in his address. This challenge is increased by the knowledge that this address will appear in the twenty-first birthday issue of the Journal in company with articles by eminent members of the Institute on developments in their own fields.
Human Factors and the Collision Problem
Authors: Calvert E. S.
Published: January 2010

Everyone now knows that radar has not fulfilled expectations as a means of preventing collision at sea, and that, because of this, its legal status is merely that of an aid to navigation. Nevertheless, everyone seems to feel that such a good technical instrument should enable ships to proceed safely in fog without reducing speed, and the fact that the collisions per fog day have increased by about thirty times in the fifteen years since radar became operational, shows that many mariners are in fact relying on it for collision avoidance. During these fifteen years, many papers have been published pointing out the dangers and giving advice, but in spite of this, the number of vessels involved in collision every year seems to have settled down to a constant figure of about 1700, or 7 per cent of the world fleet.
The Ordering of Seaborne Traffic
Authors: Oudet L.
Published: January 2010

In 1945, when the end of hostilities restored freedom of commercial traffic, it seemed as though technical advances would enable it to acquire an ever increasing measure of safety. Soon, however, it became apparent that if ships were immune from the dangers of the past, it was only to meet other dangers which had been introduced by those very advances.
Astronomy and Navigation
Authors: Sadler D. H.
Published: January 2010

My first reaction on being invited by the Editor to contribute a ‘twenty-first birthday’ article on the above subject for the Journal was that there is little new to say. However, it is now 13 years since I prepared the presidential address on ‘The Place of Astronomy in Navigation’ (this Journal, 9, 1, 1956) and, apart from any other developments, space navigation has since become established as an operational science as well as a theoretical discipline. There have, in fact, been many developments and much progress in these 21 years; and, although these appear in the Journal and elsewhere mainly as gradual changes, a comparison over the whole interval reveals drastic changes, particularly in outlook and appreciation.
Oceanography and Navigation
Authors: Deacon G. E. R.
Published: January 2010

Position finding and hydrography—the plotting of coasts, channels and dangers to navigation—are the most obvious applications of science to the oceans, and they are the basis of well-established professions in which the use of accurate methods and the presentation of precise information are of paramount importance. Navigators can also make good use of knowledge of waves, tides and currents, but these are more variable in time and space, and, needing to be understood as well as charted, offer plenty of scope for academic study as well as a professional approach.
Jester's Transatlantic Passage, 1968
Authors: Richey Michael
Published: January 2010

During the summer of 1968, to celebrate his twenty-first year with the Institute, the Executive Secretary sailed his boat Jester in the third single-handed transatlantic race, from Plymouth to Newport, Rhode Island. Of the 35 starters Jester was the last of the boats which completed the course. He here describes the reasons which led him to take a route which extends the distance of the course from 3000 to 5000 miles, and gives an account of the passage and of some of the problems of single-handed sailing.
Navigation and the Science of the Sea
Authors: Deacon G. E. R.
Published: January 2010

The aim of the Duke of Edinburgh's lecture is to extend the horizons J. of navigational interest. I shall try to show how modern scientific methods are greatly increasing our understanding of how the oceans themselves work, and, at the same time, do all I can to maintain that this new knowledge is not just a matter of curiosity. If vigorously developed it will be of much practical use to seamen, and of great benefit to us all. The time is opportune. Scientifically inclined nations recently have been making organized all-round exploration of the human environment. As well as major Antarctic operations, and the rush to Space, there is growing realization that the oceans are coming within our grasp for major technical exploitation.
Safety of Navigation on Inland Waterways in Europe
Authors: Beattie J. H.
Published: January 2010

Most collisions on inland waterways occur in daylight and in good visibility and it is here there is most scope for improvement. Elaborate traffic control schemes such as that planned for the Panama Canal may not be suitable on European rivers where the density of shipping is very high and the nature of the traffic mixed. Local control may be feasible, but between control areas vessels will have to rely on self-contained aids, ship-to-ship communications and local navigational rules to avoid collision. The congestion of traffic, particularly at Customs clearance points, must be relieved.

The paper discusses various aids to river-radar navigation, which are making fundamental changes in the methods on European inland waters.
Increasing Radar Target Information
Authors: Welsby V. G. , Davies D. E. N.
Published: January 2010

Collision-avoidance devices are all based on the use of either electromagnetic or acoustic waves, although the former (i.e. radar) is of particular interest for this purpose.

After reviewing briefly the fundamental theory which underlies all methods of detecting, locating and recognizing a distant target, reference is made to the successful development, in the Electrical Engineering Department of the University of Birmingham, of a narrow-band sector-scanning sonar system employing a multiplicative array to give improved target resolution. It has been demonstrated experimentally that the same principle can be applied to obtain a sector-scanning radar system capable of scanning rates as high as one million scans per second, which has applications for airfield surveillance radar. Attention is now being directed to the possibility of using wide-band signals, either to improve target detection and location for an array of a given size or to obtain additional information about the nature and behaviour of the radar target itself. Two possible methods of using wide-band signals are described.
Separation of Aircraft in the Approach and Departure Phases
Authors: Woodruff W. C.
Published: January 2010

Separation of aircraft in terminal areas is made difficult by the convergence of tracks, continual changes of height, and traffic density. The application of longitudinal separation is too restrictive at busy aerodromes. Vertical separation is suited to the approach phase, but has limitations in the departure phase. The most useful form of separation is lateral, although it is often difficult to apply. The difficulties arise from organizational rather than operational causes and efforts to overcome them can be most rewarding.

Other difficulties of a terminal area arise from the conflicting patterns of adjacent aerodromes, the mixing of terminal and overflying traffic, and the mixing of departing and arriving traffic. Lateral separation can assist in all these problems.
Flight Plans and Flight Programmes
Authors: Williams J. E. D.
Published: January 2010

In areas of sufficiently high traffic density, air traffic control in some form will always be the primary mode of ensuring aircraft separation. Any traffic control system is concerned with separating aircraft in the future; therefore, the nominal separation criteria are determined by the accuracy of prediction of future movement of the aircraft and by the ability of the control system to correlate flight path predictions. The utilization of an airspace of a given capacity is determined by the distribution or flow of traffic.

The accuracy of prediction depends on track-keeping and maintenance of planned ground speed. Since improvements in track-keeping will be limited for some time by past I.C.A.O. decisions on short-range navigation aids, attention is directed in this paper to maintenance of flight-planned ground speed. The effect of this on the operating cost of a modern jet airliner is examined and compared with the cost of flying at minimum cost mach number at a less than optimum altitude. It is concluded that in a crowded airspace, speed maintenance is preferable in short-range operations.

The increase in space utilization by flow control is illustrated for a simple model, showing that speed control by A.T.C. increases utilization of a space capacity, which has already been increased by speed maintenance.
The Risk of Encountering Hail in Flight
Authors: Crossley A. F.
Published: January 2010

In the April 1961 number of the Meteorological Magazine, A. F. Crossley discusses Hail in Relation to the Risk of Encounters in Flight. Since it is probable that the Meteorological Magazine does not readily fall into the hands of members of the Institute of Navigation the following brief summary may be of interest, though of course anyone wishing to pursue the subject further should refer to Crossley's original paper and the numerous references therein.
Mathematics and the Collision Regulations
Authors: Wylie F. J.
Published: January 2010

Recent articles in this Journal will have suggested that there is a conflict between certain mathematicians and certain mariners on the subject of the efficacy of the Collision Regulations. The controversy is really philosophic rather than mathematical and, although it would never be suggested that the mathematical system we have seen is anything but flawless in isolation, there are grave doubts that it would work, even on a planet composed solely of deep water and supporting ships staffed only with mathematicians, having collision avoidance as their single preoccupation.
Collision Avoidance in the Air
Authors: Fairbairn E. P.
Published: January 2010

In June 1958 the writer submitted to the Ministry of Aviation a paper, summarized below, on the avoidance of collisions in the air. The views expressed are his own and not necessarily those of the Company for which he works.

1. The rules of the air should recognize that the information available to the pilot, whether obtained by visual or ‘electronic’ means, is likely to be limited by the following:

(a) the pilot's ‘field of view’ is at most ± 90° in azimuth and some ± 20° in elevation relative to his aircraft heading.

(b) a collision course can be recognized, but not the heading, course or speed of the other aircraft.
Anomalous Radar Propagation
Authors: Cooper G. R.
Published: January 2010

Whilst steaming westwards at night along the coast of South Africa, echoes were received on the radar screen that gave the impression the vessel was about twelve miles off the coast. At the time, the vessel was about thirty miles S. by W. of Seal Point.

The radar set, a Decca Mk. 12, was operating on the twenty-five mile range. It was receiving strong echoes from a sighted ship seven miles away on the port quarter. The set had been switched on to clear an unlit buoy fitted with a radar reflector. The position of the buoy was about ten miles WSW. of the vessel's position.
Manœuvres to Ensure the Avoidance of Collision
Authors: Calvert E. S.
Published: January 2010

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 per cent) 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 per cent 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’.
Factors Affecting Radar Operator Efficiency
Authors: Baker C. H.
Published: January 2010

This paper briefly reviews some of the research findings with respect to factors which affect the efficiency of radar operation. One of the most important factors in determining whether or not a radar target will be visually detected is the brightness of the radar scope. A simple method is described for setting optimum scope brightness. Visual search habits are discussed and the implications of such habits for the design of radar displays are pointed out. Reference is made to some of the design factors which determine the accuracy with which target range and bearing are reported. It is shown that human monitors perform less efficiently as a watch progresses and factors which impair or aid their vigilance are described. Finally, a brief account is given of illusions on radar displays.
Automatic Echo-sounding Systems
Authors: Ahrens E.
Published: January 2010

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.
The Rate-integrating Gyro as an Aircraft Heading Reference
Authors: Fraser D. O. , Lee J. A.
Published: January 2010

A description is given of a floated rate-integrating gyroscope and of the way in which it may be used to provide a high-accuracy aircraft heading reference. The sources of error of the system are examined and the overall heading accuracy is estimated as being comparable with the distance accuracy of a doppler system. This paper was presented, on 15 January, at the same Ordinary Meeting of the Institute as the preceding paper by Green and Glenny.

The advent of the high-accuracy single-axis floated gyroscopes which have been developed so rapidly over recent years, primarily for inertial navigation use, has raised the question of whether the accuracy of these instruments can be made use of in other applications. Can systems which have been employing the older established types of gyroscope benefit from the greater stability of the new type? If a direct change of instrument with no modification of the method of use is considered, the answer will in many cases be no. For example, an improvement in the accuracy of the north-seeking marine gyro compass may not be found rewarding with existing marine navigation techniques, as other factors such as the accuracy with which a ship can be steered would become limiting, defeating the advantage of improved compass accuracy. The introduction of the doppler system has created a different situation in the field of aircraft navigation. Doppler navigation equipment enables an aircraft's drift angle to be measured accurately. That is, the aircraft's track can be defined with an accuracy dependent on the accuracy with which its heading can be measured. In this new situation the overall navigation accuracy is limited by the accuracy of aircraft compasses. These have in general been magnetic compasses, given improved dynamic performance in later years by the incorporation of a gyroscope or use of an associated directional gyro but still dependent on the magnetic element for long-term accuracy. Such a direction reference, though simple and reliable, is at no time precise by modern standards, and as the region of the magnetic pole is approached it becomes practically of very little value. For this reason in recent years the technique of using a free gyro alone as a long-term memory, to store direction information, has been developed, particularly by the airlines operating transpolar services. It is a system such as this that can reap most benefit from use of the new gyroscopes.
‘The Effective Use of Airspace’
Authors: Southall A. W.
Published: January 2010

It is almost two years since Wing Commander Dickie's survey (11, 259) emphasized the importance of improving methods of control so as to allow more movements in a given volume of airspace. Since then, much effort in many countries has been devoted to the problem. The magnitude of these difficulties is not surprising when it is recalled that, in addition to the professional difficulties of flying, navigation and control, various sections of industry are involved, and international agreement must be obtained. At every turn there are political and commercial problems which cannot be ignored by those responsible for initiating action to solve a very difficult practical problem. This note is written in an attempt to examine once again the various possibilities for improving airspace utilization, with the object of discovering some pattern which will lead to progress.

It has been stated that at all times both the controller and the pilot must know the absolute ground position of the aircraft, but it is by no means clear that this really is a requirement. It could well be sufficient to maintain the position of the aircraft relative to the traffic pattern, for this would satisfy the pilot's aim which is to travel in accordance with his flight plan, and also the controller's aim which is to ensure safety while making best use of the available airspace.
Four Steps to Longitude
Authors: Taylor E. G. R.
Published: January 2010

Four steps to Longitude! If we chose, we might interpret the phrase by a sequence of four names: Ptolemy, Charles II, Tobias Mayer and Nevil Maskelyne—the last in 1763. But in fact the steps represent the four marine timepieces made by John Harrison—familiarly known as H1, H2, H3 and H4 of which the last proved its efficacy in 1762. The longitude was found, and by a ‘machine’, just two centuries ago. Now the bi-centenary is being celebrated by a very elegant and informative exhibition at the National Maritime Museum, Greenwich. No navigator should miss it. Even if he thinks scorn of ‘ancient history’ he owes the inventor of the first English chronometer a tribute of respect.
The Marine Radar Photoplot System
Authors: Parsons S. R.
Published: January 2010

This paper, having first reviewed briefly the operational characteristics of present radar displays, deals with a new technique for presenting the radar data whereby a large, bright, high-contrast radar picture can be produced on a flat plotting surface by projecting in sequence rapidly processed photographs of a PPI cathode-ray tube presentation. It is followed by an account, by the radar officer in S.S. Canberra, Mr. D. W. Sims, of the use of the system at sea.
Aircraft Accidents and High Ground
Authors: Freer T.
Published: January 2010

In recent years there have been a number of accidents caused by aircraft flying into high ground. The aircraft were mostly on nonscheduled rather than scheduled flights. This has resulted in much publicity being given to such questions as the licensing of the operators, the sufficiency of the radio or radar carried, and the route-experience of the pilots. These questions are of course relevant, but there is one further question which ought to be investigated and which has received little attention: it is the adequacy or otherwise of the means employed to show relief on charts.

Under present policy the only picture of the relief is on topographical maps (Fig. 1), but it is on charts (Fig. 2) that the route and aids are shown. If the pilot is to check his safety-height in the air, he can do so only by coordinating the maps with the charts. This is cumbersome when he is pressed for time, and generally he does not do it; he flies on the charts using flight altitudes that have been pre-calculated, and the maps remain in the navigation bag unused.
Precision Celestial Navigation Experiments
Authors: Shufeldt Henry H.
Published: January 2010

The following report, here printed in a slightly abridged form, was prepared under a contract with the U.S. Office of Naval Research and covers the results of research at Key West, Florida, and near Newport, Rhode Island, as well as afloat during the period January 1958 to May 1961. It has so far been unpublished. It describes the results of investigations into the use of high-magnification sextant telescopes and makes recommendations for the improvement of marine sextants and their use. It is here published with a prefatory note and final general comment by Mr. D. H. Sadler, Superintendent of H.M. Nautical Almanac Office.
Mathematicians and Navigators
Authors: Calvert E. S.
Published: January 2010

As Mr. Sadler points out, there can be no conflict between mathematicians and navigators, provided the mathematicians have adequately fulfilled their job. If, however, the navigators fail to follow the mathematics, or even to check the results by taking a few examples, then there will be plenty of misunderstandings; to bring ‘philosophy’ into the discussion is to return to the attitudes of the Middle Ages, and to obscure technical issues which are perfectly clear and simple.
The Treatment of Navigational Errors
Authors: Anderson E. W.
Published: January 2010

In recent years, the most striking development in the philosophy of navigation has surely been the change in attitude towards errors. Ten years ago an error was regarded as something that just did not happen in the best navigational circles; today we accept it as the normal concomitant of observation, and we study to reduce it.

This change in philosophy is really nothing more than theory following in the footsteps of the practical man, for the practical man has always regarded a position plotted on a chart with a certain amount of healthy scepticism. It may therefore be of value to discuss the whole business of errors from the point of view of the practical man, avoiding complicated mathematics and dealing in demonstrations rather than in rigid proofs. Navigation has been described as the business of conducting a ship on its way across the sea or an aircraft on its way across the sky. The word conducting implies safety. Indeed, safety is the keyword in navigation.
Radio Position Lines and the Intercept Method
Authors: Freiesleben H. C.
Published: January 2010

In 1877 a two-volume book, Nouvelle Navigation Astronomique, edited by the astronomer Villarceau and a naval officer, Magnac, was published in Paris. The book, which may be considered the most comprehensive work on astronomical position lines up to date, covers completely the theoretical treatment of circles of equal altitude on Mercator projections and their practical evaluation, and considers the effects of possible mistakes and errors. In the present writer's view these factors have not yet been sufficiently appreciated. It is surprising that similarly detailed descriptions of the other position lines used for navigation have not yet been published; although, apparently, the attitude towards these questions has altered since that time. The change in methods of navigation, particularly with the introduction of radio aids, has brought a variety of other position lines to the fore, and the predominance of Mercator's projection is not as universal as it was eighty years ago. In order that these premises may be clarified, a summary of the various position lines in use today is here given.
The Work of the International Hydrographic Bureau
Authors: Nares J. D.
Published: January 2010

The sixth International Hydrographic Conference, at which the Institute will be represented by an observer, is being held in Monaco at the end of April. It is therefore appropriate that we should at this moment publish an account of the work of the International Hydrographic Bureau, which has been written for the Journal by the President of the Bureau's directing committee.
The Refraction Table in theAir Almanac
Authors: Sadler D. H.
Published: January 2010

A description is given of the basis and method of calculation of the new table of refraction included in theAir Almanacfor 1943 onwards; the table caters for heights up to 55,000 ft. and all altitudes above the visible horizon.

As already announced theAir Almanacand theAmerican Air Almanacwill become a single publication, under the title of theAir Almanac, as from 1953. To cater for the greater heights at which aircraft now fly, and for the possible use of observations at very low altitudes, the refraction table has been completely redesigned. The explanation of the table in the Almanac is naturally restricted to instructions for and illustrations of its use, and, in view of the current interest in refraction, especially at low altitudes, it seems desirable to place on record a full description of the theoretical basis of the table and of the method by which it was calculated.
The Treatment of Simultaneous Position Data in the Air
Authors: Parker J. B.
Published: January 2010

The theoretical determination of a fix from a number of simultaneous, or near simultaneous, positional data has attracted considerable attention during the last five years. A problem is presented whenever the amount of information obtained is more than sufficient to determine the fix, the most common case being when a set of three position lines is obtained. In this instance the size of the triangle of intersection can be used to estimate whether or not the position lines are likely to be consistent with each other; if they are, some central point inside the triangle is accepted as the fix. In doing this the influence of the position provided by the vessel's past history (the dead reckoning position) is ignored; once the fix is decided on, however, a comparison between the two estimates of position may be of value either in enabling a blunder to be detected or, possibly, in selecting some intermediate point as a position from which subsequent navigation should be based. Although the determination of a position from a number of data is, mathematically, a single problem whether these data include the dead reckoning estimates or not, it is usual navigational procedure to consider first the latest positional information. It is the study of this problem that is the object of this article.
Early Units of Measurement and the Nautical Mile
Authors: Moody Alton B.
Published: January 2010

To find out the origins of the nautical mile it is necessary to go back to early times, for, like so many other things, it did not spring up in full bloom in a day, but evolved by slow degrees.

Early man, seeking units of measurement, logically looked about him for something in nature that he might use as a standard. For very short distances he used the width of his finger, the width of his hand, his span, the length of his foot, or the length of his forearm. As these varied between men, so the length of the derived units varied. The foot, for instance, varied from 11 to 14 inches. Even greater variation occurred in the length of the cubit, which originally was taken as the length of the forearm, from the elbow to the end of the middle finger. This unit was widely used, but varied from country to country, and was not even constant within various parts of the same country in some instances.
Navigational Aspects of Gravity Determinations
Authors: Cooper R. I. B.
Published: January 2010

Men have always been curious to know the shape and size of the planet upon which they live. Most people have heard of the experiment by which Eratosthenes determined the circumference of the Earth, and the principle of his method underlies all subsequent determinations. What he did amounted to finding the difference of astronomical latitude between two places and measuring their distance apart in terms of a standard length (Fig. I). Astronomical latitude may be denned here as the complement of the angle between the vertical at the point in question and the direction of the Earth's axis.
Navigation and the Shipping Industry
Authors: Watson-Watt Robert
Published: January 2010

The Institute was planned to bring together not merely the professional navigators, but all who could contribute to the exchange and advance of knowledge bearing on navigation. The founders were wise when they gave effect to the thought that the small-boat sailor and the sailplane aviator could contribute to the progress of our science and art, and could greatly strengthen the hand of the professional provider and the professional user of the processes and material of navigation. The reasons for exchanging and advancing our knowledge are as diverse and yet as closely interacting and mutually reinforcing as are the individual interests of our members.
Some Recent Work on Polar Navigation
Authors: Foster L. R. R.
Published: January 2010

During the Antarctic summer season of 1949 the Norwegian sealer Norsel, which had been chartered by the expedition, landed the Norwegian-British-Swedish Antarctic Expedition in Queen Maud Land in the Antarctic. In January 1951 the ship took down relief personnel and stores and for this trip the Admiralty, at the invitation of the planning committee, appointed the author as an observer. The decision to appoint a member of the navigation branch was made partly so that the techniques of ship handling and navigation in ice could be studied; and since the captain of Norsel, Captain Jakobsen, was extremely experienced in every aspect of ice navigation, a great deal of valuable information was acquired. The Institute had also suggested a number of astronomical observations that might usefully be made in polar areas and the Admiralty gave its approval for the observer to make them.
Marine Navigation in the Canadian Arctic
Authors: MacLean J. H.
Published: January 2010

The history of marine navigation in the area to the north of Hudson Straits and west of Greenland dates back to Martin Frobisher in 1567, John Davis in 1585 (who reached N. 72° 15′), and William Baffin, who got as far as Smith Sound (N. 77° 45′) in 1616. All of them were searching for a short route to the East. There was little exploration in the area for the next two-hundred years, until, in 1818, the British Government recommended explorations for the Northwest Passage: This activity continued throughout the Franklin era up to 1875, when Captain George Nares proceeded to N. 82° 25′ on the northern end of Ellesmere Island. After this, the role of exploration gradually passed to American hands, largely culminating in 1909 with Robert E. Peary's attainment of the North Pole.
Course and Distance Correction from an Estimated Position
Authors: Tyrrell A. J.
Published: January 2010

After taking a latitude at noon and obtaining a position, a course and distance to a position nearer the destination is usually required. A course and distance from an estimated noon position may be worked prior to noon and then corrected at noon by the observed latitude and morning position line, by means of a plotting chart, giving reliable results quickly and accurately.

In Fig. 1, BA and CA represent the course and distance from B to A and C to A respectively. BD and EC are arcs of concentric circles with centre A; and AC = AE and AB = AD.

If BD and CD are small in comparison with AB, arcs BD and EC may be considered straight lines and the figure BECD a rectangle. If the rectangle can be solved, the distance AC can be deduced from AB, i.e. AC = AB - DC or AC = AB + DC if C lies the other side of BD.
Three-star Position Tables for Air Navigation
Authors: de Jonge Joost H. Kiewiet
Published: January 2010

This paper was written in 1946 when Mr. Kiewiet de Jonge was a student at Harvard College Observatory. Subsequent developments in astronomical navigation, particularly the publication by the U.S. Hydrographic Office of H.O.249, have overshadowed the practical advantages of the three-star position tables. But the principles of the method, which have not previously been described in print, are of sufficient importance and novelty for permanent record.

In this paper we will develop a fast tabular solution of the position deduced from three ‘simultaneous’ sights. This is achieved in a novel way, through principles not generally associated with the traditional approach to the problem. The solution is based on the fact that the measured altitudes of a set of three stars uniquely define the most probable position of the observer projected on the celestial sphere.
Navigational Work in Ocean Weather Ships
Authors: Frankcom C. E. N.
Published: January 2010

The ocean weather ship. In 1946 an international conference was held in London as a result of which thirteen ocean weather stations were established. In 1949, for reasons of economy, the number of stations was reduced to ten, and that is the situation at present.
The Correction of Astro Fixes for Precession
Authors: Sadler D. H.
Published: January 2010

On page 268 of Volume I of this Journal, published in July 1948, A. H. Jessell called attention to a simple method of correcting fixes, or position lines, deduced from astronomical data referred to a fixed epoch, for the effect of precession and nutation since that epoch. This paper has generally been regarded as the first reference to this method, but it now appears that (as so often happens!) it was anticipated by Lieut.-Commander M. Bini, Italian Navy, in ‘Principi di un nuovo metodo per la determinazione immediata del punto nave astronomico’ (On the principle of a new method for the immediate determination of astronomical fixes), a paper presented at the meeting of the Italian Academy of Sciences on 8 November 1947 and later published in Atti della Academia Nazionale dei Lincei (Series VIII, Vol. III, Nov. 1947).

An article by Bini, in which the possibilities of the method were touched upon, was also published in March 1947 in Rivista Marittima.
Astrograph-time Star Tables for Air Navigation
Authors: Ashton Philip
Published: January 2010

The writer has compiled a table of altitudes and azimuths for the star Rigil Kent using as argument astrograph times, which are tabulated at four-minute intervals. The tables have been compiled for latitudes S. 35° to S. 39° but could, of course, be extended to all latitudes and for any star. In this note they will be referred to as the Astrograph-time Star Tables.
Jean Rotz and the Marine Chart, 1542
Authors: Taylor E. G. R.
Published: January 2010

At the time (1542) when Jean Rotz presented Henry VIII with a variation compass, and an accompanying treatise1 on its making and use, the question of magnetic variation was an acute one. It formed part of a wider controversy concerning the general validity of the sea-chart which had been raised among seamen. As to this, Dr. Pedro Nuñez, writing a treatise in 1537 addressed to his friend and pupil the Infante Dom Luys of Portugal, said that there were skilled pilots who derided the chart and declared it to be ‘a mais falsa causa do mundo’—the falsest thing in the world. Hastening to its defence, Nuñez dealt at length with the navigating errors introduced by ignoring the convergence of the meridians, and showed besides that a rhumb, or line of constant bearing, was a spiral curve on the globe. He dealt only incidentally with the variation of the compass needle and how to measure it, and this may explain why Rotz made this second source of error his main theme. The parallel N.–S. lines and E.–W. lines of the compass roses making a rectangular net on the chart are completely misleading, he says, for only the ‘diametral line’ (agonic line, line of no variation) actually runs through the poles of the world, the others lie at angles one with the other according to the magnetic variation.