bluuebunny/crossref_metadata_2025 huggingface dataset:
The Costs of Terminal Area Delays
Authors: Attwooll V. W.
Published: January 2010

Delays in the terminal area lead to increases in the operating cost of the aircraft involved. We assess these costs as one criterion of the effectiveness of the air traffic system in the terminal area, and to give a measure of the desirable expenditure on methods of reducing delay (e.g. improved radar, additional runways or even an extra airport). This note discusses methods of assessing the cost penalty of delays exclusively to the airline operator and gives examples for three types of aircraft, a short-range subsonic jet, a long-range subsonic jet and a supersonic transport.

Terminal area delays occur essentially because aircraft apply for use of the runway, either for take-off or landing, in a random fashion and because the acceptance rate of the runway is limited by the need to maintain safe separation between aircraft on and in the vicinity of the runway. Such delays involve penalty to the aircraft operator in terms of extra time and fuel consumed and hence of extra operating cost.
The Effect of Surveying Techniques on Underkeel Clearance
Authors: Weeks C. G. McQ.
Published: January 2010

In the paper which he read on 19 April 1967, Captain Dickson described in some detail the investigations which have been carried out to determine the underkeel clearance which should be allowed in any given circumstance. These investigations have concentrated on the vertical movement of a tanker under different conditions, particularly in determining squat and the effect of wave motion. However, another factor in the underkeel clearance equation is the charted depth and this also is affected by ship movement, in this case the movement of the surveying vessel which obtained the soundings. In the following note the probable effect of this movement is discussed and suggestions made by which the effect might be reduced.
Limitations of the Dead Reckoning Reference at Sea
Authors: Freiesleben H. C.
Published: January 2010

The basic values for dead reckoning, course and speed, are ascertained by inadequate references. The log does not measure the ground-speed but the speed relative to the water. The accuracy of magnetic compasses is limited by the instability of variation and deviation; gyro-compasses are better, but neither does away with steering errors. All classes of position-fixing permit the derivation of course and speed from two fixes but are influenced by the errors inherent in the methods. An astro fix is subject to irregularities of dip and the inefficiency of artificial horizons. The uncertainty of course and speed errors in running fixes is estimated and does not give very satisfactory results for astronomical and radio fixes, with the exception of methods giving an accuracy of 1 n.m. (e.g. Decca). Standard errors are referred to throughout.
The Limitations of Airborne Dead Reckoning Today
Authors: Anderson E. W.
Published: January 2010

Development of Dead Reckoning in the Air. Air navigation is the child of sea navigation. Hence navigation across the skies tended to follow the pattern of navigation across the oceans. It was built around the dead-reckoning plot, into which was fed all varieties of information. At take-off and landing, there was also a little pilotage, but this was hardly mentioned in polite air navigation circles.
The Information to be Displayed on an Automatic System in the Air
Authors: McKinlay W. H.
Published: January 2010

The paper outlines some of the factors to be considered in the design of any complete airborne automatic navigation and control system. It is pointed out that such a system should lower the work-load on the pilot or navigator as well as contributing to flight safety. Modern engineering techniques have produced a wide range of navigation devices, and their safe and economical use in a complete system involves the consideration of a control loop including the displays and the human navigator. The paper examines this navigation loop in some detail. Some simple and some more complex methods of securing safe operation are suggested.
Inertial Techniques for Marine Navigation
Authors: Bailhache H. N.
Published: January 2010

The requirements of navigation entering or leaving harbour or in narrow waters are exacting, and a very accurate position is usually essential. For this reason it is believed that inertial techniques should be applied in the first instance only to ocean navigation as, although the system will give the ship's position continually, the accuracy will be of the order of one mile.

The latitude and vertical references are absolute, but the longitude reference is relative to a known starting point. Besides position, an inertial system can also provide course, sidereal time and roll and pitch and, by comparison of successive positions, course and speed made good, and leeway. Furthermore the system could be used to feed position into an automatic plotting table, with a chart of suitable scale superimposed, so that the vessel's geographical location would be visible at a glance.
Self-contained Polar Navigation
Authors: Pedersen E. S.
Published: January 2010

Three types of self-contained navigation systems may perhaps be found, operating independently on airliners flying polar routes; doppler, astro and inertial. We may also find hybrid systems with doppler, astro and inertial components. The combination of doppler and astro systems should be the first step towards self-contained automatic navigation and this combination could be used with great advantage by the airlines for global operations. The more sophisticated doppler and inertial combination may be found too expensive for airline operators and may therefore be restricted to military uses.
Some Considerations of Free-gyro Failure in Air Navigation
Authors: Green J. F.
Published: January 2010

In polar regions great reliance has to be placed on the directional information provided by a free azimuth gyro. For sufficient reliability the use of three such gyros is advocated. An analysis is made of ‘the best two out of three’ principle—taking into account the fact that in practice no two gyro readings will be identical.

It is demonstrated that for a given reliability attaching to an individual gyro, the reliability of a three-gyro system represents a vast improvement over a single instrument and that there is an optimum way of using the information presented. The advantages of middle signal selection are pointed out and the dangers associated with mean signal selection are explained. Attention is drawn to the extension of this principle to the problems of triple-signal selection in the automatic navigation system of the future.
The Role of the Computer in Automatic Navigation
Authors: Houghton P. A. , Lewis J. H. R.
Published: January 2010

This paper discusses the operation of a simple computer which, when used in conjunction with a doppler sensor, will enable automatic navigation to be performed. It is primarily designed for the civil air operator. A series of rhumb lines may be flown and position relative to the desired track and destination will then be displayed. Directional command signals to the pilot and autopilot enable the track to be closely followed.

A short technical description of the computer is given and the expected errors and methods of correction are evaluated. Procedures for turning corners, making diversions, regaining track and flying holding patterns are given, together with the limitations or inaccuracies of the navigational information under these conditions.
Recommended Routes for Ships in Congested Waters
Authors: Dickson A. F.
Published: January 2010

The need for measures to guide shipping in congested waters to reduce collision risk has received a very considerable amount of attention over the past few years. The Safety of Life at Sea Conference in 1960 recognized the danger of collision in congested areas and required ship owners to formulate ways whereby some measure of control of traffic could be introduced with a view to reducing collision risks. Shell Tankers accept this responsibility and are, therefore, anxious to make some contribution towards the solution of the problem.

Many valuable papers on the subject have been published in professional journals recently. Most of the authors have emphasized the difficulties in which Masters are placed when called to navigate their ships through heavy traffic in reduced visibility, and Calvert in his study of the collision-avoidance problem reached a first conclusion that whatever might be done to improve anti-collision manœuvring, there was an urgent need for regulation of traffic in areas of congestion.
Regulation of Traffic on the North Atlantic Routes and in Landfall Areas
Authors: Traizet J. , Le Bihan M.
Published: January 2010

The problem of introducing any system of routing at sea is how to achieve effective control at an international level without drawing up hard and fast rules or imposing restrictions that might well, in view of the impossibility of policing vast ocean areas, prove nugatory. We hold that it is better to replace the rigidity of the prescribed route (the only relevant example, and that inconclusive, is the North Atlantic Track Agreement) by the much more fluid notion of the ‘recommended and protected route’, for which we have adopted the name ‘naviroutes’.
Ara Moana: Stars of the Sea Road
Authors: Lewis David H.
Published: January 2010

Dr. David Lewis, better known for his own remarkable feats of navigation, which include single-handed transatlantic passages, illuminates the background to various theories on early Polynesian navigation. Reviewing the evidence, which includes the wide dispersion of the Polynesians and their culture as well as methods of navigation and seamanship that were still practised at the period of European contact, Dr. Lewis concludes that they could determine both course and, in effect, latitude with sufficient accuracy to make a landfall within the area of a known island group, and so proceed to any intended destination.
Lasers and their Application to Navigation
Authors: King P. G. R.
Published: January 2010

The navigator at the present time relies greatly on both optical devices and on radio systems utilizing electromagnetic waves ranging in wavelength from millimetres up to hundreds of metres. The laser extends the coherent properties of radio waves into the visible part of the spectrum. It is natural therefore to expect that this increased facility should lead to the possibility of devising systems based on the laser which might help to overcome problems that still exist in navigation.

It is the purpose of this paper to describe the principles and performance of present-day lasers, to survey some of the techniques used in navigation in order to discover those in which the laser might conceivably play a useful part, and to comment on the laser's advantages and disadvantages in comparison with existing methods. Finally, a particular form of laser called the ‘ring laser’ is described and discussed in some detail. The ring laser is of great interest in that it provides a completely novel way of measuring direction relative to inertial space, and is therefore a possible competitor to the gyroscope for inertial navigation. The ring laser can also measure the velocity of a transparent medium moving relative to it, which could be of use in determining vehicle velocity.
Long-range Navigation Aids
Authors: Williams J. E. D.
Published: January 2010

For a quarter of a century now we have struggled in a curiously impotent way with the problem of long-range navigation of civil aircraft and the associated problem of control of traffic in oceanic control areas. The deliberations of technical conferences of the International Air Transport Association alone during the past 15 years on the subject of Long-range Navigation of Civil Aircraft would fill a library.

The development of navigation has always been retarded by difficulties with the analysis of the operational requirement. It is, for example, inconceivable that if the operational requirement for astronomical navigation had been properly explained to eighteenth-century astronomers, they would have waited for practising seamen to invent the position line almost by accident. As neither the authors of Long-range Navigation of Civil Aircraft (D. E. Hampton and J. R. Mills. This Journal 17, 183) nor any of the speakers recorded in the subsequent discussion are directly involved with the operation of aircraft some remarks on the assumed requirements may be helpful.
Reduction to the Prime Vertical Circle
Authors: Cotter Charles H.
Published: January 2010

‘Surprise has sometimes been expressed by mathematicians who have been led by circumstances to look into the subject of nautical astronomy that no method is practised by sailors for reducing a longitude observation to the prime vertical in the same way that an observation for latitude is reduced to the meridian.’

This quotation forms the opening paragraph of the first of three papers by Mr. H. B. Goodwin, R.N., written in 1904–6 relating to the problem of reduction to the prime vertical. The following description of Goodwin's work in this connection may not be without interest in view of the recent interesting paper by D. H. Sadler in which the author describes the investigations into the same problem made by G. F. Cunningham.

The vast difference, to which Mr. Sadler refers, between proposing and translating into practice, a new navigational table, is exemplified in the case of Goodwin's P.V. Tables. All the intermediate steps between proposing and producing are described with utmost clarity in Goodwin's three papers.
Marketing a New Radar
Authors: Beattie J. H.
Published: January 2010

Marketing a marine radar may not sound the most promising subject for a navigational paper. But in an age when almost anything is technically feasible, the direction of progress will be governed by many considerations which, if they are not themselves navigational, are nevertheless of great interest to those concerned with the subject. A new range of equipment for example must be related to the level of skill and training which actually prevails at sea; research and development costs must be seen in relation to the cost-effectiveness of the system; and finally purely operational factors such as traffic separation schemes may have to be taken into account. In this paper, originally presented in Paris to the French Institute of Navigation, some of these considerations are discussed in relation to the new Decca anti-collision radar.

Just over 25 years ago, in the summer of 1944, a United Kingdom conference on radio for marine transport concluded that radar would be of great value to merchant ships. They asked the Royal Navy to draw up a specification for the average ship. Discussion with various shipping interests confirmed that there was in fact a requirement for a radar set ‘for navigation and pilotage as distinct from a collision warning set, which would, of course, be a much simpler and cheaper device’. The later 1946 Ministry of Transport Specification referred to the requirement ‘to provide warning of the proximity of other surface craft and obstructions which will enable collision to be avoided’. Now of course, after 25 years of hard experience, we know that the matter of avoiding collision at sea is not apparently so simple.
Inertial Navigation for the Merchant Marine
Authors: Videlo D. A. , Wright D. L.
Published: January 2010

In this paper the history and development of inertial systems for the merchant marine is traced from the gyro-compass, familiar at sea since the beginning of the century, to complete inertia systems and integrated systems such as doppler/inertia.

The paper was presented at the Marine Navigation Symposium held in Sandefjord, Norway, on 24–6 September 1969 and is reproduced with the permission of the organizers.

The gyro-compass was first fitted on board a ship as long ago as 1908. Its function has been as the main reference by which the ship is steered and to which navigation by dead reckoning and direction finding is referred. The compass has been developed continuously to provide a more reliable, more accurate, and smaller instrument costing typically £1000 to £2000.
Distance Off by Vertical Sextant Angle
Authors: Crosbie J. W.
Published: January 2010

Distance off by measuring the elevation of a mountain top above the horizon has been a popular means of finding position at sea ever since Captain Lecky published his famous tables. This popularity persists into the radar age because distance off can often be found from a vertical sextant angle long before a ship is within effective radar range of the coast. In view of this it is surprising that the standard textbooks on navigation give scant attention to this method and any seaman finding himself without Lecky's tables would find little guidance elsewhere.

Wing Commander E. W. Anderson in The Principles of Navigation indicates that the whole angle subtended by a mountain at a ship can be found by adding half the estimated distance off in miles to the visible angle in minutes, having first corrected this angle for dip and refraction. This can be proved by simple geometry by showing that the angle subtended by the part of a mountain hidden to an observer at sea-level is equal to half the distance off.
I–Airborne Doppler Equipment
Authors: Beck G. E.
Published: January 2010

When there is relative movement between an observer and a wave source the observed frequency changes by an amount depending on the relative velocity. This is the doppler effect, and it has been realized for a number of years that it might be the means of measuring the speed of an aircraft over the ground, using radio waves transmitted obliquely and received again at the aircraft after being scattered at the surface of the Earth. By 1937 radio techniques had developed so far that letters patent were granted for systems which then appeared to be practical. A number of severe problems remained, however, and not until the close of the war did development programmes to resolve these problems make headway. Since that time equipments have been successfully produced, both here and in the United States of America, and sufficient operational experience has been gained for the value of the process as an aid to navigation to be assessed.
V — The Sea Surface and Doppler
Authors: Durst C. S.
Published: January 2010

For the efficient use of doppler techniques it is necessary that the beam of short radio waves, emitted from the aircraft shall be reflected from the roughness of the surface or from a plane surface at right angles to the incident beam. Over land there are plenty of roughnesses from which the beam is always thrown back, but over smooth sea there would seem to be no surface feature which can reflect the beam. It therefore is of interest to know the effect of surface winds in producing waves and ripples with various slopes and secondly the frequency with which light winds occur in various parts of the world.
Radar Plotting Errors
Authors: Topley H.
Published: January 2010

Errors in the derived aspect, in course and speed of another vessel, or in the nearest approach, found by plotting radar ranges and bearings on a relative plot can arise in a number of ways, such as errors:

(1) in the bearing as read from the PPI

(2) in range as read from the PPI

(3) in plotting the points on the plotting sheet

(4) in estimating own vessel's course and distance run during the plotting interval

(5) in timing the plotting interval

(6) ‘blunders’.
The Probable Errors in Forecast Winds
Authors: Durst C. S.
Published: January 2010

The information contained in this paper is intended to show the reliance which a pilot or air navigator can put on his expected winds in different parts of the world, in different seasons and at different heights. From the outset it must be realized that the figures given are subjective, and, in some regions at any rate, may need modification as facilities for obtaining upper air information are improved. However, it is not thought that such modification would be great and it would certainly not alter the broad pattern which is shown in the data presented here.
II—The Passage of Gipsy Moth III
Authors: Chichester Francis
Published: January 2010

Tactics were clearly going to be vitally important in this race, and the first tactical decision was obviously which route to take across the Atlantic. Using a dry-sail method, I worked out the speed at which the boat should sail over about twelve routes or combinations of routes. The method used was to compute from the appropriate monthly Pilot Chart of the North Atlantic (issued by the U.S. Hydrographic Office) the time it would take to cross each area measuring 5° of longitude by 5° of latitude, using the average winds determined over a long period of years. For example, in the first area (Fig. 1), from Plymouth to 5° west, the average wind blows from the west for 18 per cent of the time in June, which should give a rate of advance towards the objective of something like 2½ knots for that period. For the north-westerly and south-westerly winds which, according to the chart have blown for thirty two per cent of the time, at an average of force four, I estimated that I should travel at 4 knots towards the objective: so, similarly with different speeds for beam and following winds, I calculated that I should be able to cross this area in 62 hours. In practice it took 103 hours—more than 4 days instead of 2½—due to head-winds of from force 6 to gale force. However, this wrong estimate did not spoil the value of comparing the routes.
Avoidance of Tropical Storms by German Ships
Authors: Rodewald M.
Published: January 2010

This paper describes a number of occasions on which German ships have successfully avoided tropical revolving storms by using information which is at the disposal of the mariner today. Similar accounts could obviously be given of storm-avoidance by the vessels of other countries, but it is thought that this compilation, by a member of the German Weather Service, will interest many seamen. The paper was presented at a meeting of the Ausschuss für Funkortung held at Kiel on 10, 11, 12 September 1960, and is published with the kind permission of that body.
The Physics of Collision at Sea
Authors: Morrel J. S.
Published: January 2010

When two ships encounter one another at sea, there is a possibility that they will collide. Whether there is actual danger or not depends on the physical facts of their respective positions and motions. If danger does exist, the motions must be changed. The purposes of Dr. Morrel's paper are (1) to inquire what facts must be known, both to distinguish the cases of actual danger and to choose effective remedial action; (2) to determine when and how well these facts must be known; and (3) to consider how these facts may be obtained and how they may be best utilized.

The paper attempts to construct an integrated treatment of the whole problem, in terms of the fundamentals that define its nature and shape its solution. The problem is large and complex. Consequently, a compact treatment of it must perforce omit most of the details; both of the evidence and analysis by which the principles are established and of the technology by which they may be exploited.

Much of the treatment uses mathematics; but emphasis is placed on the implications rather than on procedures.

The paper was presented at the meeting of the Ausschuss für Funkortung held at Kiel on 10, 11, 12 September 1960 and is printed with that body's kind permission.
Columbus the Navigator?
Authors: Taylor E. G. R.
Published: January 2010

1. Journal de bord de Juan de la Cosa, second de Christophe Colomb. Presenté et commenté par Ignacio Olagué. Paris, 1957, 870 frs.

2. The Journal of Christopher Columbus. Translated by Cecil Jane, revised and annotated by L. A. Vigneras with an appendix by R. A. Skelton. Anthony Blond and The Orion Press, London, 1960, 45s.

Writing an Introduction to the Four Voyages of Columbus over thirty years ago, the late Cecil Jane remarked: ‘It might with justice be added that no event of such moment can ever occur again, unless, perhaps the tracts of space be bridged and communication established between the Earth and her sister planets.’ The fact that we are on the very eve of placing a man in the Moon should enable us to appreciate more justly the various ways in which, during the late fifteenth century, different people reacted to the daring proposal of Columbus to sail west to Asia.
The ‘Twilight-setting’ Star Globe
Authors: d'E. Atkinson R.
Published: January 2010

A star globe is described which can be immediately set up for evening or morning twilight by adjusting the latitude and date only; no reference to the Almanac is involved. The azimuth of the below-horizon Sun is also directly evident. The paper discusses the theory involved, and the accuracy attainable both with and without certain simple corrections.
The Cocked Hat
Authors: Cotter Charles H.
Published: January 2010

As every schoolboy learns, a point has position but no size, and a line has length but no breadth. Nevertheless, to a navigator concerned with fixing his ship, points and lines are represented on his chart as fine pencil marks.

The manner of representing the results of observations as pencil ‘points’ or ‘lines’, has undoubtedly led to the belief that a ship's position must be represented as lying at a point on a position line which is drawn on a chart. Nothing short of perfection in position lines is ever expected by most practical navigators, and two position lines crossing at a point are usually regarded by seamen as yielding a perfect position: and if three position lines meet at a point! … there is seldom even the slightest doubt in the mariner's mind about the reliability of such a fix. On the other hand, three position lines which do not meet at a point are usually regarded as being something not quite respectable.
Port and Terminal Navigation and Control
Authors: Brandenburg H. J.
Published: January 2010

In this paper, which was presented at an Institute meeting held in London on 26 May 1971, Captain Brandenburg discusses the problems of port and terminal navigation control in the 1980s and takes up the questions whether such control will be needed and how much control will be appropriate.

This paper is not concerned particularly with problems in Rotterdam, or indeed with any particular ports, but rather with an overall evaluation of probable port developments in the near future, say the 1980s, and with the steps which may be necessary to meet the problems that will arise. In speaking of port and terminal navigation one should distinguish between pilotage, which may be defined as conducting a ship in safety from one manœuvring area to the next, and manœuvre, which is the handling of a ship in confined areas with whatever aids are available. It is well known that the danger and difficulty of manœuvre varies greatly in different areas and this was the subject of an analysis by Captain Wepster, but I shall consider manœuvres common to all terminal areas:

(i) picking up the pilot and lining up into the fairway channel,

(ii) docking and undocking,

(iii) lining up into the fairway channel again,

(iv) dropping the pilot and heading up for destination.
Sir William Thomson and the Intercept Method
Authors: Cotter Charles H.
Published: January 2010

The year 1971 marked the first centenary of the publication of a paper on navigation which appeared in the Proceedings of the Royal Society of London in which the author, Sir William Thomson (later Lord Kelvin) described a new method of determining an astronomical position line. The method was impracticable and was not, therefore, adopted by practical seamen. Nevertheless, its design is ingenious and interesting, and an investigation of its principles adds lustre to the genius of its inventor—reputedly one of the most eminent philosophers of the nineteenth century. Although the method failed in the eyes of the mariners for whom it was intended, Thomson sparked off an interest in short-method tables which has persisted even to the present day.
Collisions Involving Very Large Ships
Authors: Watt J.
Published: January 2010

Commander P. C. H. Clissold, in a contribution to Forum in the April 1971 issue of the Journal, makes a point concerning the collision-avoidance handling of very large single-screw ships. Commander Clissold writes:

‘Because of their unwieldiness an avoiding action must be initiated while still at a considerable distance from the threat, if it is to have any effect. This distance is beyond that at which the eye of the navigator can accurately assess the risk of collision or the need to manœuvre. He must, therefore, depend upon instrumental information for making his decisions; in other words, in clear weather as in thick, he must use his radar and plot continuously if he is not to hazard his ship. If the argument is put forward that this will require two men on watch together and the state of manning does not permit this to be done, the answer is that a change in organization must be made to make it possible.’
The Determination of Distance at Sea by Vertical Angle
Authors: Bosazza V. L.
Published: January 2010

The very interesting short note by Cotter in the July issue of the Journal is of importance in the history of survey methods used in charting the harbours of East Africa and the delta of the Zambezi. In my researches into the achievements of the Zambezi Expedition of 1858, I finally found in Francis Owen's book that the vertical angle method had been used in 1820 and also in the voyages of Leven and Barracouta from 1821 to 1823. In 1820 Captain W. F. M. Owen in collaboration with the staff at Woolwich calibrated rockets in order to measure distances at sea.
Collisions and Groundings
Authors: Dunne A. G.
Published: January 2010

The number of collisions and groundings and the contact damage suffered by merchant ships every year is considerable, the averages for the years 1965–70 inclusive showing that some 15 per cent of the world's shipping over 500 g.r.t. has been involved annually in such accidents. United Kingdom shipping is no exception, and collisions and groundings alone as reported in Lloyd's Daily Lists during the first four months of 1971 show that ships from some 27 companies were involved, some with more than one incident reported although none had more than three. Collisions, groundings and contact damage are likely to occur if a ship's captain and his bridge watch keeping officers do not have immediately available in a simple form, complete information about their ship and her navigational equipment, and detailed information covering the essential tasks performed on the bridge. Unfortunately however, in a great number of ships, most of this information is not provided in an easily usable form and, as a result, even the most competent of navigators is all too often unnecessarily placed in a difficult and sometimes dangerous situation.
Lateral Error on Airways
Authors: Proctor J. D.
Published: January 2010

A. White's study of navigational accuracy near Strumble is artificial and draws some wrong conclusions. He seems to assume that it is a crime to be outside the airway. But this airway is isolated, with no mountains near cruising altitude, and no one infringed a neighbouring airway. In a terminal area I am sure accuracy is much higher, because it needs to be. Airway widths vary from one country to another and are unimportant and the boundaries are not evident to pilots, who try to stay not within the arbitrary boundaries but not too far from the centre line. The area just outside the official airway is just as safe and good as the airway, and indeed safer than the centre line where traffic density is highest and only an altitude mistake by controller or pilot is needed to promote a collision—natural dispersion is still safer than extreme accuracy. Crews generally fly only as accurately as necessary, reserving their energy for the most important tasks: the study of Strumble shows adequate accuracy. Incidentally routes and airways should follow the curved path of aircraft instead of the right-angled bends, for instance the standard inbound route to Gatwick: Lydd-Cliff-Mayfield.
V—Height Measurement from Doppler Navigation
Authors: Beck G. E.
Published: January 2010

This contribution is somewhat aside from the flow of the discussion so far. Mr. Garfield has dealt with the general features of radio altimetry and I am going to describe only one version of a radio altimeter in a little more detail. What I have to say is also a progress report in continuation of an earlier note published in the Journal; at that time the possibility of obtaining altitude as additional information from an airborne doppler navigator was discussed, and it was concluded that an accuracy of ± 5 per cent ± 2 ft. over the range of 10–500 ft. was possible. It was emphasized that the work was in an investigational stage, and no specific design was described. Today, over five years later, I can report on the flight trials of an engineered equipment using these principles. The long gap is not a true measure of the total time from design study to a unit in production, but the hazards of either commercial or military supported development programmes can extend the time in a manner which is all too familiar to many people.
Hovercraft Navigation
Authors: Hammond G.
Published: January 2010

1. Hovercraft Environment. With the exception of the sidewall craft which is unlikely to achieve speeds in excess of 30 knots, all hovercraft depend on their ability to rise clear and free from water drag in order to achieve their high economical speeds. Nevertheless a hovercraft will tend to conform with the surface over which it is travelling. A rough sea produces a rough ride which at speed produces a motion not unlike that of a car going over a series of hump bridges with vertical accelerations in the order of 1½ g—one needs to be strapped into a seat. The most efficient means of propulsion is achieved by using air screws; these are noisy and necessitate crew members using an intercom. Control surfaces, rudder and airscrews are aerodynamic and to reduce air drag the hovercraft is likely to be low in silhouette and give poor all-round vision to the command. The biggest single factor is drift; being aerodynamic and free of water drag, the hovercraft is completely wind borne and in moderate beam winds can track with as much as 45° of drift angle on and turns out of wind can be alarmingly large.
The Impact of Radar on the Rule of the Road
Authors: Clissold P.
Published: January 2010

The International Regulations for Preventing Collisions at Sea, 1960, became effective on 1 September 1965 and, in spite of the sound advice contained in the Annex, it already seems doubtful whether the Steering and Sailing Rules will prove efficacious in preventing collisions. It is clear that a growing body of opinion considers that changes of some sort are necessary; the April number of this Journal, for instance, contains interesting proposals by Captain J. F. Kemp.
‘The Sector Rule and the Collision Problem’
Authors: García-Frías J.
Published: January 2010

Captain García-Frías has made the following comments on the discussion of his recent paper (this Journal, 18, 141) contributed by E. S. Calvert and S. H. Hollingdale.

Captain García-Frías observes that while Calvert and Hollingdale recognize that this paper combines his earlier suggestion for a sector rule with a set of manœuvring rules, they have failed to recognize the fundamental distinction between the structural and operational aspects of an encounter; his proposed manœuvring rules deal with the operational aspect. These rules differ from the manœuvres they have themselves proposed in that they depend only on the bearing of the target as seen on the radar at a distance of 2 miles; they derive from his sector rule and do not require a quantitative estimate of the miss distance. His rules are only the same as their manœuvres for the case of a steady bearing since their manœuvres also require the sign of the miss distance.
The Three Stages of Radar Plotting
Authors: Topley H.
Published: January 2010

Many discussions have taken place regarding the feasibility of plotting when using radar in reduced visibility and it soon becomes apparent that there is confusion in what each of us considers by the term ‘plotting’.

These notes are to suggest definitions of the various stages of plotting and to consider the conditions under which each is necessary.

Radar plotting can be divided into three stages:

(a) Record plotting

(b) Deductive plotting

(c) Forecast plotting.
The Essentials in Radar Presentation
Authors: Hugon P.
Published: January 2010

In Captain Wylie's note on ‘Radar as an anti-collision aid: the ultimate essentials in presentation’, masterly definition by an acknowledged expert aptly crowns the discussion which follows Commandant Oudet's paper on ‘Collisions and the Courts’ in the same issue of the Journal. It is interesting and gratifying to find in that discussion a suggestion by E. S. Calvert on manœuvres in close-quarter situations which recalls a similar proposal made by the French Institute at our first joint meeting held in London in 1957. It is that the manœuvre should be a turn of 2x° to starboard if a threat, an echo for example, is perceived x° forward of the port beam. This suggestion passed almost unnoticed at the time although it is mathematically sound if one assumes that the speed of the two vessels is the same.
A Probability Distribution for a Time-varying Quantity
Authors: Lloyd D. A.
Published: January 2010

In many practical situations in the field of navigation, it has been noticed that the probability distribution of measured errors has a shape which has considerable departures from that of the normal distribution. These departures are particularly noticeable in the ‘tails’ of the distribution of practical cases, which are often higher than those of the corresponding normal distributions (see, for example, ‘Is the gaussian distribution normal’, W/Cdr. E. W. Anderson. This Journal, 18, 65).
The Vinland Map
Authors: Richey M. W.
Published: January 2010

The discovery of the Vinland Map and the recent publication of its description* has been attended with considerable publicity on both sides of the Atlantic, in publications ranging from learned journals to glossies. Briefly, the map, provisionally dated about 1450, was discovered by an antiquarian bookseller of New Haven, Connecticut, in circumstances which so far have precluded a proper examination of its history. It has, as a recent reviewer put it, ‘no ancestors, no close relations and no descendants’. Its importance to the student of the history of navigation and discovery, however, is that (assuming it is authentic) it is by far the earliest surviving example of a map portraying any part of the Americas, and it ostensibly provides the first evidence for an early school of Norse cartography, for Vinland can clearly be identified with that part of the American continent settled by the Norsemen in the latter part of the tenth century.
Navigation Development and the Institute
Authors: Anderson E. W.
Published: January 2010

“Through art to science” was the theme of the second “Off the Beaten Track” programme of lectures for nautical schools and colleges. In the last twenty years navigation has changed in precisely that fashion. At the end of World War II, in spite of equipment developments, navigation remained an art, and this shines through the pages of our early Journals. Today the Journal proclaims that the art has become a science. “Sic transit gloria Astro!”
Radar at Sea
Authors: Wylie F. J.
Published: January 2010

The twenty-first birthday of the Institute coincides very closely with that of commercial marine radar. Many merchant ships were fitted with naval radars between 1942 and 1945 but these bore little resemblance to the sets which would be needed for peaceful purposes.

Even before the war had ended, the United Kingdom Conference on Radio for Marine Transport (U.K.R.M.T.) was set up under the auspices of the Radio Board of the War Cabinet, to discuss the peacetime applications of the war developments. This conference led to the establishment of an Application Committee (R.A.M.N.A.C.) which kept the administration, the user and the manufacturer in touch. Immediately after the war, the Admiralty was in collaboration with the Ministry of Transport (M.O.T.) and the shipowners to arrange the supply of surplus 3-cm (Type 268) radar to the merchant navy, pending the design and production of commercial sets. At the same time the Admiralty Signal and Radar Establishment (A.S.R.E., now A.S.W.E.) was drawing up a specification1 to meet the needs of navigation and anti-collision. A prototype to this specification was demonstrated to all concerned in 1946.
The Future of Merchant Marine Navigation
Authors: Wepster A.
Published: January 2010

Although the merchant navy is one of the earliest users of navigation, it is today by no means the most spectacular user, especially in comparison with present-day hovercraft and the coming supersonic civil aircraft. This absence of the spectacular is, however, not due to lack of imagination or progressiveness, but stems from very natural circumstances. These circumstances are the relatively low-if not the lowest-transportation speed, the application of the laws of Archimedes to obtain the required carrying capacity, and the laws of economics which dictate a delicate balance between investments and net revenue.
Money, Men And Machines
Authors: Majendie A. M. A.
Published: January 2010

At the basic level scientific knowledge has now reached a stage at which sufficient is known to make possible almost any technological achievement in the field of navigation, if sufficient effort can be deployed in its solution. And at the project and engineering level refinements in control and planning have made possible the handling of vast and complex tasks within the necessary disciplines imposed by the available resources.
J. Th. Verstelle
Authors: Powell Claud
Published: January 2010

Many readers of the Journal will have learned of the death, at the Hague on the 19 July 1968, of Jacobus Theodor Verstelle. He was aged 68. An authority of international standing on geodesy and hydrography, he was awarded the De Ruyter Medal in 1957 for ‘outstanding services in the fields of navigation and survey’ and became in 1965 an Officer of the Order of Oranje Nassau. He was elected to Fellowship of this Institute in 1955.
The Organization of Seaborne Traffic
Authors: Oudet Frégate L.
Published: January 2010

The Safety of Life at Sea Conference, 1960, recognized the special danger of the concentration of maritime traffic in converging areas and entrusted shipping companies with the responsibility of establishing the channels to be followed in these areas. The three Institutes of Navigation may be helpful to the companies in this respect through the competence and prestige of their special working groups. The problem consists in defining one-way channels and cross-overs for different streams of traffic. In entrusting this responsibility to the companies, the London conference implicitly agreed that the organization of converging areas was a simple application of the International Regulations for Preventing Collisions at Sea to the particular conditions of each area.

In converging areas ships will remain entirely and solely subject to the Collision Regulations. Agreements on the channels to be used will be covered by Rule 29 which refers to the ‘Ordinary Practice of Seamen’.
Naviroutes and the North Atlantic
Authors: Traizet J.
Published: January 2010

A revision of the North Atlantic Track Agreement would make it possible to form a larger group of subscribing companies. The existing tracks could be simplified and the danger of convergence on certain channels avoided by modifying the double landfall at Fastnet and Bishop and by moving certain junctions. This could be done without unduly lengthening the channels. One might also replace the concept of fixed channels by the more liberal one of protected channels, which one might call ‘Naviroutes’.

Ships wishing to follow these would benefit from increased safety by the use of certain simple rules, which may be summarized as follows:

A neutral zone, varying in size according to the region, of the blue-line type proposed by Oudet and Poll would separate traffic going in opposite directions. In good visibility ships crossing a ‘Naviroute’ would do so at an angle of more than thirty degrees; in fog ships would cross a ‘Naviroute’ at right angles and at low speed. Each of these rules is dictated by commonsense to every seaman with experience of crossing busy shipping channels.
The Demarcation of Traffic Lanes by Leader Cables
Authors: Le Page L. S.
Published: January 2010

The paper examines in particular the possibilities of using leader cables for establishing traffic lanes at sea. A brief history of the leader cable is given, followed by discussion of the components and variables in the system such as the cable itself, the energizing frequency and detection and indicating devices. The application of leader cables in the context of modern navigational conditions is then examined. An appendix gives a valuable list of some of the more important references on leader cables.
Marine Traffic Control in the Panama Canal
Authors: Kimball R. L. , Shepard J. R.
Published: January 2010

The Panama Canal Company's Marine Traffic Control is being designed primarily to minimize ships' average transit-time and obtain optimum use of Canal facilities, but it also includes features contributing to collision prevention. It prepares an operation schedule consistent with the number and characteristics of ships that are in transit and with operating conditions. Actual operation is continuously monitored and signals currently displayed to pilots to facilitate close adherence to the schedule. If the contemplated schedule is cancelled, as by trouble in locks or sudden periods of poor visibility, re-scheduling is rapidly formed and signals transmitted to pilots in conformity with the new schedule.

The system's contribution to collision prevention includes elimination of several hazardous situations: (a) Undue crowding of traffic; (b) Lock-entrance stand-off delays due to untimely ship arrival, during which ship handling is difficult; (c) Meets or overtakes at potentially hazardous locations.

Further, when approaching a bend on which other ships would not be visible and at which the meet would be hazardous, a pilot is advised of the number of ships which will be round the bend before he reaches it. Also indicated is the number of meets due to occur immediately beyond the bend, a distance through which the manœuvrability of his ship would be affected by the manner in which he rounds the bend. The automatically operating system is based on transmission of data comprising ships' identities and locations to a central control point where the data is analysed by an electronic computer and from which advisory signals are automatically transmitted back to the ships.
Some Meteorological Aspects of Flight in the Supersonic Age
Authors: Durst C. S.
Published: January 2010

The main meteorological features of the atmosphere from 50,000 to 70,000 ft. which are likely to be of importance to supersonic aircraft, are the ‘polar-night westerlies’ and the abrupt rises in temperature which take place in late winter in latitudes polewards of 50° or 60°.

The polar-night westerlies blow between 50° and 70° latitude and reach high velocities, increasing with height, from 60,000 ft. during the winter months; towards.the end of the polar night there is often a sudden rise (perhaps as much as 40° C.) at about 85,000 ft., which spreads downwards and is eventually associated with the termination of the polar-night westerlies.

The increase of speed of supersonic aircraft, as well as the decrease of variability of the wind with time at heights above 50,000 ft., have remarkable effects on the punctuality of arrival of aircraft. For instance, on the route from London to New York, the probable error due to wind in arrival time of a 1500-kt. aircraft at 50,000 or 60,000 ft. is about half a minute. This is in contrast with a probable error of ten to fifteen minutes for a 400-kt. aircraft flying at 30,000 ft.