bluuebunny/crossref_metadata_2025 huggingface dataset:
D.f. Loop Errors due to Heel
Authors: Chichester Francis
Published: January 2010

Yacht and other small-boat navigators must often wonder what error in a d.f. loop reading on a radiobeacon may be due to heel. The error is in fact quite small, the maximum for a 25° angle of heel being 2°.8 when the bearing is quadrantal to the boat's heading, i.e. when the relative bearing is 45°, 135°, 225° or 315°. When the relative bearing is 0, 90°, 180° or 270°, i.e. when the beacon is ahead or astern or abeam, the error is nil.

Table I gives corrections to the nearest ½ degree, to be applied to the relative bearing of a beacon for 15° and 25° of heel. It makes no difference whether the boat is heeled towards or away from the beacon.
Plane Sailing or Horizontal Navigation
Authors: Waters D. W.
Published: January 2010

Professor Taylor contends that the expression used to describe a course of action so simple as to leave no room for mistakes is plain sailing; that this is nautical in origin in that it derives from a simple or plain system of navigation based upon the use of a simple or plain (manifestly foolproof) chart; that this system of navigation was known originally as plain (simple) sailing—which expression she traces back to Richard Norwood's Doctrine of Plaine and Sphericall Triangles of 1631, and that it was sophisticated into plane sailing in the eighteenth century in the belief—which she holds to be erroneous—that the expression described a form of navigation based upon the use of a plane or flat chart on which the Earth was drawn as if the Earth and oceans lay in one horizontal plane area and not upon the surface of a sphere or, more accurately, ellipsoid; and, finally, that the Admiralty Navigation Manual is in error in teaching mariners that ‘to regard certain small triangles as plane… gives rise to the expression plane sailing, which is popularly referred to as if plane were spelt plain and the sailing free from difficulty’.
Champlain's English Log
Authors: Chilton D.
Published: January 2010

In Lieutenant-Commander Waters' paper ‘The Development of the English and the Dutchman's Log' (this Journal, 9, 70) there is an illustration (Fig. 1, p. 73) of the English log, reproduced from Champlain's Les Voyages de la Nouvelle France Occidentale. The device illustrated, though no doubt correct in intention, could not have performed the function stated, namely, of floating ‘vertically in the water presenting its full face to the ship's wake' (p. 74). This raises the suspicion that Champlain had not examined the log minutely enough, if at all, or at least had failed to instruct his draughtsman properly.
The Bicentenary of the Nautical Almanac
Authors: Sadler D. H.
Published: January 2010

In ‘A Modern View of Lunar Distances’ (Journal, 19, 131) H.M. Nautical Almanac Office has already covered most of the technical aspects of the method of lunar distances which the Almanac made practicable; in ‘The Foundation and Early Development of the Nautical Almanac’ (Journal, 18, 391), Dr. E. G. Forbes has given a scholarly, fully documented, account of the early history of the Almanac; and Mr. Sadler himself has written many articles on various aspects of the bicentenary. This general account, which necessarily must duplicate parts of these articles, is directed as far as practicable to those aspects that are likely to be of greatest interest to members of the Institute not technically concerned with astronomical navigation. The paper was presented, in an abridged version, at the Annual General Meeting on 25 October 1967.
A Series of Marine Data Systems
Authors: Mackay I. S. S.
Published: January 2010

This paper describes a series of data handling systems, termed MARIDAS, which would cater for various maritime problems and situations. Eleven specifications have been prepared, of which three, those for hydrographic work, harbour and pilotage, and merchant ships, are reproduced as Annexes here. A version of the paper has appeared in naval publications with restricted circulation.

In the past decade various navies have introduced electronic data processing to ease the strain on ship captains and their officers in order to increase their efficiency. The need is urgent as the quantity of information now available from the many sensors has grown so remarkably, and the speeds of aircraft and targets have increased to such an extent, that human reaction and ability is fully extended. However, the thought processes in all the operations which have to be performed have remained the same. These processes are largely related to the solution of trigonometrical or triangulation problems: Spherical, for astronomical or satellite navigation; Plane, using distances and angles for geographical or relative position problems and speeds and angles for relative velocity problems, avoidance of collision and intercept.
The Black Flood: Lessons of the Torrey Canyon
Authors: Oudet L.
Published: January 2010

It is not often that a drama of the sea provides the main story in the news, and it is still more unusual for such an occurrence to continue to occupy the headlines; but the Torrey Canyon disaster was unique in having done this for a whole month and more. Day after day, there was a slow and inexorable increase in the area affected by the catastrophe and in its duration: while such protective measures as could be improvised could seldom do more than repair damage that it was impossible to prevent.
Area Navigation and the Relationship to Terminal Area Capacity
Authors: Winick Alexander B.
Published: January 2010

An area navigation capability can be of considerable benefit to users as well as providers of ground facilities. A.T.C. radar terminal service and area navigation utilizing cockpit pictorial displays are complementary from a total system viewpoint. Pictorial displays, coupled with digital computers capable of storing navigation information, will greatly reduce pilot workload. Optimum usage of A.T.C. radar service and cockpit navigation will provide maximum redundancy at least total cost and reduce controller workload.

Pictorial computer procedures will have many applications of benefit to high density terminal areas, such as (1) departure paths from a satellite airport, (2) descent paths from high altitude to a terminal area, (3) missed approach patterns, (4) approaches to satellite airports, (5) simplified holding procedures, and (6) discrete paths for descent corridors. Procedures are expected to be developed as a result of a full-scale Federal Aviation Administration operational programme for selected en-route and terminal areas permitting use of area navigation facilities, using F.A.A., airline and general aviation aircraft in a live A.T.C. environment.
The Metrication of Navigation
Authors: Turner Ronald
Published: January 2010

Since government and industry have officially accepted the introduction of the International System (S.I.) Units for all forms of measurement it is relevant to examine the implications of this for marine navigation.

The present situation. Marine navigation is no different from many other fields in that a proliferation of units is used to measure the same dimension and, moreover, these units have no systematic relationship to each other. In this respect length is the worst offender: we measure heights in feet, depths of water in fathoms, distances in cables or nautical miles and moreover these nautical miles may be British standard, International standard or those precisely determined by latitude.
The Improvement of Navigation lights and Signals
Authors: Hayman Bernard
Published: January 2010

Douglas Lindsay's article in the Journal (20, 249) raises numerous interesting points and I agree with much of what he says, but he has orientated himself so strongly towards the problem of the big ship that he has recommended a change that would bring complete confusion at the smaller end of the scale.

The most useful points Mr. Lindsay raises are the need for increased ranges for ships' navigation lights, coupled with the dangers of extraneous lights. Both these points apply in their own way to small vessels. However, I disagree with Mr. Lindsay's article where he refers to the meaning of a single white light. He starts his argument by saying:
Signals for Vessels in Sight of One Another
Authors: Rodger D. A.
Published: January 2010

I Have been following the articles on this subject in the Journal 1 with some interest and hope that the personal views of one comparatively junior officer may be of some interest.

It is implicit in all these articles that, except in the close-quarter situation which the Rules are surely designed to prevent, the sound signals are unsatisfactory. What is not stated in so many words is that, international conferences notwithstanding, Rule 28 (a) is more observed in the breach than otherwise. I cannot of course be sure, but I suspect that this has been so since electric navigation lights superseded oil in general use, thus increasing the recognition range and allowing avoiding action to be taken at greater distances. There is also the natural human, if not legally commendable, desire to let sleeping captains lie.
‘Underkeel Clearance’
Authors: Ewing J. A.
Published: January 2010

I would like to comment on the change in underkeel clearance due to the motion of a ship in a seaway (A. F. Dickson, thisJournal, 20, 363).

Captain Dickson, in his conclusions, states that known techniques do not allow underkeel clearance to be calculated when ship motion is present. In fact there are a number of reliable ways of calculating the motions of a ship in waves (for example References (1) and (2), which treat the case of pitch and heave) which may help in this problem. These methods usually assume the ship is in deep water and is heading directly into the waves which are further assumed to be long-crested; but I believe it may also be possible to make reliable calculations for shallow-water effects and for waves which are, in reality, short-crested.
‘Radar and the Rule of the Road’
Authors: Burger W. , Corbet A. G.
Published: January 2010

We would like to reply to some of the comments and all the criticisms made on our suggested amendments and additions to the existing (1960) Regulations for Preventing Collisions at Sea, which have appeared in this Journal(20, 103, 340).

to Captain G. Swallow, R.N.

Upon reflection we agree to some extent with the comment on our suggested re-wording of section 16 (b). However, for the very reasons he has pointed out, with reference to certain court cases, we feel that the mariner must be made absolutely certain about his position in law with regard to this section. This section, as it stands, can be very misleading in that it gives the mariner in charge of a power-driven vessel the impression that he need not always stop his engines if he hears a fog signal forward of his beam from another vessel, which has not been sighted. Yet in all the court rulings that we have seen, concerning the interpretation of this section, there is not one case where a mariner has been excused from failing to stop his engines on the grounds of the ‘apparent’ escape clauses, i.e. because of ascertainment of position and/or practicability.
Mathematics and the Navigator in the Thirteenth Century
Authors: Taylor E. G. R.
Published: January 2010

I must forewarn you that this lecture will deal only with very elementary mathematics. Its subject is what may be termed the preparatory school stage in the education of the navigator. Nevertheless, it is a subject of particular interest and importance because it is in the field of navigation that we first meet with mathematics quite outside learned academic circles. It was among sailors that the process was begun (and it is not yet complete) of transforming the craftsman—whose skill rests on tradition and experience—into the technician—who works on established scientific principles. For the scholar, mathematics is like poetry—an end in itself.
The Nature of the Information to be Displayed at Sea
Authors: Le Page L. S.
Published: January 2010

The view is taken in this paper that an automatic navigation system should be capable of weighing up data and issuing instructions, in the same manner as a human navigator. Conventional information tends to offer static rather than dynamic data.

It is suggested that there are several stages of development towards completely automatic navigation: (i) a dynamic interpretation of the existing navigational situation, (ii) the automatic prediction of future situations, (iii) automatic navigational advice, (iv) automatic control of a ship under the supervision of a navigator. Such control would not take care of all situations but would be particularly suited to some; a list of the information likely to be required for presentation is given.

For entirely automatic navigation to be feasible, the whole of the process of transport at sea may have to be reviewed. It is suggested that the trend should be towards presenting error, rate of change and forecast data.
Inertial Methods in Hybrid Navigation Systems
Authors: Adams D. E.
Published: January 2010

Some general features of inertial and hybrid inertial systems are examined in relation to the navigational problem in its two essential aspects:

(i) The present situation.

(ii) The action required.

As the fundamental D.R. system, inertial navigation has the virtue of independence but suffers from time-dependent errors. The engineering complexity and delicacy of adjustment of purely inertial navigation systems of long-period accuracy detract from its general application where other aids are available. On the other hand, increasingly stringent demands on flight-path computation and control justify an examination of the benefits to be derived from exploitation of the particular short-period merits of an inertial element used in conjunction with other aids.

Principles of mixing are discussed in relation to quantity and quality of information inputs. Examples are then given of fallacies which may arise from the omission of essential information or from ignoring cross-coupling, and of the impracticability of mixed systems which assume too much of the quality of the input information.

After summarizing the main features of inertial, radio/radar and astro aids, examples are given of practical and useful mixed systems which do not require the highest precision of inertial components. For example, auto-astro and inertia/doppler/ground fix contain the necessary and sufficient ingredients for combining long-period accuracy with short-term memory, speed of response in manoeuvre and instantaneous outputs such as are required for precise control and for flight path monitoring.

Summarizing, it may be said that the value of true and hybrid inertial systems in the military context is evident. For more general application we may hope to see a gradual evolution of small, accurate and reliable central reference systems which will permit the employment of inertial methods suitable for mixing, especially with doppler in an accurate D.R. system. The outputs will be suitable not only for flight-path monitoring, but as providing information of a quality very well suited for integration into the control system and so into any overall system of flight automation.
A Roller Map Equipment
Authors: Wikkenhauser G.
Published: January 2010

This equipment was originally designed as a pilot aid to facilitate the use of maps on a route flight. It was used to such an extent that several different models have been developed which fall into the category of automatic navigation equipment. However, even the new concept is still an open-loop navigation device, the loop being closed through the pilot or navigator in the aircraft who reduces the accumulated position errors to zero by direct observations. In the most sophisticated form the roller map equipment is driven automatically according to aircraft ground-speed derived from doppler instrumentation and is equipped with an aural flight programme replay device to draw the pilot's attention to salient features of his flight route.
The Human versus the Automatic Navigator
Authors: Majendie A. M. A.
Published: January 2010

The title of this contribution is, in itself, misleading. All our navigation is planned and devised by human beings, whatever may be the degree of automaticity inherent in any particular system. The navigation of a space rocket is just as human as that of a Polynesian canoe, despite the absence of a working navigator going along ‘for the ride’. In considering the degree of automaticity desirable for a given navigational task we are really trying to decide how best to deploy the available human effort.
North Sea Nemedri Routes—A Collision Problem
Authors: Beattie J. H.
Published: January 2010

In the discussion which followed the Institute's proposal on routing, Captain Oudet proposed that the collision problem should be investigated in other areas where the risk was known to be high. This paper discusses the origin of NEMEDRI routes and the collision problem on specific NEMEDRI routes in the North Sea.

The origin of NEMEDRI (Northern European and Mediterranean Routing Instructions) routes is a matter of history and necessity, some understanding of which is necessary in any analysis of present problems, NEMEDRI routes are those swept routes through declared danger areas due to mining in World War II in North European waters, the Mediterranean and Black Sea. These routes take their name from the NEMEDRI publication issued to mariners giving the relevant hydrographic information for these particular areas. The swept routes and declared danger areas in many other areas, such as the remote Kerguelen Islands, Tonga or off Korea, have no such special publication and are notified in Notices to Mariners. The present navigational significance of the NEMEDRI routes is that they carry a very substantial amount of the world seaborne trade.
An Alternative to Full Inertial Systems
Authors: Stevenson J. D. , Wright D. L.
Published: January 2010

It is not the purpose of this paper to enter too deeply into the controversy between heading reference systems (combined with a velocity sensor) and full inertial systems. Rather it is intended to indicate what may be achieved at the present time, and in the next few years, using a heading reference system combined with a velocity sensor such as doppler radar. In conclusion the performance, weight, size, cost and reliability of such systems will be compared with similar figures for a full inertial system in the hope of stimulating thought and discussion as to what is the correct choice of system as well as to what the user may be able to afford.

In the early part of the last decade the most widely used heading reference was the gyro-magnetic compass—a flux-valve being used to give good long-term heading accuracy whilst short-term variations are smoothed out by the integrating action of a' directional gyroscope. The directional gyroscope was in fact slaved to the magnetic reference. Accuracies of 1°·0 (r.m.s.) are typically achieved by such a system, although higher accuracies are sometimes claimed under certain specified conditions.
French Experimental Work on All-Weather Landing
Authors: Villiers J.
Published: January 2010

During 1960 the French civil and military authorities decided to coordinate their efforts and to step up the programme of research and practical tests on landing in poor visibility. They felt that they could best contribute to the development of air transport in this vital field by adding their own vigorous and intensive efforts to the considerable body of work already undertaken by other countries. Numerous automatic landings had already been made in the U.S.A., and the British Blind Landing Experimental Unit had made several thousand. Yet, in spite of the results obtained, many problems still remained unsolved and many questions unanswered. There was evidently still room for much more practical work and theoretical research.
ILS and Landing in Zero Visibility
Authors: Lebleu M.
Published: January 2010

Only ten years ago it would have been premature to imagine that ILS was likely to provide the basic means for completed landing in zero visibility. The system, designed in 1939, had then received only technological improvements, and no feature seemed to lend itself to any notable development. A frequency of 110 Mc/s is much too low to obtain a narrow beam; all the rival systems now being developed experimentally use frequencies 10 to 100 times higher. Nor is the measurement of difference in rate of modulation the most accurate operation possible with electrical magnitudes; pulse-systems or phase-comparison systems are better adapted.

In view of the number of installations in use on the ground and in the air it was, however, practically impossible to envisage any other guidance system to replace ILS; for modifications would have to be ‘compatible’, i.e. not involve a change in airborne receivers.
The Use of Apparent Consistency in Errors of Latitude in the Identification of 16th and 17th Century Pacific Island Discoveries
Authors: Jack-Hinton Colin
Published: January 2010

In several studies of the Spanish and Dutch voyages in the Pacific in the sixteenth and seventeenth centuries it has been suggested that an apparent consistency in errors of latitude determined by the navigator in question can be used as evidence in the identification of island discoveries, and can be regarded as confirming the identification of one or the rejection of another possibility. I am extremely doubtful about the validity of using such apparent consistency of error, even as secondary evidence combined with other indications, and have no doubts about its invalidity as primary evidence.

Andrew Sharp, for instance, when considering the identification of the Los Bajos de la Candelaria of Mendaña's voyage of 1568 in his The Discovery of the Pacific Islands, remarks that whilst both Ontong Java and Roncador Reef in the Northern Solomons are possible identifications: ‘The steady southerly error in Gallego's latitudes … points to Ontong Java’.
Astrofix and Rectofix Tables
Authors: Sadler D. H.
Published: January 2010

(1) Through the above contribution by Captain Charles H. Cotter, my attention has been drawn to the fact that the essential principle of the ‘Rectofix Tables’ is not only quite old but has been incorporated in a set of published tables —the Position Line Star Tables (for fixing ship's position by reduction to meridian and prime vertical without logarithmic calculation) by H. B. Goodwin, R.N., J. D. Potter, London, 1906.

Understandably, there are considerable differences in methodology and presentation, but all the essential concepts underlying the method are incorporated in Goodwin's tables; the main improvement introduced by Dr. Cunningham (who was, of course, quite unaware of these tables) is the inclusion of tabulations for the azimuth (Journal 17, 17).

Although none of the colleagues to whom I showed my short article called my attention to the existence of Goodwin's tables, I must accept sole responsibility for not having made a more thorough search of the published literature on the subject. This omission does, however, serve to underline the general note in that article on the difficulty of assigning priority for particular methods.
Manned Spaced Flight Navigation Techniques
Authors: Wicker F. D. P.
Published: January 2010

I have read with great interest the article entitled ‘Manned Space Flight Navigation Techniques’ by Major R. C. Henry in the October issue of the Journal.

It would appear that much of the imagined difficulty in interplanetary navigation is due to the fact that until now man has really been concerned with fixing his position and controlling his path on a spherical surface, the third-dimensional problem in air navigation has been one of altitude—i.e. definition of the surface concerned. Now, for the first time, we are involved in what at first sight appears to be a truly three-dimensional problem, and its solution appears difficult, partly because we are to be removed from our familiar graticule of earthly meridians and parallels.

If the problem be divided into two parts, an obvious solution presents itself. At sea, a ship must be on the surface of the water, and is mainly concerned with its position and course on that surface. An aircraft determines its surface of reference by barometric pressure (which by tradition is termed Pressure Altitude and expressed as a linear measure), and again is then concerned with a twodimensional problem on that surface.
Navigation for Apollo Lunar Landings
Authors: Mayer John P. , Osburn Richard K.
Published: January 2010

Whatever else may be said about man's first landing on the Moon, it was surely the most spectacular navigational achievement of all time.

In the following paper Dr. Mayer, Chief of the Mission Planning and Analysis Division at the Manned Space Flight Center, Houston, and Mr Osburn give a general outline of the operational use of the space navigation systems which contributed to the success of the first manned lunar exploration mission. The ground and onboard navigation systems, their interfaces with the Apollo guidance system, and their uses in various phases of lunar landing are reviewed. The navigation procedures are then discussed, with particular emphasis on the Apollo 11 mission, the first manned Moon landing. Post-flight analyses and actual mission results from Apollo 11 are examined to give an accurate assessment of the overall performance of the navigation system.

The paper was presented by Dr. Mayer at a joint meeting of the Institute and the Royal Astronomical Society held in London at the Royal Geographical Society on 1 October 1969 with Professor Sir Bernard Lovell, F.R.S., in the Chair.

A list of the terms and abbreviations used in the paper is given on page 148.

The Apollo navigation problem may be divided into two general areas. The position and velocity of the vehicle must be determined at some specified time, present or immediate past. (This will be referred to as orbit determination.) This information must then be utilized to determine the future course of the spacecraft. (This is referred to as trajectory prediction.) Ground orbit determination may be performed in either a low-speed or a high-speed mode. Low-speed computations require 5 to 10 minutes for processing, while high-speed solutions are available virtually instantaneously. The ground system utilizes both types of processors. Low-speed solutions are used for trajectory prediction and, in a few cases, for processing astronaut observations. The high-speed processor is used to monitor manœuvres such as the descent to the lunar surface and for special situations where near real-time orbit solutions are necessary. The spacecraft system uses only a high-speed processor, modified slightly to facilitate manual use by the astronaut in some cases.
The Use of a Weather Radar as a Terrain Warning System
Authors: Cox V. J.
Published: January 2010

Although it has been technologically possible for some years to give warning of ground collision hazards, the specialized radars for this purpose have been limited to military aircraft. Because of complex cost and installation problems, radar of this type have not been installed in civil aircraft.

This paper discusses possible developments in civil weather radar to enable it to give a warning of ground collision hazards. The paper was presented at an Ordinary Meeting of the Institute held in London on 19 November 1969 with the President in the Chair.

For the purpose of this paper, ground collision is defined as an error of navigation or height management, which results in a zero ground clearance. The error can, of course, be human or instrumental but the assumption is made that the aircraft was basically capable of avoiding the hazard. There has been a tendency to associate ground collisions, particularly hill and mountain collisions, with the older piston-engined aircraft. Its importance in terms of airlines operating modern jet aircraft is not always well appreciated. It is true that the normal operating altitude of jet aircraft almost eliminates ground collision hazards in the cruise phase, but in general they suffer from a longer response time and a higher approach speed, which makes them more vulnerable in the let-down and approach phase. Since in any event the let-down and approach phase accounted for about two-thirds of the accidents with piston-engined aircraft, ground collision hazards remain a serious problem with pure jet aircraft.
Temperature Trial Forecasting for S.S.T. Cruise Levels
Authors: Wehry W.
Published: January 2010

S.S.T. flight operations are likely to commence early in 1970 and meteorological briefing for all flight levels must therefore be established, especially for temperature, wind and clear-air turbulence. This paper, which was presented to the S.S.T. Working Group, outlines the accuracy of temperature prediction over 24-hour periods and suggests forecast rules. Finally the resultant requirements are stated.

Several conceptions of possible and desirable temperature forecasting accuracy have been expressed in relation to S.S.T. performance by different panels. For example, the Fausst WP 529 (Franco-Anglo-U.S.-S.S.T. Working Paper 529), revised 3 March 1967, recommends a maximum standard error of 3°C for temperature forecasts at the S.S.T. level, which means the accuracy of temperature forecasting must be within a range of ± 3°C in 68 per cent of all cases. After other recommendations, such as the I.C.A.O. S.S.T. panel, July/August 1968, the subsonic requirements may be adopted for the S.S.T. too; these recommendations allow a standard error of 1°·8C, i.e. the accuracy of temperature forecasts must be within a range of 1°·8C in 68 per cent, or 3°C in 90 per cent, of all cases.
Integrated Navigation by Least Square Adjustment
Authors: Ramsayer Karl
Published: January 2010

For the integration of different navigational aids of an aircraft by a general purpose computer the following way is proposed: The basic navigational system is a doppler or inertial dead reckoning system (D.R.S.). The other navigational aids serve for control measurements, with the help of which the error of the D.R.-position and the most important systematic error sources of the D.R.S. are determined by least square adjustment during flight. These error quantities are then used for a corresponding correction of the D.R.S. The supplementary navigational aids are consequently used both for the correction of the D.R. position and for the calibration of the D.R.S. The method is described for the example of the integration of a doppler D.R.S. with Tacan.

From the great number of different navigational aids, which are today available or in development, we can draw the conclusion that none of these navigational systems can satisfy all requirements. Therefore, for many years it has been the custom to combine several navigational aids, and thus the human navigator has the task of evaluating the different navigational information. This evaluation is, however, often disturbed by unfavourable conditions. In a high-speed aircraft for example the navigator is overburdened by a lack of time and space, errors in the navigational sensors, &c. This necessarily means that the evaluation of the data is reduced to a minimum, and that a great deal of the available information is lost.
A Brief History of Nautical Logs to A.D. 1800
Authors: Cotter Charles H.
Published: January 2010

The name log, to denote a device for measuring a ship's speed or the distance she has made through the water, appears to have come down to us from the Saxon log—‘a hewn trunk or branch of a tree’. Harboard amplifies this by remarking that the log is so named from the word ligen (Dutch liggen=to lie down) because it lies, as it were, immovable. It therefore seemed appropriate that the primitive contrivance for measuring a ship's speed—a wooden board attached to a line—should be called a log. The principle of this—the so-called common log to distinguish it from more sophisticated contrivances—is simple: a floating object cast from a ship tends to remain stationary after entering the sea. The line attached to the log-ship is allowed to render freely as the vessel sails away after the log is hove from the vessel's stern into the sea. A specified length of line which runs out in a measured interval of time or, what became more common practice, a measured length of line which runs out in a specified interval of time, is equivalent—at least approximately—to the distance travelled by the vessel in that interval.
Rhumb-line Sailing with a Computer
Authors: Turner R. J.
Published: January 2010

Continued discussions on techniques of rhumb-line sailing might well be considered irrelevant in today's climate of navigational technology. However, there is apparently one group of navigators who have a need for rhumb-line sailing by computation as opposed to direct measurement from a chart: this group comprises the navigators of merchant ships.

It may well be argued that traditional methods are adequate and that, although imprecise, the resulting errors are swamped by the errors of the data used. This argument is satisfactory for established navigators but, with the great improvements that have taken place in nautical education, does not hold for the teaching of newcomers.
The Torrey Canyon Commission of Inquiry
Authors: Oudet L.
Published: January 2010

In a book entitled The Black Tide, Richard Petrow presents a panoramic view of the events concerning the loss of the Torrey Canyon on the Seven Stones on 18 March 1967. The massive spillage of oil made it into a world disaster which called for a complete revision of many of the principles on which maritime transport is based. For seamen, however, the really important part comes before the spillage, when the ship stranded in apparently ideal navigational conditions. The Liberian Commission of Inquiry threw little light on the subject and criticism of the master does little to satisfy those with a professional knowledge of the sea. Here Commandant Oudet, relying heavily on the facts disclosed in Petrow's book, examines the circumstances of the disaster and comes out with strong criticisms of the Commission of Inquiry. If the subject is not exclusively navigational, it must be of great concern to all navigators.

Mr. Petrow's book contains what professionals need, even though the author recognizes that many questions must still remain unanswered. He has had access to the record of the Commission's investigations, but not to the report of the observer whose presence at the inquiry was secured by the British Government in spite of the owners' protests. While Mr. Petrow was able to spend four days interviewing Captain Rugiati, six months after the accident, he was unable to pursue his investigation by speaking with eye-witnesses, either those whose evidence was received by the Commission or those whom they failed to question.
Collision and the Perspectivity
Authors: Bell Frank Coffman
Published: January 2010

Captain W. Burger and Captain A. G. Corbet in their general comment on the meeting of the Technical Committee in London, 16 April 1969, gave a curious and instructive hypothetical example of end-on encounter, a problem in navigation which they and others have found by experiments to have importance and practical difficulties. Their example is set in surface navigation at sea, and especially when using radar in fog. Two ships close with each other (in their example head-on and green-to-green), the two tracks being straight and parallel, and separated (in their example by half a mile). Should both ships stand on? My answer is affirmative, my argument difficult.

If one makes the fruitful assumption that neither ship in this example alters course or speed, and then tries to plot The Edge [ of regression of The (mutual) Line (of bearing)], he discovers that the result is not a non-singular parabola, but rather simply a fixed finite point, i.e. at best a degenerate parabola—yet clearly there can be no finite collision, and collision at infinity is an empty threat. What do plotters of The Edge make of this paradox? Here handbook summaries will not do.
Captain Mário Gama's Direct Method for Star-sight Reduction
Authors: Cotter Charles H.
Published: January 2010

In a very interesting paper which appeared recently the author, Capitão Mário Gama of the Portuguese Merchant Navy, describes a direct method for computing position lines from star (or planet) observations.

The principal feature of Captain Gama's method is the systematic manner in which he arrives at an intercept to the extent, not only of saving time in sight reduction, but also in reducing the possibility of blundering.

The method employs the Computed Tables of Altitude and Azimuth (HD 486) and involves timing a series of star-sights, the ship making headway meanwhile, by means of a stop watch which is set at zero at a noted chronometer time shortly before the observations commence. The following example, given in the original paper, in reducing sights of Vega and Denebola observed during morning twilight of 25 Feb. 1959, in D.R. position Lat. 10°10′ S., Long. 73°48′ E., will serve to illustrate the method.
Amendments to the Rules
Authors: Cockcroft A. N.
Published: January 2010

A Great deal has already been written about possible amendments to the Collision Regulations, but as there may be an international conference on the subject in 1972 the various schemes should be discussed as much as possible so that their advantages and disadvantages will be fully appreciated.

Criticism of the present Steering and Sailing Rules is mainly concerned with Rule 21. Disadvantages of this rule include the following:

(1) If a giving-way vessel on a crossing course takes no action the privileged vessel must not act until collision cannot be avoided by the giving-way vessel alone. By such time collision is likely to be inevitable.

(2) Small sailing vessels which may not easily be seen, especially at night, are required to maintain course and speed for large power-driven vessels.

(3) High-speed vessels such as hovercraft are required to maintain course and speed for low powered ships crossing from the port side.

(4) No provision is made for different types of hampered vessel approaching one another so as to involve risk of collision. If deep-draught vessels in certain areas are to be included in this category in the future the question of priorities may have to be considered.
II–The Navigational Applications of Doppler Equipments
Authors: Moorhen C. N.
Published: January 2010

When considering the navigational performance of doppler systems it is not sufficient to examine only the inherent capability of the radar system, since the overall navigational accuracy achieved is a product of the complete ensemble—the doppler, the aircraft, its pilot, the heading reference, instrument transmission linkages, and so on.
III—The Future Development of Doppler Navigation
Authors: Houghton P. A.
Published: January 2010

The continuous data (groundspeed and drift angle) given to high accuracy by airborne doppler equipments, could be adapted for handling by automatic computers which, accepting certain other inputs, can be designed to extract a great variety of information. This paper attempts to outline the contribution that such computers could make to long-range civil air navigation.
The Accuracy of Radar Plotting in Estimating Course and Speed
Authors: Holmström Stig
Published: January 2010

In relative plotting the movement of the observer's ship is ignored. The first bearing B1 and distance a1 are laid off from a chosen origin and after a determined time-interval the second bearing B2 and distance a2 are plotted from the same point. By connecting these two points the relative course of the observed ship is obtained, which enables the observer to tell whether the other ship will cross ahead or astern, what her distance off will be, and when the intersection will occur.
II—The 1957 Transatlantic Race
Authors: Richey M. W.
Published: January 2010

If you want to ride up a hill on a bicycle you zig-zag up it, because although you travel a longer distance you go much faster and get to the top quicker. There is some similarity between what the cyclist does and what you are trying to achieve when you are planning for a long ocean race. Your object is to find the fastest way from the start to the finish, and whether this is also the shortest way depends on a number of imponderables such as the weather you can expect, the ocean currents, and so on. On a long race, generally the shortest way is not the quickest. What you are interested in is time, and like the cyclist, in distance only so far as it affects time. What you have got to do is to use all the elements that make you go fast, and these include not only winds and currents, but also factors such as the sailing qualities of your boat in different conditions. In addition of course you have to consider how you will stand relative to the others, not only if what you expect happens, but also if it doesn't. In other words your strategy will be tempered by some estimate of the reliability of the predictions of wind directions and currents you are working on. Your overall plan, then, is likely to be partly geographical, which is concerned with finding the least-time route; and partly strategic, which is concerned with not getting caught out.
On the Avoidance of Hurricanes
Authors: Hilder Brett
Published: January 2010

For many generations mariners have been taught the law of storms and the rules for avoiding their centres. This paper describes some of the practical difficulties of avoiding hurricanes in the south-west Pacific area, and the failure of meteorologists to appreciate the dangers and difficulties of the mariners.

About half the tropical storms observed conform roughly to the parabolic track of the law of storms. They form about 10° South of the equator during the north-west monsoon, (from December to April), and travel west-south-west, south-west and south-south-west as they gather strength and speed to a maximum; at 20° South they pause, recurve through south-south-east and south-east as they diminish in force and pass out of our consideration at 30° South.
Yugoslav Activity in the Design of Tables for Astronomical Navigation at Sea
Authors: Sadler D. H. , Scott W. A.
Published: January 2010

The publication of Captain Flego's tables, which are of some theoretical interest, focuses attention on recent Yugoslav activity in the design of tables for astronomical navigation. The opportunity is therefore taken of adding to the review of these tables an account of S. M. Kotlaric's book; this was published in 1955 but has not previously been noticed in the Journal. English titles are used below.

It is sad to announce the death of Captain Frane Flego, after a long illness, on 21 November 1957, after this review had been written. During a brief correspondence he was able to explain one or two points about his tables in rather more detail. The authors acknowledge much assistance during correspondence with S. M. Kotlaric.
I—Sailing the North Atlantic
Authors: Hasler H. G.
Published: January 2010

The wind pattern in the North Atlantic (Fig. 1) is more or less clockwise, and therefore the easiest way to cross the Atlantic from east to west is by the southern route, and from west to east along the northern route. In between, in the middle of this rotary system, are the horse latitudes where winds tend to be light and variable. Superimposed on this wind system, of course, is a series of depressions which commonly move from west to east across the North Atlantic, each depression having its own system of winds rotating anti-clockwise: on the south side of the depression winds tend to be westerly whilst on the north side they tend to be easterly.
A Study of Currents in the Strait of Dover
Authors: Cartwright D. E.
Published: January 2010

As part of an investigation into the difference of absolute sea-level across the English Channel, a detailed series of measurements of currents at all depths was recently made in the Strait of Dover. The main object of the measurements was to relate the residual non-tidal flow of water to the voltage on a cross-channel cable generated by electromagnetic effects. Over 6000 readings of current strength and direction were made during ideally calm conditions. This paper describes the results of analysis of these measurements, which covers vertical current profiles and tidal components, besides the non-tidal flow. Distinction is made between mean current measured at a fixed depth or at the surface, and the mean volume flux of water which involves tidal variation of depth. A method of tidal analysis based on Fourier sums, which is convenient for use with an electronic computer, is outlined in the Appendix.
Error of the Closest Point of Approach
Authors: Sameshima N.
Published: January 2010

The problem of errors in radar plotting were considered by Capt. H. Topley (11, 167) and Capt. F. J. Wylie (12, 198), and it was shown that the error in the estimated distance of the C.P.A. depends upon mean range and range change in plotting interval. I want to introduce the term rate of error in the estimated distance of C.P.A., in the same way that Topley shows the percentage error in the estimated speed.
The New System of Coordinated Universal Time
Authors: Sadler D. H.
Published: January 2010

The purpose of this article is twofold: firstly to give readers a general account of the new time-system that will be introduced on 1 January 1972, and secondly to give greater detail in respect of the corrections that a relatively few navigators may need to apply.

The great majority of users will not be (and need not be) aware of any change.

In his paper ‘Time Data and Navigation’ (page 13 of this Number) H. M. Smith has given an excellent background to the change, but that paper was written shortly before the final details were agreed; a little background material is, however, repeated here.
Navigating the Osterley, 1758–1760
Authors: May W. E.
Published: January 2010

The log-book of the East Indiaman Osterley, 1758–1760 (India Office Library, L/MAR/B.400A), is of considerable interest as Captain Frederick Vincent not only gives the ordinary records of navigation—hourly reading of the log, courses steered; daily northing or southing, easting or westing; meridian distance (departure); difference of longitude (Captain Vincent measures his longitude from the Lizard, except where otherwise stated, but I have converted to longitude from Greenwich throughout); latitudes by account and by observation; variation—but in the remarks column he frequently gives his opinions on the situation of the ship and his reasons for forming them.
The Case for Fully Automatic Plotting Radar
Authors: Wylie F. J.
Published: January 2010

Collisions at sea continue to be in the news, many of them, as usual, inexplicable, navigationally as well as radar-wise (a curious phrase in this context). Little is said about radar in the Press because, no doubt, being complicated and technical to the layman, it is not newsworthy like oil pollution or wreck marking. Were the philosophy of its use more generally understood, the equipment might be better matched to the potential value of radar as an aid to collision avoidance.
The Economics of Traffic Circulation
Authors: Oudet L.
Published: January 2010

In a recent article I spoke of the situation now reached in the circulation of traffic at sea as ‘a second spring’. Indeed, after a gloomy winter marked by a sequence of disasters in the Dover Strait it was some comfort to regard them as seed sown in a soil from which new life would not be slow in coming forth. This promise of spring was clear for example in the bold propositions adopted by Imco: ‘To prohibit traffic in the opposite direction on one-way routes’ and ‘to establish a Dover Strait fund’.