bluuebunny/crossref_metadata_2025 huggingface dataset:
A Critical Table for Sextant Corrections
Authors: Black A. N.
Published: January 2010

In a paper under the above title (Journal, Vol. 1, p. 266) J. P. G. Worlledge has made the useful suggestion that sextant certificates should give a critical table for the corrections instead of the present practice of giving the corrections at a few equally spaced readings. Unfortunately the method which he gives of deriving the proposed form from the present form is unsound. The centring error is correctly stated as

where Z is the sextant reading (the difference between Z and the true angle in this formula is negligible). But part of the centring error is included in the index error, so that to obtain the part of the centring error shown on the certificate the value of C for Z= 0 must be subtracted. This yields

for the formula of the correction.
The Requirements for Radio Aids at Sea
Authors: Wylie F. J.
Published: January 2010

The seaman requires of radio aids to navigation that they should be effective substitutes for astronomical and terrestrial methods of fixing when these fail him, either wholly or in part. For normal peacetime voyaging there has been no firm demand for a radio system that will improve on the performance of the other methods at their best. The requirements for radio aids can therefore be related to the facilities which these other systems afford. This does not, of course, imply that circumstances do not exist in which radio aids can provide a degree of assurance that the other methods might not.
Early Charts and the Origin of the Compass Rose
Authors: Taylor E. G. R.
Published: January 2010

Sailors as a class may fairly claim to have been the earliest technicians; they were the first, that is to say, to graduate from the stage of simple craftsmanship, involving only the use of tools and rules of thumb, to the employment of instruments and mathematics for solving their problems. For the nautical chart and magnetic compass are instruments of precision while sailing directions, if they are to be useful, must be couched in mathematical language. All these three aids to navigation go back at least seven hundred years, and an Italian ship inventory of 1294 has been quoted which included two charts, a pair of compasses and two lodestones with their accompaniments.
The Navigational Work of the C.S.I.R.O., Australia
Authors: Bowen E. G.
Published: January 2010

Summary of a paper presented by Dr. Bowen, as President of the Australian Institute of Navigation, to a meeting of the Institute held on 15 June 1951.

Accounts of the work described in this paper have been separately published, many of them in this Journal. The paper, therefore, restricts itself to giving a summary of this work, referring the reader to the appropriate literature for further study, and to pointing to some of the outstanding landmarks over the last few years.

The work referred to has been carried out by the Radiophysics Division of the Commonwealth Scientific and Industrial Research Organization in Australia and falls conveniently into two main headings, dealing with short-range aids to navigation and with air traffic control. It has been conducted for air navigation, but one at least of the navigation aids developed may find a useful application for maritime use.
I—The Operation of London Radar
Authors: Watkins D. W.
Published: January 2010

Soon after the introduction, in March 1947, of GCA to London Airport, it was realized that the advantages which it had brought to approach control could be greatly increased if the range of the radar could be extended to give earlier and more accurate information to the flight information controllers, and eventually the airways controllers, on the position of aircraft. At the time when the Ministry of Civil Aviation had installed and were testing an MEW type radar at the west end of London Airport, the question of the extended cover required from radar in this country was under active consideration. It was thus planned to develop long-range radar control techniques and procedures to be used in conjunction with the MEW radar. The work was planned to fall into three separate stages: (1) experiments in combined MEW/GCA working (termed long-range GCA); (2) operational trials; (3) operational service.
II—Traffic Control at the Royal Aircraft Establishment
Authors: Harris G. G.
Published: January 2010

The traffic control arrangements of the Royal Aircraft Establishment, Farnborough, although they have never been the subject of intensive operational research, but have been derived by a process of steady growth, may be of interest as an example of what can be achieved by good organization on anad hocbasis under some of the most difficult operational conditions.

The Royal Aircraft Establishment has an experimental airfield situated in a highly congested area. The London control zone and area is immediately to the north and east, and it is fringed on three sides by civil traffic lanes (Green Airway i in the north and north-west, Red i in the east, and the proposed Red 2 in the south). The Blackbushe circuit of the Ministry of Civil Aviation inter-locks with the Farnborough one in the north north-west, and the circuit of the Odiham R.A.F. airfield, from which jet aircraft are regularly operating, is situated only five miles away in the line of the main bad-weather runway.
The Development of Navigation Presidential Address
Authors: Jones Harold Spencer
Published: January 2010

The institute of navigation has been formed to promote the interests of science and of practical navigation, by uniting together in a scientific body those who are concerned with or are interested in the science and art of navigation. For navigation is both a science and an art, whose development must be based upon the knowledge and experience of many different types of persons. The formation of the Institute was stimulated by the formation in 1945 in the United States of an Institute with the same aims; it is likely that similar Institutes will be formed in other countries also. Arrangements are in hand whereby the members of either the British or the American Institute will have the privileges of both, and it is planned to form an international committee to co-ordinate the work of the various separate Institutes. In navigation, as in other branches of science, there is much to be gained by international co-ordination and co-operation.
The Boundaries of Pure Science and Navigation
Authors: Darwin Charles
Published: January 2010

The scientific world will warmly welcome the foundation of the Institute of Navigation, and indeed we may regret that it was not founded long ago. The interest in scientific navigation goes back nearly 300 years, since it was with the aim of assisting navigation that the Royal Observatory was founded, and during the eighteenth century navigation was greatly advanced by the encouragement given to Harrison in his work on the chronometer. It took some time before this was extensively used at sea, but by the beginning of the nineteenth century it would have appeared that astronomical navigation had nearly reached perfection. It was a fine and accurate science, as witnessed by the world surveys made by such seamen as Captain Fitzroy in the 1820's and 1830's, and little more seemed to be called for, or indeed could be expected as long as astronomy was the sole means of location. In the seventeenth and eighteenth centuries our Institute would have had a great many interesting activities, but in the nineteenth we cannot help feeling it would have been rather dull. Even then, however, there is a matter that may excite our surprise, for the ‘Sumner’ line was discovered at a rather late date, by a master mariner at sea, whereas it ought to have been an obvious idea to anyone with even a rudimentary mathematical training.
I—Elementary Theory Underlying Pressure Pattern Flying Techniques
Authors: Fraser D. O.
Published: January 2010

Pressure pattern flying embraces a number of air navigation techniques all of which have one common feature: they relate pressure distribution along an aircraft's flight path to that component of the wind which acts at right angles to the aircraft's heading. My intention is to give a brief outline of the theory underlying these techniques.

Wind is brought about by horizontal pressure differences in the earth's atmosphere. Air tends to move from an area of high pressure towards an area of low pressure under the influence of thepressure gradient force. The direction of its motion is, however, affected by the earth's rotation in space. Considering this rotation in the horizontal plane only, it is at a maximum at the poles and zero at a point on the equator. At any intermediate point of latitude, the speed of rotation in the horizontal plane is proportional to the sine of the latitude. In the northern hemisphere the rotation is anticlockwise; in the southern hemisphere it is clockwise with reference to outer space.
II—The Navigational Value of Pressure Pattern Techniques
Authors: Banks L. F.
Published: January 2010

The navigational problem.In order to find out how an aircraft is tracking with respect to the ground, we can either obtain information from data accurately placed with respect to the ground, or assess the horizontal movement of the air masses through which the aircraft is flying and combine this motion with that of the aircraft through the air. To determine the track we require accurate knowledge of the aircraft's heading and of the drift, which is the effect of the beam component of the wind. Along any given course line the navigator can make a series of drift observations, usually visual and therefore requiring downward visibility, and estimate the departure from the course line by averaging such observations to obtain the integrated effect of the drift. Since the sole purpose of drift observation is to estimate the departure of an aircraft from a given course line, a method of obtaining this total departure from a single observation or pair of observations, under any visibility conditions, is of considerable value. Again, if it is possible to estimate before flight the total integrated effect of drift for the whole flight, and our object is merely to fly to reach our destination, then the necessity of taking drifts during flight will be obviated.
I—Aeronautical Charts
Authors: Harvey G. A. H.
Published: January 2010

The mariner has for many years been able to procure charts for practically any waterway in the world and in most cases has the selection of a variety of scales to suit his purposes. The air navigator has not been so happily placed.

Shortly after the end of the 1914–18 war the nations subscribing to the International Convention to Air Navigation agreed the need for world cover in aeronautical charts at various scales, but, up to the commencement of the last war, the 1:10,000,000 basic map, for which the French government accepted responsibility, was the only series to reach completion. Various areas were also charted at scales of. 1:1,000,000 and larger.
The Ocean Weather Service
Authors: Satow P. G.
Published: January 2010

There was, during the recent world war, and is still, an urgent A need to provide coverage over meteorological conditions in the North Atlantic, with particular reference to temperate and high latitudes, where changes are rapid and non-seasonal. In addition, and of great importance to the security of trans-ocean flying, is the need to provide intermediate points on the air routes for air-sea-rescue duties and to act, if required, as communication links. If ships can be permanently stationed at specially selected points they can form valuable additions to the W/T direction-finding network, and more accurate fixes will be obtained of any distress signals which may be sent out by aircraft.
The Navigational Aspect of Flight Refuelling
Authors: Bennett D. C. T.
Published: January 2010

British south american airways have recently been carrying out a series of tests on flight refuelling. The first of these tests took place over southern England and were carried out on a scheduled basis at various heights both by day and by night and all proved successful—with the exception of two which were cancelled on account of bad weather, that is, bad weather on the ground and not in the air. The second part of the series has now taken place and consisted of London-Bermuda-London return nights on a weekly basis for a period of three months.

The process of flight refuelling does not in fact involve any particular navigational problem, but rather the simple problem of ‘approach’. The aircraft admittedly must intercept, but thanks to the fact that various devices are used for the actual approach of one aircraft to the other the navigational accuracy required for the interception is not at the moment of a very high order.
Navigation in Automatic Flight
Authors: Boxer H. E. C.
Published: January 2010

At 2215 hours GMT on 21 September 1947 the U.S.A.A.F. All-Weather Flying Centre's Automatic C54 took off automatically from Stephenville, Newfoundland, and twelve hours and five minutes later landed at Brize Norton, England. Neither pilot nor navigator had interfered with the automatic equipment during the entire flight. What, briefly, is the navigation equipment and procedure employed on such a flight?

Equipment. The navigation equipment consists of three magnetic heading selectors, two air log units or AMUS and a radio compass which will automatically switch to a number of preselected frequencies.
The Controller's Viewpoint
Authors: Young M. A.
Published: January 2010

There has always been, since the very early days of aviation, some form of control exercised over air traffic, an attempt to curtail random activities. The earliest example is perhaps that of the somewhat unfortunate individual who was obliged to stand for long periods in a highly dangerous position at the end of a paraffin flare path. This example shows how soon it was realized that where a collection of individual units are all trying to get to the same place, some of them possibly at the same time, some co-ordination and orderliness must be introduced, and that this could only be achieved by some third party. It was soon seen that certain difficulties prohibited individual countries from making their own decisions on these matters and that, like the high seas, aviation requires a common ‘highway code’. With the ending of the first world war, and the beginnings of international aviation, came the formation of the International Commission for Air Navigation, which had amongst its objects the agreement between contracting states on standardization of rules of the air, and of visual and aural signals. It might well be said that, out of I.C.A.N., air traffic control was born in the period 1919–20.
Microwave Direction Finding for Aircraft Navigation
Authors: Burgmann V. D. , Sheridan K. V.
Published: January 2010

This paper describes a microwave direction finding equipment and gives the results of flight tests carried out to investigate its possible use for air navigation.

The system operates in the 3.2 cm. wavelength band. The aircraft equipment consists of a receiver which sweeps rapidly over a small frequency band, a directional aerial which is scanned in bearing and a cathode ray tube display. The ground beacons are low power c.w. oscillators with an omnidirectional aerial and operate at separate fixed wavelengths to facilitate identification.
Investigations into the Dip of the Horizon
Authors: Freiesleben H. C.
Published: January 2010

The dip of the horizon resulting from the observer's height of eye can be calculated from the formula Dip = 1′·06√H, where H is the height of eye in feet, or by Dip = 1′·93√h, where h is the height in metres. In this paper the latter form will be used so that comparison can be made with studies in international publications.
Five Centuries of Dead Reckoning
Authors: Taylor E. G. R.
Published: January 2010

The term ‘dead reckoning’, so the Admiralty Navigation Manual (1938) says, is a corruption of the old ‘ded-uced reckoning’ or ‘position by account’, and is used to cover all positions that are obtained from ‘the course the ship steers and her speed through the water, and from no other factors.’ (The last italics are ours.) Had Master William Borough, Chief Pilot of the Muscovy Company, and presently to be appointed to Queen Elizabeth's Navy Board, come across this definition, he would have picked a two-fold quarrel with their present Lordships at Whitehall. For his use and explanation of the term is the earliest of which we have knowledge, although it does not appear even then to have been new.
I—The Dynamics of Space Flight
Authors: Clarke A. C.
Published: January 2010

It might reasonably be considered that any discussion of interplanetary navigation at the present moment is slightly premature. So of course it is, from the practical point of view, since no well-informed person seriously imagines that space-travel will be possible for at least twenty or thirty years, despite the colossal efforts which are now being devoted (unfortunately for quite other purposes) to the solution of its engineering problems. Nevertheless the subject is one of peculiar fascination—which is a completely sufficient excuse for discussing it—and the navigation of guided missiles into astronomical space, which will precede the manned exploration of the planets, has of course already begun and will continue on an ever-increasing scale during the next decades.
II—Some Problems of Interplanetary Navigation
Authors: Atkinson R. d'E.
Published: January 2010

It is clearly not possible, in the space of one paper, even to touch on all aspects of interplanetary navigation, and some whole fields must be ruled out from the start. This paper will not be concerned with any discussion of the space-flight as such; there is no point in considering navigational problems at all unless one can assume (at least for the sake of argument) that there is to be some practicable way of lifting a ship out of the Earth's gravitational field, and then of accelerating it out of the Earth's orbit; but even granting this major premise a considerable amount of selection is still essential.
The Effect of Changes in Altitude and Azimuth
Authors: Parker J. B.
Published: January 2010

The practice of precomputing astronomical sights in the air, so reducing the delay between taking the observations and plotting the position lines on the chart, appears to be gaining in popularity. The observer selects a future instant in time, and calculates the altitude and azimuth of a suitable body or bodies, for an assumed position near the D.R. position at that time. Then, if the observation is taken at the time chosen, the intercept is obtained directly by comparing the sextant reading with the precomputed altitude, corrections having previously been made for systematic errors (e.g. dome refraction, personal error, &c.)
An Altitude Correction Computer
Authors: Bartelski J.
Published: January 2010

Recent papers on the future of astronomical navigation in the air indicate that the present trend of development is directed towards surmounting two principal obstacles: the time lag between the shots and the final fix, and inaccuracies due to accelerations of the bubble. Even in aircraft at speeds between 200–300 m.p.h. these two factors tend to discourage the use of astro-navigation even where, as is particularly the case in lower latitudes, radio aids are not available.
The Development of the Aircraft Automatic Radio Compass
Authors: Moon J. H.
Published: January 2010

The paper reviews some of the major problems which have been encountered in the development of airborne direction finding equipment, and describes, in rather more detail, the latest electrical and mechanical improvements which have been evolved to provide the modern, fast moving aircraft with a more rapid or instantaneous position indication.

Various methods of utilizing the information provided by the direction finder are discussed and questions of calibration and ultimate accuracy considered.
The Air Accuracy of Compasses
Authors: Nunn J. L.
Published: January 2010

The introduction into both the Royal Navy and the Royal Air Force of the air navigational equipment that is at present envisaged emphasizes the need for a reliable and accurate compass. Further, since no compass can be expected to give completely accurate information in all conditions of use, the errors that are likely to arise and their magnitudes must be known. Before an error can be determined, it is first necessary to define what may be regarded as an error, and then to determine its magnitude as accurately as possible. Gone are the days when an expression such as ‘plus or minus two degrees’ would be regarded as satisfactory. The determination of compass accuracy to a tenth of a degree is now an accepted requirement.
I—Thomas Hariot's Manuscript
Authors: Taylor E. G. R.
Published: January 2010

In a previous article in this Journal mention was made of an unexamined manuscript by Hariot belonging to the Petworth Collection entitled The Doctrine of Nauticall Triangles Compendious, which promised to be of interest to navigators. When Lord Leconfield, the owner of the Collection, heard of this he very kindly himself brought this manuscript to the British Museum for study there, and meanwhile Dr. Shirley of the United States, who is at work on other aspects of Hariot's life, sent over from America a transcript from a microfilm copy which was in his possession. The contents of the manuscript more than fulfilled expectation, for it appeared that the main theme was the computation of meridional parts for drawing a Mercator chart and, as Mr. Sadler, the Superintendent of H.M. Nautical Almanac Office, shows in the second part of this paper, Hariot was remarkably in advance of his time in his mathematical treatment of this problem, which continued to be a favourite one for discussion until the discovery of the calculus. As is well known, the first table of meridional parts to be published was that compiled (by simple addition of secants) by Edward Wright (1558–1615) of Caius College, Cambridge, a mathematician who had been nautical adviser to the Earl of Cumberland, and on occasion to the Lord High Admiral himself.
II—Calculating the Meridional Parts
Authors: Sadler D. H.
Published: January 2010

As Professor Taylor has described, the Hariot ms. is largely concerned with the calculation of meridional parts. These calculations are of great interest not only as regards the question of priority, but also because they are based on a method which was more than fifty years in advance of contemporary mathematical knowledge. Although the ms. is paged and cross-referenced, the calculations are incomplete and inadequately explained; arithmetical errors (remarkably few when all calculations had to be done by long multiplication!) make absolute interpretation of all figures almost impossible. Considerable detail is thus unavoidable if the essential parts of the ms. are to be put on record and explained; though the most important point must be left unexplained. There can be little doubt that Hariot's calculations are original and independent.
Navigation on some recent R.A.F. Flights in High Latitudes
Authors: Bower D.
Published: January 2010

It is now seven years since the first R.A.F. polar flight was carried out by Aries, a Lancastrian aircraft from the Empire Air Navigation School; during that period air operations in Arctic regions have become an every day occurrence. This paper describes a series of flights undertaken recently by the Royal Air Force Flying College; it is not intended as a discussion of the special techniques of navigation in high latitudes but merely as an illustration of their application in a typical case.
A Note on Chart Distortions
Authors: Sheppard H. L.
Published: January 2010

Most navigators will, at some time or another, have noticed the effect of changes in humidity on the dimensions of paper maps or charts pinned up for display purposes. A display chart, or any other large sheet of paper, neatly pinned to a notice board in a warm dry room will tend to sag in an untidy manner if the atmosphere is allowed to become damp. Similarly a chart pinned up in a moist atmosphere is liable to contract and tear away from its anchoring pins if the weather becomes warm and dry. In the same way, the size of a paper chart in use in the air will vary appreciably with changes in atmospheric conditions; and it follows that if the size changes, so does the true scale. Such changes in the scale are of little consequence so long as dividers are used for measuring distances, since it can be assumed that the distance graduations on the chart all expand and contract in proportion to the change in size of the sheet as a whole. But if a graduated rule or straight-edge is used (and this is practicable only in the case of maps or charts based on some projection giving near-constancy of scale) then, quite apart from the scale errors of the projection, changes in the size of the chart will give rise to errors.
The Vertical Reference in Aircraft
Authors: Fox W. A. W. , Barnett D.
Published: January 2010

This paper will discuss various methods of defining the vertical in aircraft. It is unrealistic to examine the vertical in navigation only in terms of providing a reference for sextant altitude measurement and the paper will therefore discuss more general problems of aircraft stability, which can themselves to some extent be studied by means of the sextant.
A History of the Dutch Nautical Chart
Authors: Schüller J. A.
Published: January 2010

The history of Dutch hydrography and chart-making is naturally closely bound up with Dutch sea power and largely follows, or at least followed until recent times, the history of the Netherlands at sea. For four centuries in Holland and for three and a half in the East and West Indies, Dutch surveyors have mapped and charted the coasts, fairways, rocks and reefs. Although in early chart-making a good deal was borrowed from other sources, the contribution of Dutch mapping to safe navigation, has, historically, been extremely important. The Dutch chart of today is a direct development of the traditions set up by the early chart makers.
Map Projections used in Polar Regions
Authors: Beresford P. C.
Published: January 2010

The problem of navigation in high latitudes is becoming increasingly important as the range of modern aircraft increases and the consequent inevitability of the extension of possible operational theatres to include polar regions becomes apparent. The provision of suitable maps of such areas is therefore a matter requiring attention in the near future, and the adoption of a standard projection together with uniformity of presentation of topographical detail must be regarded as a desirable objective in this connection. The aim of this paper is briefly to review and compare the various projections available and so assess which one is most suitable for the purpose.
Early Books and Charts in the Royal Geographical Society's Collection
Authors: Crone G. R.
Published: January 2010

The library of the Royal Geographical Society contains a great many early charts and works on navigation which will be of interest to members of the Institute. Mr. Crone, the Society's Librarian and Map Curator, describes some of them in this paper, which deals in the main with publications likely to have been used or referred to by practising navigators. Arrangements can be made for members to inspect works in the Society's collection.
Determining the Most Probable Position
Authors: Parker J. B.
Published: January 2010

There are two stages in the determination of position from current observations. The observations are first resolved into positional form on the chart and plotted so as to give either a fix or a position line. When more than two position lines are available, some of the information is redundant and a problem exists of determining the most likely fix. In the case of air navigation, the number of position lines seldom exceeds three, and the determination of position in this case has been studied in a previous article.
Navigation at Sea with a Star Lattice
Authors: Michell R. B.
Published: January 2010

This paper describes a new method for the continuous development of astronomical position lines, relative to a moving D.R. position. At present the method is restricted to observations of the stars, but it might later be extended to other bodies. A basic requirement is a precomputed ‘star lattice’, which here takes the form of a series of graduated intercept curves drawn so as to be always at right angles to curves of constant altitude. The star lattice may be prepared and printed in advance, or may be constructed by the navigator himself, immediately before observation, from the data in the new tables, Sight Reduction Tables for Air Navigation (Vol. i, Selected Stars).
Navigational Accuracy in the Eighteenth Century
Authors: May W. E.
Published: January 2010

When the maritime history of the eighteenth century is under discussion it is usual to stress the limitations imposed by the inability of navigators to determine their longitude. It is generally assumed that since the advent of the Davis Quadrant or back-staff the latitude could be observed with considerable accuracy, and that with the compass in a wooden hull and with the more accurate graduation of the log-line as shown by Norwood, the dead reckoning should, over short periods of time, be reasonably reliable.
The Transit System
Authors: Kershner R. B. , Newton R. R.
Published: January 2010

The Transit navigational satellite system is expected to be in operational use during the second half of 1962, though not perhaps with its full quota of four satellites. The system, which will be of considerable significance to both air and surface navigation, is here described by its originators, Dr. Kershner and Dr. Newton, of Johns Hopkins University in the United States. Using a single of the two frequencies transmitted by the satellite, the mean navigation error will be about one mile, limited by refraction. Using both frequencies the mean error will be about ½ mile, limited by the accuracy of the satellite coordinates that will be transmitted. With elaborate equipment, it will be possible to navigate to about 0·1 mile, although the satellite coordinates that will be available to the ordinary user will not reflect this full accuracy. When all four satellites are in orbit, a fix will be available every 110 minutes, on the average, with occasional intervals of 220 minutes between fixes.
Navigational Aid from Other Satellites
Authors: Freiesleben H. C.
Published: January 2010

Beside measuring changes of distance by means of the doppler effect on frequencies transmitted by a satellite, it is possible to observe altitudes and azimuths or the rates of change of these quantities. Advantages and disadvantages of such observations are compared with the Transit programme; the formulae for position lines determined by rates of change of altitude and azimuth are derived and discussed. Measurements of distance, at present feasible only by radar, may be possible in future by comparison of atomic clocks; the evaluation is simpler than for all other observations of satellites.
Collision-warning by Electronic Computer
Authors: Haack Wolfgang , Güntsch F. R.
Published: January 2010

This paper, a shortened version of one presented at the joint meeting of the British, French and German Institutes of Navigation held in Dusseldorf last May, reports work undertaken in Germany on the automatic detection and solution of air collision situations. The work is being carried out jointly at the Berlin Technical University and the Telefunken Company at Constanz, in close consultation with the German air traffic control authorities.
Doppler Correction for Surface Movement
Authors: Grocott D. F. H.
Published: January 2010

A doppler navigation system measures velocity relative to the surface of the Earth. If the surface is moving, as for example when flying over an ocean, the doppler will indicate a false ground-speed and/or drift, according to the direction of surface movement.

Trials carried out by the Experimental Navigation Division of the Aeroplane and Armament Experimental Establishment at Boscombe Down show that there is a positive correlation between doppler system error and the surface wind direction when flying over the sea in an aircraft which has an accurate heading reference system. The analysis of all data is by no means complete, but as the spread of errors is so small it is thought that users of doppler navigation systems may wish to see the trend of results and to accept a few simple rules to compensate for the surface movement.

The value of the surface movement for a doppler equipment having a 1 percent correction for spectrum distortion is about 3 kt. for a surface wind velocity of 10 kt., 4 kt. for a wind velocity of 18 kt., 5 kt. for a wind velocity of 30 kt. and 6 kt. for a wind velocity of 50 kt. or more. The cardinal rule is that the doppler navigation system will indicate a position upwind of the correct position.

Clearly there is little point in applying an across-track correction of say 6 kt.
Man and Machine in Navigation
Authors: Day A.
Published: January 2010

I am making my second Presidential Address the opportunity to do little more than muse aloud on a theme which is fashionable rather than original. It will be entirely personal and in no way representative of Admiralty views. I can describe the theme as the way in which man is getting along, in our particular field of navigation, with his inventions of mechanical devices, or as Shakespeare collectively and descriptively calls them—his ‘engines’. I could alternatively and not unreasonably describe it as the way in which man is becoming increasingly dependent on his mechanical aids. Yet, that would convey an impression of his going into an unduly early decline or of his doing something wrong. Obviously, he gains in being able to achieve things which he could not do unaided, but obviously, also, he must avoid rendering himself helpless if there is a chance of his inventions failing him at a critical moment.
Jean Rotz and the Variation of the Compass, 1542
Authors: Taylor E. G. R.
Published: January 2010

It was a trial and a torment to sailors when it was brought home to them that the magnetic needle did not point truly to the north, but ‘northeasted and northwested’ as they described it. ‘El nordeaster de las agujas pone alos mareantes en muches dudas’, wrote one of them, and many flatly refused to believe it, putting discrepancies down to the use of a faulty lodestone or to bad workmanship on the part of the compass-maker. In the far-off days when the use of ‘needle and stone’ to recover lost bearings was first discovered, they believed that by some magic or divine sympathy the needle turned and pointed to their star, which they called the Shipman's Star, or Stella Maris, the only one that never moved. But Peter Peregrinus, writing the first scientific treatise on magnetism in 1269, remarked that they were wrong. The needle pointed to the celestial pole, round which the Pole Star circled like any other. And three centuries later Peter in his turn was faulted by the Elizabethan mathematician John Dee, who scribbled a note in the margin of the medieval writer's book to the effect that it was neither the star nor the pole which was the centre of attraction, but a spot on the Earth—the magnetic pole.
The Precision of the Air Almanac and the Sight Reduction Tables, A.P. 3270
Authors: Sadler D. H.
Published: January 2010

Ever since the introduction of the Air Almanac and the Astronomical Navigation Tables, requests have been received for information as to the errors that can arise in their use. Estimates of error, for particular combinations, were made on several occasions and, in 1947, the calculation was systematized; but the methods and results were not published. It is now probable that the Sight Reduction Tables for Air Navigation, A.P. 3270 (H.O. 249 in U.S.A.), and possibly the Air Almanac, will increasingly be used for surface navigation and it therefore seems desirable to put on record a precise statement of the errors that can arise through their use. The earlier work has accordingly been modified for the changes in the publications.
Priming and Lagging
Authors: Mann E. E.
Published: January 2010

The term ‘Priming and Lagging’ has been defined in two different ways.

The Admiralty Manual of Navigation (1922) defines it as occurring when the resultant of the solar and lunar tides arrives before or after the lunar tide would arrive. This is here called definition A. The Admiralty Manual of Tides (1941) defines it as occurring when the interval between successive diurnal high waters is less or more than the average 24h 50m. This is here called definition B.
Introduction to Inertial Navigation
Authors: Adams D. E.
Published: January 2010

Inertia is that property of matter which opposes change of motion. Inertial navigation systems utilize this property for the detection and measurement of linear accelerations and rotations in order to arrive at velocity change and displacement relative to some known initial state in a particular frame of reference.
‘Bottle Post’ and other Drifts
Authors: Carruthers J. N.
Published: January 2010

Most readers of this Journal will know a good deal about the long-established practice of setting adrift in the sea sealed bottles or other watertight vessels containing messages or questionnaire papers. There are numerous records stretching over a very long term of years of this having been done with the aim of conveying information—often in a jovial sort of way, but sometimes when it was feared that a ship seemed likely to be lost. In the latter case to which very few authentic records relate, mariners fearing the worst adopted the practice for obvious enough reasons. In the former case, records of the practice are legion and, a century or so ago, it was a common thing for floating bottles with papers inside to be flung overboard from outbound emigrant ships. The habit was still fairly common in much more recent times, and the writer once had quite a goodly number of missives recovered from stranded beer and wine bottles which, after the conclusion of a farewell party, had been thrown out from ships bound for America from the Elbe and other departure points. Generally speaking, such corked bottles were used empty (apart from the enclosed message), and so would perform journeys decided in large part by the winds. Where a serious intent lay behind the launching of a bottle designed to convey true news of distress, no very strong hopes could ever have been reposed in the glass messenger, since there could never have been any idea as to when it might go ashore and be found. It is probable that many bottles carrying messages of the sort have, over the years, been broken on rocky coasts or have stranded on unvisited shores perhaps to suffer burial in shifting sands.
I—Strong Winds in the Upper Atmosphere Above 15,000 ft.
Authors: Bannon J. K.
Published: January 2010

This paper gives a description in very general terms of where and at what seasons may be found the strong winds which occur in the upper atmosphere above 15,000 ft. and discusses briefly the clear air turbulence which is sometimes found in and near these strong winds.

Jet streams of temperate latitudes. Navigators are now well aware of the comparatively narrow bands of strong winds, known as jet streams, which occur in the upper troposphere in temperate latitudes. These jet streams, which can stretch for over 2000 miles on occasions, are very variable in position and in strength. It is probably true to say that there is a jet stream with wind speeds exceeding 60 kt. somewhere between Jan Mayen (N. 71°) and Gibraltar (N. 36°) every day, except in quiet summer weather and exceptionally on quiet days in other seasons. Fig. 1, from Durst and Davis shows a typical jet stream; these winds are associated with fronts though the fronts are often of the dry type with very little associated weather. For example, the strong northerly jet stream over the British Isles on 14 November 1949, with speeds of over 150 kt., occurred over a surface anticyclone; it was in this jet stream that the Comet I, on an early flight, experienced very severe turbulence. The level of the maximum wind in these jet streams is about 30,000 ft. though the exact height varies from case to case. Since they are so variable in position and strength the navigator must take particular note of them and a close liaison with the forecaster is clearly essential.
A New History of Navigation
Authors: Collinder P.
Published: January 2010

Professor E. G. R. Taylor's review, in the April 1955 issue of this Journal, of my book A History of Marine Navigation has passed unnoticed by me during a long absence, and I beg leave to offer a few comments.

The reviewer's introductory remark is indisputably correct; the title is not an adequate one. The Swedish title, literally translated, is From Noah's Dove to the Gyro-compass: navigational art, ancient and modern. In the earlier chapters I have not followed a chronological sequence but rather proceeded in order of the degree of complication of the methods used. In the later part of the book, I admit that there are many lacunae. However, as the reader will find, there was no ‘final jump’ to electronic navigation; there were several stepping-stones, viz. wind- and current-charts, the gyro-compass, radio-location, and echosounding.
Spheroidal Sailing and the Middle Latitude
Authors: Sadler D. H.
Published: January 2010

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

where C is the course and α is known as the middle latitude. It is approximately the mean latitude when both points are on the same side of the equator; tables of the correction to be applied to the mean latitude to give the middle latitude are given in most collections of nautical tables.
Navigation during the break through the Channel in 1942
Authors: Giessler Helmuth
Published: January 2010

Captain Giessler, who is now assistant to the director of the Auschuss für Funkortung (the German association concerned with radio navigation) was navigating officer of the Scharnhorst when that ship with the Gneisenau and Prinz Eugen broke through the English Channel in February 1942. It is thought that this account of the operation will interest many navigators, even though it is not entirely navigational in content.

Towards the end of 1941 the repairs to the battle-cruisers Schamhorst and Gneisenau, lying at Brest, and to the heavy cruiser Prinz Eugen were already so far advanced, in spite of continual very heavy air attacks, that a decision had to be made as to the further use of these forces.
II—The Use of the Flight Log
Authors: Wright E. R.
Published: January 2010

The use of the Decca flight log is most simply illustrated by referring to an actual flight, in this case on a Viscount service out of London Airport.

Fig. 1, which is a section from the chart roll used on a recent service, shows the London Control Zone chart. Take-off was from runway 2 8 RIGHT on an IFR day and the outward bound clearance was Chertsey 2000 ft., Dunsfold 3000 ft. with a radar climb en route to Seaford. At the time when the pilots are fully occupied with after take-off drills, r.t. &c., and maximum concentration on instrument flying is necessary, a quick glance at the flight log is all that is necessary to check that the aircraft is on track. At this stage, in the event of radar failure, an accurate position of the aircraft can be passed to air traffic control at any time it is requested, and ‘flying well right of the centre line’ and subsequent resumption of track is easily effected.
III—Dectra
Authors: Hawker G.
Published: January 2010

Dectra (Decca Track/Range) is one of two British systems recommended at the March 1954. meeting of Com. Division of I.C.A.O. in Montreal for evaluation by interested States. Arrangements are now being made to commence proving trials of Dectra at the end of this year or possibly the beginning of 1957. The trials will be made under the auspices of the Ministry of Supply and Ministry of Transport and Civil Aviation in this country and with the support of the Department of Transport in Newfoundland. The system is primarily designed for the navigation of fast jet aircraft across the North Atlantic, a problem intensified by air traffic control when more than 100 aircraft are in the air at the same time on those routes. It is, however, likely to prove valuable for other similar applications. The trials installation will cover the main route Prestwick–Gander.
A Modern Flight Instrument System
Authors: McKinlay W. H.
Published: January 2010

Almost all the long-range civil transport aircraft entering service during the next few years will be equipped with some form of instrument system. It is proposed to describe here some aspects of the developments which have been embodied in one such system, the Smiths Flight System, and to indicate its scope when applied to the operation of such aircraft.

Since the war the operation of a high-performance transport aircraft on congested and competitive routes has become an increasingly complicated process. With the advent of the gas turbine, cruising speeds have doubled, and at the same time there has been a tendency towards higher standards of economy and safety. The development of the air traffic control system has brought about a demand for greater precision in navigation, and in the most congested areas by far the greatest number of flights are conducted under instrument conditions. Meanwhile, aircraft have also become more complex, and the pilots themselves are often expected to monitor the operation of the controls and instrumentation associated with the engines, electrics and pressurization as well as carry out the navigation. This extra work has had to be undertaken without any relaxation of the general vigilance which constitutes good airmanship.
Position Finding in Captivity
Authors: Beeham P.
Published: January 2010

In December 1940 some 500 captured allied seamen, including the author, were transferred from a German commerce raider to an ex-Norwegian tanker under the command of a German prize crew, with the original crew still aboard. The ship was in the Southern Indian Ocean—in about S. 32°, E. 70°—just cruising about aimlessly; apparently awaiting orders to proceed. The captured Chinese and Indian ratings were accommodated aft somewhere, the shipmasters and passengers were housed amidships; and the rest were forward.

This vessel was very effective for the purpose to which it was being put as it was easy to position machine guns to cover all ways of approaching the midship house; in particular the fore part of the bridge was a solid wall right up from the foredeck to the high dodgers. Nothing could be seen of those on watch and no bells were struck, so that the officer prisoners were denied the sight of anything which might help them to guess what was happening, and any sound to give them an idea of the passage of ship's time.
The Region of Collision
Authors: Slater W. T.
Published: January 2010

Captain Wylie's paper on ‘The Region of Collision’ raises some interesting points but if one accepts the view that graphing of some sort is not wholly ‘academic’ the writer feels that there is an alternative graph which Captain Wylie has not mentioned and is worth considering.

As Captain Wylie has shown, the time-distance plot gives very little useful information except that it does keep prominently in mind the distance between the two vessels. The time-bearing plot is much more informative as to the element of danger present in the situation but if the time-bearing is the only plot kept then the fact that it shows no distance between the vessels is a serious disadvantage. The writer suggests that it might be worthwhile considering the advantages of plotting change of bearing against distance between the vessels, especially if this is done on a graph having precomputed curves for various minimum separations between the vessels. The sort of graph obtained is illustrated in Fig. 1 which shows a family of curves for vessels maintaining steady courses and passing at minimum separations of ½, 1 and 1½ miles, curves A, B and C respectively, on the assumption that plotting is begun from the point where the vessels are four miles apart.