In a recent paper I endeavoured to give a statistical solution of the problem of the separation of aircraft tracks with safety. In it I assumed that the distribution of errors of navigation made by the aircraft was a normal gaussian one; but I added a proviso that the effects of blunders might modify the result. From enquiries of various navigators as to the frequency with which they considered they were likely to make blunders I gathered that with a good navigator an undetected blunder might occur on 1 per cent of occasions and further it seemed reasonable to assume that a blunder might be defined as an error greater than three times the standard error of normal navigation. These assumptions are of course quite arbitrary but they seemed to be suitable to give examples of the effect on track separation; this was done in an unpublished paper. In these examples it was supposed that aircraft flying in the same direction were using two parallel tracks distant L apart and on each track aircraft were flying at fixed intervals but quite independently of the aircraft on the other track.

C. S. Durst has tried to discover the frequency distribution of aircraft navigational errors from D. C. Willis's data. But how reliable are Willis's data for this purpose?

D.R. errors and track-keeping errors are differences between assumed and true positions. Evidence of assumed position is ayailable, but how can true position over the Atlantic ever be discovered accurately? Willis estimated true position by post flight analysis of navigational and meteorological data, but any such analysis must be based on some doubtful assumptions, for instance that compass error or wind was constant between fixes or that the true position was at the ‘middle’ of a ‘reliable’ fix. The analysis must also comprise many delicate judgments, for instance that the true position was at A, not B, because if it were at B an abnormal wind change must have occurred for which there is only slight evidence.

Two years ago I gave an account to a meeting in this series of the establishment of Shackleton Base and of Theron's voyage (Journal, 10, 161). The second part of the expedition began with the sailing of the Magga Dan for the Weddell Sea and Shackleton Base. The ship, of some 1800 tons and 2000 s.h.p., with variable-pitch propellers, was built especially to withstand ice pressures. Even so, the Weddell Sea proved too much for her at one point; but fortunately not for long, and she was soon moving down to Shackleton, calling at Halley Bay, to see the British I.G.Y. base, and Emperor Bay, where an estimated ten-thousand birds gather and nest each year.

The problem considered in this note is that of determining an upper limit for the chance that an error will not exceed some given quantity. Where the pattern (or frequency distribution) of the errors is either known or assumed, the solution to the problem is merely a matter of calculation. This note starts by making the minimum assumptions about the pattern of errors, and then examines the effect of gradually increasing the restrictive assumptions.

Captain H. Topley in his article on radar plotting errors (11, 167) has endeavoured to simplify the arithmetic and introduce an approximate formula which will be of practical use to the navigator. He admits that his approximation has limitations and it appears to me that some danger may arise from the difficulty which the non-mathematical navigator may have recognized when he has passed the point at which the formula will be safe to use. Further, Topley tends to concentrate on the errors in the estimated course and speed of the other vessel and to give rather less attention to the problem of errors in the closest position of approach (C.P.A.). The latter may be by far the most significant factor.

In the course of the development of the practice of astronomical navigation, a straightforward approach to the subject could never be adopted mainly because time (that is, Greenwich Mean Time) either could not be obtained or could not be relied upon to adequate precision. Methods of observation and techniques of reduction were introduced to give the best results from the equipment then available; and these traditional methods, which have continued long after the need for them has vanished, have tended to obscure and to complicate the fundamental simplicity and generality of astronomical navigation.

In 1854 a bearing plate was invented by Matthew Curling Friend and William Browning to facilitate the taking of bearings where the compass was inconveniently situated for observation.

Friend was born at Ramsgate on 21 January 1792 and entered the Royal Navy as a First Class Volunteer at the age of 14½. Though continuously employed in ships, which carried him to Africa, the West and East Indies and to China, he does not seem to have caught the eye of his superiors for he did not obtain his lieutenant's commission until February 1815. He subsequently served in the Bucephalus, 32, one of the ships which escorted Napoleon Bonaparte to his exile at St. Helena. While on board the Bellerophon in Plymouth Sound, waiting for the great powers to decide his fate, the fallen emperor used to exhibit himself daily at the gangway and the populace came out in boats and thronged round to see him. On the day that he was transferred to the Northumberland for his yoyage there was an even greater press of boats than usual and one was capsized, throwing its occupants into the water.

Having had for some time to navigate small craft in all weather in the western approaches to the Clyde and on the west coast of Britain, the writer would like to submit for the consideration of other small-craft navigators some modification in chartwork which has proved useful, especially in rough weather when parallel rulers are an abomination and flying dividers can be lethal.

On a violently moving platform the navigator can only work with maximum efficiency when he is himself chocked off in a position in which he is sheltered, has the widest possible field of view, can take bearings and can brace himself securely to leave both hands free to carry out a limited amount of geometrical plotting with reasonable accuracy. The obvious position is of course the fore part of the wheelhouse, where there is very seldom sufficient room for a fullsized chart table with all the frills and trimmings.

IT is not often that the exact meaning of the Collision Regulations is the subject of a dispute in a court of law. However, a translator would be shirking his duty if he were to put the easiest interpretation upon each phrase.

The author recently attempted to translate the Collision Regulations into the Urdu language. This article presents his main findings on the subject of drafting.

Two defects recur too often to be greeted at each encounter and it would be convenient to deal with them collectively. They are:

1. (1) The use of unnecessary words, and

2. (2) The use of different words to convey the same purport.

However much opinions may vary as to the proper way to treat the problems raised by the use of radar, there is no doubt that something must be done to help navigators resolve them. The International Conference on Safety of Life at Sea held in London in June 1948 saw fit to declare in its Recommendation No. 19 that the possession of radar in no way relieves a vessel from the obligation of strictly observing the requirements laid down in the Rules for Preventing Collisions, and in particular with Rules 15 and 16 (sound signals in fog, moderate speed in fog, &c). It is common knowledge that navigators have not found constructive guidance in this text, and accidents have multiplied. It has been argued that the increase in accidents has not been proportionately as great as the increase in tonnage, but the argument is not very weighty. In the first place, accidents have become particularly serious because of the size and crossing speed of ships; and in any case it is a poor consolation to masters anxious to observe the Rules, but not quite certain how to do so, to be told that there is no cause for anxiety as there are not as many accidents as all that. This argument, even if it does not actually discourage navigators anxious to observe the Rules still runs the risk of making hesitant navigators err on the wrong side. It is therefore necessary to do something, and the first thing seems to be to state the problem concisely.

The flight instrument systems used in large modern transport aircraft represent a considerable development from the standard instrument panel in use at the beginning of this decade. Radio and navigational information is coordinated in a single display and flight direction is provided by means of a separate instrument in which it is normally composited with attitude information. The system contains sufficient redundant information to provide positive warning of a malfunction, and is normally used in conjunction with an automatic pilot which is capable of carrying out the approach accurately and reliably, monitoring control being exercised by the pilot by means of the flight system. Synthetic damping and automatic throttle control of airspeed may also be provided.

Statistics based on autopilots in current airline service suggest that an acceptable standard of safety for scheduled automatic landing is not attainable by single-channel autopilots. Adequate safety during the automatic landing manoeuvre can, however, be attained by a multiplex autopilot now under development. Provided that the necessary ground aids are installed, it appears feasible to introduce scheduled automatic landing by 1970.

The accuracy of winds measured in flight using a doppler navigation system has been investigated by comparison with simultaneous measurements from a Meteorological Office radar wind-finding station and also by flying different tracks using a modified multiple-drift technique. The errors of wind measurement arise from errors in the ground-speed vector as measured by the doppler navigator and also from errors in the true airspeed vector as obtained from the readings of the airspeed indicator, altimeter, outside air thermometer and compass. The trials, which were made at various altitudes to 48,000 ft. in a Canberra aircraft of the Meteorological Research Flight, showed that, providing suitable in-flight calibrations are carried out, the error in the vector wind can be reduced to about 5 kt. but that without these calibrations it may be 10 kt. or more.

In this paper, a group of eight directional stones on the coral island of Arorae in the Gilbert Islands are described. The stones seem to have been used to direct canoe voyages to distant islands with the help of horizon stars en route, the stars' movements and bearings being studied and memorized in relation to the correct stone on the night before departure. They perhaps mark the site of a Polynesian navigation school which existed somewhere between A.D. 1000 and 1500. The directions given by the stones appear to have been corrected for drift due to the Equatorial Current. So far as is known these stones are unique, and have not previously been reported in print.

On the island of Arorae in the Gilbert Islands there is a group of eight or nine stones which are said by the natives to have been used by early canoe voyagers to set their courses on departure to distant islands. No other such stones for navigation have been reported from the Pacific, which makes the coral stones of Arorae of unique value in the history of navigation. The stones are some of the few pieces of real evidence in the long-standing controversy on the nature and range of Polynesian navigation. The stones are called ‘Atibu-ni-Borau’ by the natives, which means ‘stones for voyages’. They have no legends or traditions which shed any light on the origin or actual use of the stones, but there are several clues available from elsewhere in the Pacific which enable the use of the stones to be determined with a high degree of probability.