Precise navigation upon the ice-cap depends largely upon the accurate steering of a chosen course. This operation can be rendered difficult by three major problems commonly faced by Arctic and Antarctic expeditions. First, the absence of topographic features as points of reference; secondly, the loss of precision of the magnetic compass inside a moving vehicle and in areas adjacent to the Magnetic Pole; thirdly, the dependence of the astro-compass and similar instruments upon an unobscured Sun.

A simple method by which these difficulties are overcome was tested and found satisfactory during an inland traverse from Wilkes Station in November–December 1960 into an area not previously explored by land. The principle of this method is the use of a periscope-like arrangement of mirrors combined with a suitable sighting system to enable the driver to use his track astern to steer a straight course ahead.

The original device was installed upon a vehicle (a ‘Weasel’), already fitted with an astro-compass and a magnetic compass in order to function as the navigation vehicle of the train. The rear vision mirror taken from a ‘Traxcavator’ was used as the main ‘Track mirror’. It was pivoted at its centre point through the shorter axis. The mirror was mounted on a frame of two half-inch steel pipes bolted on to the vertical wall of the well between the windscreen and the forward hatch of the Weasel.

The previous paper described how the two components of a compound system could be combined, through the medium of a pictorial display, in a common coordinate system. This essential process can be carried out by an airborne digital computer with considerable advantage, and with a degree of refinement—e.g. data smoothing— which would be beyond the scope of the simpler manually-operated system. In other words, the computer can introduce a second mode of compound operation which differs from the simple relationship between position-fixing and D.R. systems described earlier, in that by continuously combining the incoming information from the position-fixing system and the dead-reckoning device it can deliver an output of a substantially higher quality than that of either input taken separately.

It is well known that in low-frequency hyperbolic navigational systems the phase differences measured by the receiver do not correspond precisely to the hyperbolas on the plotting chart. This is largely because of variations in the terrain over which the waves are propagated. The system service area may be sampled so that the curve distortions can be ascertained at selected points. This article discusses how the whole service area can be calibrated, given a knowledge of the grid distortions at a sample of points. The mathematical treatment takes into account the correlation between the grid distortions at adjacent sampling points by using autocorrelation theory.

The degree to which fixing accuracy is improved by the proposed method of calibration is assessed against the background of an actual set of field measurements.

Mr. Sullivan is Head of the Applied Research Group of the Navigation and Guidance Laboratory at the Institute of Science and Technology. Dr. Porter is Assistant Professor of Electrical Engineering at The University of Michigan, and Head, Analytical Research Group of Navigation and Guidance Laboratory at the Institute of Science and Technology.

In low-frequency ground-wave navigation systems such as Loran-C and Decca, position information is determined from measurements of time and/or phase differences in signals received from several separately located transmitter stations. A pair of stations generates a family of hyperbolic lines which are the loci of points of constant time/phase difference. Two station pairs provide a grid of hyperbolas. By measurement of the time/phase difference between the signals from two transmitters, the receiver is located on a hyperbolic line. The same receiver is located on a second line by similar measurement which uses another pair of stations; the receiver is thus fixed specifically at the intersection of the two lines.

Accepting the technical fact of automatic landing, an examination is made of the basic human problems in its application to commercial air transport. This examination starts with an analysis of the use of human operators and automatic machines applied to operational tasks. Consideration is given to both control and monitoring functions, and conclusions are drawn about the correct approach to man/machine system design.

The required standard of safety for commercial automatic landing is briefly reviewed, with particular reference to the official British attitude. It is shown that automatic landing can be a tool for improving safety in future. The role of the pilot is considered. It is concluded that there is no real conflict between man and machine: that the automatic system will not affect the crew complement, or the basic responsibilities of an airline pilot: and that the potential of automatic systems can only be realized by a proper understanding of their true implications.

The original paper, of which this is an abbreviated version, was presented at the Institute of Aerospace Sciences National Meeting held in Seattle, Washington, on 10 and 11 August 1962.

Automatic landing systems are already in full production in Britain for Bomber and Transport aircraft of the Royal Air Force, and many thousands of successful landings have been made in both jet and propeller driven aircraft in all sorts of weather conditions. Second generation equipment is now clearing the prototype stage and entering production for application to passenger carrying aircraft at a civil standard of safety. This equipment is destined initially for application to the De Havilland Trident for British European Airways, and to the Short Belfast heavy transport for the Royal Air Force.

In the discussion which followed the papers on Hovercraft Navigation, Captain M. J. Edwards raised an important point. ‘If the hovercraft is the stand-on vessel, it may be impossible for a large slow-moving vessel to take avoiding action in the short period between sighting and collision.’ This implied that both were following the International Collision Regulations, and these cannot be altered (except by local authorities in ‘inland waters’) without international agreement and the attendant delay.

Recent correspondence in the Shipping Press brings to mind many of the sayings, writings and judgments of the last 10 years and stimulates thought once more in search of some basic weakness in the partnership between the seaman and his radar which, all too often, turns the risk of collision into the fact. Re-examination of the circumstances of some of the better annotated and sometimes more publicized cases is frustrating, partly because of the lack of personal detail in the evidence and partly because some of the conclusions which may be drawn point to failure of bridge personnel to understand the obvious fundamentals and so suggest that there must be undisclosed and more complicated causes. This latter, it is believed, is debatable.

In the days of sail a merchantman's success as a trader was governed by the seamanship of her master and the sailing qualities of the ship. A vessel which could turn easily to windward in difficult conditions could sometimes manœuvre under sail, in and out of port, without assistance while her more ungainly sister was dependent upon warping, kedging and towage by craft under oars. More important still, when on passage the efficient sailing ship could get herself out of trouble if she found herself in a tight corner on a lee shore in a gale of wind.

In his Presidential Address (Journal 16, 1) Dr. G. E. R. Deacon, C.B.E., F.R.S., says: ‘We have learnt from the Journal that one of the most frequent sources of error is a poor horizon, and recent (my italics) experiments by our American colleagues have shown that much can be gained by fitting a more powerful telescope in the sextant so that stars can be used while the horizon is better illuminated. They showed that it is better to look at the star directly and to make the horizon the reflected image.’

Dr. Deacon has been misled. In the ‘old’ Discovery from 1925 onwards (and before that in various surveying ships, whilst on passage), in which I was Navigating Officer, the horizon was always brought up to the star. A ‘sounding’ sextant also was always used. This is lighter than an ordinary observing sextant and mine had a large, aluminium telescope, of much greater power than the star telescope of an ordinary sextant, and with a very large object glass.

It was, however, graduated only to minutes of arc. To overcome this the altitude was pre-set for every contact to fixed intervals of, I think, 5′; this had the additional advantage that if the time of the middle contact agreed with the mean of the others it formed an excellent check on the accuracy of the sights and could be seen at a glance.

The problem of estimating equipment serviceability when the apparatus consistsof a large number of individual components (possibly with standby features) islikely to be of increased interest now that navigational thought is being concentratedquite as much on the design of instruments the navigator uses as on theproblems of finding position at sea or in the air. The resulting exercise in combiningprobabilities of component failure is a fairly straightforward one but inview of the accelerating interest in the matter (see, for example, Cluley's articlein this Journal, 15, 387) a brief systematic treatment might be of interest toworkers in these fields.

This paper, which was presented at a meeting of the Deutsche Gesellschaft für Ortung und Navigation held in Berlin on 24 April 1963, briefly discusses some of the factors which will affect navigation and control of supersonic transport aircraft. Attention is directed to the special problems of determining optimum flight path and estimating position and E.T.A. during three phases of the flight: acceleration, supersonic cruise and deceleration.

Whereas it is doubtless true that the two largest contributions to the errors of sights at sea are those referred to by Mr. Sadler in his Prefatory Note to Captain H. H. Shufeldt's paper on Precision Celestial Navigation Experiments, it cannot, I think, be gainsaid that the principal avoidable error in sights is due to faulty use of the sextant, especially in respect of collimation error.

The planetarium consists of an optical projector centrally situated under a dome. The viewers sit around the projector instrument in chairs designed to give a comfortable view over the whole interior. The instrument used by the writer is the Spitz A2, manufactured by Spitz Laboratories, Inc., Delaware, U.S.A. Seating is provided for 40 persons under a 20-ft. dome in the particular installation at the South African Nautical College General Botha, Gordon's Bay, Cape.