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.

In this paper two collision cases and four cases of ships grounding will be examined and the circumstances analysed with a view to drawing some useful conclusions from them. In the case of the collisions no general theory can be advanced but they both have a navigational interest from the point of view of the International Regulations Jor Preventing Collisions at Sea and a certain amount of useful comment can be made on them.

This paper describes tests of an approach procedure in which aircraft approach the airport on a radial track, circle the airport on an orbit and finally approach to land on another radial track in line with the runway. Ninety-six approaches were made with a representative selection of airline pilots in an aircraft fitted with the Australian Distance Measuring and Multiple Track Range Equipment.

The flight tests provide information as to the accuracy with which pilots can follow a set track, both for track accuracy and turning, when provided with adequate navigation aids. The average time for the particular procedure used was 18 minutes, and 90% of all times were within ±1 minute of the average. Maximum departures from the correct track occurred during orbiting where the average track was 0·2 mile inside the nominal orbit, and in 90% of approaches the departure did not exceed ±0·8 mile. Detailed analysis of the turns is also given in which it is shown that, on the average, turns occupy ¾ minute instead of the ½ minute required for a correctly executed Rate 1 turn.

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.

The King William Banks buoy is situated about 12 miles east of the northern tip of the Isle of Man. It marks the eastern extremity of the bank of this name and is an important turning point, especially for the British Railway ships on the Heysham to Belfast run. This buoy, which is unlit, is a third class spherical buoy and thus presents a poor radar target. The British Railway ships are fitted with radar and always pass the buoy at night so that if it could be detected by radar regularly it would be of great assistance to navigation. In fact complaints were made about its radar reflecting properties, and accordingly a pentagonal cluster of 12 in. corner reflectors designed by the Admiralty Signal and Radar Establishment was supplied to Trinity House and mounted on the buoy on 3 March 1949 (see Notice to Mariners 619/49) at a height of 11 ft. 6 in. above the water.

The history of mechanical transport has been one of increasing speeds and there seems to be little doubt that air transport will follow this pattern. To the passenger, increased speeds mean a saving of time, and time is money. To the operator, increased speeds mean more flights per week and therefore greater earning capacity for his aircraft. This year indeed has been marked by the appearance of the four-jet air liner, the forerunner of the four hundred knot air transport.

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.

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 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.

The necessity for an accurate instrument to indicate the height of an aircraft above the ground over which it is flying at any instant has long been recognized and a variety of types have been suggested.

Probably the most important single factor governing the value which can be obtained from a given radar equipment in a ship is the presence or absence of blind or shadow sectors. This is entirely dependent, on the siting of the scanner. There is no arc of bearing on which the careful seaman does not keep a visual lookout, constant or periodic, when his ship is at sea. As radar is capable of providing him with a means of detection on all bearings, which will often be more effective than his eyes, it would be surprising if he were not prepared to go to some lengths to avoid obstructions to its ‘view’.

The technical processes of navigation are much the same in all craft, but there are certain requirements and problems which are peculiar to ocean racing. Compared with big ship navigation, the principal differences are:

(1) The ship's speed is irregular and is not always exactly known; it is also much lower so that the tidal streams and other sets play a much more important role.

(2) The course steered is often a constantly varying one, particularly when the vessel is on the wind, or before the wind.

(3) Leeway is a far larger factor.

(4) The violence of the motion and the lack of space greatly increase the difficulty of plotting and calculating.

(5) The methods of fixing the ship are generally less exact and less readily available.

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.)

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.

A variety of marine requirements has prompted the Hydrographer of the Navy to design a plotting diagram printed on a transparency which is now under trial in prototype form. British Admiralty chart 5028, as this project is officially called, comprises a thin sheet of flexible and transparent material slightly frosted on one side to take ordinary black lead pencil work. The plotting area is printed on the frosted side and its circular portion has a diameter of 20 inches.