The ability to map terrain by means of an airborne radar raises many possibilities. Some few years ago it was recognized that a mapping radar which scanned to the side of an aircraft (rather than ahead) might, additionally, have important military potential. The research described here concerns the early operator evaluation of a prototype sidescan equipment which promised, among other things, to permit accurate fix-point navigation at lower flight altitudes.

By recent standards our aircraft was to progress at a fairly gentlemanly rate, somewhat below the speed of sound. Hence the radar map, produced as a moving strip by a rapid photo-development technique, did not threaten to flash past the navigator's eyes at an impossible speed. Nor, in general, did we expect the operator to be provided with anything unsatisfactory in the way of briefing. What is more, the navigator would be able to devote his undivided attention to the radar material whenever a fix-point was due.

This paper, which will be presented for discussion at the Eastbourne tripartite conference, 12–14 May, examines the efforts made in recent years to improve marine radar in three respects, namely greater expressiveness of the display, simplification of measurement and computation, and increased reliability. Particular developments in each of these directions are discussed, their effectiveness and shortcomings mentioned and the conclusion reached that there is still a long way to go.

This article treats integration of navigation data from a variety of sensors in a submarine using extended Kalman filtering in order to improve the accuracy of position, velocity and heading estimates. The problem has been restricted to planar motion. The measurement system consists of an inertial navigation system, a gyro compass, a passive log, an active log and a satellite navigation system. These subsystems are briefly described and models for the measurement errors are given.

Four different extended Kalman filters have been tested by computer simulations. The simulations distinctly show that the passive subsystems alone are insufficient to improve the estimate of the position obtained from the inertial navigation system. A log measuring the velocity relative to the ground or a position determining system are needed. The improvement depends on the accuracy of the measuring instruments, the extent of time the instrument can be used and which filter is being used. The most complex filter, which contains fourteen states, eight to describe the motion of the submarine and six to describe the measurement system, including a model of the inertial navigation system, works very well.

Over the past few years several papers have been written based on the results of surveys of marine traffic in different parts of the world. The general knowledge of the overall picture of the behaviour of ships at sea has increased considerably but there are still many aspects which need to be explored. One of the main fields of interest of the Marine Traffic Research Unit at the City of London Polytechnic is the use that mariners make of available sea room. For any particular area the navigational difficulties are going to vary considerably in situations where ships enter the area at different points, travelling indifferent directions, from situations in which the ships tend to keep to a number of defined routes through the area. If ships do tend to adopt a routing structure through an area, the next question of interest is how wide the various routes are, given no physical limitations for their width. The behaviour patterns may vary for different types of ship, and speed is another variable which may affect the situation. Answers to all these questions would be needed if one wanted to analyse the efficiency and safety aspects of marine traffic in an area.

This paper and the following three papers were presented at the EURNAV92 Conference on Digital Mapping and Navigation. This was held in London and was jointly sponsored by the RIN and the DGON. Forty-five papers were presented at the Conference and copies of the complete proceedings may be obtained from the Institute, priced at £65 for Members and £85 for Non-Members.

Judging from what is written in early Sailing Directions and navigation manuals it would appear that seamen of North-west Europe laid great store in their knowledge of the nature of the bottom in the seas in which they traded. And indeed, even at the present time, mariners are provided (although they may seldom use it) with fairly detailed information about the sea-bed, designedly to assist them in pilotage. A navigator may read, for example, that:

‘The bottom in the Western Approaches appears to consist, mainly of fine or coarse sand, a great deal of broken shell, occasional patches of pebble, gravel, small stones, and, now and then, mud. The sand is mostly white, but in numerous places yellow sand and also black specks are met with…. The greater proportion of yellow sand is found to lie southwards of 49°30′ N and the far larger portion of black specks northwards of that line. This peculiarity is so marked, especially between 9°40′ and 7°30′ W that the mariner running eastwards, and supposing his vessel to be to the southwards of this parallel, should certainly suspect his having been set northwards of his reckoning if the soundings disclose this mixture of black specks to any great extent and with any frequency.’

Following the Amoco Cadiz disaster in 1978 proposals were put forward, and ultimately accepted by IMCO, for a revision of the traffic separation schemes off Ushant and the Casquets, the broad effect of which was to keep large tankers (and those carrying hazardous cargoes) further off the French coast. The modifications came in for some criticism and recent Anglo-French proposals have now secured IMCO agreement. Prior to that a purely United Kingdom working group sought to formulate a comprehensive and continuous routing scheme for the whole English Channel.

Captain Cockcroft who, as an observer for IAIN at IMCO and as RIN representative on the UK working group on Channel Routing, has played a leading part in these discussions, here describes some of the problems and considers issues raised by concepts such as ‘areas to be avoided’, and finally, within the context of traffic separation in straits, proposes alterations to the Collision Regulations which govern the crossing of traffic lanes and the use of inshore traffic zones.

In October this year an international conference on the revision of the International Regulations for Preventing Collisions at Sea will be held in London. A working party appointed by the Maritime Safety Committee of Imco, under the chairmanship of Captain A. C. Manson of the Department of Trade and Industry, has drawn up proposals for the revision of the present regulations. Captain Manson described these proposals to an open session of the Technical Committee held in London on 17 May 1972 with Captain D. A. G. Dickens, an Elder Brother of Trinity House, in the Chair. Introducing the subject the Chairman said that the Institute, through its Journal, the discussions it had promoted on previous occasions, and through the working party set up in 1970, had taken a significant part in forming opinion on the issues involved. In particular perhaps it had ventilated the suggestions that collision avoidance might better be based on positive manœuvring instructions rather than by simply apportioning responsibility. The long-term influence of these suggestions may well be considerable even though they might not in the event be reflected in the Rules now being proposed.

The three basic problems of navigation are determination of position, definition of direction, and steering the direction required. In polar regions, all these problems are affected either by the high latitude, or by the polar climate, or by both. In this paper the various problems which arise are reviewed, possible solutions are discussed, and it is indicated where further research and experiment might be desirable.

The author of this paper, which was presented at a meeting of the Institute in London on 16 March 1977 with Captain B. J. Calvert in the Chafr, is the President of Jeppesen Sanderson Inc. He traces the history of the Jeppesen Company's charts from their early beginnings when map reading and dead reckoning were the only aids to air navigation to their adaptation to modern automated airborne systems.

The problem of underkeel clearance is not new; since time immemorial navigators have been concerned to know the minimum depth of water in which they can sail with a ship of given draught. Until quite recently, underkeel clearance requirements were determined almost entirely empirically, and in many cases the rule of thumb values used can be shown to be greater than the requirement of navigational safety would dictate.

In the years since the war the pattern of the oil industry has changed and very large ships are now commonly used to carry crude oil cargoes to a large number of ports around the world. It is obvious that use of these ships, with their deep draughts, has meant that a number of expensive dredging projects have been put in hand to provide adequate access to the ports served. Continuing escalation in size means this will probably continue.

Spherical trigonometry formulae are widely adopted to solve various navigation problems. However, these formulae only express the relationships between the sides and angles of a single spherical triangle. In fact, many problems may involve different types of spherical shapes. If we can develop the different formulae for specific spherical shapes, it will help us solve these problems directly. Thus, we propose two types of formulae for combined spherical triangles. The first set are the formulae of the divided spherical triangle, and the second set are the formulae of the spherical quadrilateral. By applying the formulae of the divided spherical triangle, waypoints on a great circle track can be obtained directly without finding the initial great circle course angle in advance. By applying the formulae of the spherical quadrilateral, the astronomical vessel position can be yielded directly from two celestial bodies, and the calculation process concept is easier to comprehend. The formulae we propose can not only be directly used to solve corresponding problems, but also expand the spherical trigonometry research field.

Binary Offset Carrier (BOC) modulation signals have been applied in Global Navigation Satellite Systems (GNSS) because they offer a higher positioning accuracy and higher multipath rejection. However, there is a drawback in that the autocorrelation functions have multiple side peaks, meaning that this technique also leads to the large main peak estimation error problem and a low correlation decision efficiency problem. In this paper, we propose a new Main Peak Extraction (MPE) method for high-order BOC signals to solve these problems. In the new method, the synthesis cross-correlation function is established, and the geometry graph is formatted to calculate the estimation main peak. We eliminate all side peaks and improve the main peak phase estimation precision under the condition that the sub-carrier phase is offset. The results of the simulation demonstrate that the new method can achieve better main peak decision efficiency, side peak cancellation ability and phase estimation performance than traditional methods.

In the first aerial crossing of the South Atlantic, by Gago Coutinho and Sacadura Cabral in 1922, several methods of astronomical maritime navigation were used with adaptions to aerial navigation. In order to apply these methods, the navigator needed to know the approximate altitude of the aircraft so that its position could be determined. The instrument available at that time, the altimeter, did not give reliable values for altitude. Therefore, Coutinho had to devise a method that enabled the navigator to determine the altitude quickly and efficiently. The method Coutinho devised is based on a mathematical and geometrical procedure. In this paper, we study in detail Coutinho's method to determine altitude, with diagrams to aid understanding of the deductions and calculations. We also present a real example of how this method would be used during the flight.

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.

Each navigational aid has its advantages and disadvantages and for that reason the optimum aid will be a combination of several aids. The best way of combining the aids seems to be by means of an automatic dead reckoning computer which continuously computes position from true air-speed and wind-speed and other data which can be fed into the existing navigational aids by means of a data transformer. Data from the integrated system can be transmitted by data link to air traffic control to correct the flight programme, &c. This paper, which was presented at Dusseldorf at the German Navigation Society's meeting (5–7 June 1962), surveys the field of integrated navigation systems and describes a number of possibilities. Formulae are derived for the accuracy of Vortac and D.R. and Vortac and doppler. It is published with the kind permission of the German Navigation Society.

If we look critically at the navigational aids which are available today we find that all have advantages and disadvantages, and that no one aid can be claimed to be suitable for all purposes. This situation will still exist for many years. Therefore it seems very advantageous to combine the available navigational aids to form an integrated navigation system in such a way that the possibilities may be fully utilized.

Whilst unmanned aircraft (UMA) can be said to encompass missiles, targets for weapon training, preprogrammed reconnaissance drones and civilian systems such as radio-controlled models used to carry cameras, for the purpose of this paper we will restrict ourselves to aircraft which are capable of sustaining autonomous flight and accepting navigation commands whilst airborne. The terms applied to unmanned aircraft are variously UMA, remotely piloted vehicle (RPV), Drone and Unmanned Aerial Vehicle (UAV).

The idea of an ‘Altitude-Azimuth’ almanac is not new though most effort (see this Journal, Vol. 1, 185, 1948; Vol. 2, 285, 1949) has been concerned with the Sun and planets rather than the stars. For the stars the simple problem is that observations are recorded in mean time (say G.M.T.) whereas the positions of the stars depend on sidereal time (L.H.A. Aries) given by: L.H.A. Aries = G.H.A. Aries + west longitude. A full account of star tables (and diagrams) using a mean-time argument (and thus avoiding using the Almanac to give G.H.A. Aries) is given in ‘The Genesis of the E. A.N.T.s’ (this Journal, Vol. 6, 333, 1953).

The weather is rarely out of the news. Weather can be hazardous at times almost anywhere on Earth, and the media are always keen to report dramatic events. On the global scene, weather, climate and the environment are issues of great international public concern at present because of the likely implications of increases of greenhouse gases in the atmosphere. The contributions of the meteorologist to the understanding of this global problem are increasingly recognized, as is the progress which has been made in the accuracy of day-to-day forecasts. This paper provides a brief résumé of our present ability to model and forecast the behaviour of the global atmosphere and the ocean surface, and also demonstrates how these models are applied to the practical problems of operational ship-routeing by the UK Meteorological Office. It is worth remembering that it was the very high incidence of losses at sea in the 1850s which brought about the establishment of the UK's first meteorological service.