Increasing the stability and reliability of navigation for mobile objects of different classes is becoming increasingly significant. Satellite navigation systems have a fundamental defect: a vulnerability to hacking and spoofing. Observation of the horizon line is significant for two applications. The first is stellar inertial navigation systems. In this case, the horizon line can be used for local vertical estimation. Errors in local vertical estimation directly affect coordinate errors. The second is correlation-extremal navigation based on the observed horizon line shape (when islands or continents are observed from aerial vehicles). In both cases, instability of the horizon line produces navigation errors. A measurement procedure for horizon line position estimation was proposed and realised. Around-the-clock horizon line shooting was undertaken in 2013. Processing of the results shows a horizon line direction instability of about 5–7 angular minutes during the day time.

Maritime traffic has significantly increased in recent decades due to its advantageous costs, delivery rate and environmental compatibility. With the advent of the new generation of marine radars, based on the solid-state transmitter technology that calls for much longer transmitted pulses, the interference problem can become critical. Knowing the positions and the heights of the ships, the mean number of the vessels in radar range can be estimated to evaluate the effects of their mutual radar interferences. This paper aims to estimate the probability density function of the mutual distances. The truncation of the density function within a limited area related to horizon visibility leads to a simple single-parameter expression, useful to classify the ships as either randomly distributed or following a defined route. Practical results have been obtained using Automatic Identification System (AIS) data provided by the Italian Coast Guard in the Mediterranean Sea.

There are endless regulations concerning the speed and size of vehicles on our roads, but none that apply to vessels using our maritime routes, even though there is a regular increase, in step with technical advances, in both the size and speed of ships. For reasons of economy roads are narrow, and the necessity to avoid obstacles means that they have to be winding. No such considerations apply at sea; changes of direction are slight and widely spaced out, nor are there any ditches or hedges to limit the width of the routes that are used. Nevertheless, studies of maritime traffic have shown that overcrowding is becoming more and more pronounced on the busiest routes, and the present tendency to develop oneway routes is an implicit recognition of the fact that the remedies for such overcrowding on the roads and at sea have something in common. One-way traffic, for example, is derived from the Collision Regulations (Rule 25). It is worth examining what help the Regulations can give in solving problems raised by the size and speed of ships.

The History of Air Navigation Group commissioned the author to provide a brief account of airborne DR development by discussing both the methods and the equipment used in the air. This first part covers the period before 1940. The split is arbitrary, although it is obvious from a British perspective that military events around that date had a major impact on the pace of navigation development. However, it is equally obvious that airborne DR developed alongside a worldwide technical and intellectual revolution. This aspect of the story is abstract and involves some conjecture, so the paper takes it for granted and concentrates instead on practical matters. Accounts of air navigators' experiences as well as material on DR theory and descriptions of DR equipment in navigation manuals, journals and various surviving research documents have been used as the source material.

This paper discusses the necessity and feasibility of the application of Pulse Doppler Radar in vts through analysing the limitations of the non-coherent, single frequency, radar and the advantages of PD radar.

Readers of Captain Cotter's paper under this title in the April 1976 issue of the Journal may be interested in some evidence that Dutch seamen in the seventeenth century were aware of this phenomenon of ship magnetism.

Abraham de Graaf in De seven Boecken van de Groote Zeevaert, published at Amsterdam in 1658, warns ships' officers taking bearings with the compass-that metal objects in their clothing can seriously deflect the compass, and mentions iron buttons and buckles. This was an important contemporary work on navigation and de Graaf was an examiner of officers of the Dutch East Indies Company from 1679 to 1714.

The following proposed system of rules was presented to the Collision Regulations Working Party of the Institute by Admiral García-Frías and is referred to in the January issue of the Journal (24, 56–9).

IT is evident that the revision of the Collision Regulations would only be effective with a system of Rules able to cope with all situations that may arise at sea. The system must include all that it is necessary and sufficient to solve the collision problem in the easiest and most effective way and consequently it must apply both in clear weather and in restricted visibility using radar; differences between these situations being defined, if necessary, in every Rule.

Successful ship handling depends upon acquiring the right information, making the right decisions and performing the right manœuvres; this paper concentrates upon the last of these. Manœuvring here is taken to include starting, stopping and steering. The ship is a vehicle with remarkably low resistance to motion; merchant ship drags commonly lie in the range one-hundredth to one-thousandth of the all-up weight force. This is comparable with that of a railway wagon (say 1/500 of its weight) and the low drag accounts in part for the ship's extreme economy as a carrying machine.

A draft of this paper was circulated for the open meeting of the Technical Committee on 17 May 1972, when the forthcoming revision of the Collision Regulations by Imco was discussed (see page 427).

Radar has been in general use in merchant ships since the end of the Second World War and during this time the Regulations for the Prevention of Collision at sea have undergone two amendments at International Safety Conferences, in 1948 and 1960. The amended regulations were ratified and brought into use in 1954 and 1965 respectively. The 1948 regulations made no reference to the use of radar whatsoever—radar for commercial use was still in its infancy in 1948 and indeed little was then known about its capabilities and limitations, nor of the operational difficulties it was going to present even before these 1948 regulations were finally ratified in 1954.

The loss of Admiral Sir Clowdisley Shovel with several ships on the Bishop and Clerks on 23 October 1707, and the subsequent attribution of the disaster by Captain Sir William Jumper of the Lenox, 70 guns, to defective compasses, led to the compiling of reports on these instruments by the Commissioners at Chatham and Portsmouth, by order of the Navy Board. Captain George St. Lo, the Commissioner at Chatham, was at this time about fifty years of age. We first hear of him being appointed a Lieutenant of the Phoenix, 42, in 1678; he was made Post into the Dartmouth, 30, in 1682. With the three years qualifying service necessary before he obtained his first commission he must have had fourteen years almost continuously at sea before his career was cut short by his being severely wounded and taken prisoner when he had to surrender the sorely battered Portsmouth, 46, to superior French force in 1689. While a prisoner of war he took the opportunity to study the dockyard methods of his captors and this, with his reputation for steadfast opposition to all corruption, made him particularly suited to fill the post of commissioner in a dockyard. In 1707 he had already been five years at Chatham, following eight in Plymouth dockyard.

A Joint Navigation Satellite Committee has been formed to determine the potential for a common satellite system to meet the needs of various agencies. As a potential aid to air traffic, satellites would appear to be most effectively used in cooperation with ground stations at which measurement and computation would be made. Possible user benefits include more effective communications, more reliable and possibly less expensive airborne navigation equipment, reduced diversions and delays, obstacle avoidance capability, more effective emergency warnings, and reduction of communication traffic. For the provider States benefits may include more reliable communications, reduction in number of control centres, improved data collection and distribution capability, reduction in number of facilities, and improved search and rescue capability. A systematic approach to long-range goals is indicated.

The first point to note about the North Atlantic air traffic system is the diurnal pattern of flow. This is strongly tidal, with westbound flow predominant during daylight hours and eastbound flow overnight. There is some traffic which flows against the main stream, particularly during the day, but the strong tendency for one-way traffic results from the difference in local times on opposite sides of the ocean, together with the transit times of flight at current speeds. This means that the general pattern will probably persist, unless and until aircraft speeds change radically.

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.

In this paper, which was presented to an Ordinary Meeting of the Institute held in London on 22 November 1978, Captain Woodfield, who was for nineteen years master of Royal Research Ships in support of British Antarctic Survey operations, discusses some of the problems of navigating in this ill-charted and ice-ridden area. The presentation was made jointly with Lieutenant Commander P. Le Pla, formerly Navigating Officer of the Ice Patrol Ship HMS Protector whose paper on Antarctic navigation was published in Vol. 31 of the Journal. The President was in the chair.

The proposal by A. J. Wright (this Journal, vol. 34, no. 1, p. 142) that banded contour charts should be introduced, appears attractive at first sight. It appears to provide immediately recognizable indication of safe areas for the navigation of those ships whose draught is within certain limits. However, I feel that the system as proposed suffers from some major weaknesses

Allowance for height of tide. Tidal ranges of several metres are by no means uncommon. Failure to make proper allowance for this could result in a wrong assessment by the user of where navigationally safe water lies. Such tidal ranges frequently occur in areas of high-density traffic. Here, the pressures on the mariner are such that the temptation to ‘eye-ball the navigation’ is greatest – yet it is in such areas that positional accuracy based on sound chartwork procedures is vital.

Gyro magnetic compasses are subject to a large number of errors, some of which may be eliminated, or at least greatly reduced, by careful design on the part of the instrument manufacturer and an intelligent operating drill on the part of the user. Table I shows errors under five basic headings, and allots to each error a symbol classifying it as:

(a) The responsibility of the instrument manufacturer (I)

(b) The responsibility of the aircraft manufacturer or its operator (A)

(c) Inadequate knowledge of the geomagnetic structure of the Earth's field (K)

Some sources of error in Table I are marked with an asterisk. It is these which the designers of the compass system described have endeavoured to eliminate.

The collision avoidance of a pair of uniformly moving bodies is considered in three dimensions. The relative motion of the bodies yields an expression relating the time to closest approach, the minimum range, the current range and its rate of change, other variables being unobservable. A Boolean relation is then proposed that is satisfied whenever the minimum range and time to closest approach simultaneously fall below given thresholds. The relation is further studied, in particular with regard to the issue of false and premature alarms. An airborne collision avoidance system is a possible application.

The purpose of this paper is to look at the nature of the advances being made in inertial navigation and in navigation displays. In avionics as a whole the advance from one generation of equipment to another can take different forms; sometimes, notably in flight control and instrumentation, the potential of new technologies is exploited almost immediately to provide more advanced operational facilities and systems become more complex. Alternatively, as in the application of solid state electronics to produce equipment for general aviation, the technology is exploited to reduce weight, volume and costs. Inertial navigation exhibits both trends but to a comparatively small degree; the basic system requirement is simple to define and has changed very little, one of the reasons being the particularly demanding nature of the technology and the very long development time scales involved.

The design of an almanac is a highly technical matter in which principles may have to yield to practical detail. In order that the proposals shall be fully appreciated and fairly discussed the basic principles that have led to the present proposals, and their practical alternatives, will be indicated as briefly and as objectively as possible.

In the Nautical Almanac Office we have much experience in the presentation of astronomical and numerical data; but we are not navigators and we have little experience of the practical use of the Abridged Nautical Almanac. While all criticisms will be welcomed, those relating to practical requirements will therefore be particularly valuable.