For many generations mariners have been taught the law of storms and the rules for avoiding their centres. This paper describes some of the practical difficulties of avoiding hurricanes in the south-west Pacific area, and the failure of meteorologists to appreciate the dangers and difficulties of the mariners.

About half the tropical storms observed conform roughly to the parabolic track of the law of storms. They form about 10° South of the equator during the north-west monsoon, (from December to April), and travel west-south-west, south-west and south-south-west as they gather strength and speed to a maximum; at 20° South they pause, recurve through south-south-east and south-east as they diminish in force and pass out of our consideration at 30° South.

The star sensor field of view varies from several arc-minutes to 20 degrees, which directly determines the star vector orientation in the field of view (FOV). Although the relationship between star vector orientation in the FOV and attitude accuracy has been revealed, the influence mechanism of star vector orientation on the integrated navigation performance of a stellar inertial navigation system has not been analysed. In order to improve the integrated accuracy, the main errors such as star sensor installation error, gyro error and initial platform angle error should be estimated online. It is significant to study the influence mechanism of star vector orientation on estimation of the above errors. In this paper, the star sensor sensitivity and the geometry factor are defined to feature the difference between the optical axis direction and the non-optical axis direction. The formulised mechanism and quantification results between star vector orientation and integration attitude and error estimation accuracy are clearly given. Simulation and ground testing were conducted and it was found that the larger the star vector orientation along the optical axis, the better the error estimation accuracy. In contrast, the attitude accuracy is weakly sensitive to the orientation of the star vector in conditions of appropriate posture adjustment and star observation scheme. This conclusion can offer universal guidance for the design and evaluation of stellar inertial navigation systems with narrow field of view or large field of view star sensors.

Collisions are one of the major accidents in the shipping industry, causing significant losses. In this work, a framework of marine collision risk identification strategy was developed to quantitatively analyse collision risks and provide an easy and convenient way to monitor traffic flow in relevant waters to mitigate the chances of collision. The model was verified by using automatic identification system data obtained from Tianjin Port. When compared to previous research, the proposed model can identify risks earlier and give people more time to analyse and take action. The results indicate that it also can provide a visual display to alert relevant personnel. The model can be used as a reference to identify potential collision risks or as an information source for future research.

The complementary radio navigation system based on the Very Low Frequency signals produced by lightning is an alternative to today's Global Navigation Satellite Systems. The system operates on different principles and uses different radio frequency bands. The signals have higher availability in problematic places. The analyses based on the historical data of Word Wide Lightning Location Network demonstrated the good availability of the service, sufficient number of lightning strokes and good geometry calculated for a 10-second time window for positioning based on the Time of Arrival principle. The geometry was evaluated with the help of the Geometric Dilution of Precision coefficient. The Geometric Dilution of Precision median for the reception of the lightning signal from a range of 10,000 km moves around one except at the southern polar regions and the probability of the service availability exceeds 80%.

In the July Journal (14, 362) Klerk and Steensma describe a new and ingenious method of radar plotting. The following comment, sent in at the invitation of the editor of the Journal, follows closely my remarks on a similar article in the Dutch review De Zee (December 1960).

In this paper, methods of defining heading are enumerated and the limitations of magnetic and gyroscopic devices are analysed in detail. Particular attention is paid to the development of the rotated race principle which is likely to be responsible for a large improvement in the basic azimuth gyro. The gyro-magnetic combination is scrutinized and the errors inherent in this compass system are classified. The possibility and consequent effect of diminishing certain categories of error are presented. The current position is summarized and an attempt is made to suggest possible future trends. The authors are, respectively, with Smiths Aircraft Instruments and the Sperry Gyroscope Company.

In the January 1966 edition of this Journal Captain Wylie has given a lucid summary of the factors involved in the presentation on radar displays of true and relative motion. He also stated a conclusion on the combinations of display and ancillary equipment which he considers best satisfy the requirements for use when plotting to avoid collision at sea. Whilst acknowledging with respect all the work he has done to clarify the issues raised on this important but contentious subject over a number of years, a number of us has found it impossible to agree with his latest findings. As these may influence opinion in the shipping industry, the Board of Trade, the Courts of Law and the radar manufacturing industry, both at official and unofficial levels, they should not go unchallenged. Our disagreement concerns the priorities defined for display equipment and the method to be used for plotting. There can be no disagreement on academic principles.

The geometry of the skeg in the Escort Tractor Voith tugs is the result of a series of intense investigations in the forms of the tug and its fins, oriented to get a significant improvement in the forces on the towing line when the indirect method is used in the escort towing. For that, and with the aim of getting the best behaviour of this fin, a variety of options have been investigated for years, evaluating its merits in terms of lift force and complexity to reach the present designs, which are adapted to the functions which the tug is destined to carry out. With the object of optimizing the lift force in the skeg when the indirect method is used in the escort towing, and after long investigations, the Voith Turbo Marine has incorporated a rotating cylinder at the leading edge to its design in escort towing for the first time at the beginning of 2005. The leading edge is the part over which the water flow first falls upon in normal escort operation conditions, calling this new development Voith Turbo Fin (VTF) to the system as a whole (skeg and rotating cylinder). This fin is analyzed in this article especially with regard to its basis, ways of operation and efficiency of the novel joining rotating cylinder.

Marine casualties usually arise through a combination of complex conditions. To trace any one of the conditions involved, and its reaction on others, not only helps to reveal the cause of an accident but is also important in understanding the nature of such casualties.

Like accidents on land, marine casualties do not arise spontaneously but have ascertainable causes, rarely a single cause but rather a combination of causes. Thus in a collision in fog in a narrow channel we must consider not only faults in carrying out a manœuvre but also the natural phenomena of fog and the narrowness of the channel.

Dr. Freiesleben, an Honorary Member of this Institute, discusses the geometry of ellipses and hyperbolae on the sphere. These are the curves which correspond to position lines based on the constant sum or difference of distances from two fixed points. Originally applied to astronomical position lines they now have a wider application to electronic fixing systems of global coverage like Omega.

In the field of modernised Global Navigation Satellite System (GNSS) signal design, several Dual-frequency Constant Envelope Multiplexing (DCEM) methods have been recently proposed. However, the existing DCEM methods, such as Alternative Binary Offset Carrier (AltBOC), generalised AltBOC and Asymmetric Constant Envelope Binary Offset Carrier (ACE-BOC), are only applied in some special cases. In this paper, we present a unified DCEM design framework for GNSS signals. The existing DCEM methods can be unified in this framework. First, the signal components at two carrier frequencies are combined into two single-frequency constant envelope signals. Then, the linear sum of dual-frequency signals with non-constant envelopes is obtained. Finally, the linear sum is converted into the corresponding DCEM signal by solving an optimisation problem. The proposed design framework has no strict constraints on the number, power ratio and phase relationship of the signal components. Moreover, some special design cases under this framework are also analysed in detail. The analytical results show that the proposed design method can reach higher multiplexing efficiency compared with the existing methods. Based on the proposed method, we suggest a scheme to multiplex the BeiDou regional signals and global signals at the B2 frequency. The simulation results of correlation functions and Power Spectrum Density (PSD) verify the correctness and effectiveness of the proposed design method.

This, and the following three papers were presented at the Royal Institute of Navigation meeting ‘Management of Air Traffic Flow in Europe' on 15 November 1989.

One of the growth industries in Europe is the production of articles in newspapers and programmes on radio and television which deal with European air traffic control. They usually have titles like, ‘The Crisis in ATC’, or ‘European Air Traffic Meltdown’. Jane's Airport Review, in October 1989, had an article entitled ‘Wanted: One ATC System for Europe’.

Dr. Ramsayer's paper, presented at the tripartite meeting on automatic navigation held in Paris last April, describes a dead-reckoning computer on which position is presented instantaneously on a map.

The so called Automatische Koppelkarte has been developed by the Institute of Air Navigation of the Technical University of Stuttgart, and is a new type of dead reckoning computer differing from the usual navigation computers in that position is immediately indicated on a map; there are many possibilities for combining the device with other navigational aids.

Fig. 1 shows a schematic diagram of the computer. It consists of the computer, the map display and the course and track indicator. The station selector and the coordinate transformer shown in Fig. 1 are additional units, only used when monitoring by tacan is desired, as will be described. The computer is fed by a gyro-magnetic compass and a true airspeed transmitter. The wind is set at the map display, and ‘grivation’ at the course and track indicator. From these data both the flight path and the track are computed. The flight path is resolved in two rectangular components and is displayed by a light pointer on a map of conformal conical projection. The standard parallels of the map are selected in such a way that the distortion in length is practically negligible for the area of interest.

In the first six months of 1979 there were six collisions in the area of the Dover Strait (extending from the Greenwich meridian to 2° 30′ E and from 50° 30′ N to 51° 30′ N) that involved at least one vessel of 500 grt or more. (Two further collisions took place during the next four months.) Collisions have not occurred in these waters at a rate of one a month since 1969. Yet since then there have been several notable changes that should have led to greater safety. The IMCO traffic separation scheme has been made compulsory for ships of all nations through the coming into force of the new Collision Regulations on 15 July 1977. Secondly, the Channel Navigation Information Service was established in England in 1972, and it and its counterpart in France have been monitoring the traffic by radar and making regular broadcasts for more than five years. Finally, traffic discipline has steadily improved, as measured by the number of ‘rogue’ vessels that are held to contravene the routing scheme (Fig. 1).

To decide whether this spate of collisions represents a marked deterioration in navigational standards it is necessary to do rather more than merely count occurrences (Fig. 2). In the first place, any evaluation must take account of the amount of damage to the ships involved and to the environment, and of deaths and injuries to personnel.

Various surveys have been carried out in narrow waters throughout the world and provide data on the traffic volume, traffic density, velocity distributions of ships, &c. Although these surveys certainly contribute to the safety of local navigation they do not give any information on traffic movements between terminal points in a marine traffic system. There are a few papers on voyage distribution based on traffic surveys, statistical reports or questionnaires to mariners and also a few based on radar observation, including one in Osaka Bay in Japan which was carried out by the traffic research group of the Kobe University of Mercantile Marine and Nautical Technical College.

Digital Selective Calling (DSC) is causing serious problems for Search and Rescue (SAR) providers. Administrations must seriously consider the humanitarian and legal implications of continuing the implementation of DSC. They may be in violation of the Safety of Life at Sea Convention, the International Convention on Maritime Search and Rescue, 1979, and the United Nations Convention on the Law of the Sea, 1982, by knowingly implementing communications technology that may jeopardize lives at sea even though the primary intent of DSC is to establish a suitable distress alerting method. States may very well open themselves to legal liability if loss of life or environmental damage can be linked in any way to the known faults of DSC.