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.

This paper presents further research on the SNUGL pseudolite-based navigation system presented in this journal in 2003. This system has centimetre-level accuracy, but has an error source arising from right-hand circularly polarized (RHCP) transmissions, unlike outdoor Global Positioning System (GPS). The GPS satellites and pseudolites use RHCP signals, and the polarization affects carrier-phase measurements according to the Line-of-Sight (LOS) vectors from transmitters to receivers. The RHCP error is eliminated by a double differencing process in outdoor GPS, but the error remains in the pseudolite-based system because the LOS vectors from transmitters to a reference and user receivers are different for the close transmitter constellations. This paper shows the RHCP effect on the pseudolite-based navigation system through simulations and experiments. It then shows the RHCP-compensation method improves the measurement and position accuracy by over 10%.

The development of augmentation services, such as EGNOs and WAAS, requires careful modelling and simulation before any deployment of equipment takes place. The ideal location of ground stations, and the potential impact of temporary failures of ground equipment, must be assessed in detail, to ensure that proposed service levels of accuracy and integrity are maintained at all times. The correct analysis of these parameters can only be achieved if the various wide area processing models, and their respective error propagation characteristics, are suitably simulated. This paper describes the use of a sophisticated and versatile suite of GNSS analysis tools in recent studies. It describes the incorporation of realistic error budgets for WADGPS and LADGPS corrections, and the potential use of different combinations of GPS, GLONASS, geostationary and other satellites in both GNSS-1 and GNSS-2.

This paper covers the wide area and short range locational technologies that are available for vehicle tracking in particular and mobile user security in general. It also summarises the radio communications services that can deliver information to the user. It considers the use that can be made of these technologies, when combined with procedures for delivering a response, in the security field, notably in relation to personal security, high-value load protection and the after-theft tracking markets.

This paper compares the differences between the rhumbline courses and distances calculated by three methods: the classical formula, precise formula and by software contained in a typical GPS receiver. It concludes that, while the calculations made by the GPS receiver are generally more accurate than the classical method, navigators must use Tables of Latitude Parts to calculate rhumbline distances accurately.

Self-organising radio systems have been proposed for aeronautical and maritime communication, navigation and surveillance applications. In aviation, the introduction of the VHF Data Link (VDL) Mode 4 is currently being discussed, while the implementation of Automatic Identification Systems (AIS) is planned in the maritime domain. Operating in an autonomous mode, a self-organising radio system employing Time Division Multiple Access (TDMA) does not require a terrestrial infrastructure, such as base stations. The concept of self-organisation is based on the cooperative behaviour of a large number of users sharing a common VHF radio channel. Analyses have shown that uncoordinated stations, so-called hidden users, can cause interference in self-organising radio systems. This paper presents two different approaches to autonomous self-organisation together with the results of investigations of intra-system interference. Such analyses may help to introduce potential improvements to the system performance, which reduce the effect of hidden users in this very promising GNSS-based technology.

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.

Integrated electronic marine systems are becoming part of the numerous screens which are to be found on ships' bridges and in wheelhouses of fishing vessels. This paper continues previous work which has focussed on perceived safety aspects of integrated electronic marine systems, in particular, a small study completed within the last two years which showed that some fishing skippers had negative perceptions of integrated electronic marine systems. This present study uses semi-structured interviews with skippers in the United Kingdom fishing fleet to show that integrated electronic marine systems can be perceived as increasing safety as well as being of good value in terms of need and cost. It is possible that such perceptions are dependent on experiencing the use of integrated electronic marine systems within off-shore trawling.

A theoretical analysis of the effects of dual frequency ionosphere propagation correction on GNSS code tracking noise is presented. The effect on tracking noise of using different combinations of the proposed Galileo signals for ionosphere propagation correction is investigated. It is concluded that, for the open or commercial service user, the Galileo signals E2-L1-E1 near to and around GPS L1 should be used to apply ionosphere propagation corrections to the E5 signals. This produces a tracking noise standard deviation about three times larger than that on an E5 signal alone. An ionosphere correction-smoothing algorithm is presented that reduces the tracking noise on the corrected pseudo-range measurements.

An application of the model to manoeuvre ships based on the range to domain over range rate (RDRR) concept is described. A simulation of a training simulator has been set up on which the target ships manoeuvre by the RDRR model in response to mariner controlled ships. Results of experiments show that the RDRR model manoeuvres targets realistically. The applications are reduced instructor work load and increased simulator reality. The method has the potential for development to manoeuvre ships at sea.

B. A. Colley is now with Plessey Marine, R. G. Curtis is with the Department of Trade and Industry and C. T. Stockel is at Plymouth Polytechnic.

A revision of the North Atlantic Track Agreement would make it possible to form a larger group of subscribing companies. The existing tracks could be simplified and the danger of convergence on certain channels avoided by modifying the double landfall at Fastnet and Bishop and by moving certain junctions. This could be done without unduly lengthening the channels. One might also replace the concept of fixed channels by the more liberal one of protected channels, which one might call ‘Naviroutes’.

Ships wishing to follow these would benefit from increased safety by the use of certain simple rules, which may be summarized as follows:

A neutral zone, varying in size according to the region, of the blue-line type proposed by Oudet and Poll would separate traffic going in opposite directions. In good visibility ships crossing a ‘Naviroute’ would do so at an angle of more than thirty degrees; in fog ships would cross a ‘Naviroute’ at right angles and at low speed. Each of these rules is dictated by commonsense to every seaman with experience of crossing busy shipping channels.

Inertial navigation systems have for many years been mechanised as a cluster of gyros and accelerometers mounted in a servo-controlled gimbal system which isolates the cluster from the motion of the carrying vehicle. Until the spectacular advance in computer technology over the last decade no other mechanization was really feasible, but serious consideration is now being given to strapped-down systems. This paper compares the two mechanizations, outlines some of the advantages of strapped-down systems, and considers some of the contenders for rate-sensing in such systems.

Navsat is a civil satellite-navigation system which was presented by the European Space Agency. It is still at the system definition phase as distinct from the pre-operational stage, but since the original presentation it has been the subject of studies which have included analysis and synthesis of the main parameters.

The underlying principles of the concept as initially described by Rosetti remain unchanged but sufficient progress has now been made to predict the capability of the system in satisfying a number of objectives in the civil fields of navigation, position fixing and survey.

Before turning attention to the problems of heavy weather sailing in yachts it is useful to attempt to define what a yachtsman considers to be a gale.

When I first took up ‘going foreign’ in my own boats cones were hoisted at signal stations when winds of Force 7 or above were anticipated. Thus it may be said that gales started at Force 7, but skippers of commercial craft such as Brixham trawlers (in which I occasionally sailed), barges and other coasters did their own forecasting and used their own judgment of what constituted a gale without bothering too much about the Beaufort notation. Amateurs followed suit in this matter and when wind or sea rose too high for their own particular yachts they would describe the conditions as a gale. It was not until the radio became a commonplace in yachts that a more scientific approach came to be made. Of recent years few yachtsmen will make even a cross-Channel passage without first receiving a weather forecast and the tendency is to rely entirely on forecasts. In passing, I would comment that the vagaries of the weather are such that some of the severest gales have occurred with only very short warning.

Many problems in navigation can be best viewed and solved as problems in analytical geometry. We only need to understand the geometry of two ‘navigable’ surfaces; the sphere and the ellipsoid of revolution. The ellipsoidal model is generated by revolving an ellipse about its minor axis and this model is used as a global model for the surface of the Earth. The eccentricity of the meridian ellipse is small (≈0·082) so we sometimes refer to this surface as a ‘spheroid’ since the surface is still ‘sphere-like’. The physical Earth is, in fact, referred to as a ‘geoid’ whose surface is that which approximates global mean sea level. The mathematical representation of the geoid is not trivial and the ellipsoid of revolution is an extremely good approximation to it.

It is over 10 years since this ill-fated Fastnet Race claimed the lives of fifteen yachtsmen and the total loss of five yachts. A total of twenty-four crews abandoned their yachts and in all, 136 people were saved by being winched into helicopters and taken on board merchant and naval ships as well as other yachts. Some eighteen yachts needed the assistance of lifeboats because they had lost their rudders.

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.

This paper considers the issue of operating aircraft through the North Atlantic's Minimum Navigation Performance Specification (MNPS) airspace. Noting that aircraft constantly strive for reduced fuel burn and uplift, it describes how flight operators and pilots conduct safe, efficient flights through the region. Reference is made to mechanisms of the North Atlantic MNPS airspace in terms of its Organized Track Structure and other routes that exist. These different structures emphasize the level of flexibility available. Flight planning procedures and requirements necessary to obtain oceanic Air Traffic Control (ATC) clearances are mentioned, as is an account of how communication and position reporting procedures operate to apply the Mach Number technique. Other aspects of MNPS operations such as ETOPS operational restrictions, meteorological effects, the employment of Reduced Vertical Separation Minima and planned regional changes aim to provide an overview of the MNPS system's current and future air traffic management.

This study of Columbus' navigation is unique because it was written by an historian who is also a trained and experienced professional global (and ocean) navigator, rather than an academic historian with only superficial knowledge of the science of navigation as practiced by Columbus and other early navigators. The study is also unique in that as an American historian author disagrees with his colleagues in the USA who present the “politically correct” view of Columbus as an unskilled entrepreneur who obtained his limited knowledge of navigation as a crew member or passenger on Portuguese voyages, rather than as one of the most skilled and experienced of the cadre of respected Genoese captains and navigators used by kings throughout Europe to perform their maritime enterprises.