This paper and the following three papers were presented at the RIN97 Conference held in Oxford under the auspices of the Animal Navigation Special Interest Group, April 1997. The full proceedings, under the title Orientation and Navigation – Birds, Humans and Other Animals, can be obtained from the Director (£30 to Members, £50 to non-Members).

Studies of the compass mechanisms involved in the migratory orientation of birds have revealed a complex web of interactions, both during the development of orientation behaviour in young birds and in mature individuals exhibiting migratory activity. In young birds, the acquisition of compass orientation capabilities involves the interplay of apparently genetically programmed information with a suite of innate learning rules. The latter canalise the ways in which experience with relevant orientation information from the environment impinges on development. There are many general similarities with the development of singing behaviour in songbirds, although that system is more thoroughly understood, especially at the neuronal level.

Here we shall attempt to synthesise what is known about the development of compass mechanisms in a framework of innate information and learning rules. The way in which orientation behaviour develops leaves open the possibility for plasticity that enables birds to compensate for variability in the environmental cues that form the basis of their compasses. For at least some components of the system, behavioural plasticity remains into adulthood, allowing the bird on migration to respond in apparently adaptive ways to spatial and temporal variability in orientation information that it may encounter while enroute. We have studied these questions in the Savannah sparrow (Passerculus sandwichensis), a medium-distance North American emberizine nocturnal migrant. We will focus on that species, relating the results of our work to relevant studies on others.

This and the following six papers were selected from the many papers presented at the 9th World Congress of the International Association of Institutes of Navigation (IAIN) held in Amsterdam, The Netherlands, 17–21 November 1997.

During the past several years, a number of important investigations, policy initiatives and national commitments relating to the future of GPS, GLONASS and their augmentations have occurred. Substantive and on-going studies of the character and configuration of a Global Navigation Satellite System (GNSS) have also been evaluated worldwide, especially by the International Civil Aviation Organization (ICAO). These efforts have been principally directed toward the definition of near- and far-term GNSS implementations that meet the needs and concerns of the international community. This paper briefly reviews some of the investigations and addresses, in particular, the concerns and requirements that may affect the future capabilities and the dual (civil/military) character of GPS. The main issues relating to the modernisation of GPS and its subsequent transition to a component of a GNSS with a viable international character are presented. These include a discussion of new signal structure options, certain changes in operating frequencies, increased signal power levels, other system alternatives and their potential impact on system performance. International issues are briefly addressed, including future performance capabilities, assurance of service, economic participation and benefit, reasonable cost, standards and international participation.

This paper, and the following five papers, were presented during the NAV 97 Conference held at Church House, Westminster, London on 11th and 12th November 1997. A full listing of the Conference, and how to obtain a copy of the proceedings, is shown on Page 279.

The Government of the Russian Federation has made available, subject to certain conditions, the GLONASS satellite radionavigation system for civil use. Use of the system is free and there is no intention to introduce coding or to cause any deterioration to the accuracy of the signals. Discussions are currently taking place between the European Commission and the Russian Federation on cooperation concerning the implementation of a navigation satellite system for civil purposes. Discussions are also taking place between interested European Governments and the Russian Federation into the possibility of developing joint Chayka/Loran-C chains wherever this is feasible, and in particular, to cover the Barents Sea, the Baltic Sea and the Black Sea. The development of a concept on integration of radionavigation systems would probably be a significant contribution to the European Radionavigation Plan.

As new technologies contribute to the expanded functionality of Loran-C, and as concerns for limitations in GPS and its augmentations are raised, specific aspects of Loran-C have been developed and applied to ameliorate those limitations. Specifically, GPS availability is a concern, particularly in over-land applications. This paper discusses recent developments using very high-precision synchronisation of Loran-C transmissions, new data compression and Loran-C signal modulation techniques to augment GPS accuracy, availability and integrity over a very wide area at very low cost.

The lives of sea turtles consist of a continuous series of migrations. As hatchlings, the turtles swim from their natal beaches into the open sea, often taking refuge in circular current systems (gyres) that serve as moving, open-ocean nursery grounds. The juveniles of many populations subsequently take up residence in coastal feeding areas that are located hundreds or thousands of kilometres from the beaches on which the turtles hatched; some juveniles also migrate between summer and winter habitats. As adults, turtles periodically leave their feeding grounds and migrate to breeding and nesting regions, after which many return to their own specific feeding sites. The itinerant lifestyle characteristic of most sea turtle species is thus inextricably linked to an ability to orient and navigate accurately across large expanses of seemingly featureless ocean.

In some sea turtle populations, migratory performance reaches extremes. The total distances certain green turtles (Chelonia mydas) and loggerheads (Caretta caretta) traverse over the span of their lifetimes exceed tens of thousands of kilometres, several times the diameter of the turtle's home ocean basin. Adult migrations between feeding and nesting habitats can require continuous swimming for periods of several weeks. In addition, the paths of migrating turtles often lead almost straight across the open ocean and directly to the destination, leaving little doubt that turtles can navigate to distant target sites with remarkable efficiency.

Marine radiobeacons have been used to broadcast differential corrections for global navigation satellite systems (DGNSS) for nearly a decade. The method has become the accepted international standard for maritime applications. The background to the development of the system is described and the current status of radiobeacon DGNSS services around the world reported. The applications are discussed, including the function of radiobeacon DGNSS as the position sensor within integrated systems, together with the performance requirements imposed by associated systems such as ECDIS and Automatic Identification Systems. The advantages and disadvantages of the radiobeacon system in regulatory, administrative and technical terms are discussed and the potential for development of the system is considered. The future role of radiobeacon DGNSS in the overall mix of systems is assessed taking into account the introduction of geo-stationary overlays, and possibly Loran-C, for provision of DGNSS corrections.

Dead reckoning (also called path integration) is the process by which a navigating organism derives its current position relative to an Earthbound reference point from its own locomotion. Dead reckoning requires the continuous estimation of changes in direction and location through self-generated signals and the computation of position on the basis of these signals.

(i) Hymenopterous insects measure rotations and translations mainly with the help of optical references such as the Sun and translational visual flow. By contrast, mammals are able to estimate their position on the basis of purely ‘internal’ information; that is, signals generated in the vestibular system by inertial forces, somatosensory feedback, and efference copies (copies of central commands that control the performance of rotations and translations). Obviously, the assessment of the angular and linear components of locomotion is much more precise if it is assisted by external references than if this is not the case.

(ii) Only man-made dead reckoning systems yield precise position information through the twofold integration over time of inertial signals deriving from angular and linear acceleration. On the biological level, all species tested so far seem to rely on a simplified form of path ‘integration’: in certain test situations, arthropods and mammals (including humans) commit similar systematic errors. This suggests that species from unrelated taxa update position according to a similar algorithm.

This paper gives details of the failure rates and the failure modes experienced with SPS GPS receivers certificated for aviation use to the TSO-C129 specification. These failure rates are significant compared to those from other modern avionics and the rates are comparable to that currently experienced from un-scheduled failures in the GPS signals-in-space. To achieve certification, Flight Management System (FMS) design should consider the way in which the satellite navigation receivers fail. The paper also gives details concerning the 2-D errors that have been experienced with these receivers, and indicates further work that needs to be done with C 129a receivers.

The helicopter traffic over the North Sea is performed in uncontrolled airspace over international waters. The lack of radar coverage makes the establishment of controlled airspace difficult. The development of Automatic Dependent Surveillance (ADS) and use of satellite technology for Navigation, Communication and Surveillance (NCS) have made it possible to evaluate Modified Automatic Dependent Surveillance (M-ADS) as a basis for establishing controlled airspace over remote areas without radar coverage.

Recent advances in technology have encouraged proposals for new approaches to ATC in Europe and elsewhere. Two such proposals, both rather loosely framed, are for ‘free flight’ or for ‘seamless contracts’; otherwise ‘tubes of flight’. These concepts, and variations on them, aim to increase the traffic capacity of the airspace. They have been the subject of numerous published papers. Given the declared objects of these systems, it is surprising that, nearly without exception, these papers discuss the proposals only in qualitative terms. The present paper discusses idealised versions of these systems on the basis of quantitative studies. It is concluded that the ‘seamless contract’ is very probably unworkable in Europe. ‘free flight’ is workable in principle, but there is a need for investigation of possible mechanisms by which last-minute problems may be resolved.

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.

Although conditioning techniques are the most powerful way to study behavioural responses by animals to external stimuli, the magnetic sense has proved surprisingly resistant to conditioning approaches. This study demonstrated learned discrimination of magnetic field intensity stimuli by a new species, the rainbow trout (Oncorhynchus mykiss). In a unitary conditioned discrimination technique, four juvenile rainbow trout were trained to strike a target at the end of a response bar in anticipation of food. In successive experiments, the trout failed to discriminate the presence and absence of a vibration stimulus, but subsequently learned to discriminate the presence and absence of a magnetic field intensity anomaly (peak intensity of 75 μTesla). The authors conclude that the necessary conditions for training animals to magnetic intensity are the use of spatially distinctive stimuli and of a conditioned response that requires movement.

Of the great oceans of the world, the Atlantic, because of its violence, was the last to be mastered by man. The task in its entirety had to wait for the Portuguese sailors of the Renaissance. Isidore of Seville (c. 570–636), a Christian writer of the late Roman Empire, had written of the Atlantic that it was ‘incommensurable and uncrossable’. Although Pliny (a.d. 23–79) refers vaguely to the Canary Islands, all knowledge of them disappears in the Middle Ages until a Portuguese expedition under the command of the Italian Lanzarotto Malocello ‘re- discovered’ them in 1336. Italian charts of the XIVth century begin progressively to show the Canaries, Madeira, Porto Santo and the Azores, but all aligned along a N/S axis without any appreciation of the relative distances between them or how far they lay from the European shore. The first written evidence of the Portuguese ‘discovery’ of the islands of Madeira and Porto Santo appears in 1419–20 and of the Azores in 1427, about the same time as they began to be colonised under the aegis of Prince Henry of Portugal, called the ‘Navigator’. The difficulties of returning to them on regular voyages was to motivate the Portuguese to develop methods of measurement using the Pole Star as a navigational aid and this led, not only to a greater accuracy in placing the islands on the charts, but also to a greater precision in the charting of the west African coastline which they were progressively exploring during the second half of the XVth century.

Claims that Portuguese nautical astronomy originated in Aragon and was transmitted from there to Portugal or was introduced into Portugal from Germany by Regiomontanus and Martin Behaim have long ago been shown to be baseless.

This paper addresses two aspects of high accuracy GPS positioning : single point positioning and real-time kinematic positioning. In both cases, it is shown that use of the correct models significantly improves the quality of the resulting positions. In the first case, emphasis is placed on physical models, especially the satellite orbit, and in the second case, emphasis is placed on the stochastic model, i.e. understanding the statistics of the GPS observables.

There is still fierce debate in the international community regarding the use and standards of electronic chart data and equipment. Whilst the standards for ecdis are now virtually complete and type-approved equipment will be entering the market during 1998, there is currently no IMO/IHO compliant enc data service from any national hydrographic office. It is expected that it will be 1 to 2 years before there is any appreciable quantity of enc data supported by a proper update service. It will be many more years before enc data becomes available to match the present coverage of paper charts, but we can expect that most major routes and the port entries of the majority of the world's trading nations will be available within a few years. This situation is examined, together with the ideas that IMO is considering to improve the availability of official electronic chart data. In addition, the distribution of electronic charts is discussed and the future trends in navigation that will occur with the availability of ecdis equipment and related data are explored.

High-precision ‘autofarming’ makes possible farming techniques previously impractical using metre-level Differential GPS-based control systems: techniques such as tape irrigation, the elimination of guess rows, and precise contour farming. A Carrier-Phase Differential gps positioning and attitude system with centimetre-level and 0·1° accuracy was installed in a large farm tractor. Four types of trajectories (lines, arcs, spirals, and curves) were identified as basic building blocks necessary to generate a ‘global’ trajectory for a realistic autofarming path. Information about each trajectory type was translated into reference state specifications that a linear controller used to control the tractor over velocities between 0·7 and 2·8 m/s to within approximately 6 cm (1 σ) without implement and 10 cm (1 σ) with implement on sloped terrain using a previously developed tractor model. These results are a significant step towards a realistic autofarming system because they not only demonstrate accurate control over various realistic operating speeds but over different types of trajectories necessary for a commercial system.

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 gives an overview of navigation and positioning requirements of the European offshore oil industry in the context of consideration now being given to the role of GPS in the European Radio Navigation Plan. An outline is given of how these requirements are currently achieved and of the criticality of the operations.

There is no generally accepted definition of the difference between a map and a chart. A widespread feeling probably exists favouring the old saying that maps are to look at and charts to work on. It is true that the term ‘aeronautical chart’ gained a general currency over alternative terms as contact flying gave way to aerial navigation. But, in this paper, the terms ‘map’ and ‘chart’ will be used as seems appropriate to each occasion, without attempt to conform to any particular definition.

We can get an idea of what was available to the earliest aviators by looking at an Ordnance Survey reprint of one of their nineteenth century maps (Fig. 1). They are printed in one colour only, black on white. By far the predominant feature is the hill shading. Quite gentle hills are hachured with a heaviness which tends to obscure both natural features like rivers, lakes and woodlands and man-made constructions such as towns and villages, roads, canals and railways. Hills are, of course, very important features to those on the ground, since they limit the extent to which other features can be seen. To the soldier, the significance of high ground is self-evident, and it was principally for the ordnance requirements of soldiers that these maps had been developed. But when men began to view the ground from the air, the perspective changed. Hills appeared flattened out and, provided that you knew the height of the tallest in the area and were sure none would impede your take-off or landing, were of minor significance. Lakes and woods, though, were spread out before you in their distinctive shapes, while railway lines and canals presented bold straight lines and curves, and rivers their unique courses, to your view. The need was for new kinds of maps which would give due prominence to such features.

This paper is based on work done originally for the Chevron Shipping Company, whose agreement to its publication in its present form is gratefully acknowledged.

Ever since the International Regulations for Prevention of Collision at Sea (IRPCS) were introduced as a control system for collision avoidance, there have been disputes and arguments about exactly what they mean, and how they should have been applied in particular collision incidents. The principle of deciding by international agreement which ships should be given the duty of keeping clear of other ships generally works well but, as traffic volumes increase, so do situations in which the IRPCS alone do not provide a clear indication of what is expected of the mariner. Various solutions have been addressed to this problem, ranging from proposed radical revisions of the whole principle of collision avoidance, through periodic thoughtful adjustments to the details of the IRPCS, to informal additions and requirements imposed by individual shipowners on their fleets. The residual problem with any solution (except perhaps the first mentioned) is that there will always be exceptions where the rules are unclear or ambiguous. Adding adjustments may reduce these exceptions but, unless all uncertainties can be removed, the adjustments may create a new and even more complex set of exceptions, which are yet more difficult to interpret.