This paper is based on the President's Invitational Address given by the author at the 54th Annual General Meeting on 25 October 2000.

The paper outlines the changes in the physical form in which hydrographic information has reached the chart tables of ordinary navigators over the last five hundred years and traces its development from a purely verbal aid to a graphic one.

This and the following paper were first presented at the RIN01 Conference held in Oxford under the auspices of the Animal Navigation Special Interest Group, April 2001.

Flight paths of homing pigeons were measured with a newly developed recorder based on GPS. The device consists of a GPS receiver board, a logging facility, an antenna, a power supply, a DC-DC converter and a casing. It has a weight of 33 grams and works reliably with a sampling rate of 1 Hz for an operating time of about three hours, providing time-indexed data on geographic positions, ground speed and altitude. The devices are fixed to the birds with a harness, and the data are downloaded when the bird is re-captured. The measured flight paths show many details : for example, initial loops flown immediately after release and large detours flown by some pigeons. Three examples of flight paths are presented from a release site 17·3 km northeast of the home loft in Frankfurt. Mean speed in flight, duration of breaks and total length of the flight path were calculated. The pigeons chose different routes and have different individual tendencies to fly loops over the village close to the release site.

Human wayfinding in the natural environment has been practised for thousands of years. In the urban or built environment, few natural cues are available and other aids to wayfinding are needed. This paper considers the problems of wayfinding in airport terminals, what cues are available and how passengers use them to reach their destinations. The use of signs and maps is discussed, and conclusions are drawn on how wayfinding in airport terminals could be improved.

The principles of wayfinding are simple; the practicalities are very complex.

Nainoa Thompson.

This paper presents the results of a research project that investigated the potential benefits of a combined Galileo/GPS navigation system. The research addressed in detail the two key required navigation performance (RNP) parameters of accuracy and integrity. The project was supported by Alcatel Space and was a contribution to the Galileo definition studies (supported by the European Community under the GALA project). The results show significant improvements in both accuracy and integrity (achievable through RAIM) when a combined constellation is used rather than Galileo alone.

The basic concepts safety at sea and the maritime safety system have remained almost unchanged for a comparatively long time. However, the components and elements of these concepts are now subject to many changes created by the ‘information age’. This paper presents thoughts on today's concept of the maritime safety system, its main components and their elements. Although the thoughts and ideas presented are those of the authors, they take account of the legal instruments in force and recent developments in technology, especially developments in radio-communications. The paper provides an overall review of the institutions, regulations and procedures concerned with safety at sea.

Earlier papers, based on a computer model of European air traffic, deal with the probability of conflicts arising between pairs of aircraft operating under free-flight rules. This paper discusses the problems of resolving these conflicts. When a potential collision takes place in the neighbourhood of other intruding aircraft, these must be taken into account when choosing an escape manoeuvre. A suggestion is made that may ease the problem.

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.

Three textual works by Olaus Magnus (1490–1557) hold the key to the ‘compass’ on his invented island of Hvitsark, shown on his 1539 Carta marina. Although Olaus had little general understanding of the magnetic compass or of navigation in the Far North, he evidently did not intend the navigational device he drew on Hvitsark to represent a magnetic compass, but a sundial. His muddled ideas about the relationship between 12 wind-directions and direction-finding at sea by means of such a dial appear related to his second-hand information about a gnomonic navigational device used by the medieval Norse.

This paper presents the preliminary study of a stratospheric segment within a satellite navigation system of present and future generation (GPS and Galileo) implemented by means of High Altitude and Very long Endurance (HAVE) platforms. The paper discusses a possible scenario in which the main features of the HAVE platform are exploited to define an innovative Aerial-Based Augmentation System (ABAS) for the provision of differential services. This particular local segment improves the provision of a differential navigation service. It is suited to the broadcasting of differential corrections in critical areas such as mountainous and sea regions where, to guarantee wide coverage, a large number of terrestrial reference stations would otherwise be required. The study includes a description of the proposed DGPS augmentation system, and a discussion of the system architecture and expected performance.

Geometric Dilution Of Precision (GDOP) is a factor that describes the effect of geometry on the relationship between measurement error and position determination error. It is used to provide an indication of the quality of the solution. Conventional closed-form GDOP calculation formula applied to all possible combinations of visible satellites is rather time consuming, especially as the number of satellites grows. Approximations, such as the maximum volume method, are faster but optimum selection is not guaranteed. In this paper, a more concise but efficient solution for the calculation of GDOP value in the case of four Global Positioning System (GPS) satellites is firstly reviewed and then extended to cover the other forms of dilution of precision (DOP) values, including vertical DOP (VDOP) and horizontal DOP (HDOP). Secondly, a review and extension of the conventional solution is performed in the case of three GPS satellites aided by an altimeter. Based on the ideas gained from these two approaches, a simpler closed-form DOP formula for three GPS satellites aided by an altimeter is derived. The advantage of the proposed formulation is that it is simpler and thus reduces the computational load in comparison to the conventional one.

In the near future, Spaced-Based Augmentation Systems (such as the Wide Area Augmentation System in North America) will become operational, permitting the use of GPS as a primary system for all phases of flight. Recently the International Civil Aviation Organisation (ICAO) has recommended the use of un-augmented GPS as a supplemental navigation system for all phases of flight including non-precision approaches. In this paper, the salient features of the Air Traffic Control (ATC) system in India, and the use of conventional navigational aids are described. A new landing procedure is proposed using un-augmented GPS known as ‘a non-precision instrument approach procedure with vertical guidance (IPV)’ for Hyderabad Airport, Runway 27. This procedure, if implemented, would be cost-effective and reliable for many airports in India. An algorithm has also been developed for determining the range and bearing between the departure and the arrival waypoints of an aircraft using the IPV.

Although GPS positioning errors are now well described, there are still some uncertainties regarding the impact of some rare space weather phenomena on GPS positioning accuracy. Solar eclipses have been considered as one source of such rare events, so the 1999 solar eclipse gave the opportunity to collect horizontal GPS positioning data for further analysis. The results of statistical analysis show no deterioration of horizontal GPS positioning accuracy. Space weather, ionospheric and geomagnetic conditions were also carefully analysed and showed no significant activity. In conclusion, the experiment confirmed negligible impact of the 1999 solar eclipse on horizontal GPS positioning accuracy, and opens discussion concerning application of satellite positioning systems in space and ionospheric weather monitoring.

An integrated multi-sensor vehicle navigation system is presented that uses a low-cost rate gyro and differential odometry to supplement GPS under signal masking conditions such as tree foliage and urban canyons. Signal masking is often accompanied by extreme multi-path in urban centres with tall buildings, and is also found in wooded areas, enclosed car parks, tunnels, etc. The purpose of the system tested is to provide an accuracy of better than 20 metres almost 100% of the time throughout these interruptions, which are assumed to last up to a few minutes. The equipment used is discussed in detail, as is the method used for filtering measurements. Results are presented from tests carried out in an urban core with relatively long periods of signal loss – up to several minutes over a 6-km test circuit. Tests in urban canyons demonstrate that it is difficult to reach the above specifications with aiding from differential odometry alone due to the high precision of the wheel-scale factor required. However, with the use of a rate gyro and odometry, RMS errors are below 20 metres while availability is nearly 100%. Some of the large deviations could probably be better controlled if GPS multi-path errors were detected before they are allowed to corrupt the filtered solution.