In his Presidential Address at the 52nd Annual General Meeting of the Institute, held in London on 21 October 1998, Air Commodore Pinky Grocott gave an analysis of the causal factors that resulted in the loss of 913 large sailing ships during the period of the Revolutionary and Napoleonic eras (1793–1815). Navigation and weather factors predominated, often aggravated by poor and untimely decision-making. Many of the lessons learnt are equally relevant today.

This paper, and the following six papers, were presented during the NAV 98 Conference held at Church House, Westminster, London on 9th and 10th December 1998. A full listing of the Conference, and how to obtain a copy of the proceedings, is shown on Page 300.

The existing Loran-C and Chayka infrastructure can, with some minor changes, become a very powerful augmentation system for GNSS (GPS, GLONASS and the future Galileo). Delft University initially proposed the Eurofix concept in 1989. Although the necessary modification to the LF navigation systems are minimal, the GNSS user may get significant benefits from the Eurofix signals in terms of accuracy, integrity and availability. The reason is the high signal structure, signal propagation, and the operations dissimilarity of both systems. The broadcast correction and integrity data improves GNSS accuracy down to the metre level. In this way, the measured Loran-C and Chayka ranges are continuously updated. Thus, in the case of GNSS signal interruptions, highly calibrated Loran-C/Chayka may take over the navigation function. Tests carried out in Europe at the Loran-C station at Sylt (Germany) drew large international attention, leading to further tests in the USA by the US Coast Guard in 1998. Recently, a Dutch–Russian consortium implemented Eurofix on the Chayka transmitter at Bryansk (Russia) which is now successfully broadcasting DGPS as well as DGLONASS correction data. This paper highlights some on-air Eurofix DGPS performance experiments carried out in Europe and the USA. With all the European Loran-C and Chayka transmitters modified, Eurofix can be used all over the European continent. As multiple stations can normally be received simultaneously, the user may locally apply networked DGNSS, which may reduce spatial decorrelation effects significantly. Post- processed results of this Regional Area Augmentation System are presented.

The rapid development of differential GNSS transmissions via low-frequency maritime radiobeacons has further increased the occupancy of an already over-crowded frequency band. This has resulted in interference between stations, with consequent reductions of coverage. The paper suggests a re-allocation of channels within this band in Europe to be carried out, taking careful account of the known groundwave and skywave propagation of both wanted and interfering signals and the distribution of atmospheric noise. A novel algorithm is proposed for re-allocating frequencies. The resulting band plan is shown to offer substantially increased coverage for DGNSS radiobeacons while preserving the performance of marine and aeronautical direction-finding beacons, the latter remaining on their original channels.

The following paper reports on the progress of a large collaborative project in the UK to investigate novel strategies for the implementation of GNSS within all phases of marine navigation. The project is funded by the UK Government (Engineering and Physical Sciences Research Council) under the leadership of the IESSG at the University of Nottingham. The project receives the support from a prestigious team of collaborators which include the UK Ministry of Defence Hydrographic Office, Trinity House Lighthouse Service, Northern Lighthouse Board, Commissioners for Irish Lights and the Port of London Authority. This consortium is of strategic importance, as their operations encompass the provision of aids to navigation for all phases of marine transport within the UK and elsewhere.

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.

A variety of operational systems are vulnerable to disruption by solar disturbances brought to the Earth by the solar wind. Of particular importance to navigation systems are energetic charged particles which can generate temporary malfunctions and permanent damage in satellites. Modern spacecraft technology may prove to be particularly at risk during the next maximum of the solar cycle. In addition, the associated ionospheric disturbances cause phase shifts of transionospheric and ionosphere-reflected signals, giving positioning errors and loss of signal for GPS and Loran-C positioning systems and for over-the-horizon radars. We now have sufficient understanding of the solar wind, and how it interacts with the Earth's magnetic field, to predict statistically the likely effects on operational systems over the next solar cycle. We also have a number of advanced ways of detecting and tracking these disturbances through space but we cannot, as yet, provide accurate forecasts of individual disturbances that could be used to protect satellites and to correct errors. In addition, we have recently discovered long-term changes in the Sun, which mean that the number and severity of the disturbances to operational systems are increasing.

The US Federal Aviation Administration (FAA) is developing and planning to field the Local Area Augmentation System (LAAS). LAAS is a Ground-Based Augmentation System (GBAS) to GPS, and is designed to serve all categories of precision approach. The purpose of this paper is to provide the latest technical and status information on the LAAS programme. The technical aspects of the LAAS specification are discussed, followed by a description of specification validation field testing and results. Institutional and programmatic aspects are then summarized along with a chronology of events leading up to the Government Industry Partnership (GIP) for the initial development and fielding of LAAS.

Satellite Based Augmentation Systems are being developed in Europe (EGNOS), the USA (WAAS), and in Japan (MSAS). As part of their support to EGNOS, NATS and Racal have developed and deployed a prototype SBAS system called the Northern European Satellite Test Bed (NEST Bed). NEST Bed uses GPS L1/L2 reference stations at: Aberdeen, Rotterdam, Ankara, Cadiz, Keflavik, and Bronnoysund. Data is sent to the Master Control Centre at NATS Gatwick Services Management Centre for processing. The resulting 250 bits-per-second message is sent to Goonhilly for up-linking by BT to the Navigation Payload of either the Inmarsat AOR-E or F5 spare satellite. NEST Bed was deployed and commissioned during summer 1998, and flight tests were successfully demonstrated at the September 1998 Farnborough Air Show where approaches were flown to Boscombe Down on the DERA BAC1-11 aircraft. In October 1998, a NATS/FAA flight trial was held in Iceland involving NEST Bed and the FAA NSTB. NEST Bed is also being used for SARPS validation.

This, and the following two papers, were presented during the European GNSS98 Symposium held at the Centre de Congrès Pierre Baudis, Toulouse, France, from 20–23 October 1998.

It is now clear that Global Positioning Systems (GPS) will be the primary navigational and positioning tool used as we move into the 21st century. As a result of the continued expansion and development of GPS, concerns have been voiced about the liability associated with development, construction, and use of the system. No short paper can explore all of the various liability issues associated with GPS. However, this paper will touch upon various liability issues in the hope that this analysis will continue with the development of GPS.

This paper describes selective tests performed in the areas of Gdansk and Gdynia VTS Centres. The main goal of the tests was to determine the accuracy of position, speed and course estimations measured by shore-based radar VTS tracking systems by using measurements of the same parameters available on board a tracked vessel equipped with GPS and GLONASS receivers. Six DGPS/GPS/GLONASS receivers were installed on board a survey vessel, and all of them recorded the vessel's route simultaneously with two different VTS radars – one at Gdansk and one at Gdynia (20 km apart). All DGPS receivers tracked the same reference station. Presented results show that the radar information can be used by VTS operators to provide navigation assistance within certain limits, but these limits must be understood. A more detailed description of the experiment was presented during the IALA Conference in Hamburg in June 1998.

This paper discusses the impact of a new generation of mobile communications, Mobile Satellite Services (MSS), on the reception of GLONASS signals in the future. The two systems are very closely located in the frequency spectrum, and the effect of this co-location has been derived. It is shown that the performance of GLONASS in a future GNSS-1 will be heavily affected by the current emissions proposed by the Globalstar consortium.

This paper presents a novel approach to computing minimum-time paths based on a technique originally developed for use in geophysics. The technique is based on a finite difference scheme and is quite efficient in terms of both computing effort and storage. A particular strength of the technique is that it provides optimal paths to all locations in the field, thus being useful in situations where the goal is not known at the outset of the search. Details are presented on the basic technique and extensions are derived to include the integrations of resources (such as fuel store), and to provide flexibility in the objective. Two examples are given: minimum-time planning for vehicles under the influence of drift, and planning to minimise the risk of detection for a stealthy vehicle in the presence of threats.

The DGPS technique can be used for navigation over baselines up to approximately 100 km. However, DGPS positioning accuracy is highly correlated and degraded with the extension of its operational range. It is, hence, improper simply to carry on using conventional DGPS for navigation over longer ranges. An approach aimed at providing sufficient accuracy with the use of a minimum network of reference stations, and the modelling of GPS errors, has been proposed and tested for regional navigation over the Taiwan area. It has been shown from the test results that medium-range DGPS based on using multi-reference stations is capable of improving the RMS coordinate differences by 35%, when compared to the use of a single reference station. The RMS values can be further improved by 14% and 6% in plan coordinates and height respectively, when the modelling of atmospheric delay is applied to the differential corrections based on the pseudorange observables collected from the multi-reference stations.

In an earlier study, the author attempted to give some quantitative estimates of the problems that free flow might face in Europe. The study was based on a traffic sample from the Eurocontrol Route Charges Office for a busy day in 1991. More recently, they generously made available a similar sample for a day in 1997. Using this new data, the study has been extended to cover wider aspects of the free flow problem. The central problem is that of ensuring safety. This will require a mechanism to detect collision threats and safely to resolve the problems. Possible tools are ground-based surveillance and/or airborne systems. This paper will use computer modelling to predict the loads that these detection and resolution systems must face.

One of the first occasions that navigators became aware of the potential problem generated by the (then) recently-invented radar, was the so-called radar-assisted collision which occurred outside of New York between the Stockholm and the Andrea Doria in 1956. Forty-seven lives were lost in the Andrea Doria and five on the Stockholm.

Radar (Radio Detection And Range) had been invented and began its sea service during the Second World War. Its use had been, as its name implied, to give initial warning of, and the range of, another vessel on a simple Cathode Ray Tube. As the system was enhanced and the Plan Position Indicator (PPI) style of display came into prominence, complete stretches of the coastline were shown. Its usage was enhanced so that ships began to be navigated by radar. However, the navigator himself was still very much in touch with the natural elements, through the very open design of the bridge at that time.

Following the Stockholm/Andrea Doria tragedy, navigators came to terms with the fact that their PPI view of the world was a relative one rather than the actual world. Plotting the observations became the norm.

In anticipation of the TOTAL Solar Eclipse on 11 August 1999 (see the January/February issue of Navigation News), it seemed very appropriate to repeat this short article by one of the Institute's most respected Fellows. It was first published in Vol. VII, October 1954.

A TOTAL eclipse of the Sun provides an opportunity, rare though it may be, of obtaining an instantaneous fix from the Sun alone. Eclipses vary greatly in character, in position on the Earth, in the width of the path of totality, in the duration, and also in the direction of the path. However, the shadow of the Moon cast by the Sun is always a right circular cone which, in the case of a total eclipse, intersects the Earth's surface at some point before its vertex. Owing to the motion of the Moon in its orbit round the Earth, the shadow moves at a speed of about 2000 m.p.h. from west to east (it varies considerably according to the distance of the Moon from the Earth). The intersection of this cone with the Earth's surface is an ellipse, which moves over the surface at speeds which are very high when the cone is nearly tangential (i.e. when the Sun's altitude is low) and at speeds as low as about 1000 m.p.h., when the eclipse is central over the equator at noon and the Earth's rotation has its maximum effect. The speed of the shadow is generally low enough to give a position line of considerable accuracy from the observed time of either second or third contacts, that is the beginning or ending of the total phase. An error of 1 second corresponds, in the most favourable case, to about one-third of a mile. The position line is, of course, the portion of the elliptic shadow corresponding to the observed phase and time; these can be precomputed.

The 1998 International Conference of the Royal Institute of Navigation was held at Church House, Westminster, London on 9–11 December 1998. The full proceedings, Comprising the following papers, can be obtained from the RIN Director (£45 to Members, £65 to non-Members. Both exclusive of p & p).