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.

Within the implementation of the European Geo-stationary Navigation Overlay System (EGNOS), a significant residual error in positioning is due to tropospheric delay effects. The EGNOS guidelines recommend that tropospheric delay is modelled using an empirical correction algorithm based on a receiver's height and estimates of meteorological parameters developed from average and seasonal variation data. However, such a simple average and seasonal variation model is unlikely to emulate temporal weather changes exactly. The potential errors involved in the application of the recommended algorithm and the consequent effects on the positioning errors, under typical UK weather conditions, are detailed in this paper. This was achieved by comparing tropospheric delays produced by the EGNOS model, with tropospheric delays estimated from high precision carrier phase GPS, over a one-year period for five UK stations. The RMS EGNOS model zenith tropospheric delay errors ranged from 4·0 to 4·7 cm, with maximum errors ranging from 13·2 to 17·8 cm. The errors were also shown to be spatially correlated. The subsequent effect on position error is shown to be dependent on the satellite elevation cut-off angle adopted and on whether or not the observations are weighted according to the satellite elevation angle.

This, and the following three papers, were first presented at GNSS 2000, the Third European Symposium on Global Navigation Satellite Systems held in Edinburgh, Scotland from 1st to 4th May 2000.

This paper presents the methodology and a practical implementation approach to perform GNSS Safety Assessment and Certification with due consideration of the satellite navigation system users. It places Galileo GNSS in a total system that includes vehicles, on-board equipment, crews and traffic controllers and defines the necessary organisation for implementing safety analyses right from the early design phases of navigation systems. Civil aviation has very demanding requirements based on objectives for air navigation safety. It is much better organised on a worldwide basis than other GNSS users and is considered in this paper as the leading study case. Some methods are then proposed to build a bridge between all user organisations and to set up a common approach to certification.

This paper was first presented at a workshop arranged by the Netherlands Institute of Navigation on 5 November 1999 at the Delft University of Technology, The Netherlands.

The development and introduction of GPS in the early Eighties has led to an exponential growth in military and civilian applications. Worldwide, GPS is becoming a cornerstone in applications of transport, (offshore) survey, (precision) agriculture, network timing, military operations and many other applications. And yet, for a number of applications, GPS as sole-means or augmented – has some deficiencies, and its performance does not satisfy the user's requirements. Some of these deficiencies will be discussed in this paper. A number of maritime operations will be mentioned where (D)GPS as sole-means is considered by the author as unsafe navigational practice. Development and implementation of integrated navigation receivers using multiple navigation-signal sensors ((D)Galileo, (D)GPS, Eurofix, DR) using receiver autonomous integrity monitoring (RAIM) could solve the majority of the deficiencies of these systems in their stand-alone state.

This, and the following three papers, where first presented at GNSS 99, the Second European Symposium on Global Navigation Satellite Systems held in Genoa, Italy from 5th to 8th October 1999.

Galileo is being developed as the European contribution to the next generation of navigation satellites to replace GNSS1. Sponsored by the European Union, Galileo will be a civil, internationally controlled and operated system that will secure the long-term availability of satellite-based navigation services for multi-modal purposes throughout the European region and beyond. Galileo will be designed to support a wide variety of applications. These include professional navigation, position reference, safety, emergency, tracking, sport/leisure and governmental. Such services may be open to all, for safety-of-life applications, or for commercial users. In the case of safety and commercial applications in particular, it is imperative that the appropriate institutional control and regulatory framework is in place for purposes of safety and economic regulation. To ensure that the various parties understand their obligations and liabilities, clear legal instruments must be put in place to support the organisational framework. It is planned to attract private investment to fund elements of system development and operation through Private/Public Partnership arrangements. At present there is no institutional, regulatory or legal framework that will enable the early impetus to Galileo development to be maintained. This presents a challenge that Europe must address without delay. It has been the subject of several European Commission studies in the past twelve months. In a complementary activity under contract to the European Space Agency (ESA), a European industry consortium comprising Alcatel, Alenia, DASA and Matra Marconi Space was tasked to complete the preliminary design of the space and ground segments by the Autumn of 1999. One task of this study, led by Matra Marconi Space, relates to a study of the impact of institutional, regulatory and legal issues on the organisation and development of Galileo. This paper describes the studies undertaken into these issues within the overall Galileo development programme.

Satellite navigation has demonstrated its ability to enhance the safety and efficiency of multi-modal transport systems and act as a stimulant to economic growth and commercial development. The decision of the Transport Ministers to proceed with the definition stage of Galileo currently being funded by the European Commission and the ESA GalileoSat programme will include the complex question of security and defence considerations. Initial studies were completed over the past year in a Civil Military Interface study and by the GNSS Forum for Security and Defence Considerations. This paper presents the findings of the Civil Military Interface study undertaken for the European Commission, DGVII, that identified the security and military implications of a civil operated and controlled satellite navigation service for Europe.

This is an updated and revised version of a paper originally presented to a CNS/ATM Forum of representatives from the States, airlines and air traffic service provider organisations of the Pacific region meeting in Sydney, Australia on 16 April 1998. The Forum was organised under the auspices of the Australian and New Zealand Divisions of the Royal Aeronautical Society.

There are many legal issues involved in the provision and use of new technology based on satellite navigation and communications in Air Traffic Management Systems. These include aspects of international space law, international air law and domestic state law. Spanning these aspects are regional provisions and the role of ICAO. This paper considers these issues with particular reference to the Pacific region, which is in the lead in adopting the new technology, and concludes that much of the existing law applies, but that new law is also required if the legal framework is to keep pace with introduction of the new technology.

This paper presents the application of GNSS1, or more precisely of Satellite Based Augmentation Systems (SBAS), to vertical separation for en-route, approach and landing operations. Potential improvements in terms of operational benefit and of safety are described for two main applications. First, vertical separation between en-route aircraft, which requires a system available across wide areas. SBAS (EGNOS, WAAS, and MSAS) are very well suited for this purpose before GNSS2 becomes available. And secondly, vertical separation from the ground during approach and landing, for which preliminary design principles of instrument approach procedures and safety issues are presented. Approach and landing phases are the subject of discussions within ICAO GNSS-P. En-route phases have been listed as GNSS-P future work and by RTCA for development of new equipments.

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.

This paper is based on the results of the ‘GNSS Support Task’ study for the European Commission, DGXIII. It summarises the results of the cost benefit analysis in terms of coverage, accuracy and safety requirements for different types of user and describes the most cost-effective GNSS 2 architecture. These analyses also assume that the overall system is layered into wide area, regional and local systems. The future planning of satellite navigation is essentially driven by the wide area requirements and ensuring that these are global and seamless. There is some flexibility in coverage and accuracy for a wide area system in that it can be augmented regionally or locally if required, but it must provide the highest level of safety required. The paper approaches the architecture for a future navigation system from this safety aspect. An analysis of the chosen architecture shows that the required safety performance can be met. An implementation plan is described which allows a gradual evolution from the first system to be realized for safety critical operations to a fully civilian owned and operated system.