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.