Radionavigation - the future direction

This keynote paper takes an overview of radionavigation. It contrasts the focus on transportation in the west with the focus on consumer applications in Japan. Currently, radionavigation worldwide appears to be dominated by global satellite systems, chiefly GPS. The paper poses the key question of why any alternative to GPS might be required. It assesses the arguments in respect of: independence of the US; a share of the market; the need for more satellites and also more accuracy and integrity; the vulnerability of GPS to interference and jamming; and GPS's limited performance indoors. We see that alternatives are required not merely to GPS but to satellite systems in general. Indeed, in the extreme case of aviation, GPS is unlikely to play any major role in the near future. For other applications and modes of transport, the case for a terrestrial backup to satellite systems, and specifically Enhanced Loran (eLoran), is examined. The paper concludes with the author's predictions as to the likely future mix of radionavigation systems.