21.1 Introduction

The use of satellites as an aid to navigation can be traced back to early in 1959 when development of the Navy navigation satellite system was started in the United States. This system is based on the Doppler principle and became known as the TRANSIT system. It was introduced into service in 1964 and remains operational to this day. Around the same time, the USSR introduced a very similar system known as TSIKADA. The main limitation of Doppler systems is that they are only applicable to platforms with low dynamics, such as ships, because the time to obtain a fix is of the order of tens of minutes. For these reasons, systems based on transmission time-delay measurements have been developed. The US system is known as NAVSTAR/GPS and the Russian system is known as GLONASS. Both of these systems have been under development for fifteen or twenty years and have now been declared operational. The massive cost of developing a global, high-accuracy satellite navigation system has meant that such systems can only be afforded by the militaries of the USA and USSR.

Over recent years attempts by GEOSTAR and LOCSTAR to build a commercial system have only ended in bankruptcy. One regional and highly specialised system has been operated successfully in the Gulf of Mexico, for the benefit of the offshore oil industry, by John Chance and Associates. This system is known as STARFIX and uses capacity leased on...