Global Navigation Satellite Systems: Genesis, State of the Art, and Future Directions

The Global Positioning System (GPS) has risen from a mere paper design in the early 1970s to become a global utility of the 21st century. The system is used for diverse applications that include navigation of ground vehicles, ships, aircraft, and spacecraft, monitoring of millimeter-level shifts of the Earth's tectonic plates, and the precise timing of financial transactions and electrical power transmission. As a testimony to the system's success, the European Union is developing the competing Galileo system, partly to avoid reliance on the U.S. military, which runs the GPS, and partly as a means of increasing its market share in the rapidly growing ~ $10B/year Positioning, Navigation, and Time industry. The introduction of Galileo has forced a change of the system acronym from GPS to GNSS (Global Navigation Satellite Systems) in order to denote both systems without giving precedence to either. This paper focuses on 3 aspects of GNSS: the historical development of the GPS, current applications/research, and future directions. A selection of current applications and research topics illustrates the system's range of capabilities and can inspire the conception and development of new applications. Future directions will be driven by the development of competing and augmenting systems. One of the main future issues is the development of Galileo and its prospects for competition/cooperation with the GPS.