The Global Positioning System (GPS) is rapidly becoming as much a part of our daily lives as the Internet, and it is now being used to navigate and locate cars, commercial and private aircraft, military vehicles, ships, spacecraft, recreational vehicles, hikers, and wildlife. In addition, GPS is becoming our primary system for precision timing and an important tool for active microwave remote sensing. Finally, in the geophysics community, GPS is the primary geodetic tool for monitoring crustal deformation.
Hundreds of receivers have already been installed in areas subject to seismic and volcanic risk in the United States alone, with many more worldwide. Therefore, interest in the technical details of how the system works has rapidly increased, as evidenced by the proliferation of GPS courses in academia and professional workshops.