The civil use of satellite systems was dominated for a long time by applications like TV broadcasting, telephone backbones, and weather forecasting, whereas satellite positioning had not become popular until the completion of the military-driven GPS in the mid-1990s and its opening for an improved civil use in May 2000. Since then, satellite positioning has been gaining more and more momentum, especially in the areas of car navigation, surveying and mapping, and LBSs.

Starting with a short overview of the historical background, this chapter highlights the technical fundamentals of GPS. To understand the principal working of this system, it necessary to be clear about the orbital constellation of satellite systems in general, and hence the laws of Newton and Kepler and their application for satellite motion in space are briefly introduced in the next section. It is followed by a thorough introduction to GPS, including GPS infrastructure and devices, services and signals, and stages of future expansions planned for GPS. The chapter concludes with a brief introduction to Differential GPS (D-GPS) and an overview of Galileo.

Contents

• Historical Background
• Orbital Motion of Satellites
  • Satellite Orbits
  • Keplerian Elements
• Global Positioning System
  • GPS Segments
  • Satellite Constellation
  • Pilot Signals and spreading Codes
  • Navigation Message
  • GPS Services
  • GPS Positioning
  • GPS Error Budget
• Differential GPS
• Galileo
• Conclusion