Book excerpt: This authoritative work brings you a timely, unified analysis of the various satellite navigation technologies, applications, and services in operation or development, and of the challenges that lie ahead in this rapidly evolving field. It describes the segments, signal characteristics, performance, and securities aspects of the GPS system, including the advances anticipated in the next-generation GPS-III, and brings you up to speed on the developing European GALILEO system and its innovative characteristics, services, and potential. A look at ground-based and satellite-based augmentation systems (GBAS and SBAS) highlights their performance-improving features and how these systems may serve as connection rings between GPS and future networks like GALILEO.