Ch 3. The Navstar Global Positioning System

John W. Betz

Chapter Overview:

The Navstar Global Positioning System (GPS) is the most widely used satnav system in the world. Its availability and consistently excellent performance have revolutionized navigation and timing, enabling many previously unimagined applications. GPS is a dual‐use civil/military system, providing consistently high navigation and timing accuracies to billions of consumer and commercial users worldwide, as well as to many militaries around the world. Third party augmentations to GPS have provided additional levels of robustness, integrity, and accuracy to stand‐alone GPS, enabling even more extensive and indispensable applications.


Entire books, including are available that focus on GPS, its constituent technologies, and its applications in considerable detail. This information is complemented by extensive official documentation on GPS, its services, and its signals at the official US website that provides information about GPS and related topics.


This chapter describes Navstar GPS in summary form. Section 3.1 outlines the history and evolution of GPS, while Section 3.2 explains the current structure for managing GPS. Section 3.3 describes the geodetic and time reference system employed by GPS, and Section 3.4 depicts GPS services including their performance standards. Sections 3.5, 3.6, and 3.7 summarize key characteristics of the GPS constellation, ground segment, and signals, respectively. Section 3.8 summarizes the GPS ionosphere model, Section 3.9 describes other payloads and functions provided by GPS and its satellites, while Section 3.10 is a summary of this chapter.

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