Global Navigation Satellite Systems (GNSS) provide accurate positioning, navigation and timing (PNT) information for industrial, consumer and military applications. This book provides a primer for students and professionals looking to understand the basic concepts behind GNSS and how they enable autonomy. Easy-to-read descriptions and illustrations of how GNSS signals and information are used for PNT provide the reader with a solid foundation of GNSS fundamentals. Topics covered include the equipment required, sources of GNSS error and correction techniques, and threats to GNSS signals and mitigation solutions. The book also includes how GNSS is combined with other sensor technologies such as inertial navigation systems (INS), laser (LiDAR), sound (radar) and vision (cameras) to enhance navigation and situational awareness for autonomy. Written by GNSS experts at Hexagon's Autonomy and Positioning division, a global leader in assured autonomy and positioning, the third edition includes updates to the various GNSS constellations (GPS, GLONASS, BeiDou, Galileo and more), recent technology advancements to enhance PNT accuracy, and a new chapter on the growing field of automotive autonomy. Real-life applications across transportation, agriculture, mining, marine, unmanned vehicles, defence, survey and more demonstrate how GNSS and autonomy are enabling a sustainable future. With a foreword by Dr. Robert Thirsk, renowned Canadian astronaut, doctor and engineer, this book is sure to inspire the next generation of explorers - on and off the Earth!