The document summarizes principles of the global positioning system (GPS) and its applications. GPS is a network of 24 satellites orbiting Earth that was originally established by the US Department of Defense. It provides positioning and timing data used for navigation, vehicle tracking, surveying, mapping and resource management. The system consists of space, control, and user segments. It calculates distances to satellites to determine a user's four position coordinates. Accuracy depends on factors like visible satellites and signal multipath. Differential GPS improves precision. Civilian uses include location, navigation, tracking, mapping and timing services. Competitors to GPS include Russia's GLONASS and the European Galileo systems.