The Global Positioning System (GPS) is a space-based radionavigation system, managed by the United States, that provides accurate positioning, navigation, and timing services worldwide. It operates using a constellation of satellites orbiting Earth, which transmit signals. A GPS receiver on Earth calculates its precise three-dimensional position (latitude, longitude, and altitude) by measuring the time delay of signals received from at least four satellites.

GPS has revolutionized numerous geological applications. High-precision GPS is crucial for monitoring subtle crustal deformation, providing vital data on active fault movements, plate tectonics, and volcanic swelling or subsidence. Geologists deploy GPS networks to track minute shifts in the Earth's surface, essential for seismic hazard assessment and understanding earthquake cycles. Furthermore, GPS is indispensable for high-resolution geological mapping, enabling precise location tracking of outcrops, sample sites, and structural features in the field. It also aids in monitoring landslide movements, glacial dynamics, and ground uplift/subsidence due to groundwater extraction, offering critical insights into Earth's dynamic processes.