The Global Positioning System (GPS) is the United States’ satellite-based navigation system, operated by the U.S. Space Force and freely available to civilian users worldwide. As the first fully operational global navigation satellite system, GPS revolutionized positioning technology when it achieved full operational capability in 1995 and remains the most widely recognized and utilized GNSS constellation globally.

The GPS constellation maintains a minimum of 24 operational satellites distributed across six orbital planes at an altitude of approximately 20,200 kilometers above Earth’s surface. This configuration ensures that users anywhere on Earth can receive signals from at least four satellites at any time, the minimum required for three-dimensional positioning. In practice, the operational constellation typically exceeds 30 satellites, providing enhanced coverage and redundancy.

GPS satellites broadcast navigation signals on multiple frequencies. The original L1 frequency (1575.42 MHz) carries the Coarse/Acquisition (C/A) code available to all civilian users, while the L2 frequency (1227.60 MHz) was initially reserved for military Precision (P) code users but now includes civilian L2C signals on modernized satellites. The newest L5 frequency (1176.45 MHz) provides enhanced performance for safety-of-life applications with improved resistance to interference and multipath. Multi-frequency receivers can combine these signals to estimate and remove ionospheric delays, significantly improving positioning accuracy.

While standalone GPS typically provides positioning accuracy of 3-5 meters under favorable conditions, various augmentation techniques extend GPS capability to centimeter-level precision. Differential GPS (DGPS) and Satellite-Based Augmentation Systems (SBAS) like WAAS improve accuracy to sub-meter levels. Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) techniques achieve centimeter accuracy for surveying, autonomous vehicles, precision agriculture, and construction applications. The term ‘GPS’ is often used colloquially to refer to all satellite navigation, though technically it refers only to the U.S. system within the broader GNSS family.