GPSNavigation

GPS navigation is the use of the Global Positioning System to determine a user’s location, plan routes, and guide movement. It relies on signals from a constellation of satellites, ground control, and user receivers. In civilian applications, GPS-based navigation combines a position fix with map data and routing algorithms to provide turn-by-turn directions, current speed, estimated time of arrival, and, where available, altitude information.

How it works: A GPS receiver monitors signals from at least four satellites. Each satellite transmits a time-stamped signal that allows the receiver to measure the travel time of the signal, yielding a distance (pseudorange) to that satellite. With measurements from four or more satellites, the receiver solves for three spatial coordinates and the receiver’s clock bias. The system uses a standard reference frame (commonly WGS84) and satellite ephemeris data to compute precise positions.

Accuracy and augmentation: Civilian GPS positioning is typically within about 5–10 meters horizontally under open skies; vertical accuracy is often worse. Atmospheric delays, multipath, signal blockage, and clock errors reduce precision. Augmentation methods improve accuracy: SBAS (such as WAAS or EGNOS) can provide meter-level corrections, while DGPS, real-time kinematic (RTK), and carrier-phase techniques can reach centimeter to decimeter accuracy in favorable conditions.

Applications and integration: GPS navigation is embedded in smartphones, car navigation systems, aircraft and marine transceivers, and outdoor devices. It is commonly combined with digital maps, routing software, and sometimes inertial sensors for dead reckoning during outages. Data privacy, battery consumption, and dependence on satellite visibility are notable considerations.

History and scope: The system was developed by the United States Department of Defense and became openly usable in the 1990s; civilian availability expanded after the selective availability feature was removed in 2000. Modern receivers often support multiple GNSS constellations (e.g., GLONASS, Galileo, BeiDou) for improved resilience and accuracy.