GNSS

GNSS stands for Global Navigation Satellite System, an umbrella term for satellite-based positioning, navigation, and timing services. It encompasses all constellations that provide global coverage and synchronized timing.

The most well-known constellations are United States' Global Positioning System (GPS), Russia's GLONASS, the European Galileo, and China's BeiDou. Other regional or planned systems exist. Together they provide signals in multiple frequency bands and improve availability, reliability, and accuracy.

How it works: Satellites transmit coded signals that include precise timing information. A GNSS receiver uses the measured travel time between satellite and receiver to compute pseudorange distances; combining measurements from at least four satellites allows solving for three position coordinates and the receiver clock bias. Carrier-phase measurements and differential corrections can further improve precision.

Components and augmentation: system comprises space segment (satellites), control segment (ground stations maintaining ephemeris and clock data), user equipment (receivers). Augmentation systems such as SBAS, WAAS, EGNOS, or regional corrections (RTK, PPP) provide integrity, integrity monitoring, and improved accuracy.

Applications and accuracy: consumer handheld receivers typically achieve several meters of accuracy under open service; differential GNSS and augmentation enable decimeter to centimeter-level positioning in professional contexts. GNSS timing is used to synchronize telecommunications networks, financial systems, and power grids.

Signals and standards: civil signals on multiple frequency bands (GPS L1 C/A, L2C; Galileo E1; BeiDou B1; GLONASS G1) and encrypted military signals; receivers may support multi-constellation operation for better robustness.

Outlook: Ongoing modernization and interoperability continue to improve availability and resilience, including new signals and advanced signaling, with increasing use in autonomous systems, surveying, aviation, and timing applications.