Satellite Constellation
A group of satellites working together as a system to provide positioning coverage. The four major global constellations are GPS (USA, 31 operational satellites), GLONASS (Russia, 24 satellites), Galileo (EU, 30 satellites), and BeiDou (China, 35 satellites). Modern industrial GNSS receivers track multiple constellations simultaneously, improving satellite availability, accuracy, and reliability compared to single-constellation systems.
Each GNSS constellation operates on distinct frequencies: GPS uses L1 (1575.42 MHz) and L2 (1227.60 MHz) plus L5 for newer receivers; GLONASS uses FDMA distinguishing satellites by frequency; Galileo provides E1 (1575.42 MHz, same as GPS L1) and E5a/E5b signals; BeiDou operates B1, B2, and B3 signals. Multi-constellation receivers track all available satellites simultaneously, typically seeing 20-40 satellites versus 6-12 for GPS-only receivers. More visible satellites provide: better geometric diversity (lower HDOP), improved reliability (signal available even with some satellites blocked), faster Time to First Fix, and better multipath detection. Industrial GNSS performance in challenging environments (urban canyons, near large buildings, under overhead structures) benefits significantly from multi-constellation reception. Multi-constellation support is now standard in quality GNSS modules at minimal cost premium ($5-15 additional over GPS-only).
Key considerations for industrial RTLS: (1) Receiver compatibility - ensure firmware supports all desired constellations; (2) Dual-frequency support - L1+L5 or equivalent provides improved ionospheric correction, improving accuracy 20-40% over single-frequency in some conditions; (3) Regional availability - Galileo strongest in Europe, BeiDou strongest in Asia-Pacific, GPS and GLONASS globally consistent. Augmentation systems (SBAS: WAAS in North America, EGNOS in Europe) provide free correction signals improving accuracy to 1-3 meters for single-frequency receivers, effectively providing DGPS-level accuracy without dedicated ground infrastructure. Multi-constellation GNSS is the outdoor positioning foundation of modern industrial RTLS, providing reliable 2-5 meter accuracy (single-frequency, SBAS-corrected) as the outdoor layer in UWB+BLE+GNSS hybrid deployments.