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GNSS is the collective name for all satellite positioning systems. GPS (American) is the one most people know, but modern receivers also use Galileo (European), GLONASS (Russian), and BeiDou (Chinese). Using all four at once produces a more accurate and reliable position fix than using GPS alone.
Multi-constellation receivers achieve better accuracy in difficult environments – urban canyons, dense woodland, near buildings – because more satellites are visible from more directions.
- GPS – 31 operational satellites, US-operated, most widely supported constellation
- Galileo – EU-operated, adds centimetre-level accuracy when combined with GPS
- GLONASS – Russian constellation, improves availability in high latitudes
- BeiDou – Chinese constellation, improving coverage in Asia and useful globally
- AGPS – downloads satellite orbital data over cellular to reduce cold-start fix time from ~30s to ~5s