GPS (US)
Glonass (Russia)
Galileo (UK)
BeiDou (China)
NavIC (formerly IRNSS) (India)
QZSS (Japanese SBAS)
GPS/GAGAN (Indian SBAS)
All Bands and Frequencies of all Constellations

L1 - Military, L2C - Consumer, L5 - GPS, QZSS, E5 - Galileo, G3/B3 - Glonass/Beidou

GNSS Augmentation Systems

Types
Satellite Based (SBAS), Ground Based (GBAS), Aircraft based (ABAS)
Wide Area Augmentation System (WAAS), Local Area Augmentation System (LAAS)

DGNSS (NTRIP)
RTK (NTRIP Protocol, RTCM3.x or other open data formats) / OSR (Observation State Representation) - CPDGNSS
PPP (Proprietary Data Formats) (not DGNSS, uses internet correction providers like IGS (International GNSS), unidirectional communication, slow <3-30 min, <10 cm, long range (global))
PPP-RTK / SSR (State Space Representation) (SPARTN Data Format)- same accuracy, PPP coverage (continental), lower bandwidth than RTK, as fast as RTK, unidirectional communication); uBlox PointPerfect has SSR (cm level in <30 sec)
Trimble RTX (similar accuracy to GAGAN (from a Paper, for Sri Lanka))
Network RTK (NRTK)
Wide Area RTK (WARTK) - developed by gAGE/UPC (Research Group of Astronomy and Geomatics/Technical University of Catalonia) (Unlike RTK, doesn't assume Ionosphere delay is same for all users, instead broadcasts the data with different algorithms ref: Navipedia, the Offcial European GNSS WIki)

Wide Area DGNSS (WADGNSS)

GPS and Geo Augmented Navigation (GAGAN) (Indian SBAS)
WAAS (Wide Area Augmentation System) - USA
EGNOS - the European operational SBAS
MSAS - the Japanese operational SBAS
CDGPS - Canadian Differential GPS

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