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GNSS (Global Navigation Satellite System)
Global set of satellite-based positioning systems including GPS, GLONASS, Galileo and BeiDou, providing autonomous navigation and positioning services worldwide.
Trilateration
Mathematical method used to determine the position of a point by measuring distances from three known reference points, fundamental to the operation of GNSS systems.
Ephemeris
Precise orbital parameters of GNSS satellites broadcast in real-time or post-processing, essential for calculating the exact position of each satellite at a given time.
Dilution of Precision (DOP)
Indicator quantifying the degradation of positioning accuracy due to the relative geometric configuration between the receiver and visible satellites.
RTK (Real-Time Kinematic)
High-precision positioning technique using carrier phase measurements of the GNSS signal and real-time corrections to achieve centimeter-level accuracy.
Pseudorange
Apparent distance measurement between a satellite and a GNSS receiver, including clock synchronization errors, used for standard positioning calculations.
Phase Ambiguity
Unknown integer number of wavelengths between satellite and receiver in carrier phase measurements, whose resolution is crucial for high-precision positioning.
RINEX (Receiver Independent Exchange Format)
Standardized exchange format for GNSS observation data, enabling interoperability between different receivers and processing software.
WAAS (Wide Area Augmentation System)
American augmentation system improving GPS accuracy and integrity through differential corrections transmitted via geostationary satellites.
PPP (Precise Point Positioning)
High-precision positioning method using precise orbitography and clock products without requiring a reference station or real-time communication.
Satellite constellation
Set of satellites positioned on specific orbits to ensure continuous global coverage, typically 24 satellites for GPS in 6 orbital planes.
Satellite almanac
Approximate orbital data for all GNSS satellites enabling rapid prediction of their positions to facilitate initial signal acquisition.
Differential correction (DGPS)
Technique improving GPS accuracy by applying corrections based on errors measured by a reference station with known position.
Multi-frequency signal
Simultaneous use of multiple transmission frequencies (L1, L2, L5) allowing ionospheric effects to be corrected and positioning accuracy to be improved.
GLONASS
Russian satellite navigation system competing with GPS, using a distinct FDMA (Frequency Division Multiple Access) approach from the American CDMA.
Galileo
European satellite navigation system offering civil positioning services with guarantees of high precision and certified integrity.
BeiDou
Système chinois de navigation par satellite développé en trois phases, offrant une couverture globale avec des services de positionnement et de messagerie.
QZSS (Quasi-Zenith Satellite System)
Système japonais de satellites régionaux avec des orbites quasi-zenithales optimisant la couverture et la disponibilité pour l'archipel japonais.
Modèle ionosphérique
Représentation mathématique des retards de propagation des signaux GNSS dans l'ionosphère, essentielle pour corriger les erreurs de positionnement.
Intégrité GNSS
Capacité d'un système GNSS à fournir des alertes fiables lorsque les informations de positionnement ne peuvent plus être utilisées en toute sécurité pour une application donnée.