GNSSsignaali

GNSSsignaali are the radio frequency signals broadcast by Global Navigation Satellite Systems to enable positioning, timing, and navigation on Earth. Each constellation transmits multiple signals on different carrier frequencies, employing distinct modulation and coding schemes. Civil or open signals are publicly available, while some signals are encrypted for authorized users.

A GNSS receiver estimates position by forming pseudorange measurements from one or more signals across one or more constellations. Each signal carries a navigation message with satellite ephemeris and clock corrections, and often ionospheric information to improve accuracy. Modern receivers typically track several signals simultaneously to improve availability, accuracy, and reliability, and to help mitigate atmospheric effects.

Major signals include GPS, Galileo, GLONASS, and BeiDou. GPS provides open signals such as L1 C/A, with additional modern civil signals like L2C and L5. Galileo offers E1, E5a, E5b, and E6 signals, designed for interoperability and high integrity. GLONASS broadcasts on multiple frequency channels using FDMA, providing civil services. BeiDou operates on B1, B2, and B3 signals with regional and global services. Other systems and regional augmentation services, such as QZSS or IRNSS, contribute to broader coverage and redundancy.

Advances in GNSSsignaali focus on modernization, including more robust civil signals, improved dual-frequency observations for ionospheric correction, enhanced anti-spoofing and integrity monitoring, and better inter-system interoperability. These signals underpin applications in transportation, surveying, time synchronization, and autonomous systems, and continue to evolve to meet increasing accuracy, reliability, and security requirements.