The International GNSS Service (IGS) is a voluntary federation of over 200 contributing organizations worldwide that collaboratively provides the highest-quality GNSS data and derived products to support Earth science research, positioning applications, and education. Originally established as the International GPS Service in 1994, the organization rebranded in 2005 to reflect its expanded scope encompassing all global navigation satellite systems.

The IGS operates a global network of over 500 continuously operating GNSS tracking stations, each equipped with geodetic-grade multi-constellation receivers and precisely calibrated antennas. These stations continuously collect and archive raw observation data, which is freely available to researchers and practitioners worldwide. The geographic distribution of IGS stations ensures comprehensive global coverage, enabling precise determination of satellite orbits, clock corrections, and Earth orientation parameters.

IGS products represent the gold standard for precise GNSS applications. Final precise ephemerides achieve orbital accuracy of approximately 2 centimeters, far better than broadcast ephemeris, enabling Precise Point Positioning at the centimeter level. IGS also produces precise satellite clock corrections, Earth rotation parameters, station coordinates and velocities, atmospheric products (ionospheric and tropospheric maps), and constellation-specific biases needed for multi-GNSS processing. These products are released at various latencies, from ultra-rapid (available within hours) to final (available with approximately two-week delay but highest accuracy).

For the GNSS professional community, IGS serves as the authoritative source for reference frame realization, providing the coordinates and velocities of its tracking stations in successive versions of the International Terrestrial Reference Frame (ITRF). This connection between the physical tracking infrastructure and the mathematical reference frame is fundamental to all precise GNSS positioning. IGS products and data enable applications ranging from millimeter-level geodetic research to commercial positioning services, making the organization an indispensable component of the global GNSS infrastructure.