International GNSS Service
The International GNSS Service (IGS) , formerly International GPS Service , is an IAG data service for high-precision global satellite positioning systems.
It was founded by international geodesy organizations in the 1990s to increase the accuracy of the determination of GPS satellite orbits and - soon expanded to include GLONASS satellites - to make it possible to compare the various contributing institutions. This soon resulted in a regular data service in coordination with similar services of the IAG and the IAU , in particular the IERS (earth rotation), the ILRS (laser satellites) and the IVS (radio telescopes).