The IGS disseminates all data from the global network, globally consistent GPS orbits, and precise site coordinates. This has freed regional investigators from having to deploy fiducial networks or compute their own orbits, and has relieved concern about changing reference frames as fiducial sites change. The published global reference frame is accurate absolutely to about 1 cm. There is still room for reference frame improvement as GPS moves towards sub-centimeter global geodesy. They proposed inserting a 0.5 deg yaw bias in the satellite attitude control subsystem, which was adopted and instituted by the Air Force in June of 1994.
Early results show a clear improvement in orbit accuracy during eclipse periods.
Monument instability threatens the integrity of the reference frame and the authenticity of perceived geophysical signals. A focused effort is needed to probe site stability at the submillimeter level required by dense networks, and GPS may be an effective tool for the job. Long term GPS measurements on closely spaced monuments could answer some of the questions now being raised for the Los Angeles array.