Bias in Geodetic Site Velocity due to Annual Signals: Theory and Assessment

Unless accounted for, annual signals in geodetic data can significantly bias estimation of site velocities. For high accuracy applications, annual and semi-annual sinusoidal signals should be estimated simultaneously with site velocity and initial position. Minimum velocity bias is theoretically predicted at integer-plus-half years, as confirmed by tests with real data. Below 2.5 years, the velocity bias can bècome unacceptably large, and simultaneous estimation does not necessarily improve velocity estimates.