Abstract It has been observed that when using sea levels derived from GPS (Global Positioning System) signal-to-noise ratio (SNR) data to perform tidal analysis, the luni-solar semidiurnal (K2) and diurnal (K1) constituents are biased due geometrical errors in reflection data, which result their periods coinciding with orbital period revisit period. In this work, we use 18 months of GNSS SNR multiple frequencies constellations at three sites further investigate biases how mitigate them. We first estimate GPS, GLON…