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Global Positioning System technique has been widely used to estimate ocean tide loading displacements, but classical harmonic analysis with satellite modulation typically disregards the effects of hundreds of minor tides within the same tidal species of major tides. We present an improved harmonic analysis of eight major tidal constituents (M2, S2, N2, K2, K1, O1, P1 and Q1) that are adjusted by more adjacent minor tides in semidiurnal and diurnal species than the usual satellite modulation approach, through the tidal admittance interpolation. Our results show that this approach allows for a more reliable determination of GPS-observed N2, Q1, P1 and S2 constituents in the northwest European shelf than the classical method, as demonstrated by a comparison with FES2014b and TPXO9-Atlas ocean tide model predictions. The advantages of our method are more pronounced in the harmonic analysis of GPS time series of short duration (1–2 years) than long duration. These improvements mainly depend on some inferred minor tides with larger equilibrium amplitudes, which provide effective admittance constraints to major tidal estimation. Among the major tidal estimates, the most significant improvement is seen for the N2 constituent (with the maximum improvement of 9.9%, 9.0% and 9.7% for the up, east and north components in terms of agreement with FES2014b model predictions), particularly along the Wadden Sea coast where significant satellite modulation deviations occur. [ABSTRACT FROM AUTHOR]