Short-Term GNSS Buoy–Derived Tidal Harmonic Constants for Depth Datum Determination: Feasibility, Accuracy, and Limitations in Marginal Seas

Depth datum determination traditionally relies on long-term tide-gauge records, which are often unavailable in gauge-sparse coastal regions, while the applicability of high-rate GNSS buoys to depth datum determination under short observation periods remains insufficiently quantified. In this study, 1 Hz sea surface height data from two GNSS buoys deployed in the Bohai Sea were used to evaluate the feasibility and limitations of short-term GNSS buoy observations for tidal harmonic analysis and depth datum estimation in terms of Lowest Astronomical Tide (LAT). After low-pass filtering, short-term GNSS buoy observations retain the low-frequency variability required for tidal analysis, but the reliability of harmonic constants and LAT remains strongly dependent on observation length. Very short records yield unstable estimates, whereas longer records provide progressively more stable solutions within the present reconstruction framework. These findings suggest that short-term GNSS buoy observations can support practical depth datum estimation in data-sparse coastal and marginal-sea environments, provided that limitations in observation length, constituent resolvability, and platform dynamics are properly considered.