Retrieval of Ocean Wave Characteristics via Single-Frequency Time-Differenced Carrier Phases From GNSS Buoys

To address challenges in large-scale deployments and real-time wave observations using Global Navigation Satellite System (GNSS) buoys, we assessed the reliability and precision of the single-frequency L1 time-differenced carrier phase (TDCP) method for determining significant wave heights (SWHs) and average wave periods. Utilizing simulated dynamic velocity measurements derived from International GNSS Service static observations, this study demonstrates that the L1 TDCP method exhibits superior performance compared to dual-frequency TDCP, postprocessed kinematic (PPK), and Doppler algorithms. Notably, L1 TDCP achieves approximately five times greater precision than the Doppler method in vertical direction assessments. In the offshore waters of Qingdao, China, we deployed two GNSS buoys for wave observation experiments, complemented by a nearby accelerometer-equipped wave buoy (WB) for external validation. By integrating the velocity measurements obtained from L1 TDCP, we derived the sea surface displacement, which, after applying a high-pass filter, isolated the wave components. The experimental results confirmed a strong correlation between L1 TDCP and PPK methods in capturing SWH and wave periods. This study found a negligible difference between L1 TDCP and PPK in SWH (0 ± 7.1 mm, 99% correlation) and in average wave period (0 ± 0.13 s, 97% correlation). The wave observations from two independent GNSS buoys at the same location also exhibited remarkable consistency, with a difference in SWH of 0.0 ± 2.5 cm and in average wave period of 0.0 ± 0.1 s. Compared to the independent WB, the L1 TDCP method demonstrated a difference in SWH of
$- 1.9\,\,\pm \,\,5.8\,\,\text {cm}$
with a 93% correlation and in average period of 0 ± 0.1 s with a 94% correlation. Further, our analysis into GNSS data sampling frequencies highlighted the efficacy of 1-Hz GNSS data in wave inversion though certain spectral limitations were noted. Implementing the L1 TDCP method at 1 Hz offers a substantial reduction in associated hardware costs, storage requirements, and computational demands. Notably, in contrast to PPK, it negates the need for delayed precise ephemeris, facilitating real-time computations. This study highlights the potential of L1 TDCP for broader, real-time GNSS buoy wave observations, harmonizing with the United Nations Decade of Ocean Science’s aspirations for an augmented Global Ocean Observing System.