Comparison of vector wave displacements from a moored and a drifting Spotter buoy—From an accidental Indian Ocean voyage

Accurate measurement of ocean wave parameters is essential for marine engineering and environmental monitoring. This study analyses a unique dataset from a Sofar Spotter buoy that detached from its mooring in the Southern Indian Ocean. Originally deployed in 330 m deep water offshore of Perth, Western Australia, the buoy drifted southwest towards the Southern Ocean during the austral winter before returning to the coast, where it was eventually recovered. The complete deep-water displacement record, covering both moored and drifting modes, provides a rare opportunity to evaluate the Spotter buoy's performance across different configurations. Analysing ten months of data, we developed methods to detect and correct signal spikes, assessed how buoy motion affects measurement fidelity, and compared these findings to theoretical expectations. Additionally, we examined variations in buoy performance between moored and drifting modes, providing insights into buoy trajectories and movement patterns. This research advances the understanding of buoy-based wave measurement systems and lays a foundation for improving data accuracy in various oceanographic applications.