In a groundbreaking discovery from Knoxville, TN, researchers have found that global ocean analysis products can effectively replace the costly in-situ sound speed measurements traditionally used in seafloor positioning. The new study highlights how sound speed profiles (SSPs) derived from the HYbrid Coordinate Ocean Model (HYCOM) can provide centimeter-level accuracy, rivalling conventional methods while significantly cutting costs.

Accurate seafloor positioning is vital for researching tectonic movements, monitoring earthquakes, and exploring marine resources. The Global Navigation Satellite System-Acoustic (GNSS-A) technique typically combines satellite data with acoustic measurements to achieve high precision. However, the reliance on expensive in-situ SSPs has limited its application, as these measurements are time-consuming and complicated by variations in ocean temperature, salinity, and pressure.

A Game-Changing Approach to Marine Geodesy

Published on June 30, 2025, in the journal Satellite Navigation, the research from the First Institute of Oceanography and Shandong University reveals that HYCOM’s ocean analysis products can replace traditional SSP measures. By analyzing and comparing data, the researchers confirmed that global ocean analysis could provide similar accuracy without the logistical headaches and high costs associated with field surveys.

The findings are striking: global ocean analysis-derived SSPs achieved horizontal positioning accuracy of 0.2 cm (RMS) and vertical accuracy of 2.9 cm (RMS), almost identical to in-situ measurements. In contrast, the commonly used Munk empirical profile introduced substantial vertical errors due to its oversimplified assumptions.

Unlocking New Potential for Global Monitoring

The HIYCOM analysis particularly excelled in dynamic ocean regions like the Kuroshio Current, with horizontal displacement discrepancies as low as 2.3 cm, though slightly more significant variations (~3 cm) occurred in complex areas. With eight years of long-term data confirming its reliability, this method promises to revolutionize tectonic monitoring, offering insights down to sub-millimeter yearly displacement levels.

Dr. Yanxiong Liu, the leading author of the study, emphasizes the significance of these findings: "Our study shows that global ocean analysis sound speed profiles serve as a feasible alternative to traditional in-situ measurements. This innovation not only reduces expenses but also democratizes access to advanced seafloor geodetic technology across various scientific and industrial landscapes."

Wider Implications for Science and Industry

The implications are vast: using global ocean analysis rather than expensive in-situ measurements could facilitate frequent and precise surveys, particularly beneficial for earthquake-sensitive regions like the Japan Trench. The offshore industry could significantly lower costs for infrastructure projects, while seismologists gain improved tools for understanding plate tectonics. Furthermore, this methodology holds promise for unmanned vehicle navigation and deep-sea exploration, unlocking a new frontier in marine geodesy.

By eliminating the need for costly SSP measurements, this research could expand the realms of marine science and contribute profoundly to our understanding of the seafloor ecosystem.