A groundbreaking study suggests that global ocean analysis products may effectively replace costly in-situ sound speed measurements for precise seafloor positioning. The research, published in Satellite Navigation, reveals that using sound speed profiles (SSPs) from the HYbrid Coordinate Ocean Model (HYCOM) global ocean analysis can achieve centimeter-level accuracy, comparable to traditional methods. This innovation promises to significantly reduce the costs and logistical challenges associated with marine geodetic surveys, particularly for unmanned vehicles or long-term monitoring.
Accurate seafloor positioning is crucial for understanding tectonic movements, earthquakes, and marine resource exploration. Traditionally, the Global Navigation Satellite System-Acoustic (GNSS-A) technique has combined satellite and acoustic measurements to achieve this precision. However, GNSS-A has relied heavily on expensive in-situ SSPs, which are time-consuming and resource-intensive to collect. Variations in ocean temperature, salinity, and pressure further complicate these measurements, limiting the efficiency of seafloor geodesy. The study underscores the need for cost-effective alternatives to in-situ SSPs.
Revolutionizing Seafloor Positioning
The research, conducted by the First Institute of Oceanography, Ministry of Natural Resources, and Shandong University of Science and Technology, evaluated the feasibility of using HYCOM global ocean analysis products for GNSS-A positioning. By comparing global ocean analysis derived SSPs with traditional in-situ and Munk empirical profiles, the study found that global ocean analysis delivers comparable accuracy while significantly reducing operational costs.
The findings revealed that global ocean analysis derived SSPs achieved horizontal positioning accuracy of 0.2 cm (RMS) and vertical accuracy of 2.9 cm (RMS), closely matching traditional in-situ measurements. This eliminates the need for costly sound speed field surveys. In contrast, the Munk empirical profile introduced significant vertical errors of 10.3 cm (RMS) due to its oversimplified assumptions, making it unsuitable for high-precision applications.
Performance in Dynamic Marine Regions
HYCOM global ocean analysis excelled in energetic and eddying marine regions, such as the Kuroshio Current, achieving a seafloor displacement linear fitting residual of 2.3 cm horizontally. However, slightly higher discrepancies (~3 cm horizontally) were observed in complex dynamic zones like the Kuroshio-Oyashio confluence region. Long-term data over eight years confirmed the reliability of HYCOM global ocean analysis, with displacement trends aligning at sub-mm/year levels horizontally, proving its viability for tectonic monitoring.
Dr. Yanxiong Liu, corresponding author of the study, stated: “Our results confirm that global ocean analysis sound speed profiles are a practical alternative to in-situ measurements. This advancement not only cuts costs but also expands access to seafloor geodetic technology for broader scientific and industrial applications.”
Implications for Science and Industry
The study’s findings could transform seafloor geodetic monitoring by making GNSS-A positioning more affordable and accessible. Utilizing global ocean analysis sound speed profiles instead of costly in-situ measurements facilitates frequent, high-precision surveys, which are particularly valuable for earthquake-prone regions like the Japan Trench. Offshore industries could benefit from cheaper seafloor positioning for infrastructure projects, while seismology scientists gain better tools to study seafloor plate tectonics.
Moreover, the approach holds promise for unmanned vehicle navigation and deep-sea exploration. By eliminating the need for expensive SSPs measurements, this innovation could expand marine geodesy and advance our understanding of seafloor science. The cost-efficiency and compatibility with unmanned vehicles could facilitate broader access to seafloor geodesy, offering a practical alternative for both scientific and industrial use.
Looking Ahead
The adoption of global ocean analysis for seafloor positioning represents a significant shift in marine geodetic practices. As researchers continue to refine these methods, the potential for widespread application in various fields grows. The integration of this technology could lead to more comprehensive monitoring of tectonic activity and better preparedness for natural disasters, ultimately enhancing our ability to manage and protect marine resources.
As the scientific community and industry stakeholders digest these findings, the next steps will likely involve further validation and integration of global ocean analysis into existing geodetic frameworks. This development could pave the way for more efficient and cost-effective marine exploration and monitoring in the years to come.
