Ship detection and tracking from single ocean-bottom seismic and hydroacoustic stations

Area of Science:

• Oceanography
• Acoustics
• Seismology
• Signal Processing

Background:

• Traditional methods for tracking surface acoustic sources often rely on active sonar or visual identification, which have limitations in terms of coverage and environmental impact.
• Ocean-bottom seismometers (OBS) are primarily used for seismic monitoring but possess the potential for passive acoustic surveillance.
• Detecting and tracking erratic, continuous signals from surface vessels using single-station hydroacoustic data presents significant signal processing challenges.

Purpose of the Study:

• To investigate the feasibility of utilizing ocean-bottom seismometers (OBS) as passive sonar for detecting, localizing, and tracking moving acoustic sources at the ocean surface.
• To develop and validate single-station algorithms capable of handling complex acoustic signals from ships.
• To establish a robust, automated tracking system based on a Bayesian framework.

Main Methods:

• Development of single-station methods employing direction of arrival (DOA) and multi-path interference measurements.
• Implementation of a Bayesian mathematical framework to create azimuthal and radial detectors.
• Integration of detectors into a fully automatic tracking system and testing with seismic and hydroacoustic data from an OBS in the Indian Ocean.

Main Results:

• The developed algorithm successfully detected acoustic sources up to 100 km from the OBS.
• Achieved high azimuthal accuracies (within a few degrees) and distance accuracies (within a few hundred meters).
• Demonstrated effective performance on real-world data, validated against Automatic Identification System (AIS) vessel trajectory archives.

Conclusions:

• Ocean-bottom seismometers can be effectively repurposed as passive sonar systems for maritime surveillance.
• The developed single-station detection and tracking methods are robust and accurate for surface acoustic sources.
• The methodology is adaptable for tracking other acoustic sources, including marine mammals.