Deep ocean long range underwater navigation

Area of Science:

• Oceanography
• Geophysics
• Acoustics

Background:

• Underwater navigation traditionally relies on surfacing for Global Navigation Satellite System (GNSS) fixes.
• Existing methods often require prior knowledge of position or sound speed, limiting autonomous operation.
• Accurate underwater geolocation is crucial for marine research, resource exploration, and defense applications.

Purpose of the Study:

• To introduce and validate a novel long-range Underwater Navigation Algorithm (UNA).
• To demonstrate the algorithm's capability for autonomous underwater geolocation without surfacing.
• To assess the accuracy and feasibility of the UNA using real-world experimental data.

Main Methods:

• The UNA utilizes measured acoustic travel times from a constellation of fixed underwater acoustic sources.
• Position calculations are performed without any a priori track, position, or sound speed information, enabling a "Cold Start".
• The algorithm was tested using data from the Philippine Sea Experiment with six sources and a drifting vertical line array of hydrophones.

Main Results:

• The UNA successfully computed 502 hydrophone positions with a mean error of 58m and a standard deviation of 32m from ground truth.
• The system operated effectively with acoustic sources positioned 129-450 km from the receivers.
• The computed UNA positions provide a reliable starting point for acoustic model runs, enhancing accuracy.

Conclusions:

• The developed Underwater Navigation Algorithm provides a robust solution for long-range, autonomous underwater geolocation.
• The "Cold Start" capability significantly enhances operational flexibility for submerged platforms.
• The UNA's accuracy is sufficient for integration with acoustic modeling to further refine underwater positioning and environmental analysis.