Estimating uncertainty in subsurface glider position using transmissions from fixed acoustic tomography sources

Area of Science:

• Oceanography
• Acoustics
• Robotics

Background:

• Autonomous underwater vehicles (AUVs) like Seagliders are crucial for oceanographic data collection.
• Accurate positioning is vital for interpreting acoustic data, especially in resolving sound speed and location ambiguities.

Purpose of the Study:

• To assess the positioning accuracy of acoustic Seagliders in the Philippine Sea.
• To evaluate the Seagliders' capability to record and process broadband acoustic transmissions over long ranges.

Main Methods:

• Four acoustic Seagliders were deployed in the Philippine Sea from November 2010 to April 2011.
• Seagliders used GPS and a kinematic model for positioning, recording over 2000 acoustic transmissions up to 700 km.
• Acoustic travel-time offsets were analyzed to estimate range and positional uncertainties.

Main Results:

• Seaglider positioning uncertainty was estimated at 106 m rms horizontally.
• Acoustically derived positions differed by 914 m rms from modeled positions.
• Range uncertainty from the kinematic model was 639 m (426 ms) rms, with 70 ms rms uncertainty from sound speed variability.

Conclusions:

• The study demonstrates the feasibility of using acoustic Seagliders for precise underwater acoustic measurements.
• The findings highlight the importance of accurate glider positioning for acoustic tomography and oceanographic research.
• Seaglider acoustic data collection contributes to a better understanding of ocean sound propagation and variability.