North Atlantic Right Whale Up-call Localization with a Four-Element Acoustic Array on a Slocum Glider (PDF)

MacGillivray, M., M.L. Seto, S.B. Martin, and L. Bolt

UACE2025

North Atlantic right whales (NARW) are critically endangered, with an estimated 350individuals remaining. Passive acoustic monitoring offers a means to localize the whales, improving the accuracy of exclusion zones to mitigate vessel strikes and fishing entangle ments. This study evaluates multiple time-difference-of-arrival azimuth estimation meth ods for a compact volumetric array (CVA) integrated onto a Slocum glider. The methods tested include minimum difference estimation, k-means clustering, kernel density estimation (KDE), TDoA maximum likelihood estimation, and azigram-KDE estimation. Simulations in a ROS/Gazebo environment, incorporating realistic underwater acoustic conditions, are used to test each of the methods. Verification was achieved with an in-water trial off the coast of Clam Harbour, Nova Scotia, Canada (2024). The NARW upcall is emulated using a moored source producing linear frequency modulated pulses. The trial revealed that the azigram-KDE estimator performed the best, yielding a mean absolute error of 25.6◦ (20.5 % improvement over next best method) and an interquartile range of 10.2◦ (40.7 % improve ment). Successful localization of NARWs with a glider-mounted CVA advances autonomous marine mammal monitoring and supports ongoing conservation efforts.