Acoustic tracking system for monitoring under‐ice movements of polar seals

An acoustic tracking system is described that has been used to track Weddell seals in Antarctica and ringed and spotted seals in the arctic. The seals are released with a small, depth‐modulated acoustic transmitter attached. They are tracked in real time based on the time difference of arrival at four hydrophones of the pulse from the acoustic transmitter. Working ranges are approximately those predicted by acoustic equations. Closed‐form solutions of the tracking algorithm allow rapid calculation of position. The effect of different array geometries on accuracy of tracking is explored analytically.