Tracking multiple sperm whales with widely spaced bottom-mounted hydrophones.

Abstract

One dataset from the 2nd Int. Workshop on Detection and Localization of Marine Mammals Using Passive Acoustics Data featured multiple clicking sperm whales recorded for 20 min. Data were recorded on five widely spaced bottom-mounted hydrophones at the Atlantic Undersea Test and Evaluation Center. This dataset is used to develop and apply a model-based time difference of arrival (TDOA) method that is capable of simultaneously tracking multiple animals. Clicks on all hydrophones are detected. For every receiver pair, all possible time-differences of arrival (within reasonable time limits) are formed from the detected clicks. A scatterplot of TDOAs versus time, although noisy due to many false TDOAs formed from incorrectly associated clicks, reveals clear “tracks” of slowly varying TDOAs. These tracks are extracted and input to a TDOA tracking algorithm that gives 3-D likelihood surfaces of whale position. Local maxima in the likelihood surfaces are extracted and clustered to give estimated whale tracks.