The localization of marine mammal with LoPAS-D system

Abstract

Marine mammals are always swimming in a random trajectory, which makes it challenging to monitor and locate marine mammals with passive acoustic methods. They emit acoustics signals for hunting, localization and so on. The spectrum of the signals spread from several kilo hertz to more than two hundred kilo hertz. In this study, a portable towed array system, Low Power data Acquired System-Double channel (LoPAS-D) is developed in order to detect and locate marine mammals with passive acoustics methods. The LoPAS-D system consists of a towed receiving array and a data acquisition module. The towed array includes two broadband hydrophones spaced at 50 cm. The data acquisition module consists of high-speed data acquisition and storage modules. It is capable of sampling at 512 kHz with 16-bit resolution. Synchronized sampling can be realized for multiple LoPAS-D systems in several hours after initialization, which makes it possible to locate marine mammals with two LoPAS-D systems. Then two LoPAS-D systems used for localization of marine mammal after synchronization is discussed. The time difference of arrival (TDOA) and direction of arrival (DOA) methods are estimated individually. Localization is realized according to triangulation. Monte-Carlo simulation is used to evaluate the localization accuracy. The results show that the relative range error is less than six percent at a distance of 200 m.