Using Time of Flight Distance Calculations for Tagged Shark Localizationwith an Auv

--Tracking fish has primarily been accomplished using acoustic telemetry. Typically, a fish is tagged, released, and manually tracked using hydrophones that detect acoustic tag transmissions. More recently, such hydrophone receiver systems have been mounted on Autonomous Underwater Vehicles (AUVs) to increase system mobility. This paper presents a new method for determining the distance from a tag to an AUV equipped with such a hydrophone system. By first estimating the transmission time of a tag signal, the time-of-flight can be used to calculate the distance to a tag. Furthermore, the calculated distance can be incorporated into an online state estimator to more accurately localize a tagged target. Results indicate significant improvement in an AUV’s ability to localize a target when the distance to tag calculations are used in combination with angle-to-tag measurements.