Localization of Southern Resident killer whales using two star arrays to support marine renewable energy

Abstract

Tidal power has been identified as one of the most promising commercial-scale renewable energy sources. Puget Sound, Washington, is a potential site to deploy tidal power generating devices. The risk of injury for killer whales needs to be managed before the deployment of these types of devices will be approved by regulating authorities. A passive acoustic system consisting of two star arrays, each with four hydrophones, was designed and implemented for the detection and localization of Southern Resident killer whales. Performance evaluation of the passive acoustic system was conducted at Sequim Bay, Washington. A total of nine sound source locations were chosen, within a radius of 250 m around the star arrays, to evaluate the accuracy of our localization approach. A localization algorithm, a least square solver, was applied to obtain a bearing location to a sound source from each star array. The sound source location was estimated by the intersection of the bearings from the two star arrays. Bearing and distance errors were computed to compare calculated and true (from Global Positioning System) sound source locations. Observed bearing errors were within 1.04° for eight of the nine test locations; location 3 had bearing errors slightly larger than expected due to a high level of background noise. The distance errors for six of the test locations were between 1.91 and 32.36 m. The other two test locations, 8 and 9, were near the line passing through the centers of the two star arrays, where large errors were expected based on theoretical sensitivity analysis results.