Tracking HARP location (star) on the west side of the San Nicolas Basin, west of San Clemente Island in the Southern California Bight. Contours are 1000 m.
(A) Geometry of plane wave arriving at two sensors i and j. (B) Sensor configuration for tetrahedron small-aperture array providing six pairs of TDOAs.
(A) Schematic of tracking high-frequency acoustic recording package (THARP) with four-channel hydrophone array arranged in a tetrahedron configuration about 3 m above the seafloor. (B) Photo of tetrahedron array with sensors about 0.5 m apart.
Analysis of echolocation clicks from two separate beaked whales (A = east and B = west) during a simultaneous dive near the tracking HARP: azimuth (top) and elevation (middle) angles and received amplitudes (bottom) over a 43 min period. Times are GMT on 31 May 2009.
Tracks of two beaked whales (dashed lines) using azimuth and elevation angles from Fig. 4, assuming a vertical descent rate of 1.5 m s−1 and horizontal swim speed of 1.0 m s−1 (3.6 km h−1). Circles indicate time along track. The triangle depicts the four-channel tracking HARP location. The thick contour is at 1000 m and the other contours are separated by 10 m with deeper seafloor to the upper right and shallower to lower left.
Azimuth, elevation and received amplitude plots for a two hour echolocation bout presumed to be from common dolphins. Azimuth and elevation tracks for the dolphin group as a whole are apparent. Outliers (gray) were removed for sea surface track estimation (Fig. 7). Times are GMT on 23 May 2009.
Plan view of dolphin group track using azimuth and elevation angles from Fig. 6 and assuming the dolphins are at or near the sea surface. (A) Location black dots were calculated from Fig. 6 angle black dots (gray outliers removed). Median locations were calculated every three minutes to provide an estimated track (white with black outline). (B) Black solid circles indicate time along track and standard deviation error ellipses show group spread. The triangle depicts the four-channel tracking HARP location near the 1000 m contour. Other contours are separated by 100 m, deeper to the upper right and shallower to lower left.
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