Step 3: Error AnalysisThe final step brings together the data collected in the previous two steps to create an error map for the JSATS array. • Algorithms developed in MATLAB are used for signal processing, data filtering, and creating 3-D tracks of the beacon signals.• Time of arrival (TOA) data on at least four hydrophones in known locations is required for determining a valid acoustic tag

detection and locating that tag in three dimensions (x, y, z).

Introduction:To 3-D track acoustically tagged fish with measured certainty, error analyses are needed to verify the tracking system‘s performance. The methods detailed below utilize JSATS cabled hydrophone array systems and acoustic micro-transmitters. These processes are conducted after deployment of the array systems, and verify the positional accuracy of tagged fish movements through the tracking baseline of a detection array.

Where Are the Fish… Really???Verifying the Accuracy of Acoustic Estimates of Fish LocationDarin J. Etherington, Shon A. Zimmerman, Bishes Rayamajhi, Tyler D. Mitchell,Zhiqun (Daniel) Deng, Tao Fu, Mark A. Weiland, and Gene R. Ploskey

RTK-GPS and total station survey data collection

• After finalizing the survey data, a test boat is driven throughout the study area in the next step.

• Use modified hydrophone deployment trolley with either a survey prism or RTK-GPS receiver(shown at right).

Step 1: Survey of Sensing Equipment Positions• Use traditional and GPS land surveying techniques and

equipment, local control data, and surveyed benchmarks.

• Establish local control points and measure both horizontal and vertical coordinates at deployment locations.

• Process the survey data in Trimble Business Center.

• Adjust coordinates, based on dam configuration, to account for piernose slope, project azimuth, and deployment depth.

Front view of a “saw-toothed” hydrophone deployment at three dam turbine units to form two independent detection arrays. The circles denote hydrophones of one array and triangles are hydrophones of a second array.

Contour plots of RMS errors for a single spillbay location at John Day Dam

• GPS data is post-processed with a network of permanent Trimble reference base stations and exported to the same coordinate system and datum as the project survey data.

• After the boat movement data have been checked and finalized, it is combined with the Step 1 survey data to complete the fish tracks in the final step.Test boat setup for collecting GPS data

Remote test boat, with suspended beacons/tags, being lowered into the water

Remote test boat in operation

• Fish tags and beacons, suspended directly under the test boat antenna, transmit coded sounds every 1 or 2 s from known coordinates as the boat moves, provided by the on-board GPS. These signals are detected and decoded by the hydrophone array.

• Perform error analysis by comparing actual tag GPS locations (suspended from the test boat) with locations calculated from the acoustic time of arrival data collected by the hydrophone arrays.

• Several major factors affect the accurate location of an acoustic tag, including:

Position of the tag respective to the hydrophone locations Signal to Noise ratio of decoded signal Velocity of sound in water Error in GPS time synchronization

For more information on the scienceyou see here, please contact:

Darin EtheringtonPacific States Marine Fisheries CommissionP.O. Box 241North Bonneville, WA(509) 427-4521detherington@psmfc.org

Step 2: Remote Test Boat Operation• A remote controlled test boat, equipped with twin propeller

trolling motors and handheld Trimble GPS receiver with antenna, operates throughout the detection range of the hydrophone array. JSATS tags are fixed below the boat at known depths. The tracking baseline is within about 150 m of the dam face.

Screenshot of Trimble Business Center

Comparison between GPS positions and 2-D tracked positions at John Day Dam spillway

Conclusion:This process ensures that a JSATS cabled array system will provide accurate positional data for tagged fish location, movement, and dam-passage location.