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.

1. Step 3: Error Analysis
The 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 Location
Darin 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 science
you see here, please contact:
Darin Etherington
Pacific States Marine Fisheries Commission
P.O. Box 241
North Bonneville, WA
(509) 427-4521
detherington@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.