NetTrack is an acoustic measurement system designed for highly precise real-time geometry measurements underwater. Developed to measure the opening area of trawl nets to improve the accuracy of fish stock assessments by the California Department of Fish & Game, NetTrack can also be used for a variety of other applications, such as monitoring the changing geometry of towed arrays in real-time.
The standard NetTrack system consists of four small responders, one mounted in each corner of the net opening. Cables link these responders via a junction box to the surface station PC. Using a sequence of twelve independent distance measurements with millimeter precision, the geometry of the net opening is computed every four seconds. The measurements also yield an error metric, indicating in real-time the margin of error and providing a warning when accuracy is insufficient.
The surface display shows the current net geometry as a simple graphic and computes the net opening in square meters or other desired units.