After years of collecting, presenting, and delivering raw echo-sounder data, we have (finally) got around to confirming the calibration of our echo-sounder systems and can now produce calibrated backscatter volume values [Sv]. Shown here is the ZAP echo-sounder data from April 18, 2012 in Saanich Inlet.
The raw counts have now been converted into proper volume backscatter values [dB re 1/m], taking into account system source and receive levels, beam pattern, range and spreading affects, and acoustic pulse settings. For reference, we expect smaller targets like zooplankton to produce values in the -80 to -55 [dB re 1/m] range, depending on the volume density of scatterers, while small fish will produce values in the -65 to -50 [dB re 1/m] range, also depending on target density and where in the beam they are. Calibrated Sv values should be available for download shortly.