Comparing two scientific echo sounders

The Simrad EK500 and EK60 scientific echo sounders have been operated with the same 38-kHz, 12-deg-beamwidth, split-beam transducer, with alternate pinging by means of an external triggering-and-switching system. The respective performances of the two systems are compared by means of standard-target calibrations conducted at the acoustic calibration facility on Iselin Dock at Woods Hole Oceanographic Institution with a 60-mm-diameter copper sphere. Principal comparisons include those of time series of echo strength and target strength, split-beam-determined angles, and derived measures of directivity.