Evaluation of performance of Son Tek Argonaut acoustic doppler velocity log in tow tank and sea

Abstract

Performance of a 500-kHz, 3-beam downward-looking Sontex Argonaut acoustic Doppler velocity log (DVL) based on measurements at tow-tank and sea is addressed. Its accuracy and linearity under tow-tank measurements were largely scattered and inconsistent within the towing speed band of approx. or equal to plus or minus 50 cm/s. Outside of this band, its motion speed output exhibited unexpectedly large error (within the range of -52% and -72% of towing speed) as a result of a computational error in its 'beam' mode of operation. However, it was possible to improve its mean accuracy to better than plus or minus 5% of the towing speed by recalculating the motion speed based on beam-velocity outputs and the orientation of the three beams relative to the direction of motion. The DVL's 'XYZ' mode of operation at sea exhibited motion speed accuracy better than plus or minus 5 cm/s beyond the towing speed of 250 cm/s. Tow tank measurements under static conditions exhibited speed output values up to 120 cm/s. Measurements have indicated deteriorated performance at speeds within plus or minus 50 cm/s under constricted environments where the signal-to-noise ratio might be poor