Evaluation of AUV-based ADCP measurements

Recent development and commercialization of relatively portable and inexpensive autonomous underwatervehicles (AUVs) have led to new methods for making hydrodynamic, chemical, and biological measurements innear-coastal, lake, and estuarine systems. Equipped with Doppler velocity log (DVL) technology to allow for deadreckoningnavigation, this new class of AUVs has the potential to log not only vehicle motions, but water velocitiesas well. In this article, we assess the performance of the DVL acoustic Doppler current profiler (ADCP) equipped onthe REMUS AUV (Hydroid) in three different environments: a tidally forced lake; a wave-forced, near-shore fringingcoral reef; and a gently sloping continental shelf. In all three data sets, the water velocities measured by the AUVDVL compare favorably with measurements from nearby stationary acoustic Doppler current profilers. Nevertheless,the water velocity component measured parallel to the vehicle’s tracks exhibited a bias in the direction of AUVmotion, consistent with a previously reported bias found for the ship-mounted ADCP application in low-scatteringenvironments. The fringing reef data suggest that DVLs are capable of partially resolving wave motions.