An Improvement in the Calculation of ADCP Velocities

Michael W. Ott School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada

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Abstract

Acoustic Doppler current profilers are used to measure currents in a variety of aquatic conditions. When nonzero pitch and roll angles occur, a number of complications arise in the conversion from beam velocities, which are measured parallel to the acoustic beams, to earth velocities. One such difficulty is correcting for the vertical difference between bins in each beam. It is demonstrated that the default algorithm may lead to errors in the recovered velocity field, particularly in the presence of strong shears. An alternative correction is proposed, one which reduces the error by an order of magnitude for a flow field recently measured in an estuary.

Current affiliation: College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Corresponding author address: Dr. Michael W. Ott, College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Admin. Bldg., Corvallis, OR 97331-5503. Email: mwott@coas.oregonstate.edu

Abstract

Acoustic Doppler current profilers are used to measure currents in a variety of aquatic conditions. When nonzero pitch and roll angles occur, a number of complications arise in the conversion from beam velocities, which are measured parallel to the acoustic beams, to earth velocities. One such difficulty is correcting for the vertical difference between bins in each beam. It is demonstrated that the default algorithm may lead to errors in the recovered velocity field, particularly in the presence of strong shears. An alternative correction is proposed, one which reduces the error by an order of magnitude for a flow field recently measured in an estuary.

Current affiliation: College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Corresponding author address: Dr. Michael W. Ott, College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean Admin. Bldg., Corvallis, OR 97331-5503. Email: mwott@coas.oregonstate.edu

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