Intercomparison Between Towed And Stationary Acoustic Doppler Current Profilers

This paper discusses the use of a towed acoustic Doppler current profiler (ADCP) for the purpose of evaluating in situ current meters. Data are presented from comparison tests between a towed and bottom-mounted ADCP. Velocity contours parallel and transverse to the main navigation channel under the Sunshine Skyway Bridge (SSB) in Tampa, Florida from a 600 KHz towed ADCP are compared to bottom-mounted current profiles from a 1200 KHz ADCP placed under the SSB. Data are presented to show instrument differences which are a combiination of random and systematic error. The study finds that the bottom-mounted ADCP is measuring current speeds accurately and is in the optimal location to report maximum channel currents under the SSB. The present location of the bottom-mounted ADCP under the SSB in the middle of the main navigation channel reports velocities accurate to 5 cmls. This metho+ is considered a viable technique for evaluating the reliability of moored or bottom-mounted units.