Intercomparison of acoustic and electromagnetic current meters during leeway drift tests

Abstract

The U.S. Coast Guard Research and Development Center (USCG R&DC) and Analysis & Technology, Inc. (A&T) have been investigating techniques to estimate the leeway drift of targets for possible search and rescue applications. In previous leeway drift studies, the Interocean S4@ electromagnetic current meter was used to measure search target velocity relative to the l-meter surface layer. A recently developed compact Doppler current sensor, the Aanderaa DCS 3500, may provide a new technique to measure the motion of floating objects relative to the surrounding water. The smaller size and larger sampling capability of the DCS 3500 make it a good candidate for use with small leeway targets.Intercomparisons of the DCS 3500 and S4@ were conducted by towing the meters in-line behind a large leeway target in Long Island Sound and off shore of Delaware Bay.The results of the comparisons reveal that the differences in velocity between the t w o sensors are within expected variances.However, there does seem to be a slight bias in the direction measured by the DCS 3500 when compared with the 5 4 0 .