An intercomparison of electromagnetic and acoustic current meters in a shallow estuary

The authors describe and compare the performance of a well known electromagnetic current meter and two types of acoustic Doppler current meters. Two Aanderraa Instruments DCS3500s were separated by 84 cm and deployed on a mooring between two Interocean S4s and allowed to collect data for 145 hours in a shallow (10 m depth) site in Eastern Long Island Sound. Contemporaneously, two 300 kHz R.D. Instruments Workhorses were deployed on the bottom 30 m to the north and south of the mooring. The results of the intercomparison experiment showed that: (1) there were intermittent, unreasonably large amplitude spikes in the velocity records obtained by the DCS3500, and (2) that once the data spikes were removed and the vertical sheer of the tidal flow has been accounted for, the mean difference between the DCS3500 and S4 observations was within the range expected.