Field comparison tests of a bottom-mounted Aanderaa RDCP600 with an RDI Workhorse 600 ADCP, and a moored string of Aanderaa RCM9 MKII current meters

Detailed field testing of a bottom-mounted Aanderaa RDCP600 Doppler profiler was conducted at a protected coastal embayment. The RDCP600 was compared for 30 days to a string of seven moored Aanderaa RCM9 MKII in situ Doppler current meters, and an RDI 600 kHz workhorse ADCP. The test buoy was equipped with outriggers to allow measurements very close to the surface and to examine the acoustic and wake effects of the buoy on the performance of the RCM9 standard. The two 600 kHz Doppler profilers were deployed on the same bottom frame in order to ensure the same tilt and distance (approximately 50 m) from the moored RCM9 current meters. The Doppler profilers were programmed to sample during alternating time windows within a 20-minute sampling interval in order to avoid acoustic cross talk and interference. A common time base was achieved via post-deployment linear interpolation. Results of vector correlations and difference statistics show excellent agreement between all of the current measurement devices. Mean differences were generally less than 0.005 m s´ and the RMS differences were on the order of 0.02 m s^-1.