Spectral evaluation of motion compensated adv systems for ocean turbulence measurements

A motion compensated ADV system was evaluated to determine its ability to
make measurements necessary for characterizing the variability of the ambient current in
the Gulf Stream. The impact of IMU error relative to predicted turbulence spectra was
quantified, as well as and the ability of the motion compensation approach to remove
sensor motion from the ADV measurements. The presented data processing techniques
are shown to allow the evaluated ADV to be effectively utilized for quantifying ambient
current fluctuations from 0.02 to 1 Hz (50 to 1 seconds) for dissipation rates as low as
3x10-7. This measurement range is limited on the low frequency end by IMU error,
primarily by the calculated transformation matrix, and on the high end by Doppler noise.
Inshore testing has revealed a 0.37 Hz oscillation inherent in the towfish designed and
manufactured as part of this project, which can nearly be removed using the IMU.