Surface wave measurements from an autonomous underwater vehicle

Bottom-mounted Acoustic Doppler Current Profilers (ADCPs) have been demonstrated to be a practical method of obtaining high quality observations of surface wave height and direction in shallow water (typically less than 30-40 m). This restriction has motivated several groups over the past few years to investigate the possibility of using ADCPs for wave measurements in deeper water by deploying them on subsurface floats. Because these platforms move in response to forcing by waves and currents, it is necessary to measure both their attitude and translational velocity accurately in order to remove their motion from the observed velocities. We report here the results of a field experiment addressing the related problem of measuring ocean waves from a small Autonomous Underwater Vehicle (AUV) flying close to the surface that was equipped with an ADCP and an inexpensive Attitude- Heading Reference System (AHRS).