Motion Compensation for a Shipboard Doppler Current Profiler, Considerations and Implementation

Velocity profiles generated from a non-motion compensated Doppler current profiler in a moving shipboard reference frame are subject to a number of systematic distortions. The effect of neglecting the instantaneous static orientation of an AMETEK STRAZA DCP4400A/300 shipboard profiler is illustrated using an approximate numerical model and reference to pitch and roll ground truth data collected aboard C.S.S. DAWSON under heavy sea conditions. Motion compensation algorithms are outlined based on use of a 50 s period compound pendulum and pendulum stabilized accelerometers for inertial reference. These algorithms are presently being implemented on an enhanced IBM PC-XT realtime data acquisition and display system. Included are provisions for static beam geometry correction and noise rejection based on beam redundancy. First order dynamic motion correction is also discussed.