A technique for making unbiased estimates of current shear from a wave-follower

Estimates of currents from velocities measured in a surface-following reference frame are biased due to the correlation between the sensor motion and wave orbital velocity. We demonstrate a technique that reduces this bias by an order of magnitude in cases where the motion of the sensor is known. As an example, we applied the technique to data obtained from a fixed tower with a miniature acoustic current meter attached to a mechanical wave-follower.