Current velocities measured by means of instruments suspended from shipboard may err significantly if the ship's motion at anchor is permitted to tow the instruments through the water while observations are in progress. Two current meter designs are described which employ a propeller linkage by electromagnetic induction to permit continuous observation of current velocity through, and to determine the extent of, the periods when the anchored ship is essentially at rest. The motions of an anchored ship are described.
Arx, William S.. 1950. "Some current meters designed for suspension from an anchored ship." Journal of Marine Research 9, (2). https://elischolar.library.yale.edu/journal_of_marine_research/723