A curr ent meter that is capable of measuring the high-frequency fluctuations of the three-dimensional velocity vector has been developed. The meter works on a doppler-shift principle. At high velocities, the meter has been shown to have an accuracy of better than 3%.
Wiseman, Wm. J., R. M. Crosby, and D. W. Pritchard. 1972. "A three-dimensional current meter for estuarine applications." Journal of Marine Research 30, (1). https://elischolar.library.yale.edu/journal_of_marine_research/1234