A new method for measuring ocean and tidal currents

Currents induce changes in the travel time of an acoustic signal. This effect can be exploited to measure current velocity. Theoretical calculations are compared with experimental measurements over a 33-km range. Equations and a system layout are presented for measurement of current velocity when the sound speed is spatially variable. Simplifications that are possible when the current direction is known and/or the sound speed is constant are discussed.