High frequency radio measurements of ocean currents

HF radio waves backscattered from the ocean surface can be used to remotely measure ocean surface currents. Measurements of the range-Doppler spectrum of these signals yields the wavelength and frequency of the scattering ocean waves, and thus their phase velocity.This velocity is subtracted from the velocity the wave would have in still water, and the difference is a measure of the average (over depth) of the surface current.To test these ideas, we measured currents using a conventional and the HF technique, and found reasonable agreement between the two measurements.