Acoustic
Profiling current meters are capable of measuring and recording currents
remotely up to 600 m distance from the instrument. They utilise the principle of
Doppler frequency shift. Sound
waves are reflected at floating objects. Acoustic Doppler current profilers (ADCP)
are used on roving ships, lowered CTD probes and can be moored
above the sea floor.
Floating objects
in the water column reflect sound pulses emitted from ADCP. At the time of
arrival of the reflected signal, the ADCP is transformed from an emitter into a
receiver. Depending on the travel time between emission and reception
information about current direction and speed can be gained in different depth
horizons of the water column. By the remotely observed speeds at different
layers vertical profiles with high resolution can be measured for which
otherwise a significant number of conventional current meters would be needed (Bild).
