Acoustic Doppler Current Profile (ADCP) hydroacoustic current meter data is similar to a sonar, attempting to measure water current velocities over a depth range using the Doppler effect of sound waves scattered back from particles within the water column. The term ADCP is a generic term for all acoustic current profilers although the abbreviation originates from an instrument series introduced by RD Instruments in the 1980s. The working frequencies range of ADCPs range from 38 kHz to several Megahertz. Data collected includes bin depth from bottom, bin depth from surface, component velocity, current magnitude, current direction, vertical velocity, nearest surface and nearest bottom.