Acoustic Doppler current profiler
In recent years, more functionality has been added to ADCPs (notably wave and turbulence measurements) and systems can be found with 2,3,4,5 or even 9 beams.
Finally, the results are saved to internal memory or output online to an external display software.
Depending on the nature of the deployment the instrument usually has the ability to be powered from shore, using the same umbilical cable for data communication.
By adjusting the window where the Doppler shift is calculated, it is possible to measure the relative velocity between the instrument and the bottom.
The method requires a vessel with an ADCP mounted over the side to cross from one bank to another while measuring continuously.
The method is in use by hydrographic survey organisations across the world and forms an important component in the stage-discharge curves used in many places to continuously monitor river discharge.
In this case the velocity of the vehicle is combined with an initial position fix, compass or gyro heading, and data from the acceleration sensor.
[5] ADCPs with pulse-to-pulse coherent processing can estimate the velocity with the precision required to resolve small scale motion.
A typical approach is to fit the along beam velocity to the Kolmogorov structure configuration and thereby estimate the dissipation rate.
The application of ADCPs to turbulence measurement is possible from stationary deployments but can also be done from moving underwater structures like gliders or from subsurface buoys.
The two major advantages of ADCPs is the absence of moving parts that are subject to biofouling and the remote sensing aspect, where a single, stationary instrument can measure the current profile over ranges exceeding 1000 m. These features allow for long term measurements of the ocean currents over a significant portion of the water column.
As any acoustical instrument, the ADCP contributes to noise pollution in the ocean which may interfere with cetacean navigation and echolocation.
