Conclusion
Determination of fluid flow rate using the velocity-area method

The method of determining fluid flow by integration of the velocity field remains the historical reference method for canals, natural watercourses and large pipes. The mechanical propeller current meters widely used in the 20th century are increasingly being replaced by electro-magnetic or acoustic Doppler current meters. New technologies, such as hydro-acoustic profilers (ADCP), ultrasonic transit time stations in channels or pipes, or non-contact gauging techniques (radar, image), operate on the same measurement principle and are now widespread. Quantifying and controlling measurement uncertainties, in particular those associated with integration methods, remains a current topic of research and development.