Velocimetry is the measurement of the velocity of fluids, as often used to solve fluid dynamics problems, or to study fluid networks, as well as in industrial and process control applications, or in the creation of new kinds of fluid flow sensors. Methods of velocimetry include particle image velocimetry, laser-based interferometry, Molecular tagging velocimetry, Doppler sensors and new signal processing methodologies. Temporal integration of velocimetric information can be used to totalize fluid flow.