Surface water velocity measurement using video processing: A survey

Measurement of velocity has been a challenging task in the surface water studies. Several attempts to measure the turbulences with contact sensors could not yield accurate results as they alter the flow pattern. The aim of this paper is to implement the noncontact velocity measurement system that is based on an image based technique, named Particle Image Velocimetry (PIV). This paper provides a summary of previous work done in this area and also about the application domains in which noncontact sensors can be used. The process of measurement is initiated by taking video of the water surface using a digital camera which is fixed at a strategically chosen environment. The recorded images are transformed to their undistorted appearance and then processed to obtain velocities at the water surface. The movement of the flow is estimated from pair of consecutive frames through statistical inference conducted on the image patterns floating on the free surface. Velocities are then calculated over the entire image by dividing the estimated displacements by the time interval between successive frames. The main motive of this survey is to provide the summary of the methods observed till now to the researchers.