Research for measuring velocity and direction of current from dynamic image

The speed and direction of coastal ocean surface currents are very important elements in examining land reclamation or establishment of coastal levees. Measuring the speed of sea surface currents generally employs a radar system using Doppler effect. However, there is a problem that it is unable to measure the current in a wide area because the system is costly to introduce that it is difficult to install two or more systems. Thus, this study extracts characteristic spots from each of the frames of dynamic images of the sea surface shot using a common digital video camera, and calculates movement of the characteristic spots between the frames by means of image correlation. Using the positional information from the video camera, this study also converts the movement on the image into actual speed, and shows it together with the direction of movement. By doing so, we perform research and development of a system capable of grasping the speed and direction of the surface currents of the coastal ocean.