TSV
                   ATSIS for measuring 3D breaking waves (Wanek and Wu, 2006)                                      TSV software (Bechle and Wu, 2007)
 
A novel Automated Trinocular Stereo Imaging System (ATSIS) is developed for non-intrusively measuring temporal evolution of three-dimensional wave characteristics. The system consists of three progressive digital cameras to provide three independent stereo-pairs, i.e., left-right, left-center, and center-right, for accurately estimating depth of a scene. A third camera assists to resolve correspondence problems due to specular reflection on the water surface and provides additional constraints on image matching, dramatically reducing the chance of a mismatch. An oblique configuration for the trinocular system effectively increases spatial coverage, allowing observations of wave phenomena over a broad range of spatial scales. A new exterior calibration procedure is also developed to determine the orientation of cameras in the field. The height resolution is increased with the optical axes of the cameras pointed at an oblique angle with respect to vertical surface wave displacements.  Results for a 3D breaking wave evolution can be seen here.  A software package, Trinocular Stereo Vision (TSV), has been developed to faciliate the tedious/challenging tasks of camera calibration and steroe matching on moving surfaces.  The combination of ATSIS and TSV assists us to realize four dimensional surface wave or solid body motion measurements.

In recent years, a virtual wave gauge (VWG) technique based on stereo imaging is developed to remotely measure water wave height, period, and direction. VWG minimizes computational costs by directly tracking the elevation of the water surface at selected points of interest using an Eulerian based dynamic searching algorithm. Results show that the VWG technique developed in this paper dramatically improves efficiency by two orders of magnitude compared to the traditional Lagrangian-Eulerian based point cloud method of stereo image processing. VWG is tested against traditional wave wire gauges to within 98% accuracy for significant wave height. Furthermore, the flexibility of the VWG is demonstrated in several field applications. For example in an offshore breaking wave case, an array of VWGs is used to efficiently measure wave directionality. Furthermore to investigate the reflection coefficient of a rock-mounted structure interacting with nearshore waves, linear and spatial VWG arrays are designed and implemented based on a priori information of the wave field from a preliminary VWG measurement. Overall, we demonstrate that the VWG technique has the flexibility and computational efficiency to potentially make real-time remote stereo imaging wave measurements a reality.
VWG1               VWG2




References: