Field observations in coastal waters

Double camera set-up

A reconstruction of the water surface was obtained using two high definition digital cameras fixed side by side and aligned vertically, aiming at the same area on the sea surface in order to obtain a stereoscopic view. Field work to obtain images and data for stereo matching and analysis was performed in several locations of the Mornington Peninsula. Once images are taken, they are stereo-matched of using the Wave Acquisition Stereo System (WASS) software that implements an algorithm, matching images from the left camera with images from the right camera.

Example of reconstructed surface elevation

The output of the stereo-matching procedure, a three-dimensional vector (x,y,⁡η) was obtained for each frame (at 24frames per second) creating a spatio-temporal data series. Once all images were stereo-matched and a data series was obtained, extensive post-processing is required to clean and smooth data and to obtain time series and wave spectra. The WASS algorithm recognises identifiable features in both images, matching pixels from each image based on correlation factors in the image window, ultimately producing a scattered cloud of 3-D points (Figure 6). These points are then interpolated to obtain a smooth 3-D model of the ocean surface.

Timeseries of the surface elevation nearshore

For each region a wave elevation time series was produced. A representative time series from the nearshore is shown to demonstrate variation in wave elevation. Significant wave height for each region has been
calculated using the standard deviation of each wave height time series

 

Benetazzo, A. (2006). Measurements of short water waves using stereo matched image sequences. Coastal engineering, 53, 1013-1032.

Bergamasco, F., Torsello, A., Sclavo, M., Barbariol, F., & Benetazzo, A. (2017). WASS: An open-source pipeline for 3D stereo reconstruction of ocean waves. Computers & Geosciences, 107(6), 28-36.