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Transformation of Directional Wave Spreading in the Surf Zone Using Video Image Data Zikra, Muhammad; Hashimoto, Noriaki; Yamashiro, Masaru; Suzuki, Kojiro
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 4 No 1 (2014): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v4i1.517

Abstract

In present study, video images technique is used to investigate the transformation of the directional wave spreading in shallow water. The technique is based on time series of the pixel brightness on video images. The Bayesian Directional Method is conducted in estimating the directional wave spectrum for evaluating the change of the directional wave spreading in the surf zone area. Video image data recorded at Hasaki beach in Japan are used in the analysis. Estimation of principle direction and spreading parameter in the surf zone regions indicated that principle directions at peak frequency are not strongly affected by wave breaking process. In contrast, the broadenings of directional spreading were observed when the waves start breaking on the sand bar and toward the shore area.
Non-Linear Inversion Method to Derive Bathymetry from Video Images Zikra, Muhammad; Hashimoto, Noriaki; Suzuki, Kojiro; Plant, Nathaniel G.
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 17 No 1 (2015): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v17i1.455

Abstract

This study investigates the capabilities of optical remote sensing to monitor bathymetry in nearshore area using video images. The technique is designed to extract wave number components based on variation of intensity of brightness at each pixel in the images using cross-spectral correlation approach. This approach is based on pixel array analysis that utilizes a nonlinear inverse method 'Levenberg-Marquardt’. The technique is applied to the data collected at Hasaki beach in Japan from August to December 2006. The results indicate that the cross-spectral correlation approach have the capability to derive wave number estimate from time series data of video images with small rms errors (0.0342-0.0421). Also, the estimate of nearshore bathymetry is proved reasonable accurate near shoreline and breaking area where the differences between estimated and survey water depth are less than 10-30 cm.