Optical Remote Sensing of Wave Surface Kinematics

by Stephen Riedl, Texas A&M Univ, College Station, United States,
Richard Seymour, (M.ASCE), Texas A&M Univ, College Station, United States,
Jun Zhang, (A.M.ASCE), Texas A&M Univ, College Station, United States,



Document Type: Proceeding Paper

Part of: Ocean Wave Measurement and Analysis

Abstract: The measurement of the directional properties of surface slopes, velocities and accelerations is difficult, even in the laboratory, under conditions of steep, random and short-crested waves. A technique has been developed to use small surface marking floats, color-coded to facilitate identification, as targets for stereo video imaging of the kinematics of the wave surface. The images from successive frames are compared, using both stereo and standard image processing techniques for enhancement and target detection, to determine changes in target position in three dimensions. This provides an unusual synoptic view of the wave surface that is comparable to having a dense array of wave probes with co-located current meters capable of operating in the uppermost water layer. Since it has been amply demonstrated that surface velocities of steep waves are not well predicted by any existing theory even under long-crested waves, it follows that accurate measurement of the kinematics of the surface of short-crested waves will provide valuable data against which to test improved models. The paper describes a multi-year research to develop a fully operational laboratory instrument. Results from the first year's work, utilizing 2-D waves initially, will be presented in detail.

Subject Headings: Surface waves | Wave measurement | Wave velocity | Kinematic waves | Imaging techniques | Water waves | Surface properties | Slopes

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