Accurate high frequency recording of water surfaces is of primary importance to laboratory and field studies in engineering science. The application of fixed and scanning LiDAR (Light Detection and Ranging) instruments to the measurement of water waves is a recent complementary technology to classical single point wave buoys. It is of particular interest to ocean engineers and represents significant opportunities to investigate in greater detail wave processes of interest in the coastal and deep ocean environment. The LiDAR method presented herein is non-intrusive, operates with high accuracy, is cost effective, and records high frequency detailed temporal and spatial measurements of the water surface. The purpose of this study is to evaluate scanning LiDAR as a new measurement technique for laboratory water wave studies. This method potentially allows timely extraction of characteristics such as wave group envelope properties, local wave geometry, and wave group evolution to breaking, amongst others. Application of the method and implementation within a preliminary laboratory surface wave study is shown and discussed in this paper. In our experiments we undertake a laboratory study to optimize shortcomings commonly experienced with LiDAR. Of particular note is ensuring reliable specular reflection of the incident light beam, overcoming the light absorption by the water, and eliminating spurious reflections associated with look angle. Statistically sound data filtration and evaluation is undertaken based on spectral analysis smoothing, where the key parameter for resolution of data is the signal to noise ratio. Results pertaining to a suite of experiments conducted for a range of frequency and steepness magnitudes are presented, including agreement with capacitance type wave. Complete description of the detailed laboratory investigations and comparison with wave probes are presented within this paper.
Accurate free-surface water profile measurements provide the means to formulate reliable insights into numerous oceanographic engineering and research disciplines.