Space-Time Imaging of Shoaling Waves and Surf

A fundamental barrier to consequential evaluation of modern, very capable shoaling wave and surf models has been the inability to provide high-quality ocean data with which to test model results. This paper describes a development intended to satisfy this need by providing a time series of visible images of the nearshore from which three parameters crucial to such evaluations are simultaneously retrieved, namely the 2-D fields of the directional wave spectrum, bathymetry and currents. In addition, the images provide direct information on where the breakers occur, thereby furnishing critical data for comparison with model results. A digital camera-based imaging system has been constructed, mounted on a small aircraft and used to collect long sequences of images of waves as they shoal and break. The fields are retrieved using recently developed algorithms that operate on space-time variations in the images. The results are evaluated by comparing the retrieved fields with in situ data collected at the U.S. Army Corps of Engineers Field Research Facility during the SHOaling Wave Experiment (SHOWEX).