Phase Profilometry Measurement of Wave Field Histories

A series of experiments were conducted to determine if wave fields in hydraulic models could be measured with Phase Profilometry. Phase Profilometry uses the distortions of periodic shadows to measure surface topography. The wave fields were photographed using a vertically-looking digital video camera operating at 30 frames/s. Several methods for making the water opaque were evaluated to insure reflection of the shadow pattern. A specially developed algorithm was used to analyze each frame of the digital video and deduce the topographical history of the wave field. A comparison was made between wave height histories measured by Phase Profilometry and by a capacitance wave gage. There agreed within 5–7%. These results are presented as well as an analysis of the accuracy of Phase Profilometry for wave field measurements. We conclude that Phase Profilometry is a practical remote sensing method for measuring surface wave field topographical histories for many applications, and is a significant improvement over the current practice of measuring surface wave histories at discrete points using intrusive methods.