Method for measuring water depths using visible images of shoaling ocean waves

摘要

To estimate water depth, photos of shoaling ocean waves are analyzed in view of primary wave frequency and length, mean water level, and known error sources. Primary wave frequency and mean water level are found from independent surface-wave and tide-level hindcasting systems for the time and place of the photos. Primary wave length is calculated from the two-dimensional Fourier transform for various subregion sizes and maximizing the peak value as a function of subregion size. Error is reduced by analysis of the above parameters and also the noise of higher-frequency wind waves and other image artifacts such as fronts and slicks. Error residuals are reduced through statistical analysis, again using independent images. Robustness is significantly enhanced by collecting images on different days.