Here is a the "coherent-PADS" view up into the crest of a breaking wave. The vertical and horizontal scales are in meters. There are "ghosts" and other false images from beamforming problems, but the general behavior of the surface and subsurface flow field comes through. The surface is tracked by looking for the first drop to 10 dB below the maximum intensity. A straight line is then fit to estimates formed along the central 8 "beams" of sonar data, providing a height and slope estimate (black line; a bit unstable). The magenta line is from the pressure data; the slope is assigned based on the time-derivative of the pressure, assuming the wave(s) are propagating to the left. The grid of *'s are derived from time-lagged cross-correlation (PIV) techniques, yielding velocity estimates (arrows), and integrated to estimate net displacements (locations of *'s).
A video clip shows the above-water view of the same wave breaking. The sonar is approximately directly below the camera; the camera is aimed a little toward FLIP's hull so the surface height can be tracked along the ladder. Note: this is NOT a pier piling! The ocean depth below the camera is about 4000 m (2.5 miles deep).