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Acoustic seafloor classification systems tap into raw signals from echo-sounders, and attempt to extract measures descriptive of the bottom type. The current theory is that the length of the return of the code (post-first-break echo) indicates something about seabed roughness, and the strength of the second return (multiple off the surface, back down, and then back up) indicates something about the seabed hardness. Both ECHOplus and Roxanne use the same patented "E1/E2" (roughness/hardness) algorithm, and provide similar data. Users are expected to plot E1 vs. E2, and observe clustering of data associated with different bottom types. New samples are then classified as being of the bottom type to which their E1/E2 signature is most similar. A simple single-frequency plot of this concept is shown below, compliments of SEA. |
