Figure 1. Echoes from the rough bottom last longer than those from the smooth bottom. In the echo traces on the left of each sketch, time increase down.

Figure 2. Typical deployment of a QTC VIEW Bottom Classification System.

Figure 3. Typical QTC VIEW display after a survey. From upper left: the features of the echoes processed to extract three components of their variance, a trackplot showing locations of the seven classes, a bathymetry plot showing how the classes are distributed by depth, and at bottom, bar graphs of the statistical confidence of the class assignments.

Figure 4. The first canonical variables for the geotechnical data set and the frequencies of occurrence at 38 kz. Values plotted are the sum of the standardised variables at each site, each multiplied by its canonical weight. Symbols indicate the predominant acoustic class at the site.