Abstract: The composition of the seabed can be estimated by measuring the amplitude of echoes back-scattered from the seabed. However, the amplitude measured varies not only with the type of material present on the seabed but also with the range travelled to and the angle of incidence of the transmitted pulse at the seabed. This invention is a method for adjusting the amplitudes of backscattered echoes to compensate for the attenuation due to range and angle of incidence. A compensation table is created, each cell of which is associated with a unique combination of a partition of range and a partition of angle of incidence values. Each cell contains summary data for all echo amplitudes associated with that cell. The echo amplitude values are then adjusted using the summary data held in the compensation table.

Abstract: This invention describes a method and system for classifying a survey area according to an attribute of the seabed. More particularly, the classification technique uses echoes recorded from sonar pings transmitted towards the seabed. The echoes are resampled at a sampling frequency which takes into account the depth of the water, sediment conditions generally in the area and the duration of the ping, resulting in an improved classification of the seabed according to the selected attribute.