Sidescan Sonar Beam Function and Seabed Backscatter Functions From Trace Amplitude and Vehicle Roll Data

A sidescan sonar's beam function (BF) (the sonar's transmit-receive response versus inclination angle in the sonar's frame of reference) can be extracted from an ensemble of contiguous sonar traces affected by sonar vehicle roll for a uniform seabed. The rotation of the sonar's frame of reference relative to the seabed's frame of reference is employed to extract a number of discrete overlapping beam subfunctions each with angular extent corresponding to the extent of vehicle roll. These are then reconciled to form a composite sonar BF. A seabed backscatter function (SF) (the backscatter response of the seabed versus inclination angle in the seabed's frame of reference) may subsequently be inferred with respect to the BF from trace data, whether affected by roll or not. Independent sonar BF and seabed SFs allow the effect of sonar vehicle roll to be corrected when BF compensation is applied to images, and the effect of seabed slope to be corrected when SF compensation is applied. In an alternate approach to extracting a sonar BF, a seabed SF may be extracted first from the sonar traces affected by vehicle roll, by extracting a number of overlapping backscatter subfunctions, and reconciling these into a composite SF. The sonar BF may then be inferred from the trace data with respect to the SF. Seabed SFs inferred from trace data with respect to the BF may be used as a basis for seabed characterization.