APPROVED FOR PUBLIC RELEASE Removal of Range-dependent Artifacts from

A "radiosity correction " algorithm to improve the quality of sidescan sonar mosaics is reported. The algorithm removes consistent range-dependent variations from sidescan sonar imagery caused by failure of the TVG (time-varying gain) to completely compensate for variations due to transducer beam profiles and sediment backscatter strength. The correction is appropriate to high-frequency sidescan sonars with constant gain characteristics, such as the Klein 5000. The algorithm appears robust in situations where the bottom is relatively flat and the towfish altitude does not change much