This work has involved the use of the Naval Postgraduate School's TRITECH ST 725 high frequency mechanically scanned sonar system to acquire sonar images of simulated surface roughness on an aluminum plate. Signal post processing for such image data is reviewed, and post processed data is analyzed and compared to the known roughness locations on the plate. The simulated roughness pattern of one half inch steel nuts is used as a preliminary experiment in the development of a sonar detection system for marine growth on ship hull plating. Such a sonar system will be an integral part of any ship hull cleaning robot (SHACR). Contained in this report is a description of the experimental arrangement, typical sonar returns, a summary of image processing techniques, and results of processed data. The algorithms presented here will ultimately lead to a real time processing capability for the specification of location and extent of roughness as needed for the automatic direction of the robot's motion. Sonar imaging, Robotics, Hull cleaning, Autonomous systems.