Automatic Brightness Correction Method for Side Scan Sonar Echograms

Side-scan sonar is very important in marine survey such as seafloor exploration, topography, underwater pipeline investigation and so on. SSS-echograms classification and mosaicking are essential during those tasks. Initial side-scan sonar images have uneven brightness distribution. Mosaicking proved difficult due to grayscale gradients on sonar echograms. Brightness equalizing is necessary prior to processing of SSS-echograms. This article discusses methods for brightness equalizing of the echogram images from side-scan sonar in order to identify local inhomogeneities of the seafloor. It provides results of comparative experiments using different approaches to solve this problem. The paper also evaluates the possibility of using these methods on board autonomous underwater robots in real time.