Quantification of regions of interest in swath sonar backscatter images using grey-level and shape geometry descriptors: The TargAn software

摘要

In this paper, the TargAn software package that is dedicated to parameterizing regions of interest (ROIs) in greyscale images that reflect backscatter information derived by marine geo-acoustical instrumentation (e. g. Side Scan Sonar and Multi-Beam Echo-Sounder) is presented. The ROIs, whose boundaries are marked out either manually or via simple segmentation techniques, are analyzed for as many as 37 features. The adopted and developed methodologies lead to the extraction of: (1) grey-level intensity (1st order) and texture analysis statistics estimated from the inner ROI, (2) descriptors that measure the separation of the ROI in comparison to the intensity characteristics of the peripheral seabed, (3) shape geometry descriptors of the ROI's boundary itself and (4) regional statistics of distinct (segmented) objects possibly included in the ROI. TargAn is implemented in Matlab with a graphical user interface that helps the user to have control over the digitization, segmentation and feature extraction processes involved. It also provides tools for the construction of compact geo-databases, suitable for geostatistical analysis and visualization in popular Geographical Information Systems, concerning the extracted descriptors and the geographic features (e. g. ROIs' boundaries, skeletons, segmented objects) that have been considered for ROIs' analyses. The TargAn software is particularly useful when large amounts of image ROIs need to be objectively quantified and is demonstrated through two case studies regarding Side Scan Sonar imageries. The first one concerns the quantification of marine biohabitats (coralline formations) while the second exhibits the geometrical analysis of pockmarks.