ORIGINAL RESEARCH PAPER Quantification of regions of interest in swath sonar backscatter images using grey-level and shape geometry descriptors: the TargAn software Elias Fakiris • George Papatheodorou Received: 24 September 2011 / Accepted: 29 April 2012 / Published online: 15 May 2012 Ó Springer Science+Business Media B.V. 2012 Abstract 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 pre- sented. The ROIs, whose boundaries are marked out either manually or via simple segmentation techniques, are ana- lyzed for as many as 37 features. The adopted and devel- oped 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 sep- aration of the ROI in comparison to the intensity charac- teristics 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 con- struction of compact geo-databases, suitable for geostatis- tical analysis and visualization in popular Geographical Information Systems, concerning the extracted descriptors and the geographic features (e.g. ROIs’ boundaries, skel- etons, 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 con- cerns the quantification of marine biohabitats (coralline formations) while the second exhibits the geometrical analysis of pockmarks. Keywords Regions of interest  Quantification  Sidescan sonar  Shape  Texture Introduction In this paper, we present TargAn, 1 a new Matlab software application dedicated to quantifying Regions Of Interest (ROIs) in textural images for applications in the geosci- ences. TargAn’s design was inspired by the need to objectively quantify coralline agglomerations in georefer- enced images reflecting sea-floor backscatter intensities like those derived by mosaicking swath sonar (e.g. Side- scan Sonar (SSS) and Multi-Beam Echo-Sounder (MBES)) records. However its use can be extended to any kind of grey-level intensity images. An earlier version of TargAn software has been presented by Chalari et al. (2008) with application to SSS targets of archaeological interest in the coastal zone of Alexandria, Egypt and detailed in Fakiris and Papatheodorou (2010). The quantification of a ROI is achieved by deriving a large amount of statistical properties from the corre- sponding portion of the image. TargAn is able to calculate 37 features for each ROI including grey-level (first order) and texture analysis statistics, shape geometry descriptors, features showing the interrelation of the ROI with the surrounding sea floor (ROI Separation statistics) and others E. Fakiris (&)  G. Papatheodorou Laboratory of Marine Geology and Physical Oceanography, Department of Geology, University of Patras, 265 00 Rion, Greece e-mail: fakiris@upatras.gr 1 The software, instructions and example files are available for download at: http://www.fakiris-geomarine-softwares.com or: http:// www.oceanus.upatras.gr/sites/default/files//Targan.zip, for the Win- dows operating system. 123 Mar Geophys Res (2012) 33:169–183 DOI 10.1007/s11001-012-9153-5