This map shows the distribution of seabed substrate classes within Irish waters. High resolution grids of MBES bathymetry and backscatter data have been interpreted into 5 substrate classes: Rock, Coarse sediment, Mixed sediment, Sand and Mud to muddy Sand classes. Backscatter is the primary dataset used in the classification of seabed sediments. The grey scale features correspond to the different signal strengths recorded from the returning echo. These features can be clustered into acoustic classes using automated tools. The acoustic classes are classified using overlying sediment sample data classified according to Folk. (Sample data are analysed in a laboratory where they undergo a quantitative, classification process based on the percentage of mud/sand/gravel present in the sample). Bathymetry data, viewed with shaded relief effects, highlight the hard, rough textured features that are quite evidently rock. The use of automated tools or a manual digitising approach will extract the rock outcrops as a distinct feature. Both rock and sedimentary features are converted into vector polygon format and merged into 1 dataset