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Research ships working at sea map the seafloor. The ships collect bathymetry data. Bathymetry is the measurement of how deep the sea is. Bathymetry is the study of the shape and features of the seabed. The name comes from Greek words meaning "deep" and “measure". Backscatter is the measurement of how hard the seabed is.
Bathymetry and backscatter data are collected on board boats working at sea. The boats use special equipment called a multibeam echosounder. A multibeam echosounder is a type of sonar that is used to map the seabed. Sound waves are emitted in a fan shape beneath the boat. The amount of time it takes for the sound waves to bounce off the bottom of the sea and return to a receiver is used to find out the water depth. The strength of the sound wave is used to find out how hard the bottom of the sea is. A strong sound wave indicates a hard surface (rocks, gravel), and a weak signal indicates a soft surface (silt, mud). The word backscatter comes from the fact that different bottom types “scatter” sound waves differently.
Using the equipment also allows predictions as to the type of material present on the seabed e.g. rocks, pebbles, sand, mud. To confirm this, sediment samples are taken from the seabed. This process is called ground-truthing or sampling.
The seabed classification map is created by grouping seabed areas that are alike. Areas where there is no multibeam data have either been filled by EUSeaMap (predictive broadscale habitat map) or have been left as unclassified.
Sediments have been classified to the European Nature Information System (EUNIS), Marine Strategy Framework Directive (MSFD) Benthic Broad Habitat Types (BBHT), Folk (5 Themes) and European Marine Observation and Data Network (EMODnet) classification systems.
It is a vector dataset. Vector data portrays the world using points, lines and polygons (areas).
The sediment data is shown as polygons. Each polygon holds information on the classification for EUNIS, MSFD BBHT, Folk, substrate (EMODnet), biozone (EMODnet), data source and resolution.
The dataset was mapped as part of the Irish National Seabed Survey (INSS) and INFOMAR (Integrated Mapping for the Sustainable Development of Ireland’s Marine Resource).