Seabed Mapping

Over 83% of Ireland's designated shelf area has been mapped to date, resulting in one of the largest resources of multibeam bathymetric data in the world. 

The seabed is mapped acoustically using multibeam echosounders (MBES) mounted onto purpose-built research vessels.  The data is interpreted to produce information on bathymetry and the sediment composition of the seabed.

Ireland has been mapping its territorial waters since 1999.  The offshore waters were mapped by the Irish National Seabed Survey (INSS) and the inshore waters are currently being mapped by the INFOMAR project. INFOMAR and INSS are joint ventures between the Geological Survey of Ireland and the Marine Institute. 

INFOMAR has produced a series of bathymetric and seabed substrate charts for coastal and offshore waters and these data, along with raw multibeam data, sample data and GIS data, are freely available to view and download from designated services on the INFOMAR website: www.infomar.ie

INFOMAR/INSS provide acoustic data collected using multibeam echosounder systems (MBES). These systems employ technology to send multiple, adjacent beams of sound simultaneously from the vessel to the seabed. The time it takes for the echoes to return provides information on depth (or bathymetry) data, while the strength of the returning echo gives information on the groundtype (e.g. bedrock or sand). These data are used to create backscatter charts.

Bathymetry
High resolution, continuous, multibeam bathymetric datasets are processed into bathymetric charts for priority bay areas around the Irish coast. The “Real Map of Ireland” is a series of merged bathymetric datasets which highlights subsea geological features such as seamounts and canyons in deeper offshore waters. It was fundamental in the delineation Irelands designated continental shelf area.

Backscatter
The INFOMAR project has produced a series of substrate maps using an integrated software package that classifies sediments using the amplitudes and statistical properties of the backscatter images. The resulting classifications using this technique are unsupervised, meaning they are not ground-truthed using corresponding sediment samples.

Physical sediment sampling undertaken by the INFOMAR project is used to verify the results of remotely sensed sonar data. Grab sampling of surficial sediments is standard on most INFOMAR surveys. Core sampling is survey specific.

Grab Sampler
The grab sampler is the most popular method of ground truthing used by the INFOMAR project. A range of grabs have been used depending on which vessel it is operated from. Day, Shipek and Van Veen grabs are all used to recover sediment samples from the seafloor. These grab samples are used to provide a cross reference to the seabed type classifications that are made from the MBES backscatter datasets.

Vibrocores
Core samples penetrate through the seabed and retain the vertical structure of the sediment. It can recover cores of 3 or 6 metres depending on the sediment type, with best penetration in fine grained sediments.

 

Magnetics and Gravity
Magnetic and Gravity field data are acquired and QC’d during acquisition where operationally feasible. These are post processed as required for delivery as ASCII grids and maps.

Sub-bottom
Sparker and pinger sub-bottom profile datasets are acquired during survey activity and are delivered in various formats such as CODA raw files, SEGY and geological interpretation maps. Sub-bottom profiles can also be inserted into Fledermaus “scene” files for the presentation of features of geological interest.


Species distribution and habitat maps can be generated from remotely sensed seabed data. Multibeam echosounder (MBES) backscatter data are classified into acoustic classes and then refined into more detailed habitat maps by comparing data from overlapping areas that contain information on sediment type and biological assemblages.

Habitat maps have been produced for offshore coral reef sites and inshore Special Areas of Conservation (SACs) and to show the general distribution of habitats in Irish territorial waters. Although the methodology used to create habitat maps differs, MBES data and oceanographic data are fundamental layers in the process of producing habitat maps.

The MeshAtlantic habitat mapping project (funded by INTERREG IV) produced a high resolution habitat map of Kenmare SAC, and the EU-funded EMODnet project will deliver a broadscale habitat distribution layer for the Northeast Atlantic.

Of added importance is the use of habitat maps to monitor the marine environment by providing a baseline dataset against which change, either natural or anthropogenic, temporary or permanent, can be measured and quantified.

A variety of habitat maps can be viewed and downloaded from the Irish Marine Atlas and INFOMAR websites: http://atlas.marine.ie/ and www.infomar.ie