Which information layers?
Users have access to the following geographical information system layers:
Mean depth full coverage with water depth to LAT reference from EMODnet DTM in gridded form over whole of maritime basin on a grid of 1/16 * 1/16 arc minutes (ca 115 meter grid) complemented by land DTM in traditional atlas style colours
Mean depth in multi colour style with water depth to LAT reference from EMODnet DTM in gridded form over whole of maritime basin on a grid of 1/16 * 1/16 arc minutes (ca 115 meter grid) but no land
Mean depth in rainbow colour style with water depth to LAT reference from EMODnet DTM in gridded form over whole of maritime basin on a grid of 1/16 * 1/16 arc minutes (ca 115 meter grid) but no land
Source references is a layer which allows to identify the prevailing data sources used for each DTM grid cell. Activating the identification function in the sources layer will reveal for each DTM cell which survey data set or composite DTM was used with a link to their metadata from the CDI Data Discovery and Access service or Sextant Catalogue service. Grey areas are derived from GEBCO.
Quality Index is an improved source reference layer with quality indication. Metadata has been expanded with characterization of the dataset by vertical, horizontal and temporal indicators, purpose of the survey, and information about commonly adopted standards. Analysis has resulted in extra maps with Quality Indicators for each source reference. A report about the Quality Index analysis method and results can be downloaded, while the maps can be viewed and interrogated for metadata.
High Resolution bathymetry is a multi-resolution layer which allows to view, zoom in, interrogate for metadata, and download of a collection of higher resolution composite DTMs (HR-DTMs) for selected areas. The resolution of HR-DTMs varies between 1/32 and 1/512 arc minutes, depending on local data policy of data providers.
Survey tracks/polygons is another layer to view the locations and retrieve (CDI) metadata of the so far collated bathymetric survey data sets. Users can define a lat - lon box that will jump to the CDI Data Discovery and Access service for retrieving CDI metadata for the survey data sets within that geographical search window. This will then facilitate the users to refine their query and to request access to the high resolution survey data sets themselves by means of a shopping mechanism.
Land geography and topography as derived from OpenStreetMap
Geographic names on land is a customized layer of geographic names derived from Open Street Map.
Coastline as derived from OpenStreetMap 2014 WMS. It is a highly detailed coastline and a topographic representation. In addition best-estimate coastlines were determined from satellite data (typically Sentinel-2 and Landsat-8) and in combination with the Global Tide Surge Model (GTSM) processed into digital coastlines for the European seas at LAT (Lowest Astronomical Tide), MSL (Mean-Sea-Level), and MHW (Mean-High-Water). The level of detail is bound to the resolution of the satellite sensor (e.g. 10m for Sentinel-2). These satellite derived coastlines can be viewed as extra layer while a report gives background information. Furthermore, an inventory and report was compiled with official baseline and coastline data as collected from 21 national authorities in Europe. It describes the information available per country, the resolution, the source of the data and the institute providing/ hosting the data. Users can download the inventory and shapefiles of the baselines and coastlines.
Underwater features which is provided by GEBCO as GEBCO Undersea Features WMS. The GEBCO Sub-Committee on Undersea Features (SCUFN) maintains and provides a gazetteer of the names, generic feature type and geographic positions of features on the seafloor. The level of detail is dependent on the viewing scale.
Wrecks which is provided by partner OceanWise as proprietary WMS service and uses the UKHO Wrecks database as source. This Wrecks layer covers all European seas and the level of detail is dependent on the viewing scale.
GEBCO bathymetry basemap giving a back drop map with General Bathymetric Chart of the Oceans and Blue Marble satellite land cover at circa 1.000 m grid resolution
All these layers are made available in the Bathymetry Viewing and Download service and for many layers additional functionalities are offered such as depth profiles along user drawn transects, 3D viewing of the bathymetry in the browser, retrieving metadata of surveys, and downloading of DTM tiles and other data products.
The bathymetric data as collected from the data providers, are supposed to be referenced at the Lowest astronomical tide (IHO resolution 3/1919) which is relevant for the vertical reference for nautical charts. Most Hydrographic Offices in Europe have adopted this IHO guideline.Therefore, the EMODnet Digital Terrian Model has been developed and is published for viewing and downloading in LAT.
Although IHO recommends LAT as the vertical reference for nautical charts, it is not a good vertical reference for several other applications such as hydronamical modelling near the coasts (tide, storm surge or waves). For this reason, efforts have been undertaken by EMODnet Bathymetry to enable converting the bathymetric model from LAT to MSL. Therefore, the following steps have been applied:
1. Modelling of LAT with respect to MSL with a numerical tide model for Europe
2. Extending this, relatively coarse data, in very shallow and inter-tidal waters
3. Adding the LAT-MSL difference to the LAT-referenced gridded bathymetry
The numerical tide model ‘Global Tide Surge Model (GTSM)’ as developed and run by Deltares (NL) has been used as a robust model. This model is a worldwide model which is based on an unstructured mesh with the mesh decreasing to 25km in the middle of the oceans to 1.25km along the coasts of Europe. This model has been forced by the most recent and publicly recognised bathymetric and topographic information (EMODnet Bathymetry DTM in Europe and GEBCO 2014 for the rest of the world), along with tide generating forces including amongst other winds and surface pressure. Also the model has been extensively validated against tide measurements.
Using this method, the EMODNet DTM is also made available for downloading in MSL. This applies only for the DTM tiles in the most downloaded ESRI ASCII format.
3D visualization of the new EMODnet DTM is made possible without plug-ins. For this purpose a method and software was developed for generating a TIN model from the EMODnet DTM which is instrumental for supporting stable 3D viewing using Cesium. The approach for the 3D software is described in a document while the software source can be found at GitHub.
The portal also provides a CDI Data Discovery and Access service to identify and request access to bathymetric survey data that are acquired and managed by distributed data providers. A selection of these data sets are used for the EMODnet Digital Terrain Model (DTM). Moreover the portal provides a Sextant Catalogue service to describe and identify composite DTMs that were contributed by data providers instead of bathymetric survey data as input for the EMODnet DTM. Furthermore a special section of the Sextant Catalogue is used to manage the metadata of the High Resolution hot spots which are included in the High Resolution layer and which can be interrogated for its metadata.