In addition to the Shom data, the surveys of external organisms have been exploited, the contributors of which are as follows: CIAT, CLAREC, Conseil Régional Nord-Pas-de-Calais, Conseil Général des Côtes d'Armor, DDTM Calvados, Charente Maritime, Gironde, Ille-et-Vilaine, Morbihan, Pyrénées-Atlantiques, Vendée, GIP Loire Estuaire, GIP Seine Aval, Grands Ports Maritimes de Dunkerque, Rouen, Le Havre, Nantes/St-Nazaire, La Rochelle, Bordeaux, Ifremer, IGN, Institution d'Aménagement de la Vilaine, INSU, IRSN, Port du Médoc, Ports Normand Associés, UKHO, Université de Bordeaux (laboratoire EPOC), OLEX, Ordnance Survey, Service Hydrographique Belge, Syndicat Mixte de la Ria d'Etel.

The DEM use data from the global EMODnet DEM: « This portal was initiated by the European Commission as part of developing the European Marine Observation and Data Network (EMODnet). The overall objective of EMODnet is to create pilots to migrate fragmented and inaccessible marine data into interoperable, continuous and publicly available data streams for complete maritime basins. The Hydrography portal development started in June 2009 and now provides a range of options for freely browsing and downloading new Digital Terrain Models (DTM) for a large part of the European seas. The downloadable tiles are freely available in a number of formats. The EMODnet digital bathymetry has been produced from bathymetric survey data and aggregated bathymetry data sets collated from public and private organizations. These are processed and quality controlled. A further refinement and expansion is underway, by gathering additional survey data sets, expanding geographical coverage to all European sea regions and upgrading the DTM grid resolution, and will result in new releases in time. The portal also includes a metadata discovery service that gives clear information about the background survey data used for the DTMs, their access restrictions, originators and distributors. ».

GEBCO bathymetric grid may be used to prepare the DEM for any non-commercial purpose, without need for prior approval.

The main tasks involved in producing this range of solutions are based on 4 key aspects, each intended to reduce uncertainty for the DEM:

1) collecting, evaluating, pre-processing and selecting data from multiple sources after acquisition using survey systems from various eras;

2) homogenising the vertical and horizontal datums for data sets;

3) using interpolation algorithms suitable for a heterogeneous distribution and the variable density of data, and

4) evaluating and qualifying the final product and preparing documentation.