The DTM is a compilation of multibeam echosounder surveys acquired in 2013. The resolution is 1/64 arc-minutes (~30m). Surveys are located on the Capbreton Submarine Canyon (France) with depths from -4.7m to -344.9m. Depths are referenced to the Lowest Astronomical Tide and the coordinates are expressed into the WGS84 reference frame. The surveys which compose the DTM are S201306500-09 and S201306500-11. Data and metadata associated to these surveys are available on the website http://diffusion.shom.fr/pro/lots-bathy.html. The DTM is not to be used for navigation.

The regional bathymetric Atlantic – Channel – North-Sea DTM has a resolution of 0.001° (~111m). Its geographic coverage includes the Bay of Biscay, the English Channel and a part of the North Sea. The DTM extends from the coast to the continental slope (about of 4800m deep). This DTM is produced in the framework of the HOMONIM project which aims at improving operational forecast capabilities for the national coastal flood warning system. This DTM is offered openly on the Shom diffusion website (http://diffusion.shom.fr/produits/bathymetrie/mnt-facade-atl-homonim.html). http://dx.doi.org/10.17183/MNT_ATL100m_HOMONIM_WGS84

The Shom uses a 2D barotropic version of the HYCOM code (https://hycom.org/) to compute water level /surge forecasts (astronomical tides and meteorological surges) for the Atlantic, Mediterranean, Antilles-Guyane and Indian Ocean domains. The configurations use curvilinear grid with resolutions of several km offshore and ranging from 1.5km to around 500m on the french mainland coasts and the Antilles-Guyana coast. A downscaling by nesting allows a resolution of 800m to 200m over the Indian domain. These models have been adapted by the Shom to be operable in coastal areas by taking into account, in particular, the tide and high resolution bathymetry in these areas (from 100m for DTMs of facade to 20m for coastal DTMs) using Litto3D surveys by airborne LIDAR. The models are operated by Météo-France and the Shom in the framework of the HOMONIM project for the coastal flood/wave warning system.

Tidal ranges on the French coasts of the Channel and the Atlantic for a coefficient of 95 : tidal range for mean neap tides for average atmospheric conditions..

Bathymetric datasets are an extraction of surveys belonging to the Shom public database. For depth up to 50m, the vertical precision of soundings varies from 30cm to 1m and the horizontal precision varies from 1 to 20m. In deep ocean, the vertical precision is mainly around 1 or 2% of the bottom depth. It is sometimes more, it depends on the technology used. The data are referenced to ZH which is assimilated to LAT. Data are corrected for sound velocity variations. <br /> October 27 2025 version

Impulsive or transient sounds of short duration and of high intensity constitute one of the criteria for defining good ecological status for descriptor 11 relating to the pressure of noise generated by human activities within the framework of the MSFD (D11C1). Good ecological status for sound energy is achieved when the risks of acoustic disturbance, excess mortality from sound exposure and reduction in communication distances of mysticetes are cumulatively low or moderate. For this, the spatial distribution, the temporal extent and the acoustic levels of the sources of anthropogenic impulsive sound must not exceed the levels harmful to the populations of marine animals. These criteria are evaluated at the scale of the marine sub-region for the “English Channel and North Sea”, “Celtic Seas” and “Western Mediterranean” regions; and at the scale of the "North" and "South" subdivisions in the "Bay of Biscay" sub-region. One of the indicators selected for the evaluation of criterion D11C1 is the distribution of the acoustic levels of impulsive emissions (D11C1.3). The pressures considered for the evaluation of the criterion are: acoustic emissions from air guns ; acoustic emissions from impulsive sources other than air guns ; emissions from non-impulsive (transient) sources ; underwater explosions ; emissions due to pile driving. The data used for the calculation of this indicator are declarative emissions data traced by the operators of the activities generating impulsive noise.

The product contains a description of submarine cables and pipelines brought to the attention of Shom on French areas of responsibility. These are 2D linear objects of the seabed that divide into two categories: • The submarine cables: these are cables placed on the seabed where electricity or information (telecommunication) flows. They represent the vast majority of objects (more than 90%); • Emissaries and submarine pipes: these are pipes that allow the discharge, sampling or circulation of fluids.

Shom uses HYCOM 3D (Hybrid Coordinate Ocean Model) digital models to model changes to the ocean environment (currents, temperature, salinity, water depth). These HYCOM 3D models include a scalable (space and time) vertical grid, which is particularly suitable for the coastal regions and physical phenomena modelled (particularly the transition from a deep sea zone to the continental shelf, and the presence of frontal zones). These models were adapted to coastal models at Shom, particularly by integrating tides and the effects of rivers. These models focus on changes and variability in the different physical processes affecting coastal areas (continental shelves and slopes), such as tidal fronts, river plumes, tides and internal waves, upwelling and the dynamics of the mixed layer at an hourly frequency and with high spatial resolution (1/60 deg for the Biscay Channel model).

The "Sovereignty and jurisdiction maritime spaces of France" product contains the areas of sovereignty and jurisdiction maritime spaces of France all around the world.<br /><br /> It is constituted of 2D areas objects split into four categories :<br /> - the territorial sea (from baselines to a distance of 12 nautical miles or to maritime boundaries with neighbouring countries);<br /> - the contiguous zone (from 12 nautical miles to 24 nautical miles from the baselines or to maritime boundaries with neighbouring countries);<br /> - the exclusive economic zone (EEZ) (from 12 nautical miles to 200 nautical miles from the baselines or to maritime boundaries with neighbouring countries);<br /> - the continental shelf over the 200 nautical miles limit (from 200 nautical miles from the baselines to the limits recommended by the Commission on the Limits of the Continental Shelf (CLCS) or to the maritime boundaries with neighbouring countries).<br /> Internal waters, which constitute a space of sovereignty beyond the baselines, are not included in the "Sovereignty and jurisdiction maritime spaces of France" product.<br /> The "Sovereignty and jurisdiction maritime spaces of France" product may not be considered as an enforceable right. Only the “Maritime limits and boundaries” product, that can be displayed and interrogated on the website data.shom.fr (maritime boundaries category) and also downloaded on the French national portal of maritime limits (https://maritimelimits.gouv.fr), may be considered so.<br /><br /> December 2022 version.

The product “Maritime limits and boundaries” (French: “Délimitations maritimes”) gathers all the elements used for the definition of the maritime spaces under the French sovereignty or jurisdiction through the world. Those spaces are defined by the Ordonnance n° 2016-1687 of 8 December 2016 relating to maritime spaces under sovereignty or jurisdiction of the French Republic. This ordonnance is the transcription in the French legislation of the United Nations Convention on the Law of the Sea (UNCLOS) which was signed in Montego Bay (Jamaica) on 10 December 1982 end ratified by France on 11 April 1996. These elements of maritime limits and boundaries come from the limits computed by Shom on the basis of International Law, from the international agreements relating to maritime boundary and the technical conventions ratified between France and other States, from the decisions of international juridical bodies, from the recommendations of the Commission of the Limits of the Continental Shelf (UNO) or from unilateral claims from France in the absence of agreement. The elements are divided into seven themes: 1- Straight baselines 2- Outer limits of the territorial sea (12 nautical miles) 3- Outer limits of the contiguous zone (24 nautical miles) 4- Outer limits of the exclusive economic zone (200 nautical miles) 5- Maritime boundaries established by a bilateral agreement or decided by an international juridical body 6- Maritime boundaries unilaterally claimed by France in the absence of agreement 7- Outer limit of the continental shelf beyond 200 nautical miles December 2022 version