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 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.

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..

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.

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

Information layer containing the SAR Zones (Search and Rescue). This layer contains a description of the French search and rescue (SAR) areas and the location of the associated Maritime Rescue Coordination Center (MRCC). it covers the areas of responsibility of France. The layer was produced by the Shom pursuant to the Circular Circular of the International Maritime Organization (IMO No. SAR.8 / Circ.4 of 1 December 2012).

This product includes the boundaries of tidal zones for French Channel, Atlantic and Mediterranean coasts in shapefile format. Information on the characteristics of tidal zones is available as part of the "Maritime Altimetric Reference Values" product.

Shom manages a network of permanent digital coastal tide-gauges on French coasts: the RONIM Sea Level Observation Network. Most tide-gauge observatories are partnered with one or more local partners.<br /><br /> Four main types of data are available for download:<br /> - “Raw high frequency" data: raw observations neither validated nor evaluated, obtained directly from the sensor. 1-minute measurement; integration time 15 seconds (on the minute); sampling period: 1 second.<br /><br /> - "Raw non-real time" data: raw observations neither validated nor evaluated, obtained directly from the sensor. 10-minute measurement; integration time 121 seconds (around every 10 minutes); sampling period: 1 second.<br /><br /> - "Validated non-real time" data: observations checked and validated by Shom from the "Raw non-real time" data. 10-minute measurement; integration time 121 seconds (around every 10 minutes); sampling period: 1 second.<br /><br /> - "Validated hourly" data: observations checked and validated by Shom, generated from "Validated non-real time" data. Hourly measurement obtained from the Vondrak filter with triangular weighting. The hourly height cannot be calculated in the event of an observation gap greater than 1.5 hours.

These maps are prepared on the basis of vector-based mapping data (IHO S-57 format) including the detailed description of each object (beacons, wrecks, submarine cables, regulated zones, survey systems, etc.). These maps are the digital equivalent of printed nautical charts.

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.