Land-sea boundary

Publié le 26 October 2020 — Modifié le 20 April 2021

This page, regularly updated, shows progress on land-sea boundary works. Once these works finalised, you will be able to visualise and download the repositories directly from the SAR catalog.

Faced with the need for a reference boundary between land and sea, the French Hydrographic and oceanographic service of the navy (Shom) and the National Institute for Geographic and Forest Information (IGN) had joined forces in 2009 to produce a repository on a 1:25000 scale, the HISTOLITT® coastline (TCH).

Recent advances in topographic and bathymetric laser surveys, through the national Litto3D® program, as well as in geomatics, enable the Shom and IGN to produce a very high quality land-sea boundary (mean planimetric accuracy of 7 meters). Coastal users’ needs were collected as part of the GT GIMeL’s works (Working Group for Marine and Coastal Geo-Informations). Funding is granted by a partnership between the French Biodiversity Agency (OFB), the Directory-General of Planning, Housing and Nature / Directorate of Water and Biodiversity (DGALN/DEB), the Shom and IGN.

This updated land-sea limit, more accurate than the HISTOLITT® coastline, will eventually replace the latter on data.shom.fr and on geoportail.gouv.fr. The updated boundary is derived from the intersection of a high resolution digital terrain model with highest astronomical tide (HAT) levels, extended to official maritime limits, and to the beds of estuaries and lagoons. This product allows for a finer grasp on the limit between land and sea, and contains metadata relative to the boundary type (artificial or natural), nature (rocky, sandy), date and geometric quality.

Production, shared between the Shom and IGN and issued per french department, will occur from 2020 to 2021.