In its planimetric dimension, the land-sea limit product is designed for use, in an analogous way, at scales smaller than 1:2 000; but it is imperative to consult the attribute POSACC (planimetric uncertainty) before any use at a very large scale.

In its altimetric dimension, the user attention is drawn to the necessity to consult the VERACC attribute (altimetric uncertainty combining the DTM and HAT uncertainties).

However, the knowledge of the HAT not being exhaustive on the entire territory (rivers, end of estuaries…), the 3 administrative maritime limits are identified (attribute "limarc" at the passage of the land-sea limit) and used for the closings. Note that some administrative maritime limits, although defined by decrees, present planimetric uncertainties of several hundred metres (commented in the attribute "descrp"). The land-sea limit product specification also explains the choices made concerning the administrative maritime limits.

The land-sea limit is not intended to be used at scales larger than indicated.

The land-sea limit has not been designed to develop or populate indicators of coastline artificialization; other approaches have been adopted under the Marine Strategy Framework Directive. However, because of its design that identifies the natural and the artificial limit, it can effectively contribute to reach completeness in this area.

The land-sea limit has not been designed for use in the operation of nuclear facilities, air navigation or communications systems, navigation or air traffic control systems, or any other area referred to as "hazardous activities", where a failure of the product could result in death, personal injury or serious physical or environmental damage.

The source DTMs used to calculate the land-sea limit are the following:

- LiDAR topo, bathy or mixed topo/bathy point clouds from the Litto3D® programme: these are point clouds produced by Shom or IGN as part of the Litto3D® programme from "pure" topographic, "pure" bathymetric or mixed topographic and bathymetric LiDAR flights.

"Pure" topographic LiDAR: the measurement density is at least 2 points/m2.

"Pure" bathymetric LiDAR: the measurement density, on land and at sea, is 3 to 4 points/25 m2 on average; this density increases regularly with the arrival of new sensors on the market.

Mixed LiDAR: the density of measurements at sea varies between 1 point/m2 (in the very shallow waters) and 1 point/25m2 (beyond). The density of measurements on land (intertidal area and land-sea limit area) is higher (4 points/m2).

These data have been cleaned of any "overground".

- Other LiDAR topo, bathy or mixed topo/bathy point clouds: these are point clouds produced by Shom or IGN outside the Litto3D® programme from LiDAR flights and according to specifications that are at least as demanding as the previous ones.

- Litto3D® DTM: it is the elevation model (1 m grid) generated by IGN and Shom resulting from the fusion of LiDAR topo and bathy acquisitions.

- RGE ALTI® DTM: it is the IGN high-resolution DTM reference (1 m grid), produced from topographic LiDAR acquisitions on the coast.

- Other DTMs: other "local" DTMs can be used (Shom photogrammetry, local GRID or TIN DTMs from drone surveys, etc.).

Beyond this list in order of preference, the most up-to-date data is preferred.

The HAT surface is compiled by Shom from two "inland extent" sources:

- either from the Bathyelli product, supplemented by recent data from Shom tide/current and harmonic constants databases, for France metropolitan area;

- or from another tidal model or other sources (Maritime Altimetric References, tide station record sheet), taking into account the latest in situ observations.

The type of boundary (artificial or natural) and the nature (sand, rock, etc.) are populated from other available data sources (OrtholittoraleV2, BDORTHO®, Shom oblique imagery, etc.); it is also a question of differentiating between high and low coasts, if necessary using a slope model derived from the coastal DTM.

In addition, the 3 administrative maritime limits contribute to the coherence of the land-sea limit in the rivers and lagoons.