The Litto3D project

Abstract

In 2003 the French Institut Geographique National (IGN) and Service Hydrographique et Oceanographique de la Marine (SHOM) have been tasked by the Prime Minister to join efforts to produce together a seamless, modern, precise topographic and bathymetric model, including possibly the tides, of the entire French coasts. The area envisaged should extend from the 10 metres contour line inland to the distance of 10 kilometres seaward, or 6 nautical miles from the coastal baselines. This project was created to meet hundred or more requirements expressed by coastal managers concerned by the protection and exploitation of the littoral and by users of geo-referenced data; it should become the core of all future integrated coastal management projects. The preliminary study conducted in the Golfe du Morbihan, Southern Brittany, has already proven that France should be spared the strenuous geodetic problems met elsewhere. Thanks to the Napoleonic tradition of keeping common geodetic references inland and at sea, the historical database "Histolitt" could be assembled fairly quickly, leaving in the poorly surveyed areas gaps that could be filled efficiently by modern technologies (laser bathymetry and topography, MBES, RTK, aerial orthophotos, permanent digital tide gauges), allowing metric accuracy on the plane and decimetric precision of heights and depths. A first lidar survey has already been planned in the summer of 2005 in the Golfe du Morbihan to conduct further tests and generate a precise Digital Terrain Model (DTM) at different resolutions (2 /spl times/ 2 m and 4 /spl times/ 4 m). The survey strategy comprises three different approaches, depending on the bathymetric interest, the near shore seabed complexity and the Rapid Environment Assessment military program requirements.