Since 2021, the LiDAR HD (High Density) program has been dedicated to mapping the entire French territory in 3D with unprecedented precision. This project, supported by the State and the EU with funding of 57 million euros over five years, and led by the Institut national de l'information géographique et forestière (IGN), has just released the first 3D models of the territory.
LiDAR enables the creation of dense and precise 3D maps, essential for a detailed understanding of the territory (ground, above-ground) and monitoring its changes. This distance measurement technique uses the properties of light: mounted on an aircraft, a scanner emits light pulses (in the near infrared) towards the ground at a very high frequency. LiDAR detects the reflected waves, records their travel time, and deduces the position of the impacted points.
Whereas it previously had 2 points per square meter, with LiDAR HD, the point cloud density covering the entire metropolitan territory and overseas departments (except for Guyana) increases to an average of 10 points per square meter.
The collected point clouds, covering more than 400,000 km2 of the territory, published immediately after acquisition, have been processed and structured into several classes (ground, water, vegetation, buildings, bridges, perennial above-ground). These data then served as the basis for producing three different digital models:
- Digital Surface Models (DSM), which represent the altitude of the ground and above-ground elements (vegetation and constructions);
- Digital Terrain Models (DTM), which provide a description of the relief excluding buildings and vegetation (bare ground);
- Digital Height Models (DHM), which visualize the altitude differences between natural and artificial elements.
Various and strategic applications
The fine altimetric description of these models can be exploited in numerous fields. Among them:
- Knowledge and management of forest resources (location of forest roads, monitoring of forest health, estimation of the forest carbon sink);
- Flood risk prevention (precise visualization of the topography of flood-prone areas);
- Energy transition (estimation of solar potential, site study for infrastructure placement...);
- Fire risk management (measurement of the height and density of vegetation and its different layers to assess the risk of fire spread);
- Networks (identification of the best deployment sites and potential obstacles to installation);
- Architecture (analysis of building characteristics: size, height, and exposure);
- Archaeology (detection of remains under forest cover).
Nationwide coverage by 2026
Currently, fifty-five blocks covering nearly 135,000 km² in open data are available (https://diffusion-lidarhd.ign.fr/mnx/ ), already available, including cities like Rennes, Rouen, Poitiers, Orléans, Nancy, Toulouse, and Chambéry. The coverage will gradually expand, with a goal of 80% of the national territory covered by the end of 2025 and total coverage by the end of 2026.
The point clouds can be visualized and downloaded via https://geoservices.ign.fr/lidarhd
To better understand
What is LiDAR technology and how does it work for topographic surveys?
LiDAR (Light Detection and Ranging) technology operates by emitting light pulses towards the ground from an aircraft. By measuring the time these pulses take to return to the sensor, LiDAR calculates distances and creates an accurate 3D map of the terrain and structures.
What regulatory impacts can the LiDAR HD project have on territorial resource management?
The LiDAR HD project allows for precise and detailed mapping of the territory, influencing regulations in urban planning, environmental conservation, and natural hazard management. It provides essential data for regulatory planning and climate change adaptation.