France soon to be fully mapped in 3D thanks to a new radar

It is a titanic project which begins for the cartographers of the National Institute of Geographic and Forest Information (IGN). Over the next five years, they will sift through the entire French territory (including overseas departments and territories except Guyana) to establish three-dimensional maps using Lidar technology, a kind of radar-laser.

Some 7,000 hours of flight time are planned to scan French fields, towns, rivers or mountains. Flood prevention, forest management, land use planning, the data collected will have multiple applications. 60 million euros have been invested in this program as part of the France Relance plan, intended to revive the economy following the Covid-19 crisis.

The plane responsible for carrying out this operation carried passengers a few years ago, but today it does not have more than three seats, lThe rest is occupied by hardware, including a big black box, the Lidar. Fabien is a flight operator at IGN. “It is a radar but with light waves”, he explains. UOnce the hatch is open under the plane, these infrared waves can scan the territory. “Inside we have a system with oscillating mirrors which will allow you to sweep the surface of the ground”, continues Fabien.

Take off from Beauvais airport where the mapping planes are based. Laurent is in charge today. The pilot’s mission is to stabilize the aircraft as much as possible and follow the flight axes without deviating. With 10 points collected per square meter, the Lidar measures accurately. “We are in the process of acquiring 427,000 points per second and on an HD LIDAR site we are in the 20 terabytes of data. That represents about 400 computer hard drives.”

All this data, these clouds of millions of points, must then be processed. VSit takes place at the headquarters of the Institut national de géographie, near Paris. Loïc Gondol is the head of the Lidar project. “These data will really be used to obtain finer models and to better prevent these risks of flooding, these risks of landslides, better identify the avalanche corridors, he explains. They can also be used for other public policies. It allows in particular to discover vestiges, old Gallo-Roman sites or antiquity or better assess the areas to install photovoltaic panels. These data will allow it since we will have a description of the building with the roofs which will be well modeled. “

“We really have a description of the territory’s profile in three dimensions.”

Loic Gondol, Lidar project manager

to franceinfo

Free access, these 3D maps will also be used for forest management. For the moment part of the south-east, Corsica, Gard or Hérault have already been covered by Lidar. The Vosges mountains or the Rambouillet forest are next on the list.

These 3D maps will be freely accessible on the Geoportal site. IGN hopes to have covered the entire territory by 2025. Lidar has been used for several years by IGN, but for very specific areas, particularly swollen rivers.