Unded by the Upper and Lower Normandy, Nord-Pas-de-Calais and Picardy Councils, together with the CNRS, Lidar, an airborne laser offers fine topographic mapping of the coast stretching from Dunkirk to the Mont Saint-Michel. The project is reuniting some 60 researchers.

Lidar: how does it work?

Lidar: how does it work?
Lidar is an “active” remote sensing technique using light emission. Part of the light is diffused or absorbed by the environment and the other part is backscattered in the direction of the source of radiation. The time difference between signal emission and signal reception enables the determination of the distance covered. The device is set up onboard a small low-speed aircraft whose position is precisely controlled by a ground-based GPS system. Lidar emits a high frequency laser beam which scans the landscape across a width of 700 metres for an altitude of 1,000 metres. Laser measurement precision is approximately five centimetres on a bare soil. The rate of covering in a coastal zone is typically around 30-40km2 per hour.

CLAREC means “Contrôle par Laser Aéroporté des Risques Environnementaux Côtiers” (Control of Coastal Environmental Risks by Airborne Laser). Initiated early 2005 by Caen University’s Laboratoire de Morphodynamique Continentale et Côtière (Continental and Coastal Morphodynamics laboratory) (M2C CNRS Laboratory, UCBN), the project is close to completion. ” By early 2009, we will be ready to carry out the first measurements,” Professor Franck Levoy, director of the CREC (Coastal Environment Research Centre) and project coordinator, is delighted to announce. The project’s focal point is the acquisition of a very high technology device: Lidar, an airborne laser which will scan the coast to precisely map its relief. Although widely used in the United States and in Canada, particularly to mark out new motorways, it was inexistent in France up to a year ago, and today only two devices are in service (one private and one IGN). France’s 3rd Lidar will be based in Caen and will be devoted to scientific research.

Four regions (Upper and Lower Normandy, Nord-Pas-de-Calais and Picardy) have joined forces to finance the purchase of this device, aimed at observing the entire English Channel and North Sea coastline. A very high resolution digital camera is linked to the laser to take aerial photographs. Total cost: 1,150,000 Euros, funded by the four regions (250,000€ each) and the CNRS. The results of the call for tenders are expected late June and the first tests should start by the end of the year.

An ever-changing environment

“Lidar is of interest to researchers in the fields of geography, geosciences, biology, meteorology, climatology and even physical instrumentation”, adds Franck Leroy, “Current techniques do not allow calculations over a sufficiently large area and are difficult to implement along the coast.” For example, how can we recreate in fine detail the kilometres of foreshore comprising the Mont Saint-Michel bay, which represent a mine of essential information at a time when the site’s maritime character is actively being restored ? The stakes are all the greater since the coast is a constantly changing environment and its transformation is at the very heart of present-day concerns on global warming.

Lidar will be used during around a hundred flying hours throughout the year. The results it will provide are impatiently awaited by twelve research teams from the four regions involved ⁽¹⁾, occupying a total of 60 researchers, reunited within a Groupement d’Intérêt Scientifique (Scientific Interest Group), coordinated by Caen University. The annual operating budget is estimated at 100,000€, supported by the 2007-2013 State-Region Plan Contract, together with outside partners [Conservatoire du Littoral (Coastal Conservatory), GIP Seine-Aval…] and research programmes [ANR, INTERREG,…].  The CNRS is launching an external 2008 recruitment campaign to identify the engineer who will be in charge of the project; a team of engineers and technicians is gradually being formed. In short, everything is ready and waiting for Lidar to arrive.

(1) Intechmer, M2C, CIMAP, GEOPHEN, GEOSYSCOM, PE2M-IFREMER, CREC, Universities of Rouen, Amiens (geology departments), Dunkirk (oceanology and geosciences), Lille (geosciences), Wimereux and Luc-sur-mer Marine Stations.

CLAREC
Franck Levoy, Director of the CREC, and the project’s coordinator
Tél. : 02 31 56 57 44
Mél : franck.levoy@unicaen.fr

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