How Drones Helped Save Notre-Dame Cathedral
Sat, April 10, 2021

How Drones Helped Save Notre-Dame Cathedral

Drones played an essential role in investigating the Notre Dame fire. / Photo Credit: Loic Salan via Shutterstock

 

On April 15, 2019, the Notre-Dame Cathedral started burning and approximately 12 hours later, 400 firefighters extinguished the flames, according to Bill McNeil of insights platform Directions Mag. Videos from police drones played a significant role in identifying and directing the firefighters “to the location of roof hotspots.”

McNeil interviewed Benoit Guillot, the coordinator for Artedrones and chief drone operator. He and Artedrones employees were contacted on Tuesday evening, receiving a call from a person who asked him if they could do volumetric 3D mapping. He answered that they could do point clouds, digital elevation, digital surface maps, and 3D photomosaics. The person requested if they could produce a 3D model of the Notre-Dame church. Hours later, French authorities requested an official mission. 

The fire was out by then but Guillot and his team were warned that the church’s vault was unstable. Hence, they were forced to plan their missions without knowing what type of flying conditions they would encounter. The planning took about five days. His team sent out drones the following Saturday. Since they were concerned about losing drones due to falling bricks and debris. Thus, they decided to fly one drone at a time. 

Additionally, strong wind turbulences made each flight more complicated. Guillot and his colleagues deactivated all anti-collision features, as they needed to fly near the church walls and in between the columns. Micro SD cards were replaced after each flight in case previous data was lost during a crash. They operated the drones for six days nonstop, conducting over 200 flights and collating terabytes of data. 

From the data, Guillot and his co-workers built over 300 360-degree panoramas of the interior and exterior of the church. Each file contained “70 individual images stitched together.” The team also collected stereographic data, which helped them determine slope angles and take relief measurements. 

They used DJI Terra and Metashape to process the data, as well as using various GIS applications like Esri and ArcGis to analyze digital surface models, photomosaics. And digital elevation. The processed data was transmitted via WebGis to the French authorities. Presently, Guillot doesn’t know what the authorities are doing with the data. Per TV and newspaper reports, the authorities are still researching the church’s stability and how to proceed with its reconstruction.