On April 15th, 2019, the Notre Dame Cathedral in Paris, France, was set on fire, causing extensive damage to the historic gothic building. One of the main pieces of the cathedral, the spire, had collapsed during the inferno and the damage to its roof was severe. Most of the objects stored inside the building have been preserved, and the main structure of the building has been kept intact. Now the building can be restored with the help of technology left behind by the late Dr. Andrew Tallon who made 3D models of Notre Dame. These images can be used to reconstruct the building back to its original form.


A 3D rendering of Notre Dame using Andrew Tallon's laser imaging system. (Image Credit: Andrew Tallon)

Tallon became well-known for his work involving lasers to recreate Gothic buildings using images of them at every known angle. In 2010, Tallon had started his work on Notre Dame with a Leica Geosystems laser scanner to measure the distance between the scanner and sites the laser touches. He was able to achieve this by using light markers around the building and laser imaging data to scan the entire building everywhere - both inside and outside. The scans took 5 days to complete and required 50 scans. He also snapped high-resolution panoramic photographs to replicate the building onto 3D shapes the laser scanner could create.


The laser data is made up of 1 billion data points that act as "point clouds," allowing the software to create images of the building into 3D space. When these data points are merged and placed onto 3D models, a fully enhanced digital version of the building can be constructed. However, all the details involved in the images could be a problem. It requires a lot of storage space and huge amounts of processing power to run. The images are usually stored locally, only by a small number of people and firms usually hold onto this data because their clients don't have space anywhere for it. The files, despite high-resolution scans and photographs, would be an estimated 1TB in size. Which is suitable to be stored on a small disk drive, but too large to be stored on the cloud.


The scans are so accurate that it allowed Tallon to look further into the construction of the building, allowing him to see why some of Notre Dame's pillars don't line properly. The pillars could have been built around some of the existing structures, which gives a different perspective on the building's past. This data could be used to help reconstruct the building and can also help to improve the structure's integrity so it may last for many more years.


The laser point imaging system has more benefits due to the inaccuracy of the original sketches and photos of Notre Dame, so they can't be used to reconstruct the building in its entirety. However, it's not preferred to use laser scanning because of the costly approach. Only time will tell if using laser scanning is the preferred method to restore the building. 



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