Tallon and Blaer’s laser data consists of 1 billion data points, structured as “point clouds,” which software can render into images of the three-dimensional space. Stitch them together, inside and out, map the photographs onto the precise 3D models, and you have a full digital recreation of incredible detail and resolution.

“I saw this happening and I had two thoughts,” Blaer told me of watching the cathedral engulfed in flames. “One thought was that I was kind of relieved that he didn’t actually have to see this happen. But on the other hand, he knew it so well and had so much information about how it’s constructed, he would have been so helpful in terms of rebuilding it.”

Laser scans like Tollen and Blaer’s represent a significant development in the restoration of historic buildings.“Having the scans is incredibly important in any kind of reconstruction,” said Raymond Pepi, president of Building Conservation Associates, which was the restoration consultant for St. Patrick’s Cathedral in New York City.