Parts of Notre Dame Cathedral destroyed by the fire on April 15 could be rebuilt with the aid of a three dimensional (3-D) laser scans taken in 2015.
Late architect and historian Andrew Tallon captured every detail of the 856-year-old iconic building by employing a combination of laser technology and digital photography.

According to Wired, “architects now hope that Tallon’s scans may provide a map for keeping on track whatever rebuilding will have to take place.”

Using more than one billion points of data Tallon was able to bring the cathedral to life in what is the most accurate rendering of the building ever made. Eventually those millions of dots form a 3-D snapshot of the cathedral, and the resulting images are meticulously precise; if the scan is done properly, Tallon told National Geographic, it should be accurate within 5 millimeters.

The blaze accelerated quickly because the entire frame of the building was made from timber using an estimated 1,300 trees. Officials said that there is “nothing left” of the 12th-century cathedral’s roof.

Tallon’s work created not only a copy the building in the present moment, but also how it changed over time.

Tallon used a rotating laser machine to measure exact 3-D specifications of the interior and exterior of the church throughout more than 50 locations. He then used panoramic photos of the same locations mapped by lasers to overlay aesthetic detail, which allowed him to stitch together a replica that was not only accurate in dimension but in physical appearance

Structures, especially old ones, tend to evolve due to weather or other factors in the original construction as they age. Tallon’s analysis of the building’s evolution is a critical in uncovering the methods of how it was built, to begin with, many of which were long-held architectural mysteries.

According to National Geographic among the many things revealed by Tallon’s scans were some previously unknown shortcuts by the cathedral’s builders who actually covered up their mistakes by constructing around previous work.
As a result, the report says, the interior columns of the building don’t align and neither do the aisles.