A Penn State Behrend research team is using advanced 3D imaging technology to preserve one of the country's most powerful symbols of independence: the Liberty Bell.
Chris Shelton, an associate professor of clinical psychology and director of the Virtual/Augmented Reality Lab at Behrend, traveled to Independence National Historical Park with two recent graduates, Remington Orange and Alexander Fisher, to create laser-line, LiDAR, structured-light and photogrammetry scans of the Liberty Bell.
By developing a 1:1 digital twin of the bell and its mount, the team will enable the National Park Service to repair or replicate any part of the historic landmark with microscopic precision.
"Hopefully, nothing ever happens to the bell," Shelton said, "but things do start to deteriorate over time. You can have a million pictures of something, but trying to recreate it after the fact is going to be very hard. With these types of scans, you would be able to create molds and casts as close to identical as possible."
State Sen. Dan Laughlin arranged for the team to have access to the Liberty Bell, which is the centerpiece of Independence National Historical Park in Philadelphia. Nearly 1.7 million people visit the park every year.
The team recorded digital scans over three visits to the bell, beginning each day at 5:30 a.m., before public tours began. The team collected data by using several advanced technologies, deploying equipment donated or loaned by Lenovo, Faro, Creaform, Polyworks and Matterport:
- Laser-line scanning created a digital replica of the bell, showing surface details three to seven times thinner than a human hair.
- LiDAR scanning generated a navigable 3D "point cloud" of the bell, mount and exhibit space.
- Structured-light scanning captured additional surface details, including pitting in the bronze surface of the bell. The scan also preserves the bell's most famous feature - the crack that silenced it in 1846.
- A photogrammetry scan created a highly detailed 3D digital mesh by overlapping a series of 2D photographs of the bell and its yoke, which was cut from American elm.
The scans provide immersive, 360-degree views of the Liberty Bell, including from beneath the bell - a perspective that visitors to the site do not get.
"When you see the bell at Independence Park, you experience is as a larger-than-life national symbol," Shelton said. "You see the shape, the inscription, the crack, and you feel the presence of it in the room.
"The scan data really changes how you see it," he said. "The crack isn't just a line. The surface isn't just smooth bronze. You can see small variations, pitting, texture, edges, wear and geometry that is easy to miss when you're standing a few feet away in a public space. And the more detail you see, the more real the object becomes. It's still a symbol, of course, but it also becomes a piece of material history that has survived."
The digital recreation of the Liberty Bell also will support educational programming at schools and museums. Immersive VR platforms will make the bell accessible to those who cannot travel to Philadelphia.
"The Liberty Bell belongs to everyone," Fisher said. "A free, high-resolution digital twin means people can study it, experience it, and build on it in ways that weren't possible before."
