How one man just rewrote the history of Alcatraz

By Louise McLoughlin, CNN

(CNN) — The future of Alcatraz lies in one man’s hands. In 2023, as sea levels rose around the iconic island in San Francisco Bay, Pete Kelsey — a technologist specializing in 3D data capture — was called in to help save the site for future generations.

By mapping the entire island, as he was tasked to do, Alcatraz could be monitored in detail going forward — and future proofed.

Preserving one of the world’s most famous islands is no minor task. In December 2023, as Kelsey made his first trip to Alcatraz, he already viewed the project as a once-in-a-lifetime endeavor. There are many spaces on the island that visitors don’t get to see, and before accepting the project, Kelsey insisted that he and his team should map every inch of the site.

The motivation, of course, was primarily scientific, but for Kelsey it was more than that. It was, he says, “an Indiana Jones kind of moment” — a chance to explore a site which has been many things.

Although best known for its 29 years as a federal penitentiary, the island of Alcatraz was also a military fort, used by the army during the Civil War to protect San Francisco from Confederate raiders. A little over a century later, in 1969 it became the site of a 19-month occupation by Indigenous activists in the name of Native American civil rights.

‘Making the invisible visible’

Armed with a combination of hand-held cameras and drones, Kelsey and his team set out to 3D map the tourist spot, arriving on the island in December 2023. Their state-of-the-art kit involved Boston Dynamic’s robot dog “Spot” and a Flyability Elios 3 drone, encased in a collision-resistant cage to protect both the aircraft and the site itself.

Thanks to their equipment, Kelsey’s team of researchers, scientists and drone pilots were able to gain access to areas previously deemed inaccessible because of lead, asbestos, and other safety concerns including structural damage.

Nowhere was off limits. “They gave me the keys to the place,” Kelsey says. His team was able to enter some of the oldest structures on the island, including Civil War-era spaces such as the Guardhouse, one of the oldest structures on the island where Confederate spies were held in the basement during the Civil War.

The technology at the heart of the project, though, is LiDAR, or Light Detection and Ranging — an airborne mapping technique which uses laser scanning to create three-dimensional models which are accurate to centimeters (or fractions of inches). “Think of it like an X-ray or a CAT scan of the entire island,” Kelsey says. “It’s making the invisible visible.”

It was harder than it sounds. Alcatraz is managed by the National Park Service, which doesn’t allow drones on its land, meaning that securing a permit to use one took months. The island is also a sanctuary for seabirds, and the team had to wait twice for the end of nesting season before they could move in with their drones. In all, the project took more than a year, starting in December 2023 and finishing in January 2025.

On arrival, the team stayed on the island for three weeks — sleeping in cells in the notorious D-block where, historically, some of Alcatraz’s most dangerous inmates have been held. They left, says Kelsey, with a ghost story or two — as well as some of the best scientific and historical findings of his decades-long career.

One of those findings is the imaging of the original Civil War-era sallyport, or secured entrance — something that hadn’t been seen in living memory. Located on the east side of Alcatraz Island, the original 1857 sign on the sallyport was concealed by a century-old building that backed up onto it.

Kelsey’s discoveries have also lifted the veil on the prison’s most famous 1962 escape, when Frank Morris and brothers Clarence and John Anglin made a successful bid for freedom.

His team produced a detailed scan of the path they chipped away at through their cells before climbing up a network of pipes and escaping onto the prison roof. The men then clambered down to the water before launching a raft from the northeast shore of the island. The three inmates were never seen again and it’s unknown if they survived the attempt.

Future-proofing Alcatraz

Kelsey’s maps and will now be used as the baseline for future surveys to be compared against. Their baseline will allow for informed predictions about things like climate change, seismic activity, and general deterioration of the site, which hosts around 1.2 million tourists a year.

“We can throw a 7.0 earthquake at this data to see what would happen,” he says. His models can also be ‘aged’, meaning the park service can be better informed about where to focus limited funding for future preservation efforts.

The potential uses won’t just be scientific. Kelsey, who has also worked in both documentary and film, says his data can also now be used in the arts. Movie directors, for example, could use the models to replicate the entire prison with greenscreens. Another use is virtual tourism — using the data to physically recreate parts of the prison for those who cannot make the journey to the island.

There will almost certainly be other uses — Kelsey says that researchers often get excited about potential ways to repurpose his data. When they ask him if their vision is possible he says “the answer is always yes.” The data from this project is some of the best he has ever got.

“I’ve done this kind of work all over the world,” he adds. “This project, however, I think it just might be my Mona Lisa.”

The-CNN-Wire
™ & © 2025 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.