NEW YORK, NY.- In May 1946, chaos erupted when six prisoners who were determined to escape from Alcatraz Island overpowered guards and grabbed weapons and keys.

They seized a cell block at the federal penitentiary for two days, prompting the Marines to respond and throw grenades into the building from the roof. By the end of the “Battle of Alcatraz” in the middle of San Francisco Bay, three inmates and two guards were dead.

Seventy-eight years later, tourists at the prison turned park can still see a spray of pock marks in the cement floor that were left by those hurled explosives.

The divots, shallow in size but deep in history, will now be preserved forever, along with every other nook on Alcatraz. Scientists and technology experts spent three weeks in December using cameras, drones and a robot dog to gather 4 trillion bytes of data to build the first 3D map of the entire island in full color.

Every building inside and out was frozen in time. Every tunnel, every piece of cellblock graffiti, every rusted prison bar, every wildflower, every gull dropping. Every corner of “the Rock” was captured with precision within a centimeter.

The unusual project was born from worries over climate change and the sea level rise that will inevitably encroach on Alcatraz, where chunks of the perimeter wall are already eroding and falling into the bay. Scientists have warned that California could experience several feet of sea-level rise by the end of the century, along with ever more dangerous storm surges.

The 3D map could help local leaders track the effects of climate change on the San Francisco Bay Area. It could also allow National Park Service officials to visualize potential flooding at Alcatraz and protect the island against future damage, said Pete Kelsey, a technologist who spearheaded the mapping endeavor.

For example, he noted, the dock would be at serious risk if waters rise, and the boats that land there not only bring tourists but also deliver fresh water and remove sewage. Without a dock, the island would quickly become unusable, he said.

Because Alcatraz is so well known worldwide, the map might be “a vehicle to wake people up, to snap people into a different sort of consciousness about climate change,” Kelsey, 62, said.

Alcatraz, which sits just over a mile north of San Francisco, has had many chapters. It was originally a fort and a military prison. During its most famous stretch, from 1934 to 1963, it operated as a high-security federal penitentiary and housed such notorious convicts as Al Capone, Machine Gun Kelly and Robert Stroud, known as the Birdman of Alcatraz.

In 1969, Native Americans occupied the site for 19 months to protest the government’s treatment of their people. After opening to the public in 1973, Alcatraz has become a popular tourist attraction and bird sanctuary that is part of the Golden Gate National Recreation Area.

Like many National Park Service properties, Alcatraz is at risk on numerous fronts. It faces a possible earthquake. It is vulnerable to fires or floods. It could be the target of a terrorist attack. It also suffers from plain old wear and tear from its 1.5 million annual visitors, with some of its buildings and equipment badly deteriorating.

Traipsing around the island on a recent day, Kelsey said it was important to have a 3D baseline in order to track changes and damage to Alcatraz. Kelsey owns Seattle-based VCTO Labs, which has captured everything from military ships to football stadiums for the purposes of preservation, education and moviemaking.

“The data we capture can answer questions,” he said. “It can lead to discovery. It makes the invisible visible.”

The National Park Service will maintain the rights to the 3D map, and no money changed hands in the making of the map, Kelsey said.

He believes the 3D map provides the National Park Service with endless opportunities. It could be used by movie studios, which wouldn’t need to film on Alcatraz but could instead use the 3D data with a green screen. It could be turned into a video game or a virtual reality experience using Apple Vision Pro or Meta headsets. It could be replicated with a 3D printer.

“My selfish dream is that it’s the world’s first virtual national park,” Kelsey said.

Pete Gavette, a park archaeologist, said that smaller efforts to map the island had taken place before but that this was the first time that “every nook and cranny” had been mapped in 3D. Gavette said it would be useful for the park’s staff to see all corners of the island since staff members aren’t allowed to enter spaces that are considered too hazardous because of asbestos, lead paint or structural damage.

For example, he noted, the apartments that once housed the families of prison guards are inaccessible because entire staircases and parts of floors are missing.

The 3D map is nearly complete, but Gavette said a virtual reality tour of the island would take a while to create.

Getting permission for the project — particularly the right to fly drones, which isn’t normally allowed in national parks — took nine months. Then Kelsey had to wait for nesting season to end to avoid disturbing the island’s bird colony.

To gather the data, he recruited 26 scientists and technology specialists from around the world to work for free. Some, including Kelsey, lived on the island for three weeks in December and brought all of their food, did not shower and slept in prison cells. They were given a gold key that unlocked every door on the island.

They flew drones into hard-to-reach crannies like inside the top of the smokestack, where they had to shield the aerial devices with cages to guard against any damage that might have occurred from bashing into the walls. They sent a robot dog into other places where it wasn’t safe for humans to enter.

They mapped the power house and its “Alcatraz steampunk” vibe, as Gavette described it. They mapped the underground citadel and the dungeons where military prisoners were held. They mapped the prison hospital where inmates who were believed to be mentally ill were enclosed in tiny rooms, where their food trays were passed through skinny slots in the wall.

Kelsey said that the mapping had given him insight into the gruesome treatment of some of the people who were incarcerated there and that he sometimes still hears screaming in his head.

He has mapped other locations around the world, including Easter Island and Africatown, an Alabama community founded by former slaves. At the end of each project, he always gets a tattoo.

Soon, he said, he’ll get a new one: the key to Alcatraz.

This article originally appeared in The New York Times.