SHUTES FOLLY -- The toaster-oven-size machine whirred quietly atop the tripod as its laser recorded up to 40,000 data points a second.

National Park Service architects brought it here Tuesday, and by Thursday, they expect to have collected between 150 million and 200 million electronic measurements of one of Charleston's most neglected historic sites.

Castle Pinckney has stood guard on this island for two centuries -- and the brick fortification looks every year its age.

As the laser scanner did its work, photographer James Rosenthal with the Park Service's Historic American Building Survey lugged his 40-pound camera across the bleached oyster shells and took high-resolution black-and-white photos.

"What we're trying to do is capture the building the way it is right now because its future is unknown," Rosenthal said.

The abandoned, circular fort is owned by the State Ports Authority, which has no money to restore the fort or for archaeological work on its filled-in center. The fort is reachable only by boat and remains off-limits to the public.

Preservationists hope this week's effort to document the fort in detail will help kick-start a conversation about its future.

State Ports Authority spokesman Byron Miller said this week's work is "critically important," adding, "It helps bring attention to the site. We continue to be hopeful that we'll find a good home for it."

The Park Service's Historic American Building Survey has wanted to record Castle Pinckney's condition for years, but its remote location made that difficult, said Ashley Wilson, an assistant professor with the joint Clemson and College of Charleston historic preservation program.

"After three or four years and scheming and planning, it came through," she said.

The program's students traveled to the fort Tuesday to help the Park Service crew lug around the few hundred pounds of equipment. Others began measuring Castle Pinckney's openings.

Those measurements will complement the scanner's work and ultimately lead to a series of architectural elevations that --along with Rosenthal's photographs and a written history --will be stored in the Library of Congress.

Wilson said a student will spend most of this summer in Washington to create architectural elevations from the laser scans and other measurements. Everything should be accessible online by early 2012.

To prepare for this week's work, students helped the S.C. Department of Natural Resources clear away shrubs and other vegetation within 5 feet of the castle's walls, inside and out.

That clearing helped the scanner take its measurements across every eighth of an inch of the building. Historic American Building Survey architects Mark Schara and Paul Davidson said the scanner emits a green-tinted beam visible at night or when skies are overcast but it couldn't be seen Tuesday.

"There's nothing better to define the overall shape of the building," Davidson said of the technology. "You would have to spend too much time with a tape measure (to get the same information)."

Rosenthal's photographs will complement those measurements. He used a camera that produces a 5-inch by 7-inch film negative that contains more detail than the best digital cameras. Also, the negative -- the same technology the program used when it began in 1933 -- stores well.

"It has an archive lifespan of 500 years," Rosenthal said.

As Davidson worked his way around the fort, he made at least an informal assessment of its neglected state.

"Is it imminently going to collapse? I couldn't say. It's been here a long time, so we have that going for us," he said.

"But it's not getting any better."