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October 2, 2013

Team uses lasers to scan and preserve Sitka totems

JUNEAU, Alaska (AP) — A lens in a tiny box affixed atop a tripod spins while the box oscillates. A tiny beam of light flashes repeatedly from the lens. It pulsates. It creates a unique scan of 19 individual totem poles in the Sitka National Historical Park.

For two weeks this summer this little box completed this process three to four times around each of the poles from the ground level — and three to four times from the top of them.

These aging poles mostly were crafted or restored in the 1930s, 40s, 50s and a few in the 80s, and now they are being digitally preserved before they've decayed forever.

The park staff has been modifying its preservation methods since it started caring for the poles in the 30s.

Michael Hess, park ranger in Sitka, said most of the poles are re-carvings done between the 1930s and 1950s.

“All of the originals were collected by John Brady to take to the St. Louis World's Fair,” Hess said. “They went down there, they came back to Sitka. Nobody really knew what to do with them.”

Sitka had federal land available in 1906, and that's where the totems were moved. Many were laid on the side of the trail and left to rot, Hess said. It wasn't until the 1930s during the New Deal when money became available for restoration.

“The preservation of the totem poles has been happening since the late 20th century,” Hess said. “This is kind of the newest in that process, to keep the cultural objects intact. The climate of Southeast Alaska does some pretty horrific things to wood.”

They've also used paraffin dips to slow the decaying process, as well as sealing, painting treating and re-carving some pieces.

“The digital preservation of them is kind of the final snapshot,” Hess said. “The digital renderings are actually going to be printed out on velum and included in a special collection in the Library of Congress. The minimum standard for this preservation is to have them preserved on line drawings for the next 500 years. They're going to create what you would expect in a wire frame drawing.”

An architectural team came from the National Park Service's Heritage Documentation Program, Hess said, to do the laser scanning. The scanner looked like a box on a big tripod. The little beam of light shooting out doesn't just illuminate, it pulsates.

“Every millimeter it's shooting out a ray of light and hitting that sensor head,” Hess said. “It's collecting all of those points, every single little scratch, every beak, everything on the totem pole. If some kid had decided to carve his name on the totem pole it would capture that, too. Everything is important. The preservation of these things is just as important to the history of the park as the objects themselves.”

The architects will use software to map a data cloud with the digital scans. The technology, Hess said, has been around for about 10 years.

The images become public record at the Library of Congress so anyone will be able to pull the files and view them.




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