The Raven Crest pole, with the pixels from the high dynamic range pano-photography mapped three-dimensionally onto the laser scan point cloud, to create a three-dimensional photo-realistic model.
A scan of another totem pole in the Sitka Historical National Park.
Story last updated at 9/25/2013 - 1:36 pm
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 - most were crafted or restored in the 1930s, 40s, 50s and a few in the 80s - are now 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. Those re-carvings were completed mostly in the 1930s-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 made their new home. Except, many of them were laid down on the side of the trail and left to rot, Hess said. It wasn't until the 30s - during the New Deal era, 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 in tact. 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 of the poles.
"The digital preservation of them is kind of the final snapshot," Hess said. "the final snapshot to permanently preserve the totem poles. 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."
A specially trained architect team came out from the National Park Service's Heritage Documentation Program, Hess said. They used the laser scanning, taking a team of two. The scanner looked like a box on a big tripod. The lens in the center spun on the X-axis with the top of the box oscillating in a 360 degree movement. 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, patches. 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."
This scanning process is the same that's used on United States National Monuments.
"This is the very first time they had decided to include wood objects into the collection (Library of Congress)," Hess said.
The Heritage Documentation Program architects will take software and map a data cloud with these digital scans. The technology, Hess said, has been around for about 10 years. Later the backgrounds will be erased to focus on the main object. The architects will complete the processing phase of the project in October.
"The digital preservation is to use the laser scanner to create that line drawing that's going to the Library of Congress," Hess said.
When they become public record after being submitted to the Library of Congress, anyone will be able to pull the files and view them.
"The other benefit of that is if we ever, God forbid, lose one of the totem poles, which has happened several times in our history, (they would be preserved)," Hess said.
One was lost due to flooding, and swept out to see. It was later retrieved by the U.S. Navy. In 1959, a memorial pole was accidentally burned down from a bonfire that a teacher had lit too close to it.
Sarah Day is the editor of Capital City Weekly. She can be reached at firstname.lastname@example.org.