Virtual Archaeology

A good archaeologist needs brawn as well as brains to reconstruct a fragmented relic-pieces of objects such as stone statues can be heavy and must be manipulated carefully, since each move risks damage. Sometimes restorers even build external frames to hold fragments in position while other pieces are fitted, and there’s always concern when the time comes to glue parts together that each is in the right place.

But computer-based imaging is changing how archaeology is done-possibly eliminating much of the heavy lifting. Researchers at the Museum of Terra Cotta Warriors and Horses in Xi’an, China, want to eliminate muscle and mishap from the restoration process by handling fragments in virtual space. There, the pieces could be endlessly arranged and rearranged and imperfections smoothed over. The team has an army of artifacts to work with: The scientists have been experimenting with ways to reconstruct digitally some of the 3,000 famous life-size terra cotta statues uncovered at the Museum’s site.

Virtual assembly of relic fragments is among the most recent installments in the application of ever-increasing computing power to archaeology. Says Alan Kalvin, research scientist at IBM’s T.J. Watson Research Center in Yorktown Heights, N.Y., “Originally the computer applications were more statistical, but with computer prices coming down and performance improving, particularly in graphics, it’s opened up the field for a lot of people.” Jim Wiseman, director of the center for archaeology studies at Boston University, agrees that this is the next logical step: “This is just the kind of thing that would be useful for reconstruction of individual pieces.”

To scan statue fragments into the computer, the Xi’an researchers use a laser range finder-a standard tool normally used for precisely measuring objects as diverse as manufactured parts or human bodies for clothing design-reconfigured to be portable and compact enough for an archaeological dig site. Equipped with a digital video camera and a laser, the device records each fragment’s shape, surface colors and textures.

Far more challenging than getting the fragments into the virtual world, however, is manipulating them once they’re there, says team leader Jiang Yu Zheng, associate professor of computer science and systems engineering at the Kyushu Institute of Technology in Fukuoka, Japan. The images contain so much data, according to Zheng, that the computer can only move them very slowly through virtual space. “If I reduce the data resolution,” says Zheng, “the pieces will lose their value as art” and be more difficult to fit together accurately. Zheng and his team predict that further work on data handling, as well as faster computers, will speed the process up considerably.

Once archaeologists figure out how the virtual fragments of a relic fit together, they could use that information as a blueprint to reconstruct the object in actual space. But the ultimate value of such a system might be simply to leave the artifacts resting in peace. With an estimated 5,000 more statues still underground at the Xi’an site, Museum staff imagine it may be enough to do the restorations virtually, without ever disturbing the remains.