An Archaeological Dig without the dirt

 By George Beschen

Bringing the power of technology to the study of ancient cultures

Tiwanaku in Bolivia is the largest geophysical survey in the world. Archaeologists from the University Museum have led excavations in the ancient city for the last decade. They’ve uncovered great new insights, including when the city was occupied (between 500 and 1000 A.D.). But using more traditional data gathering methods, they found themselves overrun with gigabytes of information. Was there a better way to process and store it?

A second challenge was a matter of space: the site covers four square miles.With available tools, the Penn archaeologists could only excavate about 200 square meters a season. One archaeologist likens the pace to “excavating a block of Manhattan to tell you what the whole state of New York looks like.”

Unique solutions to both challenges have grown out of a novel collaboration with Associate Professor Kostas Daniilidis of Computer and Information Science and his colleagues. This past year, that association took on a whole new dimension— one that has the potential to affect how archaeologists do their work anywhere in the world, how artifacts are stored and conserved, and the public’s access to the treasures of archaeology.

The new three-year pilot project, made possible through a $1 million grant from the National Science Foundation, is called “Computing and Retrieving 3D Archaeological Structures from Subsurface Surveying.” Besides Penn engineers, mathematicians, computer scientists, and anthropologists, collaborators include faculty at the Center for Advanced Spatial Technologies at the University of Arkansas and the Department of Anthropology at the University of Denver.

The immediate goal distills to groundbreaking research— without the ground breaking. Daniilidis and his team are collecting detailed, three-dimensional archaeological structural data from approximately 60 subterranean acres of Tiwanaku without benefit of the archaeologist’s trowel.Work funded by the National Science Foundation grant will begin in June and continue for six weeks every summer through 2008.

“In the same way doctors get 3D models of what’s inside the body so they know where to operate, we want a 3D model of what’s inside the earth,” says Daniilidis. “We want to give them a much better sense of exactly where they should excavate.”

And as with medical imaging technology, the collection of 3D images of underground structures will be noninvasive— obtained via ground penetrating radar, magnetometry, and conductivity sensors. The end result: directions for further excavation and also 3D models of artifacts that can be studied as if they were already excavated.

Centuries of erosion have taken their toll on the site’s adobe walls. And harvesting of surface stone by local peoples created other gaps. It will take time before the full picture of Tiwanaku emerges.

“The era of the big style, Indiana Jones excavations is over, but we still have this desire and need to ask these big questions,” says Tiwanaku field director Alexei Vranich, a research associate at the Museum and a co-principal investigator on the NSF-funded project. “So we can either get smaller and smaller with our excavations or we can try to come up with something innovative.”

The collaboration began in 2002. Daniilidis helped the archaeologists devise a quicker way for recording the site, which comprises arches, walls, roads, and solid blocks of a stone not indigenous to the flat plateau (giving rise to the site’s nickname, “the Stonehenge of the Americas”). To help, he enlisted student volunteers from the School of Engineering who, for three summers, took hundreds of digital photos, from every angle, of every surface. Back at Penn, these images were blended together to create 3D images. Daniilidis’ collaborators, and fellow coprincipal investigators, are assistant professors George Biros of Mechanical Engineering and Applied Mechanics and Jianbo Shi of Computer and Information Science.

Daniilidis notes that one of the great benefits of this project is “exposing students, from our school and other schools, to this emerging technology.We can work together and show the power of technology in any discipline. I really don’t think there is any discipline right now that cannot make use of what we do at the School of Engineering.”

Now, as their counterparts at the Museum work to recover a lost civilization, Daniilidis and his team endeavor to solve the problems of recovering the lost dimension. The scientific challenge is three-part: 1. giving structure to volume data (Biros’ area of expertise), 2. grouping or segmenting boxels (a volume element, as with a pixel), and 3. creating a graphic to be displayed via a visualization program.