Researchers Gather High-Tech Data on World’s Ancient Sites

FAYETTEVILLE, Ark — University of Arkansas researchers have used high-resolution technologies to map two World Heritage sites in Bolivia and Peru and are making their three-dimensional, highly accurate models of the ancient ruins available to the public and to other researchers on the World Wide Web.

Researchers Angelia Payne and Snow Winters first traveled to Tiwanaku, Bolivia, where they used three-dimensional laser mapping techniques to create a high-density survey of the ruins of an ancient city that was abandoned by about A.D. 1000. Their work was funded by a high-performance computing grant from the National Science Foundation, awarded to the University of Pennsylvania and contracted to the Center for Advanced Spatial Technologies at the University of Arkansas. After completing the work at Tiwanaku, Payne then traveled to Peru to use the same techniques at Machu Picchu, a royal retreat built by an Incan ruler in the late 1400s and abandoned only decades later.

"Our over-arching goal is to provide a means of capturing a three-dimensional object so it can be studied without visiting the object," said Jackson Cothren, assistant professor of geosciences and researcher with CAST. The object in question could be large structures, bones or archeological sites — "things that are difficult to measure with steel tape," Cothren said.

The work Payne and Winters performed in Bolivia and Peru adds more information to a global picture.

"There’s a huge effort to scan all the World Heritage sites," Winters said, because the sites change over time due to erosion from natural processes and from the tourists who visit them. Laser scanning at a resolution of centimeters to millimeters can detect subtle changes in the landscape that may be missed by the human eye over time.

Tiwanaku and Machu Picchu share other characteristics typical of World Heritage sites — they are difficult to access, costly to visit and accessible only at certain times of the year. Detailed scans of the ruins could make it easier for scientists with limited time and budgets to accomplish their research goals.

"Suddenly these places that are difficult to reach become accessible online," Cothren said.

Payne used an Optech ILRIS-3D time-of flight laser scanner to record the data at both sites. The scanner creates a three-dimensional point cloud, with each point representing the coordinate of a point of return reflection to the laser scanner. This particular piece of equipment works well for sites with ruins. The sites were scanned at about 3 centimeter resolution, except for the Puerto del Sol, which was scanned at 5 millimeter resolution.

Payne and Winters spent nine days at Tiwanaku and completed about 200 scans, collecting about 75 million data points. Payne spent four days at Machu Picchu and collected 25 scans with 80 million data points. After returning to Arkansas, the next step was to integrate the scans to create a whole picture.

"The scans are like pieces of a puzzle that we put together," Payne said.

Once the scans are stitched together, they form a three-dimensional image of the structure that was scanned. The Machu Picchu and Tiwanaku images are available for viewing at http://www.cast.uark.edu/invirmet/projects/machuPicchu_tiwanaku/project_details.htm. The Internet Virtual Metrology Lab allows anyone with a Web browser and the proper software to view the data collected at the sites this summer.

With the appropriate software, researchers can examine the scanned structures online, manipulating the images to examine them from different angles, making measurements and calculating distances in the same way that they might were they at the site.

While performing the scanning, Payne and Winters discovered some of the limitations of the equipment they used. The laser picks up vegetation quite well, which means that high grasses or the leaves on trees can prevent the laser from getting an accurate scan. Also, the equipment cannot be used at its highest resolution for whole sites because the resulting data set would return hundreds of millions of points — enough to tie up even the largest computers for days to resolve.

Despite its limitations, the technology will allow the researchers to easily distribute their data to share with others.

"It’s going to fundamentally change access to data," Cothren said.

In addition, the work CAST has done at Tiwanaku will help field archeologists make more informed decisions about where to excavate, according to Alexei Vranich of the University of Pennsylvania, principal investigator on the project.

"We’ll never dig the whole site," Vranich said. Tiwanaku lies on a six kilometer site, and a summer excavation may unearth 30 five-by-five foot trenches. "The work CAST is doing is helping to direct the excavations."