New scanning technology unearths history of graves

Marium Chandna Dec 3, 2007

When Yang Cai trekked the rocky trails of the Val Camonica Valley in the lower Alpine regions of Lombardy, Italy, he set the stage for a groundbreaking discovery in the field of 3-D image reconstruction.

Cai, director of the Ambient Intelligence Lab at Carnegie Mellon’s CyLab, became interested in 3-D imaging technology for rock art on stones this summer when he participated in the Rock Art Archeology Field in Val Camonica Valley.

Upon his return to Pittsburgh, Cai developed a unique scanning system by combining multiple, specialized components of hardware and software that examine surfaces in 3D format for various kinds of tracings. The 3-D scanning system consists of a line pattern projector, a digital camera, and 3-D image reconstruction software.

Cai worked on this project with two team members: computer science major and research assistant Iryna Pavlyshak, and visiting scholar to Carnegie Mellon Yingchong Xia.

As a starting point, Cai and his team ventured into applying this advanced scanning system to one of the gravestones at one of the oldest churches in Pittsburgh, Old St. Luke’s Church, located in Carnegie.

According to Cai, the most interesting aspect of Old St. Luke’s is that it preserves more than 200 years of history. The church was founded in 1765 by British colonizers.

Cai said, “This imaging technology studies the 3D surface of objects and is not limited to rock art or carvings on gravestones. It can be applied to different types of medical analysis, geographical intelligence, and the reconstruction of geographical sites.”

By compiling the scanned data, Cai has also developed a digital cemetery for Old St. Luke’s Church, which is basically a virtual tour of the cemetery.
To view the different gravestones in the cemetery, all one needs is access to a computer. The program can be used on any computer, and will soon be available online and on DVD.

Cai and his team have not only adopted a new approach to recording and digitizing the information on the weather-beaten gravestones, but they have also gone one step ahead in reconstructing this data.

“Reconstruction is the key when you want to actually read the words once you have recorded them,” Cai said.

Once the high-resolution scanning system has captured the details on the gravestone, it uses two functions to reconstruct the image: digital lighting and filtering. The special filter marks out the curved and linear features on the surface.

The specialized software used for this research strips the image of any color illusion to promote clarity and improve the overall quality of the image, thus making it look more real.

According to Pavlyshak, surface points are then located on the image using laser technology. Surface points are data points with given ordinates. Various mathematical algorithms are applied to these surface points in order to shade the stone carvings for visibility.

Pavlyshak said, “The software uses a combination of surface signatures — positive signatures and negative signatures — to locate the surface points and interpret the carvings on the stone surface.”

This scanning system also blocks out any sun reflection, thus keeping the image free from any obscurity.

Cai said, “The system is simple, totally flexible, and affordable, besides being a solid technique to solve this practical problem of not being able to read the inscribed information on the gravestone. Prior to this method, the writings on the grave[stones] were not legible at all.”

For example, one of the gravestones examined by Cai and his team, which was not readable prior to Cai’s investigation, actually read, “Esabella, wife of John Seville, born in London, 1781, died February 22, 1862.”

According to Cai, this technology can also be applied to enhance accuracy of tests in the medical field, such as tongue surface inspection.

In an interview with an Australian radio channel, Cai stated, “Tongue surface has a lot of rich features connected to the internal digestive systems, such as the stomach and microcirculatory systems.”

According to Cai, certain health imbalances can be detected by inspecting the tongue’s surface.

He stated, “For example, the color and contour of the tongue surface changes when we are dehydrated or have a fever. We need a 3-D model of the tongue, because a better and accurate analysis of the color and texture depend on the 3-D model.”

Cai’s latest technology has impacted different groups interested in unearthing and rediscovering the past.

From genealogy researchers to archaeologists interested in deciphering the paroles on tombstones of the Roman army, a wide range of investigators from all over the world have approached Cai to share his knowledge and expertise.

Cai also provided some insight into his upcoming project.

“There is a 500-year-old Indian God’s rock structure in Pennsylvania, near Pittsburgh. We want to scan it and build a digital site of it,” said Cai.

For more information on Cai’s scanning system and its role in reviving history at Old St. Luke’s Church, visit www.oldsaintlukes.org.