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  • Indecipherable Inscriptions no Longer Illegible

Photonics Spectra
Mar 2008
Michael A. Greenwood

Time takes a heavy toll on everything, even gravestones. The markers in the burial ground of Old St. Luke’s Church in Scott Township, Pa., are so faded from more than two centuries of exposure to the elements and pollution that their ancient inscriptions were almost all but lost to history.

Formless shapes are all that remain.

Yang Cai, a computer scientist at nearby Carnegie Mellon University in Pittsburgh, wanted to see whether modern digital technology could decipher words that had been carved into sandstone.

He used a small scanner and a digital camera to retrieve information from the headstones, which in some cases predate the Revolutionary War, making them more than 230 years old. His high-resolution, three-dimensional scans of the markers recovered a range of historical information — including names, ages, dates and epitaphs — from some 30 tombstones.


A 3-D imaging technique is being used to decipher the worn inscriptions on gravestones at Old St. Luke's Cemetery in Scott Township, Pa. (left). A gravestone's inscription is visible after it is scanned (right). Images courtesy of Yang Cai, Carnegie Mellon University.

His system restructures an image using digital lighting and filtering. A special filter delineates the features on a tombstone’s surface. This data is then downloaded into a computer, and a software program developed by Cai strips the image of any color, a step that further sharpens its clarity and quality. Areas from the tombstone that remain illegible after this process often can be filled in with a little detective work and deductive reasoning.

Some of the headstones scanned by Cai are of prominent people from Pittsburgh’s — and America’s — past. They include a soldier from the French and Indian War and a Revolutionary War veteran who was a member of one of Pittsburgh’s founding families.

Cai plans to create a virtual tour of the cemetery for the church’s Web site and said that the technology could be commercially available in about two years. The software also has potential applications in medicine, in geography and in security checkpoints.

digital camera
A camera that converts a collected image into pixels that are black or white digital or shades of gray. The digital data may then be manipulated to enhance or otherwise modify the resulting viewed image.
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