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Off-Topic: Unlocking the Secrets of Ancient Artifacts

July 31, 2008
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The Department of Anthropology and Archaeology at Brooklyn College is using laser scanning technology to develop a new research area in the study of ancient cylinder seal impressions and clay tablets bearing cuneiform inscriptions, an early form of writing.

A small cuneiform tablet, called a tag, one of 30 used in the study. Source: Laser Design Inc.


The Department of Anthropology and Archaeology at Brooklyn College, part of the City University of New York (CUNY), is developing a new research area in the study of ancient cylinder seal impressions and clay tablets bearing cuneiform inscriptions, an early form of writing. Dr. Alfred Rosenberger, a biological anthropologist in the department, used a Laser Design Inc. (LDI, Minneapolis) RE-1208 3-D laser scanning system in the past to scan primate fossils, documenting their shapes. Therefore, using the LDI laser scanning system to scan ancient tablets was a natural transfer of the technology and good use of departmental resources. To delve into the etiology of the cuneiform artifacts, Dr. Arthur Bankoff, archaeologist and head of the department, and Rosenberger, partnering with Dr. Rudi Mayr, who has spent his professional lifetime studying cuneiform tablets, applied for and received a grant from the National Endowment for the Humanities (NEH).

A large tablet being scanned. Laser scanners measure articles quickly, picking up tens of thousands of points per second, generating huge numbers of data points without the need for templates or fixtures. Source: Laser Design Inc.

Cuneiform Forensics

The pilot research project investigated the feasibility of using laser scanning and 3-D quantification and analysis of the cuneiform signs on a series of tablets to provide a new, high-tech way of studying and learning from ancient artifacts. As the team member with the most experience in using the LDI 3-D laser digitizing system, Rosenberger became the project co-director, in charge of scanning the clay tablets, managing the technical aspects of the scanning operation and quality control of the 3-D models, as well as the database development and outreach elements.

The project sought to give archaeologists another tool for understanding and postulating ideas about a culture and people that lived about 4,000 years ago in Mesopotamia, in the region of modern-day Iraq and Iran, by using the 3-D laser scanner to create authentic, accurate digital models of the cuneiform tablet artifacts. The artifacts were scanned with the LDI laser scanning system and a digital model was created. The models were measured so that each cuneiform sign was accurately described by digital data.

The ultimate goal is to develop a battery of techniques and methods that will make “cuneiform forensics” possible. This involves analyzing the shapes of the signs as if they were handwriting and developing a database of the precise 3-D measurements to study meanings of the physical elements as well as the linguistic and language elements. Detailed analysis of the cuneiform tablet properties could give researchers some idea about literary abilities of the people of the communities that used this form of writing. It is known that a class of professional scribes existed, but questions remain: Is there reason to believe that people without extensive scribal training could read and write? How many people in the society were able to write? Were writing skills based on class distinctions? Were only the rich, priestly or scholarly able to write, or was a larger segment of the population involved?

In the field of Mesopotamian archaeology and cuneiform studies, this project may be the first time that laser-based, shape-capture techniques have been combined with digital tools for capturing 3-D micromeasurements and statistical tools for studying shape. It is one of the first times that cuneiform tablets have been studied with an anthropological approach, explicitly looking at the tablets as artifacts carrying clues to their own culturally determined production and use, and bearing information beyond what was specifically written on them.

The dataset used was a sample of 30 tablets. These well-preserved tablets were written within two months of one another, possibly by the same scribe. A homogenous sample of tablets from the same time and place provides a better base from which to make scientific inferences and postulate anthropological theories about the population. Recognizable patterns and stylus techniques are likely to emerge.

3-D solid model of a clay tablet, about 4 by 2 inches in size, with cuneiform writing. Source: Laser Design Inc.

Method

Because of their small size, each cuneiform tablet, an approximately 1.5-inch handmade equilateral triangles of clay, required only one or two scan passes to create an accurate, detailed 3-D model. Each tablet contained a few lines written in the Akkadian language, including a date by month and day. A seal "closes" the envelope, much like what a modern notary public does to prevent alterations of the contents of a message.

The details captured from the surface of the tablets are used for analysis on many different levels. The data record the precise characteristics of each wedge such as length, breadth, depth and volume, and the spatial relationships between and among wedges..

“Scanning the tablet in three dimensions gives us information that we cannot get from the language itself,” says Rosenberger. “Not only does each sign have a meaning, but each may carry the personal touch of the person who made them. How that person held the stylus, how deeply he or she pressed it into the wet clay, placed the ends of lines and arranged the crossing points of the tic-tac-toe like symbols-all of this can be analyzed.”

Scanning free-form detailed shapes, especially undercuts and miniscule changes in surface texture, such as those on the cuneiform tablets, is ideally suited to noncontact laser scanning. Because the laser scanning system projects a line of laser light onto surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along, the problems of missing data on an irregularly shaped surface is eliminated. This laser line moves back and forth over the part until the complete surface is captured. The system measures fine details and complex free-form geometry so that the object can be exactly replicated digitally. Laser scanners measure articles quickly, picking up tens of thousands of points per second, and generate huge numbers of data points without the need for templates or fixtures.

The RE-1208 3-D laser scanning system that the researchers used was equipped with a RPS-120 laser probe, with accuracy of ±0.00025 inch per point with averaging, generating point cloud coordinates of 0.001 inch. The laser probe has a Class II rating with a visible beam, for safe operation and a long standoff to prevent crashes during dynamic part scanning.

The team used LDI’s proprietary software, Surveyor Scan Control (SSC), which controlled the scanning motions, managed the laser probe settings and contained automation features. The rotary stage allowed the system to automatically scan parts from all orientations and then easily merge the data into a common coordinate system.

After scanning the object, the scan data was processed further with Geomagic Raindrop software to quickly make surface models-in essence reverse engineering the tablets digitally. The freeware software, Landmark, designed by computer scientists and anthropologists as a measuring tool specifically for anthropological studies, provided point-and-click coordinate identification and measuring capabilities, as well as spatial dimension definition for working with the scan data in this project.

Scans of the tablets were edited to isolate individual signs for easier landmarking. The measured sample was composed of the data derived from identical points taken on the same sign on each tablet. Isolation of the signs allowed for exact placement of measurement points, using both the tablet surface and the reverse side of the scan.

Just the Beginning

Once measurements were made digitally on all the samples, analyses were run to determine characteristic elements of the cuneiform writing, the seals and the tablets themselves. With this information, the archaeologists of Brooklyn College’s Department of Anthropology and Archaeology eventually hope to extrapolate their findings to tablets from other areas and time periods, as well as other ancient artifacts, and develop a method of “forensic analysis” for studying many types of objects. The final report for the project to the NEH will be the basis for more research and funding for applications of the noncontact 3-D laser scanning techniques that they have performed with Laser Design’s Surveyor system.

In the future, the Department of Anthropology and Archaeology plans to use the 3-D scan data to produce stereolithographic models of cuneiform tablets in various sizes for use in the classroom. Thus, the scanning process will help bring a dead writing technique back to life for students learning about cuneiform from exact replicas.

The sample files form the beginning of an archive of scanned Near Eastern tablets. Further research will add other assemblages to this archive, allowing others access to the data and providing more comparative data for “handwriting” analysis. The department will make available to the general public manipulable 3-D graphic models of the tablets on a Web site dedicated to this project.

“The laser scanning technology of the Laser Design 3-D scanning system opened up a whole new dimension in what we can explore, dimensions that we wouldn’t have thought of before,” says Rosenberger. “It allows us to look at our artifacts in different ways and extract new kinds of meaning. Since the noncontact laser scanning method does not touch or damage the rare tablets, we can gather immense amounts of information from them in the present while preserving their integrity for researchers to study in the future.”

Laser Design Inc.
(952) 252-3412
www.laserdesign.com

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