Computer hunt for rock carvings

By Christina B. Winge
The technology that archaeologists and ICT researchers have recently adopted is called “structured light”. It is a method that quickly and easily reads off the three-dimensional shape of an object with the aid of a camera and a video projector. The images are transferred to a computer, which constructs a detailed three-dimensional model of the object. The method is normally used in reverse engineering, the process of making a 3D computer model of an existing physical object. It has also been used for product quality control, for example in the engineering industry.

Kalle Sognnes, a professor of archaeology at NTNU, is extremely pleased with the help he has received from SINTEF research scientist Øystein Skotheim, and he believes that the new method will arouse the interest of archaeologists elsewhere, not least because the imaging technique helps researchers to see more than the human eye can manage alone. This will make it easier to reveal scratches that otherwise would have been difficult to see . The method also allows more details of such scratchings.

Need for modernisation

The background for the trials of the new system is that NTNU’s archaeologists needed better, more modern methods of documenting and characterising rock carvings. They therefore contacted SINTEF’s Dept. of Optical Measurement Systems and Data Analysis, which suggested trying out imaging with structured light. After a few preliminary experiments at the Museum of Natural History and Archaeology in Trondheim, the researchers are extremely pleased with the system.

The method makes it possible to retain the three-dimensional characteristics of rock carving for the future, using relatively inexpensive existing equipment. A problem is that rock carvings break down and are weakened in the course of time. Another important advantage is that the equipment is easy to transport and to rig up and dismantle.

“We know that other archaeology groups have tried to do the same thing with less advanced laser equipment, such equipment is time-consuming to use, and it is not easy to bring it out into the field,” says Sognnes.

More revealing

In many rock carving fields, scratches have been made at several levels on the same spot, which means that a rock carving may hide another older one lying below it. Going “into depth” with the computer model makes it possible to identify, for example, whether the carvings have been made using different types of tool or with different techniques, and thus during different epochs.

Skotheim adds that this method of imaging and processing data from ancient monuments will make it possible to produce virtual exhibitions on the Internet, or to feed data directly into a milling machine to produce exact full-scale copies of the originals. This could bring antiquities within the reach of many more people than hitherto.