They were never guaranteed to last forever, but this at least sidesteps erosion.
A system being trialled by archaeologist Kalle Sognnes and colleagues at the Norwegian University of Science and Technology in Trondheim provides a much simpler and cheaper solution. It consists of an ordinary office projector, a digital camera and a laptop running specially developed software....Other petroglyph news here.
To scan a carving, the projector is used to illuminate it with stripes of light and dark, and the digital camera records the resulting pattern for analysis on the laptop. The technique has been dubbed "structured light".
"The pattern will be distorted because of the topography," explains Øystein Skotheim, who helped create the system. "The software uses images from the camera to calculate the 3D shape very precisely."