A method of imaging rock carvings in 3D using everyday electronic equipment could help document decaying carvings before they disappear forever, researchers say.
Archaeologists are struggling to document many rock carvings before they are eroded by pollution or weather. Bulky laser scanners can capture detail in 3D down to 0.2 millimetres (see Lasers reveal invisible Stonehenge carvings. However, such instruments are too costly and cumbersome for general use.
A system being trialled by archaeologist Kalle Sognnes and colleagues at the Norwegian University of Science and Technology and The Foundation for Scientific and Industrial Research (SINTEF) 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.
Advertisement
鈥淲e are trying to find something cheaper because laser scanners are so large and expensive,鈥� Sognnes told 快猫短视频. 鈥淚n some places we are coming to the end of these rock carvings, and we hope to document them before they are gone.鈥�
鈥淪tructured light鈥�
Sognnes has been testing the simple scanning set-up on carvings held at the Museum of Natural History and Archaeology in Trondheim, Norway. The carvings date from the Scandinavian Bronze Age (900 BC to 800 BC). The equipment will also be tested this week at a site north of Trondheim, which features carvings of boats, elks, and whales, dating from 6000 BC to 200 BC.
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 鈥渟tructured light鈥�.
鈥淭he pattern will be distorted because of the topography,鈥� explains 脴ystein Skotheim, who helped create the system. 鈥淭he software uses images from the camera to calculate the 3D shape very precisely.鈥�
Weathered, hidden
Although not as accurate as a laser scanner, it is sufficient to reveal distinctive marks made by different types of tool. 鈥淟ooking at the tools used can help age carvings,鈥� Skotheim told 快猫短视频. 鈥淲e can also use this technique to look for signs of how erosion is happening or to distinguish very weathered, hidden carvings from surrounding rock.鈥�
There is an urgent need for cheaper scanning solutions, says Tertia Barnett, an archaeologist documenting rock carvings in Northumberland, UK. 鈥淟aser technology is changing but is still very bulky and expensive, and it takes a lot of time to get it into place for a scan,鈥� she says.
Barnett has been testing another cheap solution that involves taking two normal digital photos from different positions and turning these into a 3D image on computer. This can reveal details of about 2 mm in size, but Barnett believes the structured light method could be even better: 鈥淎 cheaper method with higher accuracy would be a great help.鈥�
