Tech

THE language archaeologists use to describe their finds is frequently lively, but not always helpful when it comes to comparing artefacts. Stone hand axes, for example, might be described as "pear-shaped" or "drop-like" - but more refined descriptions could capture small variations that speak volumes about the cultures that produced these objects.

Precise measurements might bring some rigour to the process - or rather, they would if archaeologists could ensure they orient objects the same way every time they take such measurements. But since artefacts are often highly asymmetrical, they usually can't. The result is measurements that reflect the variation between archaeologists rather than the artefacts.

"This ambiguity is a source of frustration," writes Uzy Smilansky, a specialist in computerised archaeology, in the Journal of Archaeological Science (DOI: 10.1016/j.jas.2008.06.011). What's needed, Smilansky says, is a system that can orient objects in a standard way time after time, and measure their key parameters irrespective of the vagaries of the beholder's eye.

Now Smilansky and colleagues at the Weizmann Institute of Science in Rehovot, Israel, have developed software that is able to do this. They begin by using a 3D object scanner to grab an image of, for example, a flint hand axe, shining ultra-thin stripes of light from a projector onto the axe head on a rotating table. Two cameras trained on the axe feed images of how the stripes look from their perspective to a computer, which creates a digital 3D representation of the object. To enable consistent measurements to be taken, the axe is then oriented in a standard direction using an algorithm which seeks out the axe's sharp edge and any major planes of symmetry.

In tests on 90 hand axes found at three Lower Palaeolithic sites in Israel, the software proved much more accurate than archaeologists at grouping the axes according to their common features.

Smilansky now plans to make the 3D scans available online for other researchers to use - if he gets a moment. "Other archaeologists are queuing up to get their artefacts scanned," he says. "One guy brought half a carload."

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