This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An archaeological excavation is a little like eating a layered cake: Once you have removed a layer, you cannot put it back. The problem becomes even trickier if two layers look almost exactly the same.
Researchers from Aarhus University and Moesgaard Museum in Denmark have now developed a relatively inexpensive multispectral imaging system that gives archaeologists more ways of looking at the soil before they dig into it. Instead of illuminating an excavation with ordinary white light, the prototype uses LEDs at 16 different wavelengths, ranging from near-ultraviolet through visible light to near-infrared. Different materials absorb and reflect these wavelengths differently.
Two deposits that both look like rather similar brown or black soil to the human eye may turn out to be quite different when viewed in another part of the electromagnetic spectrum. "We wanted to make things faster, clearer and better in the field—and at a cost that makes sense for archaeology. One way of doing that is simply to rethink the light," says associate professor Søren Munch Kristiansen from the Department of Geoscience at Aarhus University.
The study is published in the Journal of Archaeological Science. The researchers tested the first prototype at Sorte Muld on the Danish island of Bornholm. Sorte Muld—literally "Black Soil"—is an archaeologically rich Iron Age site with more than a meter (more than 3 feet) of dark cultural deposits created by centuries of human activity.
For archaeology, that richness comes with a problem. Many of the layers are thin, irregular and very similar in color, making it difficult to determine exactly where one deposit ends and another begins. The LED multispectral imaging system, or LEDMSI, photographed the same section repeatedly while illuminating it with the 16 different wavelengths.
The resulting images were then analyzed using statistical methods that combine the spectral information and enhance differences between materials. And differences emerged that were difficult to distinguish in normal color photographs. "The images looked almost psychedelic when we took them, and we only really saw what we had when we analyzed them back at the computer," Kristiansen says.
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