In February 2022, Graeme Cavers and his team of archaeologists set out in search of a mysterious underground passage called the souterrain. There are about 500 of these Iron Age structures scattered throughout the Scottish Highlands, but no one knows what they were built for and no one has discovered a single structure intact.
“Perhaps they were used for storage, such as cereal in an airtight jar or dairy products like cheese,” said Matt Ritchie, resident archaeologist at Forestry and Lands Scotland. “Perhaps they are for security, to keep valuables safe, or safe for slaves or hostages. Or perhaps they were for ceremonial purposes, for family ceremonies, like a medieval temple or private chapel.”
Cavers, whose firm AOC Archeology was employed by Ritchie to help map Cracknie Souterrain in Scotland’s Borgie Forest, said site surveys could help shed light on the condition and structure of the crusts, but it can take at least a week if traditional methods are used.
Manual measurements using a device called a theodolite—very difficult to use in cramped, dark tunnels—have been replaced by laser scanners, which have improved dramatically over the past few decades. . “They used to connect to an external laptop,” says Cavers. “Data can only be written as fast as that connection. It’s done over an Ethernet cable so it’s relatively fast. But even then, the first laptops I used with the scanner all had 2 GB of RAM. That’s the top of the range. And a laptop cost a lot of money in those days.”
Technology has come a long way since then. After entering Cracknie Souterrain through a 50-centimeter hole in the ground, Cavers was presented with a gray device the size of a shoebox: the Leica BLK360 laser scanner.
Cavers places the device on a tripod in a 1-meter-high wet aisle, adjusts some settings, and presses “scan”. It turns into action, firing lasers at the walls of the outer shell 10,000 times a second. Cavers and his team can now take millions of measurements in less than an hour without moving a finger—Cracknie made 50 million in just a few hours. “To do the equivalent of what we did with the theodolite, you would have to be there for a very long time,” says Cavers.
Collecting large data sets is a challenge in itself. “Today, we’re going back to half a terabyte” of data, he said. “And we can do a few hundred projects in a year. It’s starting to become very difficult to manage from an IT point of view. And obviously we are archaeologists; we have to create permanent, long-term repositories.”
However, data is subject to a fee. Cavers once had to draw or photograph the sky from within a dark passage, which would test his perseverance in the absence of any natural light. Now, he uses software—Trimble RealWorks, NUBIGON, and Blender—to create accessible multicolor 3D “point cloud” models.
Team members can then view the models from any angle they like and measure the distance between any two objects, and they can change the color according to variables like height and density. That means archaeologists like Ritchie can teach people about archaeological sites without having to actually go there.
“[Cracknie] Ritchie said. “It’s a long way from established walking routes and relatively difficult to access.” That means it’s not suitable for guided tours or educational boards—but 3D models can be viewed from anywhere. Ritchie was even able to print out a scale model and display it in a museum. This technology is making Britain’s cultural heritage more accessible and could one day help archaeologists like Ritchie solve the mystery of Scotland’s southern lands.
This article was originally published in the January/February 2023 issue of WIRED UK magazine.
