Archaeologists spend much of their professional lives in holes, digging deep underground to discover the remains of ancient communities and cultures. But now, some of them are taking to the skies—with a little help from drones. By outfitting these unmanned craft with thermal cameras, archaeologists have discovered a new and affordable way of seeing what’s underground while flying high above it.
Thermal imaging has been “the unexplored frontier” in archaeology for a long time, says Jesse Casana, an archaeologist at the University of Arkansas, Fayetteville. The idea behind the technique is simple: Over the course of a day and a night, different parts of a landscape heat up and cool down at different rates. Buried stones, for example, tend to retain heat longer than dry soil around them does. That means that in the early morning, the stones will be much warmer than the surrounding earth. Those temperature differences are invisible to our eyes, but a thermal camera—which detects infrared light, otherwise known as heat—can easily record and reveal them. And if those buried stones happen to be the remains of ancient buildings, that camera has just taken a picture of a lost settlement without digging a single hole.
But how do you get a thermal camera up in the air to take those pictures? In the past, archaeologists have tried everything from small planes and helicopters to hot air balloons and kites. Casana recalls that one team even sent a graduate student up in a powered parachute—basically a flying go-kart—to snap thermal pictures of a site while leaning over the side. They got “amazing results,” but the technique was time-consuming, expensive, and dangerous, Casana says. So he started thinking about alternatives. What kind of contraption could fly a thermal camera over a large area without much help from humans on the ground—and do it for not very much money? Then it hit him: a drone.
Drones, otherwise known as unmanned aerial vehicles (UAVs), are becoming increasingly popular in many kinds of scientific research. They can fly for about 15 minutes on their own, covering much larger areas than a balloon or kite can. Plus, they are cheap (and getting cheaper); anyone can buy a kit and build their own UAV for just a few hundred dollars. All Casana needed to do was strap a thermal camera onto one, program a flight plan over an archaeological site, and wait for its buried features to be revealed.