It turns out the easiest way to map an ancient Mayan city is by blasting the jungle with lasers. Traditionally, the thick canopy of the jungle would require archaeologists to find ancient structures on foot, creeping through the thick, mosquito-infested forests one step at a time. Airplane-mounted lasers are changing all that, effectively clearing out every tree and shrub that may have obscured the view of everything from irrigation ditches to hidden pyramids. Mapping that would have once taken months can now be done in less than an hour, and is understandably being hailed as a “game-changer” for archaeologists.
Looking under the trees with lasers
Importantly, these lasers aren’t actually removing any of the flora or fauna from the Guatemalan countryside. Rather than physically burning away trees, the Light Detection and Ranging (LiDAR) lasers shoot harmless pulses of light hundreds of times per second. Those might be absorbed by whatever they hit, but enough reflect back to the plane to measure the time and therefore distance they traveled. Like a light-based version of a bat’s echolocation, this allows a computer to build a detailed, three-dimensional view of the terrain below.
By firing different wavelengths of light, LiDAR can also detect what kind of materials the laser pulses are hitting. For example, a green, translucent leaf will scatter and absorb high-frequency photons differently than low-frequency photons, which can then be used to infer when a laser is hitting a leaf versus a stone. Combined with taking measurements from multiple angles in the airplane, a LiDAR map can then remove all the organic growth of the jungle, leaving behind a representation of the buildings and walls that were built by the Mayans over 2000 years ago.
New maps of Mayan engineering
LiDAR mapping has already yielded new advances in our picture of Mayan culture. So far, over 770 square miles of the Guatemalan jungle have been mapped, leading to the discovery of 60,000 Mayan structures. Aside from the sheer volume of new buildings to investigate, these surveys have also revealed new types of Mayan construction. While the Mayans were known to farm, advanced agricultural technology has been revealed, including extensive irrigation canals. Additionally, defensive structures like walls and watchtowers have been found, suggesting more advanced levels of warfare in Mayan society than had previously been appreciated. As more of these pieces of engineering are found, the overall picture of the ancient Mayans is becoming much richer than the sum of its parts. Or at least the parts that people had had time to map out on foot.
Source: 'Game Changer': Maya Cities Unearthed In Guatemala Forest Using Lasers by Merrit Kennedy, NPR