Fascinating Facts About Unseen Cities

Lidar—a high-tech cousin of radar—uses light waves to peel back the layers of time.

- Nicola Davis

WE USUALLY think of archaeology as involving intrepid explorers and lots of painstaking digging. But today, long-hidden cities are being revealed from the air, where modern archaeologists use laser beams to spot evidence of ancient life buried beneath thick vegetation.

Lidar, short for “light detection and ranging” (and a cousin of radio-based radar), involves directing a rapid succession of laser pulses— between 100,000 and 400,000 per second—at the ground from an airplane or a drone. Software captures the time and wavelength of the pulses reflected from the surface and combines it with GPS and other data to produce a precise three-dimensional map of the landscape below. These high-tech explorations have revealed long-buried Mayan cities, including Tikal, in the dense jungle of Guatemala, and Caracol, in Belize.