The big archaeological digs happening up in the sky
Archaeology is facing a time crunch. Thousands of years of human history risk imminent erasure, from tiny hamlets to entire cities - temples, walls and roads under grave threat of destruction. Urban sprawl and industrial agriculture are but two culprits, smothering ancient settlements beneath car parks and cattle pastures. International conflict and climate change are also damaging vulnerable sites, with warfare and water shortages destroying pockets of history across the world.
The endless excavations of yesteryear are no longer the best solution. Big digs aren’t the big idea they once were: mapping the human archaeological record is now moving upward, into the sky.
Lidar – short for light detection and ranging – has emerged as one of the most widely used technologies for rapid archaeological documentation. Lidar works by sending pulses of light out from a transmitter often mounted to the skid of a helicopter, then recording how long it takes for those pulses to return to a sensor. A virtual 3D map can be generated from a single large-scale survey in less than a day. Archaeological sites that would require years and years of fieldwork to excavate can now be mapped in a single afternoon, their every surface feature captured down to millimeter-scale resolution.
Thickets and woods, even entire rainforests, are no obstacle. Because individual bursts of light can pass through the tiniest gaps separating branches and leaves in a forest canopy, lidar is also able to map archaeological features beneath heavily overgrown landscapes. The technique’s accuracy, combined with its declining cost as new devices and firms enter the market, means that lidar has found enthusiastic uptake in everything from urban mapping projects and geological hazard management – such as finding previously unknown fault lines – to, of course, archaeology.
Based in a converted helicopter hangar at the Hawthorne airport in Los Angeles, California, the firm GEO1, a subsidiary of NV5 Geospatial, offers lidar services to utility companies and archaeologists alike. Ron Chapple, GEO1’s founder and CEO, came to lidar from a previous career in aerial cinematography. A few years ago, Chapple, 65, was hired to film an electrical transmission line for a municipal client. He and his team did the job so well, they joked, they should have won an Academy Award for best electrical infrastructure film. But as they were packing up their gear, another crew arrived, commissioned to capture imagery of the same transmission line. One of them pulled out a strange new device – not a camera, but a sensor. After trying it out themselves, Chapple and his team invested in their own light sensor equipment.
That decision proved transformative. Chapple now regularly finds himself on call, asked to support overseas archaeological expeditions. For a remote site in Colombia known as Ciudad Perdida, Chapple said, getting to the location on foot would have taken two and a half days of strenuous hiking, and exhaustively mapping the city’s every street and plaza would have taken years, if not decades, of fieldwork. Thanks to lidar, his team was able to capture most of the settlement in a single afternoon.
Processing the results is another story. A single survey can produce several terabytes’ worth of data, requiring powerful software to analyze and present the findings. “The original data only gets better over time as the algorithms improve,” Chapple says. “There was a time when the algorithm was throwing out too much noise – it was actually throwing out valuable points – because the filter hadn’t been adequately tightened. But with one software update, all of a sudden we had more data.” That means data captured five years ago can still reveal new features if Chapple runs it through updated software.
In the time between those two events, however, physical features,