Lasers of the Lost Ark
May. 24, 2010 — We talk about the myriad ways in which lasers will shape the future. Free-space optical communications for high-speed data transmission. Ultra-precise tumor excision, with minimal damage to the surrounding tissue. Formidable death rays to ward off the inevitable invasion of Earth. Less often discussed, perhaps, are the ways in which lasers can shed light upon the past.
Recently, a husband-and-wife team of archaeologists, Arlen F. Chase and Diane Z. Chase, reported an airborne survey of the ancient Caracol, a political center of the Maya lowlands found in present-day Belize. Using an advanced Lidar (light detection and ranging) system loaded into a twin-engine plane, they collected a wealth of data while crisscrossing the expansive site over the course of four days – the laser signals penetrating the dense jungle cover and bouncing off the ground below.
The data ultimately produced a topographic map of an area over 80 square miles in size, revealing settlement patterns, roadways and agricultural terraces. The archaeologists had spent 25 years on the ground charting the same area, but these nearly 10 hours of laser measurements, they said, yielded more topographic detail than they had achieved in all that time.
Lidar is a remote sensing technology similar to radar in that it determines the distance to an object or surface by measuring the time delay between the transmission and detection of a signal. Instead of radio waves, though, it relies on laser pulses, usually in the ultraviolet, visible or near-infrared range. GPS receivers record and triangulate the signals reflecting back from the ground, and computer processing creates images of the surface contours. The laser-based technology isn’t the only means to map archaeological sites from above, but it is the first that enables researchers to see beneath the forest canopy. Thus it can contribute in substantial ways to studies of the rainforest region and other, similar areas.
The Caracol researchers received support from what might seem an unlikely source: NASA. In fact, the space agency recently launched a funding program for remote sensing of archaeological sites from both air and space. Every two years, several three-year grants are awarded for such projects. Currently, the program is aiding two other Maya research efforts (in addition to the Caracol project), studies of settlement patterns in North Africa and Mexico, and surveys of ruins in the Mekong River Valley and in the area surrounding the temples of Angkor Wat. NASA has allotted roughly half a million dollars a year to the program. This is expected to double soon.
Even with the still-modest budget, some might question the relevance of a ‘space archaeology’ program at NASA, especially as recent changes have left the agency without a manned space program, which many consider to be its raison d’être. Anticipating this, perhaps, the program’s website provides an eloquent rationale for its efforts.
The lines of human history can be traced through the impact we have had on the environment, it says. Using remote sensing technologies such as Lidar, archaeologists can study the ways in which we have adapted to the environment, effectively and perhaps less so, where societies may have fallen and disappeared as a result. “Now we are ready to explore, and eventually colonize, the delicate environments of Space,” it continues. “Understanding how ancient man successfully managed Earth is important for the success of current and future societies.”
After 50 years, we are still finding new challenges to address using the laser, new mysteries to unlock. Continued advances in Lidar and other remote sensing technologies will only help us dig deeper, revealing yet more about the lives of the ancients and – hey, it could happen – moving us a step closer to living among the stars.
- An acronym of light detection and ranging, describing systems that use a light beam in place of conventional microwave beams for atmospheric monitoring, tracking and detection functions. Ladar, an acronym of laser detection and ranging, uses laser light for detection of speed, altitude, direction and range; it is often called laser radar.
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