Extremely Remote Sensing Remote sensing images from airplanes and satellites have become so remarkably clear that archaeologists can see things from space that can’t be detected at ground level. By Julian Smith
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rchaeologist Tom Sever was working as an image processor at NASA in the 1970s when he realized that the digital data coming in from recently launched satellites like Landsat just might revolutionize archaeology. Researchers had used aerial photographs to find sites as far back as World War I, but satellite images covered much larger areas and could be updated in days or weeks instead of years or decades. “I saw its potential from the beginning,” says Sever, now at the University of Alabama.“In my Ph.D. dissertation, I said remote sensing would be as important to archaeology as Carbon-14 dating.” He eventually convinced his superiors, and institutions like the National Geographic Society and the Smithsonian, that the new technology was worth a look, and archaeology had a new, powerful tool called aerial remote sensing (ARS). For the first time, researchers could study entire regions before setting foot on the ground, much less digging any
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holes. Sensors on aircraft (referred to as airborne) and satellites (spaceborne) could record wavelengths invisible to human eyes, mapping traces of human activity through slight changes in ground temperature, moisture, and vegetation. Some of the sensors could penetrate darkness, clouds, and forest canopies around the clock. In the early 1980s, archaeologists used NASA’s airborne Thermal Infrared Multispectral Scanner (TIMS) to find hundreds of miles of prehistoric roads surrounding Chaco Canyon in New Mexico. The scanner can measure temperature differences of 0.2 degrees Fahrenheit on the ground. With this technology, large-scale patterns in construction and settlement that can’t be detected at ground level can be seen clearly from above. Central America has been one of Sever’s most successful study areas.Working in the jungles where the Maya and other ancient peoples once lived is difficult. The dense vegetation can hide ruins, and archaeologists also have to contend
spring • 2010
