A publication of the Archaeological Institute of America
An aerial imaging system developed by NASA's Jet Propulsion Laboratory (JPL) and trained on a 700-square-mile area encompassing Angkor has yielded new data about the origins and development of the Khmer site. Elizabeth Moore of the University of London's School of Oriental and African Studies has used the data to study the paleohydrology of Angkor, the subject of much debate over the years. Images produced from the data show no evidence that a moat completely surrounded the city in the tenth century A.D., but do reveal ancient river channels, whose existence has long been disputed. Remnants of circular earthworks 30 miles northwest of Angkor may be evidence of prehistoric water management, says Moore.
The Angkor radar images were taken in late 1996 from a NASA DC-8 equipped with Airborne Synthetic Aperture Radar (AIRSAR), a device that transmits and receives three radar frequencies, including a long wavelength that can penetrate the forest canopy (see "Wonders of Radar Imagery," September/October 1996). The data were used to make a map stretching east, west, and north of the ancient city, enabling Moore and JPL radar engineers Anthony Freeman and Scott Hensley to document both central and outlying areas.
This past December, Moore surveyed a number of features revealed by the radar. Freeman had spotted a small mound on the perimeter of a mid-twelfth-century moat. French archaeologists had recorded the mound early in this century, noting three temple bases and a tenth-century inscription calling the site Kapilapura. Moore's survey indicated there were more temples, leading her to conclude that the mound had been overlooked as evidence of long-term occupation at the site.
Moore, Freeman, and Hensley plan to inventory and survey more of the features revealed by the radar imaging, with the exception of those northwest of Angkor that lie in areas of civil unrest.