Archaeologists have long studied the ancient, crumbling temples of Angkor in Cambodia as sites of worship and gathering. But how Angkor functioned as a city remained unknown.
Now, the airborne laser-scanning technology called lidar has helped fill those gaps, producing maps that reveal remnants of a highly engineered urban landscape hidden beneath a blanket of jungle and rice fields.
“In 20 hours of flying we achieved what may have taken decades of ground surveys,” said Damian Evans, an archaeologist at the University of Sydney in Australia.
Dr. Evans and an international team of researchers analyzed data from about 140 square miles surrounding three ancient Khmer sites: Angkor, Phnom Kulen and Koh Ker. From helicopters, lidar (light detection and ranging) bombards the ground with millions of laser pulses, some of which find their way to the forest floor through gaps in vegetation. It measures the distance between the instrument and the ground, allowing researchers to create high-precision elevation maps.
Researchers have greatly underestimated the breadth of urban landscapes that once surrounded the famous temples, the team concludes in a paper to be published in The Proceedings of the National Academy of Sciences. Roads crisscrossed the region and formed urban grids that extended far beyond the enclosed walls of Angkor Wat. Water management systems allowed a dense, formally planned downtown core to thrive.
The intensity of these developments may have contributed to the Khmer Empire’s undoing in the 15th century. The lidar suggests that deforestation accompanied urban growth, perhaps increasing the civilization’s vulnerability to the elements.
“We’re increasingly coming to the conclusion that these environmental factors played a role in the demise of the city of Angkor,” Dr. Evans said.
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