LiDAR Reveals Hidden Archaeological Ruins
In April 2012, McElhanney conducted an extensive aerial LiDAR survey in support of archaeological research in Cambodia. It was the first such project in Southeast Asia and the world’s largest archaeological LiDAR survey to date, covering an ambitious 270 square kilometres over Angkor and surrounding areas.
Angkor is one of the most important historical regions of Southeast Asia, containing the ruined capitals of the Khmer Empire, the major power in Southeast Asia between the 9th and 15th centuries. Believed to have been the largest pre-industrial urban complex in the world, Angkor may have supported a population of up to one million people at its peak. Its most famous temple, Angkor Wat, attracts some two million tourists each year and is depicted on the Cambodian flag.
Many of Angkor’s temples are surrounded by heavy forest, and much of the landscape is littered with land-mines and unexploded ordnance, remnants of the reign of the Khmer Rouge. Much of the exploration undertaken over the past 150 years has been carried out by ground survey, which is both difficult and dangerous. LiDAR, an acronym for Light Detection And Ranging, uses an airborne laser scanner to capture data coordinates at regular intervals. This results in an extremely detailed and accurate picture of the topography, even through dense vegetation.
Within days of receiving the LiDAR data, the archaeologists knew that the results were “going to be huge.” One of the first major findings was a settlement discovered surrounding the known temple of Beng Mealea. The area is covered by forest as well as land-mines; the only known features were a collapsed temple and a large moat. LiDAR has revealed the area as an intricate, planned settlement with a network of gridded roadways and ponds. It has been impeccably preserved, offering researchers a first-hand view of a 12th century Khmer city.
The data have also revealed evidence of settlement far beyond the traditional boundaries of Greater Angkor, including Mahendraparvata, a “lost city” in the mountains of Phnom Kulen. Residents of Anlong Thom, a modern village constructed on top of the buried ancient city, were entirely unaware of its presence.
Even in areas studied extensively, LiDAR can detect previously undiscovered features or provide a new level of detail. Some of the first data examined was of the forested enclosure of the temple Ta Prohm, best known as the site of the movie Tomb Raider. An entire ancient city has been revealed beneath the forest, with a precisely laid out grid of streets, canals, ponds, and occupation mounds, which no one had ever noticed in spite of 150 years of research and two million tourists per year.
More than a year after the data was collected, the archaeologists’ first phase of analysis is complete, and their results have just been released. Planning is now underway for future project phases, including securing the necessary funding to acquire additional LiDAR data. The archaeologists’ map ends at the extents of the current LiDAR survey, indicating an abundance of treasure yet to be discovered.