Cambodge : Record-breaking aerial laser survey to reveal Kingdom's historical secrets
Following the incredible discoveries of the first ‘lidar’ project around Angkor Wat, archaeologists have big hopes for a second, much-larger survey
In 2013, Cambodia made world headlines when an expansive survey using airborne laser technology revealed not only that the city of Angkor was even more monumental than previously thought, but that another enormous ancient city, Mahendravarpata, lay beneath the jungle-covered plateau of Phnom Kulen, northeast of Siem Reap.
Now a second, even more expansive survey is about to take place using the same laser imaging detection and ranging technology, known as ‘lidar’.
Aerial lidar surveys involve firing millions of laser beams at the ground and measuring the time they take to bounce back, using tiny differences in time to calculate elevation variations.
The Angkor project, which was the most extensive archaeological lidar survey ever conducted, used a particularly high concentration of beams to ensure that some made their way through the trees to the earth below and then back to the machine.
After a computer screened out results reflected from vegetation, the data revealed incredibly detailed images – up to a resolution of a few centimetres.
With these highly detailed topographical maps, the archaeologists were able to discern features hidden to them previously.
While the first lidar survey covered only 370 square kilometres over Angkor Archaeological Park, Phnom Kulen, and the temple complexes of Beng Mealea and Koh Ker, the new wide-ranging survey will cover 1,600 square kilometres. Locations will include Banteay Chhmar (Banteay Meanchey province), Preah Khan of Kompong Svay (Preah Vihear province), Sambor Prei Kuk (Kampong Thom province), and Longveck/Oudong (Kampong Speu province).
Damien Evans, research fellow at the École Française d’Extrême-Orient and the scientific director of the new five-year project that is being funded by a $1.6 million European Research Council grant, said it would provide remarkable new insight into the Kingdom’s history.
“What we’ll end up with is this quite amazing 1,500 to 2,000 year archive of the way that cities grew and developed over the course of the flourishing of Khmer civilisation,” he said.
“So it provides a unique overview that really doesn’t exist anywhere in the world, from nearly 2,000 years ago up until the present day, about how cities evolved and how humans interacted with their environment.”
Previously there had been little research done on the sites to be targeted, he said.
“The great value of having lidar is that it allows us to image these cities with great clarity for the first time and present us with the opportunity to identify critical points within the cities that provide the greatest opportunities for excavation,” he said.
He added that the program was supported by the Cambodian government and Deputy Prime Minister Sok An was keen to use the lidar data as a tool for UNESCO World Heritage nomination.
“What the lidar data allows us to do is more intelligently define particular protected areas, zone the areas of archaeological value, and better target resources more effectively for the management of those sites. This will therefore be a critical component of the nomination of further World Heritage sites in Cambodia.”
Tan Boun Suy, deputy director-general of the Apsara National Authority and administrative director of the new Cambodian Archaeological Lidar Initiative, said the results of the data from the first survey had been useful for the authority.
“We now better know about the infrastructure at the time. Before the lidar survey, we didn’t expect there would be such sophisticated infrastructure at Koh Ker and at Angkor,” Boun Suy said.
“We have moved the parking, for example, because we didn’t realise that it was located on ancient ponds.
“It’s been very useful to the International Committee for Coordination (ICC) at Angkor, which now recommends that all teams consult the lidar data before doing something. The role of lidar data has become very important in our work.”
Jean-Baptiste Chevance, program manager of the Phnom Kulen-based Archaeology and Development Foundation, said the data had been used to help demarcate and define protected area on Phnom Kulen.
“There is a huge deforestation problem threatening the archaeological sites,” Chevance said. “The lidar data enabled us to enlarge the area and create new buffer zones to enclose and protect those archaeological features that were not known before, including a series of mounds, ancient roads, ponds, and plots associated with the ancient capital on Kulen.
“In terms of archaeological research, it has had major input, because we have been able to see and excavate the network that was established in that city in the ninth century.
“There was also a road project that would have gone across the whole plateau from the main checkpoint right to the east side, so the data will be helpful to direct and redirect the road around the archaeological sites so as not to destroy them.”