Laser technology is revealing the secret world of medieval hidden cities in the juggles of Cambodia.
Scientists and archaeologists have joined forces to scan beneath the trees and undergrowth around old temple of Angkor Wat to discover ancient cities dating back between 900 and 1,400 years.
The scale of the discovery is breath-taking as the cities are larger than the modern capital of Phnom Penh but have lain hidden to the world for hundreds of years.
Phnom Penh has a population of close to 2 million living across a sprawling metropolis of more than 250 square miles.
Led by Australian archaeologist Dr Damian Evans, the new technique involves scanning the ground with lasers from a helicopter.
How LIDAR works
A laser pod pulses 16 lasers per square metre as the helicopter flies at a predetermined height and speed over a grid beneath.
The time the GPS guided laser pulses take to reflect back to the pod determines the elevation of each point on the ground.
Data analysts then take the read-outs collected from the lasers to make a 3D model of the ground which are converted into maps.
The lasers can see through trees, foliage and soil to solid objects lying beneath.
Previously, archaeologists would have to dig to find the hidden walls and buildings.
The technique is called LIDAR – Light Detection and Ranging.
Angkor Wat is not the only place where LIDAR is changing the maps of civilisation.
Changing the course of history
Teams of archaeologists are also remapping the Mayan cities and temples of South America. Others have plans to revisit historical sites in Egypt, the Middle East, India and Asia to update our knowledge of ancient empires.
A massive building has already been discovered at the Nubian city of Petra in the mountains and deserts of Jordan near Aqaba.
The building lies close to other ruins but was overlooked by historians walking the site but was picked up by an airborne LIDAR survey.
LIDAR also has other applications – from mapping the seabed to guiding driverless cars.
The mapping is extremely accurate, with LIDAR rendering of objects as small as 20 centimetres across.
In Cambodia, the technology has revealed huge cities over a 735 square mile area of the jungle that would have made the largest empire and populated area on Earth during the 12thcentury.