London, Nov 21 (IANS): With the help of a laser system called the Light Detection and Ranging (LiDAR) technology that is attached to an aircraft, archaeologists discovered a vast gold mining network created by the Romans more than 2,000 years ago in Spain.

Hidden under the vegetation and crops of the Eria river valley, in Leon, the researchers also unearthed the complex hydraulics system used by the Romans in the first century BC to extract gold including channels, reservoirs and a double river diversion.

"The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures," said co-author of the study Javier Fernandez Lozano, geologist at the University of Salamanca in Spain.

The specialists consider that the systems for the transport and storage of water were replicated from those already existing in North Africa, where the Egyptians had been employing them for centuries.

"We have established that the labour that went into extracting the resource until its exhaustion was so intensive that after removing the gold from surface sediments, operations continued until reaching the rocks with the auriferous quartz veins underneath," Fernandez Lozano added.

The researcher said that the real discoverer was the LiDAR technology: "Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas".

LiDAR comprises a laser sensor which scans the ground from an aircraft or drone with geographical references provided by GPS (geographical positioning system) ground stations.

This technology was developed by NASA in the '60s to analyse the retreating sea ice in the Arctic and composition of the oceans.

The study was published in the Journal of Archaeological Science.