Laser and Radar Let Researchers Peer Deep Inside Ancient Roman Bridges

Ancient stone bridges dot the Spanish hills. Some are still in use, and all play a part in defining the region's landscape and heritage. Now, researchers at Spain's University of Vigo can examine the inner structures of these bridges without disturbing a single stone, thanks to some incredibly powerful imaging technology.

The University of Vigo's Applied Geotechnology Group uses two high-tech imaging systems to scan ancient and medieval structures. Ground penetrating radar (GPR) puts a radar emitter and receiver on a mobile cart, sending short radar pulses into the ground near interesting artifacts and analyzing the signal received to understand the shape and layout of ancient structures.

The other technique, LiDAR, sweeps a laser beam over visible, above-ground structures, gathering millions of dimensions and measurements. When combined, the GPR and LiDAR data generates a virtual, 3D blueprint with precise measurements of both the visible and hidden parts of the structure.

Dr. Mercedes Solla with the project explains how the technology gave a new glimpse into an ancient bridge in Monforte de Lemos, Spain: "as well as obtaining information like the thickness of the stones inside, the GPR has reported the existence of two hollow arches in this medieval bridge, hidden underground at one of the edges."

The technique has given both historical and structural insight into about 85 structures the team has scanned. The team has identified structural cracks and centuries-old repairs in many bridges, detecting the different types of stone used in different eras to keep certain bridges sturdy. They've even discovered previously-unknown stone engravings, and gotten insight into the ancient engineering that allowed these structures to survive for millennia.

The team's findings have wide-ranging impact, according to Solla. "All this information is of historic interest, but it is also useful to civil engineers so that they can plan conservation, improvement and restoration measures in these types of infrastructures." It's just one more example of how cutting-edge technology can help better our understanding of the ancient world. [ASCELibrary via ScienceDaily]

Image: Grupo de Geotecnologías Aplicadas (UVigo)