Researchers at the University of Vigo in Spain have studied more than 80 Roman and medieval bridges to learn how they are put together. Historians and engineers alike are interested to learn what the bridge-builders of old knew. Conservationists also want to know about any flaws so they can make sure the structures last far into the future.
Since taking apart a stone bridge that has been standing for more than a thousand years would be a bad idea, they needed another way to see inside.
They were able to do that with the help of ground-penetrating radar.
A ground-penetrating radar unit is made up of an antenna that emits and receives short pulses, a control unit and a computer. The ensemble can be set up in a type of cart (pictured above), in which the system is installed or in a mobile survey vehicle to collect data along the road of the bridge.
“The information from this system is combined with the information provided by the LiDAR or terrestrial laser scanner, whose beam sweeps over the whole bridge and in a few minutes takes the XYZ coordinates of millions of points of the monument,” says Dr. Mercedes Solla, one of the authors and current professor at the Defence Academy (Marín, Pontevedra).
The result is a mathematical computer model called a “point cloud,” from which detailed plans and 3D models of the bridge can be obtained.
This sort of approach is perfectly in line with the latest trends in archaeology. Whenever possible, researchers want to learn as much as they can without digging up, taking apart, or otherwise destroying the thing they are studying.
Not only does this preserve cultural heritage for its own sake, it means that far into the future even more advanced techniques can be used to learn about the past.
Photo credits: Grupo de Geotecnologías Aplicadas (UVigo)