From GPS to GPR. A new technology

By now, GPS technology has become a household item, and GPR is opening new ways for us to explore, although with a different purpose.

GPR stands for Ground Penetrating Radar, a technology that allows us to actually “see” remains of buildings that are still hidden deep underground. This procedure is particularly interesting in those cases when a site cannot be excavated either because it is too large or because the remains are buried underneath modern cities or constructions. An extra bonus is the fact that the pictures taken by GPR are rendered in very high resolution.

The process looks rather simple since GPR works like regular radar but can reflect the pictures from different depths. The instrument can be attached to a quad bike and run over the terrain that needs to be investigated.

[Ground Penetrating Radar map of Falerii Novi, Italy. (Credit: L. Verdonck)]

This GPR recently made headlines when archaeologists surveyed the hidden site of Falerii Novi situated some 50 kilometers north of Rome. So far, they have been able to recognize the market, a bath complex, a temple and several other public monuments. What’s more, they could even study how the city evolved from its foundation in 241 BC till it disappeared around 700 AD. It extended over a surface of 30 hectares, which equates about half the size of Pompeii.

The study also revealed that the layout of Falerii Novi is far less conventional than that of other known towns. Moreover, it appears that the architecture of the buildings is more elaborate than what we would expect from a small city like this one.

At the southern end of Falerii Novi, the GPR has pinpointed a large rectangular building that is connected to a series of water pipes leading to the aqueduct. The pipes could be traced further as they run beneath houses and not only through the streets as one would expect. The rectangular construction may well be a public pool.

In the end, of course, GPR does not replace hands-on excavations, but diggings can focus on specific areas and constructions as they will immediately fit into the broader overview of the site. At present, the data is being analyzed manually, which is very time-consuming. Scholars are working on developing some new automated techniques to speed up the process.

Similar surveys have been tentatively carried out at Interamna Lirenas (south-east of Rome) in Italy and in Alborough, Northern Yorkshire in the UK. Still researchers are aiming to use GPR to survey major cities as well. Their ambition includes sites like Miletus in Turkey, Cyrene in Libya, and Nicopolis in Greece, which are all spread out over a vast area. 

Personally, I would like to consider places like Damascus, Cairo, and Ecbatana,  which are entirely hidden by modern constructions. Unfortunately, the local governments inevitably have the final say.