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A slice of ground penetrating radar data from Falerii Novi, revealing the outlines of the town’s buildings; Falerii Novi temple; GPR system.            Source: L. Verdonck / Antiquity Publications

Sacred Topography of Ancient Roman Town Revealed By Groundbreaking GPR

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Historians, architects, and archaeologists have long clashed over the way in which Roman towns and cities developed, largely because evidence of ancient urbanization is restricted to excavations at a handful of extensively investigated sites, such as Pompeii and Ostia. But now a team of researchers from the Faculty of Classics, University of Cambridge in the U.K. and the Department of Archaeology at Ghent University in Belgium have published a new research paper in the journal Antiquity detailing the results of their ground-penetrating radar (GPR) survey to investigate the sacred ancient topography at Interamna Lirenas and Falerii Novi. These methods, the paper concludes, will revolutionize the way we study ancient places.

Archaeologist posing with GPR kit at Falerii Novi (Image: F. Vermeulen / Antiquity Publications )

Mapping Ancient Urban Sites with Ground-penetrating Radar

According to the paper’s lead author, Dr. Lieven Verdonck, the historic evidence of Roman urbanization gathered from excavations at Pompeii and Ostia is “unrepresentative of the full variety of Roman towns”. The new paper presents the results of the first high-resolution GPR survey of two complete Roman towns: Interamna Lirenas, in the southern province of Frosinone in central Italy, and Falerii Novi, a walled town in the Tiber River valley, about 50 kilometers (31 miles) north of Rome and 6 kilometers (3.2 miles) west of Civita Castellana.

The paper begins by explaining that ancient Rome lay at the center of a network of cities that played a pivotal role in the administration, social organization and economy of the empire. By the first century AD, approximately 2000 cities had been established, and understanding this city network is “central to our knowledge of this period.” In the paper, the authors detail a new surveying method based on the creation of large-scale GPR datasets that they say have the potential “to revolutionize archaeological studies of urban sites.”

GPR time-slice, at an estimated depth of 0.80–0.85m. (Aerial photograph: Google Earth; image by L. Verdonck / Antiquity Publications )

Ground-penetrating Radar Provides Unprecedented 3D Detail

The reason archaeologists have failed to map ancient Roman cities is primarily because they have always focused on methods that yield evidence that is found “by chance,” for example in developer-led excavations. Consequently, according to the researchers, archaeologists are heavily reliant on evidence gathered from a small number of extensively explored Roman urban sites, such as Ostia and Pompeii.

Over the last two decades, developments in remote-sensing technologies such as magnetometry (predominantly fluxgate gradiometry) have produced increasingly detailed maps of complete Roman towns, and these scanning techniques are transforming ancient Roman urban studies. According to the new paper, GPR was used to create high-resolution 3D images of buried structures at “an unprecedented level of detail” in two complete scans of greenfield Roman towns in Italy: Interamna Lirenas and Falerii Novi .

Computer-aided object detection has been employed to create 3D representations: a) wall objects were projected onto a 2D map; b) 3D representations showing the same results, with floors semi-transparent. (Image: L. Verdonck / Antiquity Publications )

Archaeological Insights from Interpreting Enormous Datasets

To create their high resolution maps, the team of researchers assembled a database of “71.7 million readings, each consisting of 400 temporal samples, equal to 28.68 billion data points” which is equivalent to approximately 4.5GB of raw data per hectare (2.47 acres). In comparison, the writers state it would have required more than “20 hours per hectare to produce the manual archaeological interpretations.” It was this interpretational challenge that prompted the team to investigate new methods of computer-aided archaeological interpretation.

In the study, the archaeologists undertook a complete fluxgate gradiometer survey of Falerii Novi, resulting in a very clear plan of the entire site. Falerii Novi was founded in 241 BC and it was occupied through Roman times until the 7th century AD. Analysis of the GPR data at different depths allowed building plans to be understood more fully, and previously unrecorded public buildings, such as a temple, a macellum or market building and a bath complex, were identified.

Left: Falerii Novi’s temple; Right: Falerii Novi’s theatre (L. Verdonck / Antiquity Publications )

Digitizing Sacred Roman Topography with GPR Technology

The GPR work at Interamna Lirenas and Falerii Novi demonstrates the possibility of investigating ancient Roman towns as “total entities,” as opposed to the traditional method of studying a small number of extensively explored sites. Moreover, the magnetometer surveys revealed what the scientists described as a “sacred topography” of temples around the town’s periphery. Overall, GPR enormously enhanced the team’s understanding of these ancient landscapes.

Detailed investigations of expansive Roman cities produce vast amounts of data, and the interpretation of this data using manual methods is quickly becoming unfeasible. The paper’s GPR technology findings clearly show how computer-aided object detection can effectively fuse multiple geophysical datasets, and greatly enhance and speed up archaeological interpretation. The conclusion to the study was clear: there is little doubt that the future application of new analytical technology methodologies will “fundamentally change the ways in which Roman urbanization is understood.”

Top image: A slice of ground penetrating radar data from Falerii Novi, revealing the outlines of the town’s buildings; Falerii Novi temple; GPR system.            Source: L. Verdonck / Antiquity Publications

By Ashley Cowie

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