Employment of multiple GPR surveys in urban area, as part of the ERC Rome Transformed project.
Authors: Piro Salvatore , Zamuner Daniela , Verrecchia Daniele , Leti Messina Tommaso 
Published: February 2023

Important research and technical issues are related to the prospection in urban area to locate subsurface cavities and/or archaeological remains and to produce hazard mapping. In many cases, cavities, voids and collapses represent disruptions to the geometry of an originally near-horizontal layered system. Geophysical techniques can be employed to identify the feature geometries by contrasts in the physical properties, but can be strongly conditioned by cultural features that interfere with instrument measurements (utilities, structures, surficial debris).The most promising non-destructive geophysical prospection method for use in urban area is GPR. GPR measurements are less affected by the presence of metallic structures compared to magnetometer prospection and they result in the largest amount of data of all commonly employed near-surface geophysical methods, providing detailed three-dimensional information about the subsurface [1], [4]. In thist paper the surveys made with GPR to investigate different sites in the area of S. Giovanni in Laterano and Santa Croce in Gerusalemme in Rome, as part of the ERC funded Rome Transformed project (2019-2024) are presented and discussed. The aim of the GPR survey is to identify Roman and high-medieval age remains which could enhance understanding of the ancient topography and the urban evolution of the study area.For the surveys a GPR SIR3000 (GSSI), equipped with a 400 MHz (GSSI) bistatic antenna with constant offset, a 70 MHz (Subecho Radar) monostatic antenna and a SIR4000 system equipped with dual frequency antenna with 300/800 MHz were employed.All the GPR profiles were processed with GPR-SLICE v7.0 Ground Penetrating Radar Imaging Software. The basic radargram signal processing steps included: (i) post processing pulse regaining; (ii) DC drift removal; (iii) data resampling; (iv) band pass filtering; (v) background filter and (vi) migration. With the aim of obtaining a planimetric vision of all possible anomalous bodies, the time-slice representation technique was applied using all processed profiles up to a depth of about 2.5 m, [2], [3]. Ground Penetrating Radar (GPR) survey at the selected areas has produced significant and fruitful results that will be discussed during the presentation.&#160;References1 - I. Trinks, P. Karlsson, A. Biwall and A. Hinterlaitner, Mapping the urban subsoil using ground penetrating radar &#8211; challenges and potentials for archaeological prospection, ArchaeoScience, revue d&#8217;archeometri&#233;, 2009, suppl. 33,&#160; pp. 237-240.2 - D. Goodman and S. Piro, GPR Remote sensing in Archaeology, 2013, Springer (Ed), ISBN 978-3-642-31856-6, ISBN 978-3-642-31857-3 (eBook), DOI 10.1007/978-3-642-31857-3. Springer, Berlin, (Germany).3 - S. Piro S. and D. Goodman, Integrated GPR data processing for archaeological surveys in urban area. The case of Forum (Roma, Italy), 2008, 12th International Conference on Ground Penetrating Radar, June 16-19, 2008, Birmingham, UK. Proceedings Extanded Abstract Volume.4 - Piro S., Zamuner D., 2016. Investigating the urban archaeological sites using Ground Penetrating Radar. The cases of Palatino Hill and St John Lateran Basilica (Roma, Italy). Acta IMEKO, Vol. 5, issue 2, pp 80-85. ISSN: 2221-870X. DOI: 10.21014/acta imeko/v5i2.234 .&#160;