Geophysical prospection at Portus: an evaluation of an integrated approach to interpreting subsurface archaeological features

Portus, located just north of the Tiber River, Italy, was the port of ancient Rome during the imperial period. The Portus Project is a current project funded by the Arts and Humanities Research Council (AHRC) in collaboration with the Soprintendenza per i Beni Archeologici di Ostia e Porto, and the Universities of Southampton and Cambridge, and is a flagship project of the British School at Rome (BSR). Extensive and intensive geophysical prospection has been employed at Portus within recent years, providing an integrated methodology for discerning the nature and extent of the archaeological remains of the port complex. Recent excavations have allowed for a reciprocal relationship between geophysical and archaeological research, and have paved the way for a regime of meaningful, integrated geophysical research at Portus. Increasingly, archaeogeophysicists have begun to take an integrated approach to the use of multiple survey methods to investigate potential archaeological features. Here, many types of geophysical and archaeological survey methods have been employed, including magnetometry, electrical resistance, ground-penetrating radar, standing building, and micro-topographic survey, to survey the archaeological record, provide an immense volume of data to be compared and contrasted to the excavation data, and facilitate the interpretation of the archaeology at the site. Often when a multi-method approach is taken, the interpretations, analysis, and presentation of the resulting data is limited to side-by-side comparisons of gray-scaled graphical representations of the data. A distinction is made here between integrated survey methodologies and integrated data analysis. Recent developments in geophysical data analysis have suggested that in addition to a multi-method approach, data fusion techniques can offer meaningful insights into archaeological features and allow researchers to establish patterns between multivariate data sets that might otherwise go unnoticed. (Kvamme 2006a, 2006b, Neubauer et al. 1997, 2002, Piro et al. 2000) The sheer quantity of data, as well as the nature of the archaeology at Portus, have provided an ideal site for the exploration of spatial data and remote-sensing analysis techniques, as well as the assessment of their utility within archaeo-geophysical research as whole. This research attempts to critically assess the field and data processing methodologies used and examine the applicability of a variety of mathematical and multivariate analysis approaches to the prospection results at Portus.