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Rural basilicas are the most important evidence of Christianization of the countryside on the island of Mallorca (Balearic Islands, Spain). Recent investigations of rural landscape transformations suggest that some churches were built along communication routes and linked to pre-existing settlements. To obtain new data that could support this hypothesis, a geophysical survey has been carried out at the early Christian complex of Son Peretó, one of the most emblematic sites for the understanding of Late Antiquity on the island. The objective was to better define the site that is undergoing excavation, and to investigate the possible presence of other constructions further than the Christian complex. The geophysical survey was carried out combining magnetometry and groundpenetrating radar. For the magnetic investigation of large site areas, a 7-probe fluxgate gradiometer array LEA MAX was used. GPR was used to examine the areas nearby the remains already excavated and to better define areas where magnetometry revealed interesting anomalies. GPR was developed by means of the IDS GPR system, which was based on the Fast-Wave module. The results revealed both the presence of architectural remains beneath the soil that help define the early Christian complex, as well as other remains that suggest the church was part of a larger settlement.

Two rural sites on the island of Mallorca (Balearic Islands, Spain) have been investigated with geophysical methods. A previous archaeological field survey provided surface ceramics that allowed for a first classification of the sites as possible Roman rural settlements, possibly villae. The objective of the investigation was to work towards the identification of architectural remains to better understand the true nature of the sites. Using the 7-probe fluxgate gradiometer array LEA MAX, magnetic measurements were executed on a large area on each site. GPR measurements were subsequently carried out to examine selected areas of interest in detail by means of the IDS GPR system based on the Fast-Wave module. The investigated areas demonstrated excellent surface conditions with a negligible number of sources of disturbance, permitting a detailed interpretation of the geophysical data. The results helped to reveal the presence of architectural remains beneath the soil at both sites.

Archaeological geophysics is a vital part of exploring and documenting cultural heritage. Three of the most commonly used techniques are magnetometry, resistivity, and ground penetrating radar. These methods help archaeological geophysicists to unravel the complexity of many archaeological sites, including urban ones, old buildings, and built structures of cultural importance. However, local factors, such as constraints on time, local environment, pre-existing available information, and budgets, all contribute to a given site requiring unique geophysical surveying strategies. Four Spanish-based, but generally applicable, case studies will illustrate key geophysical strategy types for particular local archaeological conditions.

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner–Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.

Geophysical survey methods are broadly used to delimit and characterize archaeological sites, but the archaeological interpretation of geophysical data remains one of the challenges. Indeed, many scenarios can generate a similar geophysical response, and often interpretations can not be validated without access to the subsoil. In large geophysical surveys many anomalies are detected and validation through archaeological trenches can not be afforded. This paper analyses the validity of geoarchaeological core survey to check the archaeological interpretations based on geophysical results. The Roman site located at Auritz/Burguete and Aurizberri/Espinal (Navarre), provides a great case of study as many investigations have been carried out. After the gradiometer survey performed in 2013 a sediment core survey was designed. 132 cores were drilled using a hand-held coring machine and the sediments were analysed in situ. Site delimitation and archaeological interpretations based on magnetic data could be improved or corrected. In this regard, the core survey proved to be an useful methodology as many anomalies could be checked within reasonable time and resources. However, further geophysical investigations trough GPR revealed unexpected remains in areas where no archaeological deposits were identified through coring. Excavations showed poor conservation level in some of those areas, leading to thin archaeological deposits hard to identify at the cores. The sediment core survey, therefore, was proved to be inconclusive to delimit the archaeological site.

This paper presents the results of a multisystem survey using magnetometry and dual frequency ground-penetrating radar (GPR) carried out at the Iron Age Iberian site of El Moli d'Espigol, Tornabous, Catalonia, dated from the seventh to third centuries bce. The surroundings of the current urban area were explored with magnetometry in order to describe possible features related to the settlement. In the non-excavated part of the urban area was surveyed by GPR in order to describe the urban mesh. The interpretation of the data has allowed not only the identification of new areas of archaeological interest and priority action, but also the proposal of a new hypotheses on the evolution of the town planning and the defensive system of the site. Copyright (c) 2013 John Wiley & Sons, Ltd.

High-resolution methods are required in the non-destructive study of historical buildings, archaeological sites and cultural heritage structures in general. Ground-penetrating radar (GPR) is widely used in such studies. However, radar images of archaeological sites and cultural heritage architecture tend to be unclear and are difficult to interpret. Knowledge of the antenna’s behaviour and the optimum expected resolution could help to interpret radar data and define a limit of the real resolution in field surveys. Laboratory tests could provide information about the optimum resolution for each specific antenna. The main goal of this study was to obtain experimental data under lab conditions and thus define the optimum resolution expected in radar surveys. This could then be considered as a limit in field surveys. All of the lab tests were performed using homogeneous media (water and sand) to avoid interference and clutter. As a result, simple images were obtained. The optimum resolution was defined from radar data acquired under these favourable, controlled conditions. In all cases, resolution was defined as the distance (considered as a function of wavelength) between two targets (in the vertical or horizontal axis) that were needed to obtain separate anomalies. All the optimum values were considered to define the limits of the survey resolution in the different cases presented in this paper. In each case, the optimum values were compared with the result and with the radar images to define the best approach to the expected resolution in architectural heritage surveys. To conclude, we define some experimental values of the optimum resolution, described in terms of wavelength. These experimental data are likely to provide a better approach than theoretical estimations.

Introduction The paper presents the results of the use of alternative geostatistical and statistical methods to enhance visualization of the Tarragona Cathedral. These methods improve data homogeneity with time/depth, give alternative time-slice computation using other values than the mean value, and study the impact of the time-window thickness used when generating time-slices. The data used for the project was a GPR prospection of the cathedral accomplished in 2007 by Roger Sala and Ekhine ...

Introduction A 3D GPR investigation, combined with fluxgate magnetometer, has been carried out on a hill fort called Castro de la Magdalena in León (Northwest of Spain). The archaeological investigation started after remains of Celtiberian culture (dated from the first Iron Age) and a later Roman occupation were discovered in a town nearby. Figure 1: A shows the results of shallow excavations (15-30 cm) over the Roman settlement. B shows location of Roman villa and castro areas. C shows a sil...

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to detect the existence of archaeological remains of the Roman’s temple devoted to August. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most famous temple of Spain (12th century) evolving from Romanesque to Gothic styles. A project including electrical resistivity tomography (ERT), ground probing radar (GPR) and frequency domain electromagnetics (FDEM) has been planned over one year and conducted during a week of intensive field survey. From all the methods applied, both ERT and GPR have provided some detailed information on subsoil structures. The ERT method has been applied with different techniques and arrays, ranging from standard Wenner-Schlumberger 2D sections to full 3D electrical imaging using the MYG array. Electrical resistivity data have been recorded extensively and therefore, 70.000 apparent resistivity data were available to obtain a full 3D image after an integrated inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists.

An integrated geophysical survey was conducted in September 2007 at the Cathedral of Tarragona to search for archaeological remains of the Roman temple dedicated to the Emperor Augustus. Many hypotheses about its location have been put forward, the most recent ones suggesting it could be inside the present cathedral. A project including Electrical resistivity tomography (ERT) and Ground probing radar (GPR) was planned for a year and conducted during a week of intensive field survey. Both ERT and GPR provided detailed information about subsoil structures. Different ERT techniques and arrays were used, ranging from standard Wenner-Schlumberger 2D sections to full 3D electrical imaging using the MYG array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity points to obtain a complete 3D image after full inversion. The geophysical results were clear enough to persuade the archaeologists to excavate the area. The excavation confirmed the geophysical interpretation. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by recent archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province.