Near-surface imaging of a buried foundation in the Western Desert,Egypt, using space-borne and ground penetrating radar

ALOS/PALSAR L-band full polarimetric data have been used to detect and characterize a well-defined geometric target hidden under sand deposits in the Western Desert of Egypt. This buried object is rectangular in shape with very straight boundaries and encloses an area of 500 m². Inside the rectangular area there is a perfectly circular feature of approximately 53 m² area. High and medium resolution optical satellite images (WorldView-2, ALOS/AVNIR-2) and field investigation confirm that the topography of the study area is relatively flat and completely covered by dry sand. The electromagnetic wave scattering behavior of the detected buried object was measured by decomposing the scattering matrix of ALOS/PALSAR full polarimetric data into Entropy-Alpha (H/α) and Freeman and Durden decompositions. Furthermore, a combination of unsupervised classification algorithms and Constant False-Alarm Rate (CFAR) edge detection was performed on the polarimetric data which revealed a well-defined geometric shape with straight borders. These borders have high α angles with low entropy, which physically means double bounce scattering mechanism with low randomness and is very similar to that of an urban scatterer, indicating that the detected target might be a buried wall-like foundation of a man-made structure. Moreover, 28 ground penetrating radar (GPR) profiles were acquired using a 270 MHz shielded antenna to validate the satellite radar remote sensing results. The GPR profiles reveal very clear hyperbolic shapes at 1.5 m depth with one of them showing a large hyperbolic shape-like structure, which might indicate the presence of a buried foundation. Thus the site might have significance to archaeological studies of the Western Desert, particularly previous human occupation and the sources of water for such habitation.     

MAPPING THE UNDISCOVERED RUINS OF POMPEII (NAPLES,ITALY) USING GROUND PENETRATING RADAR*

The ground penetrating radar (GPR) technique was tested in Pompeii, in an unexplored area where the Roman ruins are partially buried in the volcanic deposits. The method was also combined with time domain reflectometry (TDR) measurements to estimate the dielectric properties of the different volcanic units. In spite of the total thickness of the covering materials and the high signal attenuation measured in some layers, the radar was able to show a detailed image of the volcanic sediments and to locate the manmade structures hidden in the ash deposits. Moreover, the present study shows that the integrated use of GPR and TDR techniques could be successfully employed to evaluate the performance of the radar in specific terrains covering archaeological sites. Since it is unlikely that a large part of Pompeii will ever be excavated, GPR could be successfully used to produce detailed maps of the ruins still hidden in the subsurface, giving archaeologists the possibility of reconstructing the entire urban development of this unique ancient city.     

GPR and inductive electromagnetic surveys applied in three coastal sambaqui (shell mounds) archaeological sites in Santa Catarina state, South Brazil

In this article, GPR – Ground Penetrating Radar and inductive electromagnetic (EM38 equipment) results are presented for three archaeological sites of shell mounds located between Laguna and Jaguaruna cities, mid-southern coast of Santa Catarina state, Brazil. The Jabuticabeira II, Santa Marta IV, and Encantada III sites were studied. These sites consist of carbonate shell mounds built by societies that inhabited this region during the pre-colonial period (7.5–1.3 ky BP). Geophysical responses obtained in these archaeological sites had allowed the identification of anomalous regions related to archaeological point targets as well as continuous targets, correlated to the shell mound's structure and buried geologic features. GPR numerical modelling studies were done in order to evaluate the performance of the GPR method in relation to materials found in that environment, besides helping interpretations of real results. The synthetic GPR model was a good match with real data obtained in the field. So, the real and synthetic results serve as a reference guide to direct excavation activities in these archaeological and geological structures. In the Jabuticabeira II shell mound, lithic materials and burials were found amidst archaeological layers characterized by sediment rich in organic material, ferruginous concretions, and loose shells. In the Santa Marta IV archaeological site, a concentration of ceramic materials, burials and fireplaces were found. In the Encantada III site, a strong anomaly characterized by a hyperbolic reflection was related to the presence of a silicified tree root; a great example of ambiguity in shallow geophysics interpretation in archaeological applications. Results functioned as a guide to archaeological excavations, allowing cost and time reduction as well as contributing to improve the knowledge of these archaeological sites situated in southern Brazil.     

Integrated near-surface geophysical survey of the Cathedral of Mallorca

This paper describes an integrated near-surface geophysical study carried out in order to obtain high-resolution images of the shallow subsurface under and around the Cathedral of Mallorca. The study was a part of a global project focused on determining the state of the building structure and on evaluating the Cathedral's dynamical behaviour (natural frequencies and vibration modes). Ground-penetrating radar (GPR) and the capacitively coupled resistivity method were used to obtain 2D images of the shallow subsurface. Refraction microtremor array measurements (ReMi) were also used to characterize the rock and soil properties and several invasive boreholes provided detailed and exact information on the stratigraphy. The information from the geophysical data was used to determine a final model of the ground, with indications of the most likely vulnerable zones.     

GPR survey at Lapa do Santo archaeological site,Lagoa Santa karstic region,Minas Gerais state,Brazil

In this work we present and discuss the results of a novel and timely GPR-2D and GPR-3D survey performed at an archaeological rock shelter site, Lapa do Santo, localized in the karstic region of Lagoa Santa, central Brazil. A total of 113 ground-penetrating radar profiles were acquired with 200 MHz and 400 MHz shielded antennas aiming in identifying geological and archaeological anomalies in order to assist archaeologists in an excavation program. The GPR results indicated clear geophysical anomalies characterized by hyperbolic reflections and areas with high amplitude sub-horizontal electromagnetic waves. The anomalies observed by GPR were confirmed by the excavation of test units, allowing the identification anthropogenic features such as a fire-hearth structure and wooden artifact, and natural features, such as, tree roots and rocky bodies such as speleothems, boulders and bedrock. The results showed the efficiency of GPR method in identifying potential buried archaeological targets in cave sites within a karstic area, and they oriented to archaeological excavations, reducing costs and increasing the probability of finding archaeological targets in the initial stages of a project.     

Assessment of fractures in some columns inside the crypt of the Cattedrale di Otranto using integrated geophysical methods

We investigate the problem of internal fracturing of the columns of a building of cultural importance (the Crypt of the “Cattedrale di Otranto”, Apulia, Italy), using a multi-disciplinary approach, integrating different non-destructive techniques (Microclimatic and Geophysical). In fact historic buildings, over centuries, may accumulate a high concentration of water and/or moisture that increases significantly the deterioration rate, diminishing the mechanical resistance.     

DETECTING TRENDS IN THE PREDICTION OF THE BURIED PAST: A REVIEW OF GEOPHYSICAL TECHNIQUES IN ARCHAEOLOGY*

Geophysical survey techniques are a highly visible part of the scientific toolkit that is now used by archaeologists. In this paper, the history of the use of geophysical techniques in archaeology will be discussed, as will significant research themes associated with the most widely used prospecting devices. It is apparent that while the use of geophysical techniques is at an all‐time high, there are many key areas where prospecting is rapidly developing. Some of the advances relate to fundamental aspects of the techniques, while others dictate how we undertake survey in the future. There is a movement away from pre‐gridded survey areas towards real‐time GPS for navigation. This allows greater integration, or fusion, of disparate data sources using visualization techniques derived from associated disciplines. The analysis of landscapes has become a major component of the application of new technology and there are many challenges to be tackled, including how to analyse and interpret significant archaeology within large‐scale, data‐rich, multi‐technique investigations. The reflective nature of the review acknowledges the important role of Archaeometry in the development of archaeological geophysics.     

Improving the interpretability of 3D GPR data using target–specific attributes: application to tomb detection

Three–dimensional (3D) ground–penetrating radar (GPR) represents an efficient high–resolution geophysical surveying method allowing to explore archaeological sites in a non–destructive manner. To effectively analyze large 3D GPR data sets, their combination with modern visualization techniques (e.g., 3D isoamplitude displays) has been acknowledged to facilitate interpretation beyond classical time–slice analysis. In this study, we focus on the application of data attributes (namely energy, coherency, and similarity), originally developed for petroleum reservoir related problems addressed by reflection seismology, to emphasize temporal and spatial variations within GPR data cubes. Based on two case studies, we illustrate the potential of such attribute based analyses towards a more comprehensive 3D GPR data interpretation.     

The mosaic of the crypt of St. Nicholas in Bari (Italy): integrated GPR and laboratory diagnostic study

The crypt of St. Nicholas in Bari, Southern Italy, is a building of cultural worldwide importance. Inside the crypt a mosaic develops on the apsidal floor and along a parietal seat placed along the apsidal masonry, in the form of cladding. A surviving portion of the mosaic pavement is also preserved in the right lateral chapel. Integrated non-destructive survey and laboratory analyses were undertaken for the diagnostic study of the mosaic. GPR prospection was successfully applied to the study of its conservation state, that is strictly related to the condition of the subsoil, in particular to the presence and distribution of water. The presence of water, whose rise interests also some portions of the masonry and water content distribution were identified by the results of electromagnetic wave velocity analysis in GPR data.     

Applications of integrated geophysical method in archaeological surveys of the ancient Shu ruins

The Jinsha site is one set of excavated ruins of the ancient Shu state, late Neolithic, early Bronze Age. The archaeological survey of the site is especially important for study of Shu culture, because there is hardly any written record of this period. As technology progresses, more and more advanced techniques and equipment have been used to conduct archaeological surveys. In this study, four nondestructive methods of geophysical detection were used to locate ancient relics at the site. The validity of these different types of archaeological detection methods (method of high-density resistivity, induced polarization, multi-frequency electromagnetic, ground-penetrating radar and so on) and techniques were analyzed. And a multi-scale, multi-method detection system to non-destructive detection of cultural relics was established.