Acquisition and processing of electric, magnetic and GPR data on a Roman site (Victimulae, Salussola, Biella)

A multi-method geophysical survey has been carried out on a Roman archaeolo gical site, where part of an apse had previously been found and then refill ed by archaeologists during an excavation test. Magnetic gradient measureme nts were performed over the whole study area and a sub-area of interesting anomalies beside the excavation test site was found. Two-dimensional filter ing of a more detailed magnetic gradient map and 2D inversion of magnetic p rofiles were performed, using an on-purpose implemented software, in order to reduce the effect of noise and to stress the eventual presence of buried structures in agreement with the archaeologists' hypothesis. Resistivity t omography and GPR profiles were carried out along some selected profiles to obtain information on the vertical distribution of the anomalous bodies. G PR profiles, carried out in the area containing the test excavation, suppli ed good results, particularly when processed as time slices. The whole stru cture of the apse was clearly outlined. The authors were then able to sugge st to the archaeologists further excavation tests on the basis of GPR resul ts and of the filtered magnetic gradient map. A comparison of the results o f the applied surveying methodologies has supplied an example of the relati ve strengths and weaknesses of the different electric, magnetic and GPR tec hniques. (C) 1999 Elsevier Science B.V. All rights reserved.