The execution of non-invasive investigation is a fundamental element of archaeological fieldwork, employed in order to achieve effectively the main objectives without adversely affecting the archaeology under investigation, thus limiting the high costs of excavation and the possibility of damaging findings.
- Among the various techniques of geophysical prospection, magnetometry is one of the most suitable methods for the study of archaeological areas because of the rapidity of investigation, for the consequent economy of use, and for the easy portability of magnetometers. Magnetometry is a passive method because it receives subsurface signals and its employment is recommended in cases of soils with a low electrical resistivity (e.g., clay) and archaeological remains with magnetic properties (e.g., furnaces and fired clays). The principle on which magnetic prospecting is based is the measurement of variations, or gradients, in the geomagnetic field. These variations are related to contrasts in magnetic susceptibility between the archaeological remains and the surrounding subsoil.Magnetometric measurements can be taken over the ground surface, in tunnels, by air, on bodies of water, and within the boreholes. From an operational viewpoint, to obtain reliable readings, it is necessary to avoid disturbances caused by magnetic fields, induced by electric currents, or metallic objects, which can distort the survey results. In general, once a starting point is established, measurements are taken over defined areas, measurements that must be corrected by evaluating geomagnetic field profiles or maps due to the variability in time and space of the geomagnetic field itself.