Altino (Venice)
Roman Town

Campagna Lupia
(Venice)
Roman Temples

MAGNETOMETER SURVEY

The magnetic method is based on the measurement of the Earth magnetic field’s. Proton magnetometers   and   more    recent   cesium   magnetometers   both    normally  used  in gradiometer configuration,  allow  to cover large areas in a limited time recording a huge amount of data. The magnetic survey, whatever is the instrument used, has as main goal to locate the Earth magnetic field’s  changes; usually the changes or magnetic anomalies are produced by underground  archaeological  structures.  Two different mechanisms are responsible of the appearance  of  magnetic  anomalies:  the thermoremanent magnetism and the induced magnetism.    The  first   is  responsible  of the anomalies associated with structures such as kilns, hearts,  foundations and  walls  made by brick or magmatic rock, the second  generates  the  anomalies connected to archaeological structures filled with a high susceptibility material,  as  in  the case of pits, graves and ditches. After finished the survey,  great  importance  is   the  way  in  which  data  are   elaborated; the   well  known image–processing  algorithms  if  correctely applied,  are able to reveale the presence of anomalies otherwise not identifiable;   but  it  mustn’t forget that the same algorithms can produce spurios artefacts.