2D Inversion Ambiguity in the Case of ERT Data Obtained from a Single Survey Line

The case of 2D ERT method, where the object is beyond the survey line, was analysed. ERT surveys for two profiles, localized next to the building containing a cellar, were made. Analogue modelling simulating field surveys was made as well. Empty underground spaces generate high resistivity anomalies visible in apparent resistivity pseudosections. 2D inversion results suggest existence of objects which are not present in reality. Although the modelled and field situations are geometrically similar, the inversion results differ. We found that the field data interpreted objects have higher resistivity. It can result from the complicated resistivity distribution in the centre.