3D electrical imaging of known targets at a controlled environmental test site

The 3D electrical tomography (ET) method has been used to investigate two known targets, commonly associated with brownfield land. Resistivity and chargeability data were collected using a network of linear survey lines. The influence of array type and orientation was evaluated, and 2D and 3D inversion results were compared. Superior geometric and electrical property resolution of 3D models was achieved using dipole-dipole as compared to Wenner array data. 3D resistivity model resolution was shown to be sensitive to electrode array orientation, indicating that to ensure adequate resolution of strongly anisometric structures orthogonal electrode configurations should be employed. Quasi-3D models generated using 2D inversion showed a marked reduction in resolution relative to the corresponding 3D models, and were characterised by highly irregular and variable electrical property distributions. The results confirm that, subject to suitable survey design, 3D ET can provide spatial images that could significantly improve the detectability of buried man-made targets.