Radio Tomography (RTFEM), Practical Image Fidelity or Resolution

Abstract

Radio Tomography (RTFEM) is applied in mine to define geological hazards in advance of coal mining, outline ore bodies in base metal exploration and a range of geotechnical and environmental applications. This paper ranks the dominant sources of image degradation in terms of significance, so as to provide guidelines on the practical applicability of the technique. RTFEM appears to have niche rather than general applicability: it cannot accurately image features oriented parallel to the survey line; it will not generally be able to probe the interior of targets unless the attenuation is such that signal is observable through the strongly attenuated zone (ie above noise level); The resolution perpendicular to the access lines will always be relatively poor. A realistic version of the actual conductivity (or attenuation) image can be achieved by using robust imaging inversion methods. For base metal imaging, it would also be desirable to develop algorithms which can deal better with signal attenuated below the noise level at the receiver, and which can take better account of the variation in antenna coupling. The current approach?s still have significant limitations. The technique is applicable for coal seam imaging, but resolution parallel to data collection lines is two to three times less. In these cases usually the only feature observable is a step in image level and not the outline of a structure. The technique is well suited for delineating the external geometry of base metal deposits when the host rock is relatively homogeneous and resistive. This precludes working in areas where the host rock is pervasively altered or pervasively mineralised with disseminated sulphides.