The finite element method is used to determine numerically the apparent resistivity anomaly caused by the presence of any body with a vertical axis of symmetry embedded in a uniform half-space. The potential for a point source of current, and hence the apparent resistivity, is determined in the form of a Fourier series. The use of the finite element method enables certain classes of resistivity anisotropy to be modelled. Several examples of bipole-dipole apparent resistivity enable us to examine assumptions that are necessarily made when inhomogeneities are approximated by models for which explicit solutions exist for the potential. An application to the Broadlands geothermal field suggests that the horizontal cross-sectional area of the geothermal reservoir increases with depth, consistent with a decrease in the permeability with depth.