However, the parameters which affects the inversion process can be modified by the user. The program will automatically choose the optimum inversion parameters for a particular data set. Topographic effects can be modelled by using a distorted finite-element grid such that the surface of the grid matches the topography.
On a modern microcomputer, the data inversion takes less than a minute for small surveys with 100 electrodes in a flat area, to several hours for extremely large surveys with 6000 electrodes in rugged terrain. It supports parallel calculations that significantly reduces the inversion time. A Intel multi-core (or compatible CPU) based microcomputer with at least 2 GB RAM and an 500 gigabyte hard-disk is recommended. Like RES2DINV, it is completely automatic and the user does not even have to supply a starting model. The RES3DINVx32/圆4 programs use the smoothness-constrained Gauss-Newton least-squares inversion technique to produce a 3D model of the subsurface from the apparent resistivity data alone. The arrays supported include the pole-pole, pole-dipole, inline dipole-dipole, equatorial dipole-dipole and Wenner-Schlumberger and non-conventional arrays.
In areas with complex structures, there is no substitute for a fully 3D survey. The main limitation of such surveys is probably the assumption of a 2D structure. In areas where the geological structures are approximately two-dimensional (2D), conventional 2D electrical imaging surveys have been successfully used.
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