ELECTRICAL IMAGING SYSTEM 16G DATA INVERSION SOFTWARE This very popular software, developped by M.H.Loke, uses the method involving the Sasaki minimum squares inversion (1992) to produce a 2D sub-soil model starting from the data of apparent resistivity (up to 2000 electrodes). It is completely automatic and does not require that the user formulates a starting model. When using a normal computer equipped with a Pentium' microprocessor, the inversion of a single pseudosection will require only a few minutes. RES2DINV supports spreading types like Wenner, Schlumberger, Pole-Pole, Pole-Dipole, line Dipole, equatorial Dipole and other non-conventional spreading types. The program automatically selects the best inversion parameters for a certain set of data (those parameters may anyway be modified by the user). Three different versions of the minimum squares method are available for the inversion: a fast 'almost-Newton* method, a slower and more accurate 'Gauss-Newton* method, and finally a hybrid technique, rather fast and accurate at the same time. The 'smoothing* filter may be adjusted in order to emphasize the variations of relative resistivity in vertical or horizontal direction; furthermore, it may be optimized for the obtainment of models with rounded edges (e.g. for pollution plumes in the ground) or net edges (e.g. for fracture areas). You may also enter information concerning the electrical resistivity coming from investigations in wells or from other sources. Furthermore, three different techniques concerning topographical correction (Loke 2000) are available. For flatticroghan Mound Measured Apparent Resistivity Pseudosection Inverse Model Resistivity Section with topography Archaeological research (grave) - Topview: pseudosection of apparent resistivity Downview: Inversion result evidencing the sepulchral chamber (Waddell, J. and Barton, K, 1955, Seeing beneath Rathcroghan, Archaeology Mineral exploration on the Magusi River (apparent resistivity+IP): a) apparent resistivity b) section of the model c)apparent'metal factor* d) model of the section (Edwards, L.S., 1977, A modified pseudosection for resistivity and Hagusi River survey Measured Apparent Resistivity Pseudosection Inverse Model Resistivity Section ■ 1M M B [ZZI [ZZ! IZZJ ZZ3 H IZZJ ZZ] EZZI [ZZI BS