Inversion can be one of two cell based algorithms or true polygon inversion.
The Interpex smooth model algorithm calculates the forward response of a homogeneous half-space using a finite element routine. It then performs a rapid least squares inversion of apparent resistivity using non-linear optimization techniques. There is also an exact inversion method available which calculates the partial derivatives of all the data and then performs the inversion. Nodes at depth are adjusted to a lesser degree than the surface nodes as the depth increases. Otherwise, the method used is the same as the standard method of Rijo.