ELETOM
is a software that performs complete 2D inversion (and not the simple
iterative deconvolution of the pseudosections) of surface electrical
surveys with any measurement array (Wenner, dipoledipole, poledipole,
polepole, user defined arrays, mixed arrays) with a maximum of
64 electrode positions that can be added by the user as required.
ELETOM
uses the finite elements method (FEM) in two dimensions to model
the electrical response of the subsurface.
The elements that define the grid are trapezoidal in form to enable
one to compensate any height differences between the electrode positions.
The current dispersion in the third spatial dimension (perpendicular
to the section of interest) is taken into consideration using Wannamaker's
correction.
When
using ELETOM it is not necessary to specify any parameter to construct
the grid. One only needs to enter the positions and numbering of
the electrodes used in the survey measurements.
The
iterative algorithm used to perform the inversion is based on the
minimisation of the mean square error between field data and the
data simulated by the FEM, according to the method proposed by Sasaki
(1994).
The
convergence of the algorithm is obtained by estimating a stabilisation
(performed with the generalised reciprocal coefficients method)
which is repeated during every iteration.
The
reduction of the noise effect that is present in the data, is obtained
through an iterative linear regression calculation (Ward, 1990)
that enables one to compensate for the fact that it is impossible
to know the statistical variance of each measurement.
The
result is given by a precisely reconstructed real resistivity section
(in two dimensions) which is equal to the smallest halved interelectrode
distance, with the possibility of selecting a set of colour shadings
to enhance the anomalies that are present in the soil in the best
possible way. The results can also be rendered as isoresistivity
curves.
