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ELETOM is a
software that performs complete 2D inversion (and not the
simple iterative deconvolution of the pseudo-sections) of
surface electrical surveys with any measurement array (Wenner,
dipole-dipole, pole-dipole, pole-pole, 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
inter-electrode 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.
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ELETOM