1 D Forward and Inverse Modeling of DC Resistivity
RESIX is an interactive, graphically oriented, forward and inverse
modeling program for interpreting resistivity sounding data in terms of
a layered earth (1-D) model. Sounding curves can be entered as a
function of a for Wenner or pole-pole soundings, AB/2 for Schlumberger
soundings, R for dipole soundings or N for dipole-dipole or pole-dipole
Sounding curve values are entered as apparent resistivity as a function
of spacing. Forward modeling enables you to calculate a synthetic
resistivity sounding curve for a model with up to ten plane layers.
Resistivity sounding curves are calculated using linear filters.
Shifting of data with overlapping curve segments is handled
automatically by shifting the synthetic curve to match the offsets
between segments in the data. This is done by assuming the data for the
longest spacings is correct and shifting segments at shorter spacings to
meet the data at longer spacings. Alternatively, you can shift the data
curve itself to meet either the longest or shortest spacing segment.
This can be done either automatically or manually in the interactive
graphics mode using the Shift Segments option.
Masking of data is achieved in the interactive graphics interpretation
module by pointing and clicking on data points. These points can be
unmasked or deleted according to the users needs. Masked points do not
influence the error or inversion calculations. Interactive model input
via the mouse allows the user to see changes in the calculated curve as
he enters the model graphically. Graphic entities of the plate output
may also be resized and positioned using the mouse.
Inverse modeling allows you to obtain a model that best fits the data in
a least squares sense, using ridge regression to interactively adjust
the starting model parameters. You can constrain some of the starting
model parameters so the inversion will not adjust them. Starting models
for inversion can have up to 8 layers. Forward models can have as many
as 10 layers. Constants can be applied by fixing (or freezing) a
parameter, or by imposing limits on a parameter. Parameters can be
resistivity thickness of layers, or resistivity/depth to bottom of
Results from forward or inverse modeling can be directed to a printer or
plotter for report ready, hard-copy output. Results can also be saved in
a binary random access disk file for later retrieval. Inverse modeling
can be carried out in an unattended batch mode. Resix provides several
options to present the observed data, the theoretical (forward) data,
and the geo-electrical model section used to calculate the forward
response. This information can be graphically presented individually on
a dot matrix printer, a laser printer, or a pen plotter. You can also
print the data and model section in a tabulated, paginated form directly
to a text printer.
Data stroage is handled by a new data base file format that holds up to
200 data sets (or sounding curves). This size of the file depends on the
number of sounding cureves it contains.
Resix v.3 software and instruction manual.