Resix IP2DI (version 4)
RESIX IP2DI
2 Dimensional Resistivity & Induced Polarization Polygon
Modeling & Inversion
General
RESIX IP2DI is a finite element
forward and inverse modeling program that calculates the
IP and resistivity responses of twodimensional earth
models. The model is composed of closed bodies, layers,
or both which are automatically mapped onto the finite
element mesh. RESIX IP2DI outputs the data as contoured
pseudosections or profiles. Batch mode calculations,
interactive graphical model construction, and control of
the mesh assist you to produce quality finite element
models. Now includes 256 colour support for both screen
and hardcopy graphics.
RESIX IP2DI v4 is written in
Fortran 90, using a protected mode compiler and is now a
single executable module. Previous limitations on size
of data sets and grids no longer exist, because the
space needed to store the pseudosection data, synthetic
results and the finite element grid are dynamically
allocated to accommodate the data to be interpreted. In
addition, the virtual memory allows the user's hard disk
to be used for storage if actual RAM is not available.
The result is that arrays with hundreds or even
thousands of electrodes and with very large nvalues can
be accommodated. The supported arrays are: Wenner,
Gradient, PoleDipole, PolePole, and DipoleDipole.
RESIX IP2DI calculates the
theoretical response using the isoparametric finite
element method developed by Luiz Rijo (1977). This Ph.D.
thesis (Modeling of Electric and Electromagnetic Data,
788,155) is available through University Microfilms
International of Ann Arbor, Michigan.
RESIX IP2DI uses Inmanstyle ridge
regression inversion of polygonbased 2D models to best
fit the 2D pseudosection data in a least squares sense.
Up to 200 model parameters can be selected from body
resistivities and IP parameters and from the x and
zposition of each vertex. In addition, groups of
vertices can be locked together to form a single unit
whose x and/or zposition can be used as an inversion
parameter. This inversion is different from other
methods currently being used in that it requires that
the user construct a geological model using the mouse by
creating polygons of constant resistivity and IP value.
The inversion is used to automatically improve the fit
of the model by automatically adjusting some model
parameters.
This inversion is a genuine 2D
inversion of 2D pseudosection data that allows the user
to select which parameters to vary and which parameters
to freeze. By default, all parameters are frozen; the
user interactively selects those parameters to be used
in the inversion using the mouse during model
construction. The 2D models can be constructed as a
combination of up to 100 bodies and layers and up to
1000 vertices per model.
Data can be imported from any
Syscal series receivers and ASCII formats.
In addition to the forward and
inverse calculations the Field or synthetic data can be
compared to analytic results from layered earth models
or quarter space models.
Models are constructed using an
interactive graphics screen that allows two
userselectable pseudosections to be displayed above
model construct area. A third pseudosection can be
displayed as a colour filled background to the model.
Topography corrections are done by
calculating a 1ohmm homogenous earth model (including
topography) for the resistivity values only. The field
data is then divided by these calculated values to
obtain the corrected data.
The finite element grid is
determined from the number of electrodes and the
electrode spacing. The package automatically creates a
fine grid for models with a topographic relief and
assigns a very high resistivity value for air. The grid
can be edited using the mouse. Vertical and horizontal
elements can be inserted or deleted and elements can be
split in half by using the mouse.
RESIX IP2DI supports 256 colour
graphics display on screen as well as hardcopy. Two
colour rasterizers are incorporated for hardcopy to
support most commercial colour and monochrome devices.
Standard Components
RESIX IP2DI v4 software and manual.
