Gravity
and Magnetic Modeling
Interpex offers two software tools
that interpret magnetic and gravity profile data. The MAGIX family of software
models data in 2, 2.5, and 2.75 dimensional earth models consisting of bodies
and layers whose forward response matches the input data along a single profile
line.
 MAGIX PLUS v3
 MAGIX XL v3
MATHEMATICAL BASIS
All the software packages in the MAGIX
family use a generalized "2.75 dimensional" model to compute the theoretical
gravity and magnetic response. The 2.75 D model represents the geology as
polygonal prisms with horizontal axes and either finite or infinite extent in
the strike direction. The strike direction need not be perpendicular to the
plane of the profile. The forward model is based on the Rasmussen and Pedersen
method.
The MAGIX family uses Inmanstyle
ridge regression for the inversion calculations. This is a nonlinear least
squares approach for obtaining the model which best fits the observed data.
Parameters that may vary during an inversion include density, suseptibility, or
the vertex of a body in X, Z or X any Z position.
The magnetic calculations take into
account both induced magnetization and possible remanent magnetization. The
remanent magnetization is entered as the inclination, declination and the
Koenigsberger ratio.
MAGIX Family
Data are read into the program via ASCII
files of various formats. Options are available for data input including profile
selection from maps and resampling of long profiles.
Data parameters are set using
interactive dialog boxes. The program can calculate Magnetic or Magnetic
Gradient data for Total Field, x, y or z components. Magnetic susceptibility
units supported now includes cgs, microcgs and SI units
Gravity density units include both gm/c3,
and kg/m3 and calculations can be set to micro or milligals.
Survey geometry is added by using a
interactive graphics screen or text dialog boxes. The graphical geometry editing
allows for animation of selected parameters. This helps the user understand the
parameters required to specify the profiles in the 2.75D space.
Options for geometry include a profile
or XY mode of coordinates and strike directions that is not perpendicular with
the profile direction.
Body entry is done using the mouse in
an interactive graphics screen. Keyboard entry into spreadsheet style editors is
also available. Bodies are entered as a series of vertices. A variety of
calculation modes can be chosen, one of which is RealTime update of the
synthetic response with changes in the model.
Body editing allows for features like
vertex locking and homing, multiple vertex locking, susceptibility and density
editing and strike extent editing. Bodies can be rotated, deleted, copied and
split. All body editing can be done in the interactive graphics screen by mouse
click and drag operations.
Keyboard entry and editing of bodies
permits the user to enter model parameters from external sources and define
bodies based on know values.
Model parameters can be saved to files
for import with new data sets or comparisons of different models for the same
data set. Models used for gravity data sets can be imported with magnetic data
sets to function as starting models.
A variety of Output functions enables
the user to save field data, synthetic data and model parameters to files for
import or processing in third party software.
Graphical viewing is an integral part
of the program and the user has full control over colors, axes labels, scales
and data symbols. Autoscaling is built in with full user control over items to
be scaled.
The regional editing allows graphical
selection of the regional. The regional may also be calculated by fitting a
polynomial to selected data points or groups of data points.
Model and data sections can be
annotated by using the label editing sections. Features include mouse
controllable sizing, placement and arrow editing. All labels can be set to a
specific size, multiplied by a factor, or constants added to increase or
decrease size.
The following table lists the
differences between the programs in the MAGIX family. Except for these
differences the the programs work the same
Product Selection Table


MAGIX PLUS v3 
MAGIX XL v3 
Maximum number of bodies 
25 
200 
Maximum number of vertices 
240 
2000 
Maximum number of data points 
200 
1000 
Graphical Geometry Animation 
N 
Y 
Regional removal by fitting a polynomial
curve to the data 
N 
Y 
File Input/Output from within the
Interactive Graphics Interpretation 
N 
Y 
Invert for density or susceptibility for
all or selected bodies only 
N 
Y 
Support for the input and output of LCT
data and model files 
N 
Y 
