Interpex is a software company dedicated to the production of high quality software for the processing, interpretation and display of geophysical data.

 P.O. Box 839 • Golden • Colorado • 80402 • USA


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Windows 11

IX1D v 2
1D Sounding Inversion

See also the newer version IX1D v 3

IX1D is a 1-D Direct Current (DC) resistivity, Induced Polarization (IP), Magnetotelluric (MT) and electromagnetic sounding inversion program with the following features:

  • Supports Most DC resistivity arrays, including: Wenner, Schlumberger Dipole-dipole Pole-dipole and Pole-pole arrays.

  • Supports Resistivity only or Resistivity with IP measurements in terms of PFE, Chargeability in msec or Phase in mrad.

  • Supports Magnetotelluric (MT) sounding inversion with Apparent Resistivity and Impedance Phase.

  • Supports Horizontal Coplanar, Vertical Coplanar and Vertical Coaxial Frequency-Domain Electromagnetic in-phase and quadrature measurements made versus frequency, coil spacing or instrument height. Measurements can be in percent or ppm of the primary field.

  • Supports EM Conductivity measurements in terms of apparent conductivity in milliSiemens/m.

  • IX1D has the capability to read in a resistivity well log from a flat ASCII file and the user can interactively reduce the log to several discreet layers by fitting straight line segments to the cumulative conductance in the log. The resulting model can be copied to the model in the current data set for further modeling.


Direct Link

Features include:

  • Creation of data by spreadsheet entry

    Data Entry Spreadsheet

    Data Entry Dialog Box

  • Import of data or models from flat ASCII files 

  • Models are entered from the keyboard as either Depth models or Layer Thickness

    Model Entry Dialog Box

  • Layer boundary elevations are shown and calculated relative to surface elevations. 
  • The Model Entry dialog box allows for dynamic column and row manipulations to make model entry more convenient. 

  • Fix Flags allow the user to fix parameters for the inversion calculations. Either the layer thickness (or depth) and/or the resistivity can be fixed in the inversion process. 

  • Forward and inverse model calculations can be carried out using buttons on the model entry dialog. Models can be inverted using either the layer depth or layer thickness.

  • Graphics are presented as the Sounding data on the left hand side with the model on the right hand side. Interactive property sheets allows for user configuration of displayed data. For DC and IP data, the model can be displayed on the same axes as the data.

  • Menu commands and toolbar buttons are available for estimating a layered model (DC and IP data only), estimating a smooth model or analyzing equivalence of the layered model.

    Axes Label Properties

  • Smooth models are generated by starting with as many layers as there are data points. Thicknesses are automatically generated from the spacing or frequency data and the model begins with a homogeneous earth (all layers set to the average resistivity found in the data). Inversion can be Ridge Regression or Occam's inversion.

  • The display can be set to show the layered model, smooth model, equivalence analysis or any combination of these three. The model(s) can also be shown on the same graph as the data, in which case the spacing axis doubles as a depth axis.

  • For MT data, the Bostick and Niblett inversions can also be shown. 

Default Graphics Screen

  • The model and data plots can be zoomed by dragging the mouse across the display with the left button depressed. This feature can be switched on and off by clicking on the Zoom menu command in the View menu or by clicking on the Zoom tool bar icon.

  • Axis labels as well as axis sizes can be edited under View Properties. Grid lines, including major and minor, for the Data and Model axes can be switched on and off under the View Grid menu subchoices. Axes can be auto-scaled from the model and data by selecting the View Unzoom menu command.

  • Data, Layered models and Smooth models can be exported to ASCII files.

  • Graphics can be exported as DXF, CGM or WMF file formats.

  • Tool bar buttons are provided for the most-used menu commands, including New Sounding or Model, Open and Import data, Save, Print, Edit Data or Model, Zoom status, Unzoom, model display selection, Forward, Inverse and Equivalence Analysis calculations, and Estimation of Layered or Smooth models.

Resistivity Well log show with layered model decomposition

Licensing and Distribution

IX1D version 2 is distributed as shareware. The license allows for a 30-day evaluation period. After the evaluation you are required to register the package in order to continue using it. Registration fee is $499.00 for DC, IP,  Frequency EM and EM Conductivity capabilities. The registration for for TEM is an additional $2,500.00 and requires a hardware key. Both USB and Parallel keys are available

Registered Versions

Registered users can obtain e-mail support by sending requests for assistance, bug fixes and feature enhancements to Please include the registration name and registration number and attach the files with which you are having problems to your e-mail request.


 P.O. Box 839 • Golden • Colorado • 80402 • USA
Tel (303) 278-9124 • Fax (303) 278-4007

Copyright 2018 Interpex Limited. All rights reserved.