IX1D v3 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. Supports TEM measurements taken with central loop, fixed loop or coincident loop configurations. 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.