Electromagnetics: Description of Modules

EM processing makes use of the SimPEG library.

TDEM 1D Inversion

TDEM inversion makes use of the SimPEG library (see references below). The inversion is 1D, so it requires as input a single measurement. Line data is imported using the Import Line Data tool in the Vector menu.

Options are as follows:

• Line Number

• Fid/Station Name

• Bird Height – height of sensor.

• Data channel prefix – prefix in ASCII data file, indicating a data channel.

• Waveform Type – an option to select the waveform for a list of standard types. This can be VTEM Waveform, Ramp Off Waveform, Trapezoid Waveform, Quarter Sine Ramp On Waveform, Triangular Waveform and HalfSineWaveform.

• Tx Peak time – time when the input VTEM waveform is at its maximum.

• Tx Ramp Off start time

• Tx Off Time – time when the waveform is completely off.

• Source Type – can be Circular Loop or Mag Dipole.

• Tx Orientation – transmitter orientation, can be x, y or z.

• Tx Area – transmitter area (only for circular loop source)

• Number of turns in loop (only for circular loop source)

• Current in loop (only for circular loop source)

• Permeability of the background

• Rx Orientation – receiver orientation, can be x, y or z.

• Mesh cell size

• Mesh number cells in x direction

• Mesh number cells in z direction

• Mesh number of cells to pad

• Pad cell multiplier

• Conductivity Air

• Conductivity Halfspace

• Data Relative Error (%)

• Data Noise Floor

• Optimization - maximum iterations

• Load window times – text file with the window times.