Towards 3D inversions with full system modelling

We describe the setup for inversion of ground based TEM data using a 3D forward code and a full description of the measurement system. The response is calculated using a finite volume method where we solve for the electric field on the edges of a staggered grid and time step solutions using backward Euler steps. We convolve the calculated fields with the system response to compare with the measured data. In this way we include all system related effects in the calculation and this is important for the very early time signal. We describe how this is done for both forward and derivative calculations. For the forward calculation and the inversion we use an iterative solver. We show that the forward code is in good agreement with the analytic response from a half space.