Processing of tTEM data is performed in Aarhus Workbench, developed by Aarhus GeoSoftware.

 

For tTEM data processing, Workbench Essentials and the ground-based towed TEM module is required.

Aarhus Workbench is a comprehensive software package for processing, inversion, and visualization of geophysical and geological data. The package integrates all steps in the workflow from handling the raw data to the final visualization and interpretation of the inversion models.

The Aarhus Workbench package includes dedicated data processing modules for many geophysical data types and an integrated GIS platform. It uses the robust and fast inversion code AarhusInv.

Processing
The Aarhus Workbench data processing module is specially designed to handle and process big datasets from towed TEM systems. The data are stored in a comprehensive database structure together with comprehensive information on the TEM system. The database serves as an archive for both raw and processed data and it records all processing steps and processing settings for documentation.

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In general, the processing is performed with user adjustable automatic data filtering and stacking. The automatic pro- cessing can be inspected at different levels and user corrections added through the interface. In brief, the processing features are:

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GPS data
• Path tracking to close minor gaps in the GPS-records and for filtering outliers.
• Lag correction to move the transmitter-receiver coil configuration to the optimal focus point
• Support for digital elevation maps or external grids

Voltage data
• Filtering of distorted data due to EM coupling to power lines and cables
• Adjustable trapezoid shaped stacking for optimizing and balancing the signal-to-noise-ratio and lateral resolution.
• Data uncertainties estimated from the stacked data
• Manuel inspection and corrections to the single data point level.

Inversion

Inversion of the towed TEM data in Aarhus Workbench is performed with the AarhusInv inversion code. Locally, a 1D model is used. The models are laterally and spatially constrained forming pseudo 2D and 3D model spaces. The inversion code has been customized to handle data from very big airborne EM surveys and support multi CPU cores with a very high parallel efficiency. Besides providing the resistivity models, the inversion code also calculates a depth of investigation (DOI) and a data residual for each resistivity model.

 

Accurate system modelling
To obtain high quality inversion results it is important to model the towed TEM system in great detail. The following parameters are therefore included in the modelling:
• Transmitter, receiver heights
• Shape of transmitter loop
• Transmitter waveform
• System low pass filters
• Front gate filter
• Width of the individual time gates

For more information see Aarhus GeoSoftware