Overview

The GCM (Ground Conductivity Meter) module includes import, processing, and inversion of GCM data. Any coil configuration can be imported and inverted. System information is easily added during data import. Processing, quality control, and inspection of inversion results are integrated with the GIS interface providing the user with a complete overview of the workflow from raw data to final results. Modelling and presentation to the customer is carried out with the well-known functions of the Aarhus Workbench so integrating with boreholes, creating reports etc. is easy and only a few clicks away. 

 

Key features​

• Flexible and easy to use importer, which supports any kind of GCM system setup

• Fully developed processing tools and automatic data filtering 

• Integrated with the GIS interface

• Automatic LCI/SCI data inversion 

• Visualization of data, inverted models on the GIS and on cross sections 

• Integrated QC tool

 

 

Data in xyz format can be imported with the following information:

 

• Data in apparent resistivity (ohmm), conductivity (mS/m) or ppm

• UTM coordinates

• Coil configuration

• Coil distances and coil altitudes

• Instrument frequencies

 

For each coil configuration, relative and absolute standard deviation can be added. Mapping of columns is done with our mapping editor and both data mapping and system information can be saved/loaded within the importer.

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The importer also supports a so-called sps format, simplifying data import and processing. If you are writing you own data acquisition software or use the software developed by Aarhus University, please enquire about the format. 
 

Processing

The comprehensive set of processing includes two different algorithms to suppress noise efficiently. These tools can be set automatically or the user can customize them for special needs. A GPS shift can also be applied to ensure the data points are aligned with the horizontal focus point of the given transmitter – receiver coil configuration. 

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The processing window gives the user several options. Raw and processed data can be compared for each channel, Data points can be removed, and individual soundings can be plotted and edited. The processing windows are directly linked to the GIS interface, so data points can always be located for easier processing.
 

Inversion

GCM data are inverted with the AarhusInv inversion code. Models can be set up as a layered, smooth, or sharp model. It can be inverted as LCI or SCI along with a calculation of the DOI (Depth Of Investigation).

 

Inversion results and quality check

The quality of the inversion models can easily be inspected to see where models can be trusted and where further processing might be needed. Very importantly a depth of investigation is calculated for each sounding precisely indicating how deep the models are trustworthy.

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Different themes can be created for showing the inversion results, e.g. resistivity themes, or a layer search can be created to visualize depth to a layer with certain conditions. Sections can be drawn on the GIS interface to make profiles. Boreholes, 3Dgrid, and other geophysical data can be added to the profiles to compare data, and geological surfaces can be drawn and saved as a grid.
 

 

Applications

Collecting GCM data is cheap, and large areas can be covered fast. Data is often detailed in the near subsurface and can be used for many purposes, including mapping of:

 

• Soils

• Dump sites

• Raw materials

• Land slide prone areas

• Permafrost

• Geotechnical engineering

• Archaeological structures

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