Helicopter frequency domain EM (HEM)

The HEM processing system features full non-linear laterally constrained 1D inversion for frequency domain electromagnetic data. The system is optimized to handle large amounts of airborne EM frequency domain data.

Main features

• Easy-to-use importer for pre-processed (levelled, averaged etc.) data.
• Full non-linear 1D-LCI type inversion of the data sets. Both multi-layered and few-layered inversions are supported.
• A priori information from e.g. boreholes easy to include.
• Post-processing of data based on inversion results.
• Comprehensive visualization features enabling detailed evaluation of the inverted data.
• Integrated with the Aarhus Workbench environment making it fast to produce thematic maps and cross sections from the inverted models.

Aarhus Workbench has advanced capabilities for inversion of airborne HEM data using the the laterally and spatially constrained inversion algorithm. The algorithm is completely incorporated into the same work frame as the inversion of e.g. SkyTEM data. On the input side the work frame lets the user control starting models and constraints and both smooth and parametrized models are supported. On the result evaluation side there are easy to use windows allowing plotting of not only the output models but also data residuals and model sensitivity analysis. Finally models can be changed to include e.g. borehole information and re-inverted directly from the user interface.

The inversion module is build for the expert as well as the non-specialist.

How to get HEM data into the system

Aarhus Workbench can read any column based data file if it includes coordinate and ppm data columns. Fiducial numbers, line numbers, bird altitude and elevation can also be imported and used later on in the presentation of results. The importer has capabilities to convert from and to about any UTM coordinate system.

The system supports any HEM configuration: horizontal coplanar (HCP), vertical coaxial (VCX), vertical coplaner (VCP) and perpendicular (PP) loops. The forward solution for all of these configurations are exact implementations.

Starting the inversion

The inversion can be started using a minimum of settings or it can be set up fully customizable. The minimum setting mode only need input on the choice of smooth or parametrized model and the number of layers. The fully customizable model allows the specification of a-priori constraints on any model parameter and lateral and horizontal constraints for the LCI algorithm.

Bird altitude is in all cases a constrained inversion parameter and the system will use the number of CPU's available on the workstation for fast performance.

Evaluation of inversion results

Inversion results are evaluated in a user interface completely linked to the GIS map. The models themselves are displayed together with e.g. inverted bird heights and data residuals. Data, forward data and model parameter sensitivity analysis is displayed with a mouse click.

Data can be culled directly form the inversion if data are distorted e.g. due to power line noise.

The system allows the user to build new starting models including a-priori information from e.g boreholes. When finished redefining the survey is re-inverted with a few mouse clicks.

Final inversion results can be presented on thematic maps or on profiles in the Aarhus Workbench data presentation system.

Contact

Contact This e-mail address is being protected from spambots, you need JavaScript enabled to view it for more information on the HEM module for Aarhus Workbench.

The HEM inversion system is a module of the Aarhus Workbench. Information about prices and license are found on the licensing page.