Instrumentation for Impedance Measurements in the ELF/VLF Band for Geophysical Investigations
Gavin T. Mogensen · Griffith Research Online · 2015
Electromagnetic investigations of the upper layers of the earth are of particular interest to earth scientists and mining geophysics companies. This thesis outlines a novel hand-held electronic instrument that performs shallow earth surface impedance measurements to depths of 100 m or less. The device named “TranSIM” (Transient Surface Impedance Meter) operates in the ELF/VLF frequency band and utilises both remote single frequency military transmitter signals and naturally occurring sferics to perform broad band surface impedance measurements. The device incorporates high precision GPS which provides survey point co-ordinates and accurate date-time stamping, enabling data synchronisation and cooperative surveying across multiple devices. A wireless communications link to a host computer was implemented, enabling high speed data transfer with the host computer for data logging and post-processing. A Windows@ based software application was developed to provide software control of on-board electronics and for advanced data processing and data logging. The application incorporates satellite map imagery with live up-dates of GPS tracking data. Pseudo real-time data analysis is presented through a rich graphical user interface.