CRC LEME
Open File Report 173
ABSTRACT
Calibration of Resolve airborne electromagnetic data - Riverland
and East Tintinara, South Australia
Brodie R, Green A, Munday T
PREFACE AND EXECUTIVE SUMMARY
This project is a subset of the Riverland and Tintinara projects
in South Australia conducted under the auspices of the South Australian
Salinity Mapping and Monitoring Project. The decision of the SA-Salinity
Mapping and Monitoring Support Project to employ a frequency domain
helicopter EM system for mapping near surface conductivity related
to the presence of clay-rich materials came with an expectation
that the careful monitoring of system performance would be an essential
prerequisite to ensuring data of a consistent quality appropriate
for inversion.
The activity reported here was conducted to assist the application
of a constrained inversion technique with RESOLVE helicopter EM
data in order to map the location and thickness of the near-surface
clay-rich units in the Riverland and Tintinara East areas in South
Australia. It is believed that this clay acts to delay groundwater
recharge where present. The RESOLVE system has very wide bandwidth
(100 KHz to 400Hz) although it does not sample this frequency range
in great detail. This under-sampling of the full frequency response
means that it is more difficult to invert the data to a complete
vertical conductivity profile.
Accurate inversion depends on having correctly calibrated data.
Correctly calibrated data is most essential for this project because
the accurate location of near surface conductive units is dependent
on subtle changes in the high-frequency response. This report describes
the calibration procedures used to process the data delivered by
the contractor, and was always planned as an integral part of the
project.
Dr. Tim Munday
Project Leader
December 2003
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