Developments in airborne gamma-ray spectrometry

ASEG Queensland Branch Meeting

Speaker: Brian Minty

Please RSVP to Megan Nightingale by 5:00 pm, Wednesday 10 Sep, 2014 if you wish to attend.

This presentation will review recent research at Minty Geophysics into airborne gamma-ray spectrometric methods with a focus on 3 areas:

• The reduction of noise in multichannel airborne gamma-ray spectra using principal component –type analyses: Both the NASVD and MNF methods can be improved by first sorting the raw spectra into clusters based on spectral shapes, and then applying the noise-reduction methods to these clusters.
• The automatic detection of radioelement anomalies from 3-channel gamma-ray spectrometric data: Two types of radioelement anomalies are identified – the classical “point” anomalies, and “spectral” anomalies that have rare spectral response signatures.
• The 3D inversion of airborne gamma-ray spectrometric data to elemental concentrations on the ground.

Most of the talk will focus on this last topic. A new method will be presented for gridding airborne gamma-ray spectrometric data that incorporates both the observation height and the 3D terrain within the field of view of the spectrometer. The method uses a model that incorporates both the directional sensitivity of rectangular detectors and a source model comprising vertical rectangular prisms with the same horizontal dimensions as the required grid cell size. The top of each prism is a plane surface derived from a best-fit plane to the digital elevation model of the earth’s surface within each grid cell area. The method is a significant improvement on current methods, and gives superior interpolation between flight lines. It also eliminates terrain effects that would normally remain in the data with the use of conventional gridding methods.

About the Speaker

Brian Minty graduated from Rhodes University (BSc) in 1976 with majors in mathematics and physics. He then received a BSc (Hons) (1977) in geophysics from the University of the Witwatersrand, an MSc (Cum Laude, 1982) in exploration geophysics from the University of Pretoria, and a PhD (1997) from the Australian National University. Early in his career, Brian worked for the Geological Survey of South Africa (1977-1981), and Hunting Geology and Geophysics (1982-1986). In South Africa he worked on airborne surveys targeting uranium, and it was during this period that he developed a life-long interest in airborne geophysics and, in particular, the gamma-ray spectrometric method. In 1986 he joined Geoscience Australia, and soon found himself in a research role. He has published techniques for mapping cesium fallout, the micro-levelling of airborne magnetic data, the estimation of atmospheric radon background, and the multichannel processing of airborne gamma-ray spectrometric data. He also developed a methodology for the automatic merging of gridded airborne geophysical survey data. After 25 years with Geoscience Australia, and its predecessors, Brian started his own consultancy (Minty Geophysics) in 2011. Over the years he has undertaken a number of international training consultancies – mainly in the field of airborne gamma-ray spectrometry. These include consultancy work for the Geological Survey of France, Geological Survey of Norway, Anglo American Corporation, the South African Geophysical Association, and the Iranian Geophysical Society. He has also represented Australia on two International Atomic Energy Agency consultancies – looking at the standardisation of acquisition, calibration and data processing procedures for gamma-ray spectrometry.