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Journal of the Australian Society of Exploration Geophysicists
RESEARCH ARTICLE

The 3D inversion of airborne gamma-ray spectrometric data

Brian Minty 1 3 Ross Brodie 2
+ Author Affiliations
- Author Affiliations

1 Minty Geophysics, PO Box 3229, Weston, ACT 2611, Australia.

2 Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia.

3 Corresponding author. Email: Brian.Minty@mintygeophysics.com

Exploration Geophysics 47(2) 150-157 https://doi.org/10.1071/EG14110
Submitted: 8 November 2014  Accepted: 26 June 2015   Published: 28 July 2015

Abstract

We present a new method for the inversion of airborne gamma-ray spectrometric line data to a regular grid of radioelement concentration estimates on the ground. The method incorporates the height of the aircraft, the 3D terrain within the field of view of the spectrometer, 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 after the conventional processing of these data assuming a flat-earth model.

Key words: deconvolution, gamma-ray spectrometry, inversion, terrain correction, topographic correction.


References

Balay, S., Abhyankar, S., Adams, M. N. F., Brown, J., Brune, P., Buschelman, K., Eijkhout, V., Gropp, W. D., Kaushik, D., Knepley, M. G., McInnes, L. C., Rupp, K., Smith, B. F., and Zhang, H., 2014, PETSc web page. Available at http://www.mcs.anl.gov/petsc

Billings, S., and Hovgaard, J., 1999, Modeling detector response in airborne gamma-ray spectrometry: Geophysics, 64, 1378–1392
Modeling detector response in airborne gamma-ray spectrometry:Crossref | GoogleScholarGoogle Scholar |

Billings, S. D., Minty, B. R. S., and Newsam, G. N., 2003, Deconvolution and spatial resolution of airborne gamma-ray surveys: Geophysics, 68, 1257–1266
Deconvolution and spatial resolution of airborne gamma-ray surveys:Crossref | GoogleScholarGoogle Scholar |

Brodie, R., and Sambridge, M., 2006, A holistic approach to inversion of frequency domain airborne EM data: Geophysics, 71, G301–G312
A holistic approach to inversion of frequency domain airborne EM data:Crossref | GoogleScholarGoogle Scholar |

Craig, M., Dickson, B., and Rodrigues, S., 1999, Correcting aerial gamma-ray survey data for aircraft altitude: Exploration Geophysics, 30, 161–166
Correcting aerial gamma-ray survey data for aircraft altitude:Crossref | GoogleScholarGoogle Scholar |

Dickson, B., and Taylor, G., 1998, Noise reduction on aerial gamma-ray surveys: Exploration Geophysics, 29, 324–329
Noise reduction on aerial gamma-ray surveys:Crossref | GoogleScholarGoogle Scholar |

Druker, E., 2012, Processing of aero gamma-ray spectrometry data as 2D inverse problem: 22nd International Geophysical Conference and Exhibition, 26–29 February 2012, Brisbane, Australia, 1–4.

Farquharson, C. G., and Oldenburg, D. W., 2004, A comparison of automatic techniques for estimating the regularization parameter in non-linear inverse problems: Geophysical Journal International, 156, 411–425
A comparison of automatic techniques for estimating the regularization parameter in non-linear inverse problems:Crossref | GoogleScholarGoogle Scholar |

Grasty, R. L., 1975, Atmospheric absorption of 2.62 MeV gamma-ray photons emitted from the ground: Geophysics, 40, 1058–1065
Atmospheric absorption of 2.62 MeV gamma-ray photons emitted from the ground:Crossref | GoogleScholarGoogle Scholar |

Green, A. A., Berman, M., Switzer, P., and Craig, M. D., 1988, A transformation for ordering multispectral data in terms of image quality with implications for noise removal: IEEE Transactions on Geoscience and Remote Sensing, 26, 65–74
A transformation for ordering multispectral data in terms of image quality with implications for noise removal:Crossref | GoogleScholarGoogle Scholar |

Gunn, P. J., 1978, Inversion of airborne radiometric data: Geophysics, 43, 133–143
Inversion of airborne radiometric data:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaE1cXhslekt7w%3D&md5=a1206cd11d666920359ca49fc645ffb8CAS |

Hansen, P. C., 1997, Rank-deficient and discrete ill-posed problems: numerical aspects of linear inversion: SIAM.

Hovgaard, J., 1997, A new processing technique for airborne gamma-ray spectrometer data (noise adjusted singular value decomposition): American Nuclear Society Sixth Topical Meeting on Emergency Preparedness and Response, San Francisco, 22–25 April 1997, 123–127.

Hovgaard, J., and Grasty, R. L., 1997, Reducing statistical noise in airborne gamma-ray data through spectral component analysis, in E. G. Gubins, ed., Proceedings of Exploration 97: Fourth Decennial Conference on Mineral Exploration: Prospectors and Developers Association, 753–764.

IAEA, 2003, Guidelines for radioelement mapping using gamma-ray spectrometry data: IAEA-TECDOC-1363, International Atomic Energy Agency, Vienna.

Kogan, R. M., Nazarov, I. M., and Fridman, Sh. D., 1971, Gamma spectrometry of natural environments and formations. Translated 1971 by Israel Program for Scientific Translations Ltd. No. 5778, available from the US Department of Commerce, National Technical Information Service, Springfield, VA, 22151, 337 pp.

Lee, J. B., Woodyatt, A. S., and Berman, M., 1990, Enhancement of high spectral resolution remote-sensing data by a noise-adjusted principal components transform: IEEE Transactions on Geoscience and Remote Sensing, 28, 295–304
Enhancement of high spectral resolution remote-sensing data by a noise-adjusted principal components transform:Crossref | GoogleScholarGoogle Scholar |

Li, Y., and Oldenburg, W., 2010, Rapid construction of equivalent sources using wavelets: Geophysics, 75, L51–L59
Rapid construction of equivalent sources using wavelets:Crossref | GoogleScholarGoogle Scholar |

Menke, W., 1989, Geophysical data analysis: discrete inverse theory: Academic Press.

Minty, B. R. S., Luyendyk, A. P. J., and Brodie, R. C., 1997, Calibration and data processing for airborne gamma-ray spectrometry: AGSO Journal of Australian Geology & Geophysics, 17, 51–62

Schwarz, G. F., Klingele, E. E., and Rybach, L., 1992, How to handle rugged topography in airborne gamma-ray spectrometry surveys: First Break, 10, 11–17

Tammenmaa, J. K., Grasty, R. L., and Peltaniemi, M., 1976, The reduction of statistical noise in airborne radiometric data: Canadian Journal of Earth Sciences, 13, 1351–1357
The reduction of statistical noise in airborne radiometric data:Crossref | GoogleScholarGoogle Scholar |

Tewari, S. G., and Raghuwanshi, S. S., 1987, Some problems on the range of investigation in airborne gamma-ray spectrometry: Uranium, 4, 67–82

Wilford, J. R., Bierwirth, P. N., and Craig, M. A., 1997, Application of airborne gamma-ray spectrometry in soil/regolith mapping and applied geomorphology: AGSO Journal of Australian Geology & Geophysics, 17, 201–217