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Keynote: Helicopter Airborne Gravity GradiometryNormal access

Author: M. Dransfield
Event name: 2nd Conference on Geophysics for Mineral Exploration and Mining
Session: New Developments in Magnetic and Gravity Methods of Mineral Exploration I
Publication date: 09 September 2018
DOI: 10.3997/2214-4609.201802688
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 785.97Kb )
Price: € 20

Summary:
Rotary-wing airborne gravity gradiometry provides both better signal-to-noise and better spatial resolution than is possible with a fixed-wing survey in the same terrain by virtue of the low altitude, low speed and close terrain following capabilities of a helicopter. In rugged terrain, these flight characteristics provide a significant advantage for the use of helicopters for gravity data acquisition. Comparing helicopter surveys over gentle terrain at Margaret Lake, Canada, and over rugged terrain at Mount Aso, Japan demonstrates that although there is some loss of spatial resolution in the more rugged terrain, the line spacing remains the limitation to resolution in these examples. The slightly higher altitudes forced by rugged terrain make the requirements for terrain correction easier than for gentle terrain. Transforming the curvature gradients measured by the Falcon gravity gradiometer into gravity and the complete set of tensor components without loss of resolution is done by a Fourier method over gentle terrain and an equivalent source method over rugged terrain. The Fourier method is perfectly stable and uses iterative padding to improve the accuracy of the longer wavelengths. The equivalent source method relies on a smooth inversion and the source distribution must be customized to suit the survey design.


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