The 3D inversion of airborne gamma-ray spectrometric data

Gamma radiation measurements are made at airborne survey heights and, through suitable processing, are converted to estimates of the count rates due to the radioelements (K, U and Th) at each observation point along the flight lines. The conventional processing of these data would include a correction for deviations in the aircraft height from the nominal survey height. The elemental count rates are then typically converted to estimates of the elemental concentrations on the ground through a simple scaling of the count rates by a “sensitivity factor” that depends only on the energy of the primary radiation and the nominal survey height above ground level (IAEA, 2003). Finally, the elemental count rates are interpolated onto regular grids for imaging and interpretation.