Bhp Billiton Innovation Pty Ltd

Ken G McCracken

James Beresford Lee

Robert John Turner

Edwin Hans Van Leeuwen

This invention concerns a method of making airborne geophysical measurements. Such measurements may be made from fixed or moving wing airplanes or dirigibles. The method comprises the following steps: taking first real time measurements from one, or more, geophysical instruments mounted in an aircraft to produce geophysical data related to the ground below that instrument. Taking second real time measurements from navigation and mapping instruments associated with or carried by the aircraft. Computing a background response of each geophysical instrument using the second real time measurements to take account of its time varying altitude, and the time varying topography of the ground below it. Adjusting an operating or data processing condition of each geophysical instrument using the respective background response and the instrument's attitude to enhance the performance of that instrument. And, adjusting the geophysical data output for that instrument having reduced effects resulting from variations in altitude, attitude and topography.

Methods of adjusting airborne geophysical measurements based on mapping instrument measurements

This invention concerns gravity gradiometers for airborne surveys for minerals. The gravity gradiometer comprises an inertially stabilized platform, a rotor that is between 0.4 and 1.5 m in diameter mounted in the stabilized platform, and between twelve and seventy two accelerometers arranged in complements of four each on the rotor; and a signal processor operative to: (i) subtract noise calculated from the mass distribution of the aircraft and the inertially stabilised platform, and by the angles of the gimbals of the stabilised platform; (ii) use measures of the accelerations experienced by the gravity gradiometer to estimate the sensitivities of the gravity gradiometer to the acceleration, and use this estimate to correct the gravity gradiometer output; and (iii), use measures of the rotations to which the gravity gradiometer is subjected to calculate the contribution of rotation to the gravity gradiometer noise, and to remove the contribution of rotation to said gravity gradiometer noise.

Growing community of inventors

Via Mittagong, Australia

Ken G McCracken