Footprints for Airborne Electromagnetic Systems
Xin Huang, Changchun Yin, Yunhe Liu, Yifeng Pei · Near Surface Geophysics Asia Pacific Conference, Beijing, China 17-19 July 2013 · 2013
Summary Airborne electromagnetic (AEM) survey often covers hundreds of square kilometers. Huge amount of survey data make 2D/3D inversion very difficult. However, due to the compact system configuration, the sensitive area for each single survey station is much smaller than the whole survey area, render it possible to invert only partial survey data. Based on a “moving footprint” technology, the whole survey can be divided into sub-areas, with the data being inverted separately, the cost for both forward modeling and Jacobian matrix can be vastly reduced. Contrary to previous EM footprints defined only for EM transmitter or for a perfectly conductive earth, we redefine the airborne EM footprint by considering a complete airborne EM system over an earth with limited conductivity. We use tensor Green's function to evaluate the footprint, within which the induced underground current contributes 90% to the total secondary magnetic field at the receiver. We take the horizontal coplanar (HCP) coil configuration as example to study the influence of earth resistivity, frequency and flight altitude on airborne EM footprints.