An improved pulse transient airborne electromagnetic system for locating good conductors

Abstract

Measuring the transient field values (H), rather than their time derivatives (dH/dt), with an inductive, pulse-excited electromagnetic prospecting system makes the device capable of reducing much of the geologic noise due to poor superficial conductors and enhancing the response from good conductors. The factor of improvement in signal-to-geologic noise ratio in H measurement may be as much as λ_s/λ_n,where λ_s, and λ_n are the expected values of decay time constant of signal and noise components, respectively. Moreover, signal-to-noise ratio increases for later sample channels, thus allowing equal gate timings for all sample channels. Field results of a comparative study with H and dH/dt measurements are shown. It is predicted that both depth of exploration and reliability of interpretation of data in quantitative terms may improve somewhat with such a system.