Effects of System Movement in Flight on Helicopter-borne Magnetic Gradiometry

Magnetic gradiometry is a quick and cost-effective exploration tool useful for mapping geological structures. This study focuses on a coherent oscillating noise of ~0.3 Hz present in triaxial magnetic gradiometric data when the system flies over low signal areas. The goal is to characterize this noise, identify its source, and apply a correction so that subtle targets are no longer masked. Stationary sensor noise and translational movements of the system have been dismissed as potential sources. Rotational movements (yaw, pitch and roll) have a frequency range similar to that of the noise but the source is likely due to vibrations related to the positioning of the tow cable attachment points. This mechanical noise is either affecting the gradiometric data directly or it is affecting the rotational movements, which are in turn influencing the gradients. Regardless of its source, the noise may be attenuated mathematically by de-rotation and notch filtering.