Abstract: An airborne electromagnetic survey system that monitors the dipole moment. A TDEM system includes a flexible transmitter loop and a receiver having three sensors with mutually perpendicular sensitive axes. In flight, mechanical and aerodynamic forces cause the transmitter loop to tilt and flex, which affects the direction and magnitude of the primary field dipole moment. The processing system measures the sign and amplitude of the primary field sensed by the receiver in each of its sensitive axes and calculates a vector which represents the orientation of the primary field in the receiver frame of reference at the receiver location. Using this vector, the processing system determines the orientation of the primary field dipole moment.

Abstract: A airborne geophysical electromagnetic (EM) survey tow assembly system for use with an aircraft, including a substantially rigid receiver coil frame that defines a central open area, the receiver coil frame forming a continuous internal passageway that extends around the central open area; a receiver coil housed within the internal passageway isolated from the central open area, the receiver coil being configured to measure the response of surveyed terrain to naturally occurring EM events; and a tow cable for suspending the receiver coil frame from the aircraft, the receiver coil frame being formed from rigid members configured to provide aerodynamic stabilization to maintain the receiver coil frame in a desired pitch and yaw orientation relative to a direction of travel and the horizontal when the receiver coil frame is suspended during flight.

Abstract: An airborne geophysical surveying system comprising a receiver coil assembly for towing by an aircraft, the receiver assembly including a receiver coil for sensing changes in a magnetic field component of a magnetic field, and a receiver coil orientation sensing system for sensing orientation changes of the receiver coil. A controller receives signals representing the sensed changes in the magnetic field component from the receiver coil and the sensed orientation changes from the receiver coil orientation sensing system and corrects the sensed changes in the magnetic field component to provide a signal that is corrected for noise caused by changing orientation of the receiver coil in a static geomagnetic field.

Abstract: A airborne geophysical electromagnetic (EM) survey tow assembly system for use with a fixed wing aircraft, including receiver coil assembly comprising a substantially rigid tubular receiver coil frame forming a continuous internal passageway that extends around a central open area, and a receiver coil housed within the internal passageway; a winch system having a tow cable secured to the receiver coil assembly for extending the receiver coil assembly into a survey position; and a latch system for mounting to an underside of the aircraft having releasable latch members for engaging the receiver coil assembly when the receiver coil assembly is in a retracted position.