Abstract: A bucking system for an electromagnetic survey system which uses a network to interconnect the turns of a transmitter coil with the turns of one or more bucking coils in which the network includes passive circuit elements which to provide accurate bucking of the transmitter coil field at a sensor location, both when the current through the loop is steady and when the current is changing rapidly.

Abstract: A method for monitoring a primary field dipole moment in a TDEM geological surveying system, including measuring a sign and amplitude of a primary field generated by a transmitter loop and sensed by a receiver in each of a plurality of sensitive axes, and in dependence thereon calculating a vector which represents orientation of the primary field at the receiver location in a receiver frame of reference; and determining, in dependence on the vector an orientation of the primary field dipole moment in a receiver frame of reference.

Abstract: A method for monitoring a primary field dipole moment in a TDEM geological surveying system, including measuring a sign and amplitude of a primary field generated by a transmitter loop and sensed by a receiver in each of a plurality of sensitive axes, and in dependence thereon calculating a vector which represents orientation of the primary field at the receiver location in a receiver frame of reference; and determining, in dependence on the vector an orientation of the primary field dipole moment in a receiver frame of reference.

Abstract: An airborne electromagnetic survey system that determines a calibration factor for its receiver system by combining low frequency sensitivity for its magnetic induction sensors, with measurements of high frequency response obtained using calibration loops.

Abstract: An airborne electromagnetic survey system in which a transmitter is airborne and receivers are located at a fixed position or positions on the ground.

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 receiver coil assembly for performing geophysical surveys, including a hollow outer shell defining a continuous internal passage that forms a loop; a multiturn receiver air coil extending around the continuous internal passage; and a first cored coil comprising multiturn solenoid windings about a ferromagnetic core, the first cored coil having a sensing axis in a different direction than a sensing axis of the air coil.

Abstract: An airborne electromagnetic survey system that determines a calibration factor for its receiver system by combining low frequency sensitivity for its magnetic induction sensors, with measurements of high frequency response obtained using calibration loops

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: 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 receiver coil assembly for performing geophysical surveys, including a hollow outer shell defining a continuous internal passage that forms a loop; a multiturn receiver air coil extending around the continuous internal passage; and a first cored coil comprising multiturn solenoid windings about a ferromagnetic core, the first cored coil having a sensing axis in a different direction than a sensing axis of the air coil.

Abstract: A geophysical survey method and system that comprises: measuring along multiple axes at multiple locations within a survey area magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a first sensor system; measuring along multiple axes magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a second sensor system; and receiving information about the magnetic field components measured by the first sensor system and the second sensor system and in dependence thereon computing parameters from the received information that are independent of rotation of the first sensor system or the second sensor system about any axis thereof.

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 geophysical survey method and system that comprises: measuring along multiple axes at multiple locations within a survey area magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a first sensor system; measuring along multiple axes magnetic field components of a low frequency magnetic field resulting from naturally occurring electromagnetic sources using a second sensor system; and receiving information about the magnetic field components measured by the first sensor system and the second sensor system and in dependence thereon computing parameters from the received information that are independent of rotation of the first sensor system or the second sensor system about any axis thereof.

Abstract: A geophysical survey system comprising: a first sensor system towed by an aircraft, having at least one airborne sensor for measuring electric components of a low frequency natural electromagnetic field in a survey area; a second sensor system for positioning at a fixed position on the ground during a survey, having at least two ground based induction coil sensors for measuring magnetic components of a low frequency natural electromagnetic field in or near the survey area, the ground based sensors each being oriented to sense the magnetic components in different directions; and a processing system for calculating a set of first vector values over time in dependence on the electric components measured through the first sensor system and calculating a set of second vector values over time in dependence on the magnetic components measured through the second sensor system and comparing one or more characteristics of the first vector values and the second vector values to identify geophysical information about the

Abstract: The invention is directed toward a retrofit jig system for use with an existing truss assembly table having multiple planks extending lengthwise along the table. The jig system includes a motor and jig assembly for moving a puck lengthwise along the truss assembly table between adjacent planks of the table. A support member supports the screw between the adjacent planks. The support member is adjustable to allow the puck to move past the support member without interference.