Abstract: An electromagnetic receiver system with an EM receiver coil is for measuring EM signals while transported by a vehicle, e.g. a helicopter. A base part serves for connection to a towing system. A coil support is fixed to the electrical conductor of the EM receiver coil. A suspension system has gimbal axles defining gimbal axes arranged in one plane. The gimbal axles are arranged within a periphery of the EM receiver coil. A central element is connected to the gimbal axles, such that the axes intersect in an EM receiver coil central part. Joints allow the receiver coil to pivot around the first and second axes. Springs provide a self-righting effect on the coil around the axes. A precise calibration of centre of mass of the suspended receiver coil can be obtained by adding masses to cause the centre of mass to coincide with the geometric intersection between the axes.

Abstract: The present application proposes an airborne electromagnetic signal observation device and a system carried by an unmanned aerial vehicle (UAV). The device includes an inner frame, an outer frame and a flexible support that are connected to each other. The device and the system can enhance the stability of the sensor in flight and greatly suppress motion noise.

Abstract: In some embodiments, a method for generating a composite image file based on multiple images of a physical product comprises: obtaining a plurality of images of a physical product; applying a plurality of data processing modules implemented in a data flow network to the plurality of images to cause the modules to process, in parallel, the plurality of images and to generate a data structure that captures a composite image file for the physical product; wherein the processing of the plurality of images by a data processing module of the plurality of data processing modules comprises: evaluating the plurality of images to determine a type of processing for the plurality of images, generating, based on the type of processing for the plurality of images, result data for the plurality of images, updating the data structure based on the result data, and transmitting the result data to one or more of the plurality of data processing modules.

Abstract: Provided are a method and a device for mobile rapid exploration of mineral resources. The device includes a main magnetic sensor, a slave magnetic sensor and a ground vertical magnetic field sensor arranged in a ground reference station. During exploration, on the one hand, a semi-airborne artificial source exploration method is used to collect signals with the main magnetic sensor and the slave magnetic sensor, in which the slave magnetic sensor collects low-frequency motion noise, and the main magnetic sensor collects low-frequency motion noise and vertical magnetic field signals synchronously. On the other hand, vertical magnetic field signals in a same survey area are collected by the ground vertical magnetic field sensor, and then the low-frequency motion noise collected by the main magnetic sensor is estimated twice through two correlation mappings, so as to obtain a final vertical magnetic field measurement signal.

Abstract: A defect detection apparatus includes a defect detection unit and a calculation unit. The defect detection unit detects a defect that appears on an external appearance of a structure through imaging processing from external appearance image data that is generated by imaging the external appearance of the structure with a surveying instrument. The calculation unit calculates defect data relating to the defect detected by the defect detection unit by using coordinate data that is correlated with the external appearance image data.

Abstract: A semi-airborne electromagnetic survey device and a semi-airborne electromagnetic survey method based on coaxial coplanar mutual reference coil assembly are provided. The device includes a measuring coil and a reference coil with linear correlation of additive motion noise; the reference coil and the measuring coil have a same bandwidth, are coaxial and coplanar and are in hard connection or soft connection; detection resolution of the reference coil only distinguishes the additive motion noise; detection resolution of the measuring coil distinguishes real vertical magnetic field signals and motion noise simultaneously; the reference coil has a much smaller outer diameter than the measuring coil. In the method, one coil only receives the additive motion noise, and an other coil simultaneously receives the additive motion noise and the real vertical magnetic field signals; and the additive motion noise received by the two coils is cancelled to obtain the real vertical magnetic field signals.

Abstract: A magnetic compensation method based on an aeromagnetic compensation error model includes: acquiring an upper limit of an error of a magnetic noise caused by both an environmental background field in an exploration area and an aeromagnetic flight platform, by using the aeromagnetic compensation error model, before an actual flight; determining, according to the upper limit, whether the environmental background field and the aeromagnetic flight platform are suitable for the actual flight, and if so, performing a calibration flight to acquire a compensation coefficient; and acquiring data of an attitude term by performing the actual flight, calculating an interference magnetic field by the data of the attitude term and the compensation coefficient, and performing magnetic compensation.

Abstract: A method of locating a coal-rock main fracture by an electromagnetic radiation from a precursor of a coal-rock dynamic disaster is provided. At least four groups of three-component electromagnetic sensors are arranged in the underground tunnels, and each group of sensors includes three directive antennas for receiving electromagnetic signals orthogonal to each other. The electromagnetic signals are collected by a monitoring host. The signals are ensured to be received by different sensors synchronously via an atomic clock. The direction of the magnetic field line is determined by performing a vector superposition on strengths of the three-component electromagnetic signals of each group of sensors. The planes of electromagnetic wave propagation perpendicular to the direction of the magnetic field line are determined accordingly. The location of the coal-rock fracture is determined by the intersection point of the planes of electromagnetic wave propagation determined by the multiple groups of sensors.

Abstract: The subject matter of this specification can be embodied in, among other things, an unmanned aerial vehicle system includes a first loop airframe structure having a transmitter loop antenna and defining a plane, a second loop airframe structure having a receiver loop antenna having a diameter smaller than the transmitter loop antenna and oriented substantially parallel to the plane, a plurality of vertical thrusters configured to provide lift substantially perpendicular to the plane and elevate the system above a ground surface, at least one lateral thruster configured to provide thrust substantially parallel to the plane, a controller affixed configured to control the plurality of vertical thrusters and the lateral thruster, and an electromagnetic sensing system (such as ground-penetrating radar) configured to transmit electromagnetic signals using the transmitter loop antenna and receive secondary electromagnetic signals of secondary eddy currents caused by interactions between the EM signals and undergroun

Abstract: An electromagnetic (EM) receiver system for measuring EM signals. The EM receiver system includes a platform; a coil for measuring EM signals; and first to third suspension mechanisms located between the platform and the coil so that the coil oscillates relative to the platform, and the first to third suspension mechanisms attenuate motion induced noise introduced by towing the receiver system above ground.

Abstract: Provided is a device for detecting precipitation conditions. In one aspect, the device includes a Yagi-Uda antenna tuned a resonant frequency and a signal generator coupled to the Yagi-Uda antenna by a transmission line, the signal generator being configured to output an excitation signal to the Yagi-Uda antenna to the Yadi-Uda antenna. The device also includes a processing system coupled to the Yagi-Uda antenna, the processing system being configured to measure the ability of the Yagi-Uda antenna to radiate a signal following excitation of the Yagi-Uda antenna by the excitation signal and, based on the measured ability of the Yagi-Uda antenna, to identify a precipitation or other meteorological condition.

Abstract: An electromagnetic (EM) receiver system for measuring EM signals. The EM receiver system includes a platform; a coil for measuring EM signals; and first to third suspension mechanisms located between the platform and the coil so that the coil oscillates relative to the platform, and the first to third suspension mechanisms attenuate motion induced noise introduced by towing the receiver system above ground.

Abstract: An electromagnetic (EM) receiver system for measuring EM signals. The EM receiver system includes a platform; a coil for measuring EM signals; and first to third suspension mechanisms located between the platform and the coil so that the coil oscillates relative to the platform, and the first to third suspension mechanisms attenuate motion induced noise introduced by towing the receiver system above ground.

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: The invention discloses a receiver section towed by an airborne electromagnetic survey system, comprising a plurality of receivers, each receiver comprising at least one receiver coil. The invention further discloses an airborne electromagnetic survey system, comprising: (a) a transmitter section for generating a primary electromagnetic field that induces a secondary electromagnetic field; and (b) a receiver section for detecting the secondary electromagnetic field, wherein the receiver section comprises a plurality of receivers, each receiver further comprising at least one receiver coil; and a tow assembly for an airborne electromagnetic surveying system, comprising a means for suspending a receiver section from an aircraft, the receiver section comprising a plurality of receivers each receiver comprising at least one receiver coil.

Abstract: An apparatus for airborne electromagnetic surveying is provided, comprising a central hub defining an equatorial plane, a transmitter loop, and radials connecting the hub to the transmitter loop. The loop generally lies in a plane during flight, and comprises loop sections, some of which are connected with flexible joints allowing the loop to flex out of the plane during lift-offs and landings. A loop section comprises current conducting elements connected to current conducting elements of adjacent loop sections forming a transmitter loop circuit. A radial connects to the hub at a point that is substantially offset from the transmitter loop plane, thereby contributing to the stability of the transmitter loop connection point in an up-down direction relative to the hub. Additionally, a loop section comprising rigid conductive elements retained in a spaced-apart relationship by a frame member is also provided.

Abstract: The present invention provides an airborne electromagnetic receiver having a large dimension to allow low transmitter base frequency. A modular and configurable suspension assembly is provided for use within a receiver support structure and suspending the support structure. The suspension assembly has a rigid support having a suspension portion, and links connecting the suspension portion and the suspended structure. The links are adjustable in length and tension to radially suspend said equipment support structure. The natural frequency of the suspension assembly and the suspended receiver motion can be optimized by adjusting mass distribution, suspension link length and suspension link tension. The suspension assembly can be used to suspend a receiver having large receiver coils. The suspension assembly converts high frequency vibration forces imparted on the receiver to a low frequency oscillation. The suspension assembly may also be tuned to avoid coincidence with the excitation frequencies.

Abstract: One embodiment describes an imaging system. The system includes a first imaging system configured to provide first signals to a target area and to receive first response signals. The system also includes a second imaging system configured to provide second signals to the target area and to receive second response signals. The first and second signals can have separate frequency bands. The system further includes a processor configured to correct the first response signals based on the second response signals, and to generate an image based on the corrected first response signals.

Abstract: A method for detecting an object, comprising the steps of defining expected characteristics of scattered electromagnetic radiation to be received at a receiver; attenuating at least a portion of electromagnetic radiation received at the receiver by a presence of an object within a path of electromagnetic information; and detecting the attenuation to indicate a presence of the object. The object may be a low radar profile object, such as a stealth aircraft. The electromagnetic radiation is preferably microwave, but may also be radio frequency or infrared. By using triangulation and other geometric techniques, distance and position of the object may be computed.

Abstract: Isotropic sensor 1, which comprises three sensor units 2, provided with a lead wire winding 3 surrounded by a conducting screen 4, the screen 4 being interrupted in two first zones I1, I2 diametrically opposite, there being in one of said zones I1, I2 the terminals VB for measuring the currents induced, wherein the two ends of each screen segment 41, 42 in the first two zones I1, I2 are connected two by two by means of conductors 5, 6 and comprises two second zones I3, I4 of interruption disposed at a halfway point of each screen segment 41, 42, in such a way that it is possible to measure at high frequencies simultaneously, independently and with precision, both magnetic field B and electric field E.

Abstract: A method for the real time volume imaging of geological structures and/or man-made objects having electrical conductivity is described, using electromagnetic (EM) sources and/or EM sensors mounted from at least one moving platform. The EM sources may include natural EM sources and/or man-made inductive sources and/or man-made galvanic sources. The EM sensors may measure at least one component of the EM field at the at least one sensor position. The EM fields measured for each combination of EM source and EM sensor may be volume imaged in real time using a moving sensitivity domain that captures the finite spatial sensitivity of each combination of EM sources and EM sensors. At least one desired property, such as conductivity, dielectric permittivity and/or induced polarization parameters, may be derived from the volume image, providing a reconstruction or classification of the physical properties of the geological structures and/or man-made objects.

Abstract: Methods are provided for conducting surveys of regions of interest, points of interest, and objects of interest. The methods typically involve using a survey instrument with programmed logic. The programmed logic may include one or more base of knowledge in an electronically accessible format, and may include statistical analysis software. The survey instrument generally includes a display and one or more sensors. The sensors may include a visible image or an infrared image sensor. The program logic may be used to guide an operator through a survey.

Abstract: A three dimensional (3D) dipole antenna system with spiral leg is described used to measure oscillatory electric field strengths. The system relies on spiral dipole leg segments of limited length attached to a cylinder. It is designed to improve the sensitivity to oscillatory electric signals in the range of 0.01 Hz to 10,000 Hz. The antenna system is connected to an object (a survey platform) that is stationary or moving in an area of interest in air, over land, on water or under water. Such antenna system is generally used as part of a prospecting survey system for water, minerals or hydrocarbons.

Abstract: Method for semi-airborne electromagnetic prospecting for hydrocarbons or other fluids or minerals. In the method, electromagnetic receivers are deployed on the Earth's surface over a subsurface region (71). An airborne electromagnetic transmitter is flown over the receivers (72) and the receivers record at least one component of electromagnetic field data excited by the transmitter (73). The recorded electromagnetic data are analyzed for subsurface resistivity (74), and the resistivity is interpreted for evidence of hydrocarbons or other fluids or minerals (75). Compared to traditional fully airborne surveys, the advantages of the method include better signal-to-noise, and data for multiple source-receiver offsets.

Abstract: A current transformer includes capacitive phase angle error correction in the secondary circuit boosted by an isolating impedance. Temperature compensation for the phase error correction and amplitude correction is also provided.

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: According to one example embodiment is a time domain electromagnetic (TDEM) geophysical survey system for producing a B-field measurement, comprising: a transmitter coil; a bucking coil positioned in a substantially concentric and coplanar orientation relative to the transmitter coil; a receiver coil positioned in a substantially concentric and coplanar orientation relative to the bucking coil; an electrical current source connected to the transmitter coil and bucking coil for applying a periodic current thereto; and a data collection system configured to receive a magnetic field time-derivative signal dB/dt from the receiver coil and integrate the magnetic field time-derivative signal dB/dt to generate, a magnetic B-field measurement, the transmitter coil, bucking coil and receiver coil being positioned relative to each other such that, at the location of the receiver coil, a magnetic field generated by the bucking coil has a cancelling effect on a primary magnetic field generated by the transmitter coil.

Abstract: A magnetic signal noise reduction and detection system has inputs configured to receive data from a first total field scalar magnetometer, data from a vector magnetometer, and data from a position, velocity and heading sensor, a signal processor configured with a pre-processor system, an adaptive noise cancellation system and a detection system, the pre-processor system configured to carry out initial processing of data received. The pre-processor is configured to convert data to the frequency domain and pass the converted data to the adaptive noise cancellation system. The adaptive noise cancellation system is configured to carry out multivariate regression on the converted data to reduce detected noise. The detection system is configured to detect magnetic anomalies and output information in real time about the magnetic anomalies to a user interface.

Abstract: A tow assembly for an airborne electromagnetic surveying system, including: a transmitter coil frame supporting a transmitter coil, the transmitter coil frame being formed from a plurality of serially connected frame sections forming a loop, the transmitter coil frame having rotating joints at a plurality of locations about a circumference thereof enabling the transmitter coil frame to at least partially bend at the rotating joints; and a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly being attached to the circumference of the transmitter coil frame at spaced apart locations.

Abstract: A tow assembly for an airborne electromagnetic surveying system including a semi-rigid transmitter coil frame supporting a transmitter coil, the transmitter coil frame being formed from a plurality of serially connected frame sections forming a loop, the transmitter coil frame having articulating joints at a plurality of locations about a circumference thereof enabling the transmitter coil frame to at least partially bend at the articulating joints; and a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly comprising a plurality of ropes and attached to the circumference of the transmitter coil frame at spaced apart locations.

Abstract: The present disclosure relates to determining the attenuation of an electromagnetic signal passing through a conductive material. An antenna is provided and placed in relatively close proximity to the conductive material. An alternating current is passed through the antenna and the impedance of the antenna is measured. The attenuation is determined using the measured impedance. A single frequency measurement may be made, or multiple measurements using different frequencies may be made. Grouped parameters based on properties of the material and the frequency of the current are used to relate the coil impedance to the attenuation. A current frequency for which the ratio of the antenna's resistive part of the impedance to the angular frequency of the current is substantially insensitive to at least one of the parameters is preferred.

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: 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.

Abstract: A stabilized field sensor apparatus collects field data, in particular magnetic field data, with reduced motion noise. The apparatus includes a tear drop shaped housing, a tow frame in the housing, a plurality of vibration isolating dampers spaced around the frame, a base assembly mounted to the dampers, a support pedestal having a bottom end fixed to the base assembly and an upper free end, a single spherical air bearing connected to the upper free end of the pedestal, an instrument platform with a lower hollow funnel having an upper inside apex supported on the air bearing for a one point support, principal and secondary gyro stabilizers for maintaining pivotal and rotational stability, and at least one field sensor mounted to the instrument platform for collecting the field data while being stabilized against motion noise including vibration, pivoting and rotation from the base assembly, from the tow frame and from the housing.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A receiver coil apparatus for an electromagnetic survey system, comprising: a tubular outer frame defining an internal passage; a rigid inner member; a receiver coil; a plurality of first elastic suspension members suspending the receiver coil from the rigid inner member within the internal passage; and a plurality of second elastic suspension members suspending the rigid inner member within the internal passage.

Abstract: A receiver coil tow assembly for geophysical prospecting, comprising: multiple receiver coils, each receiver coil being housed within a respective tubular outer frame section that defines a continuous passageway in which the receiver coil extends, the tubular outer frame sections being connected together to provide a skeletal frame maintaining the receiver coils in a substantially constant position relative to each other; and a tow cable connected to the skeletal frame for towing the frame to conduct a geophysical survey.

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: Measurements made with a multicomponent logging system oriented in a horizontal position above the surface of the earth must satisfy certain relationships. These relationships are used to establish calibration errors in the system.

Abstract: A method for generating electromagnetic waves in the ELF/ULF comprising the steps of using a ground-based Horizontal Electric Dipole (HED) antenna to send electromagnetic pulses upwardly in the E-region of the ionosphere to form an oscillatory or pulsed electric field; allowing said pulsed electric field to interact with magnetized plasma of the lower ionosphere to generate a pulsed horizontal and vertical current which have associated Horizontal and Vertical Electric Dipole moment; and allowing them to radiate.

Abstract: A probe for an NMR device is disclosed in which a saddle coil is disposed on one side of a flexible insulating material, and an additional conductor is disposed on the opposite side. The additional conductor and the conductors of the saddle coil create a capacitance across the insulating material. This capacitance acts with the inductance of the saddle coil such that the probe itself forms a transmission line. The probe is thus inherently broadband and requires no tuning. It also presents a constant impedance, thus facilitating impedance matching to an NMR spectrometer. In a preferred embodiment, a chip resistor is disposed on the flexible insulating material, terminating the transmission line.

Abstract: The present invention is a double-suspension receiver coil apparatus and system for conducting electromagnetic surveys including, both ground-based and airborne measurements. The present invention includes at least one receiver coil suspended by way of first suspension members within an inner frame and said inner frame being suspended by second suspension members within an inner ring which is further enclosed within an outer frame. The double-suspension receiver coil apparatus functions so as to maintain the receiver coil position while minimizing vibrations in order to achieve a high signal-to-noise ratio and enable accurate measurements. The receiver coil may be in an airborne system in a near-horizontal position or in a ground system in a vertical position.

Abstract: According to one example embodiment is a time domain electromagnetic (TDEM) geophysical survey system for producing a B-field measurement, comprising: a transmitter coil; a bucking coil positioned in a substantially concentric and coplanar orientation relative to the transmitter coil; a receiver coil positioned in a substantially concentric and coplanar orientation relative to the bucking coil; an electrical current source connected to the transmitter coil and bucking coil for applying a periodic current thereto; and a data collection system configured to receive a magnetic field time-derivative signal dB/dt from the receiver coil and integrate the magnetic field time-derivative signal dB/dt to generate, a magnetic B-field measurement, the transmitter coil, bucking coil and receiver coil being positioned relative to each other such that, at the location of the receiver coil, a magnetic field generated by the bucking coil has a cancelling effect on a primary magnetic field generated by the transmitter coil.

Abstract: An airborne time domain electromagnetic survey system is provided. The system and apparatus of the present invention are able to address the interest in exploring base metals and uranium deposits at depths approaching 1 kilometer. It encompasses a transmitter coil having a large magnetic dipole moment, flight stability, which is light weight, compatible with small helicopters, and can be transported, setup and repaired in the field. It is of a semi-rigid modular structure that can decrease the incidence of damage or breakage during take-off or landing in rough terrain.

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.

Abstract: A system or method of creating a map of voids in the ground based on a scattered electromagnetic signal includes traversing a receiver/probe in a near field above a target area; generating a signal from a signal transmitter, the signal having a predetermined wavelength ?; receiving a scattered signal with the receiver/probe, the scattered signal including indications of subsurface variations via reflection of the generated signal; and detecting evanescent components of the scattered signal to provide a predetermined resolution. The method includes the use of an electrically small antenna for resolution of subwavelength features. The metamaterial-based antenna is on the order of meters and has an efficient transmit/receive capability. The ESA is 1/10 of the length of the equivalent dipole length, and may be scaled down to 1/10,000. Such an antenna may include phase sensitive current injection in the metamaterial resonant structures for loss-compensation.

Abstract: Methods and systems for detecting an angular position of an electric motor are disclosed, including sending an electrical pulse through a stator coil of the electric motor, determining an approximate angular position of a rotor of the electric motor in response to detecting an timing of a returning electrical pulse from the stator coil, the timing of the returning electrical pulse being indicative of the angular position of the rotor; and determining an accurate position of the rotor in response to sensing a transition of a digital sensor in response to the rotor rotating relative to the stator, the transition being indicative of the accurate position.

Abstract: A receiver coil apparatus for an electromagnetic survey system, comprising: a tubular outer frame defining an internal passage; a rigid inner member; a receiver coil; a plurality of first elastic suspension members suspending the receiver coil from the rigid inner member within the internal passage; and a plurality of second elastic suspension members suspending the rigid inner member within the internal passage.

Abstract: A tow assembly for an airborne electromagnetic surveying system, comprising: a semi-rigid transmitter coil frame supporting a transmitter coil, the transmitter coil frame being formed from a plurality of serially connected frame sections forming a loop, the transmitter coil frame having articulating joints at a plurality of locations about a circumference thereof enabling the transmitter coil frame to at least partially bend at the articulating joints; and a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly comprising a plurality of ropes and attached to the circumference of the transmitter coil frame at spaced apart locations.

Abstract: An airborne time domain electromagnetic surveying system is provided. The system includes a tow assembly with a flexible support frame. The flexible support frame spaced apart from the aircraft includes a transmitter section with a transmitter loop and a receiver section with a sensor aligned with the central axis of the transmitter section. The flexible support frame has a lightweight modular structure that enables the surface area of the transmitter section to be increased and decreased to suit particular survey applications. The transmitter loop sends a pulse in an “ON” interval, and in an “OFF” interval the sensor measures the earth response to the pulse. The tow assembly also includes a sensor for generating selected survey data in the “ON” interval. A transmitter driver enables the creation of earthbound pulse. The system components are linked to a computer and control computer program linked thereto for controlling the functions thereof.