Abstract: Embodiments include one or more high altitude, long endurance (HALE) unmanned aircraft capable of persistent station-keeping having one or more electromagnetic (IR/Visual/RF) sensor elements or suites for purposes of survey and/or signal gathering. Embodiments include one or more high altitude, long endurance (HALE) unmanned aircraft capable of persistent station-keeping having a directable laser. Embodiments include a group of four or more high altitude, long endurance (HALE) unmanned aircraft configured as GPS repeaters.

Abstract: Aspects of the disclosure may reduce motion noise by mounting vector component sensors on a bottom-weighted instrument platform that is supported with a spherical bearing. An apparatus for data acquisition is provided. The apparatus includes a base assembly, a spherical bearing mounted to the base assembly, and an instrument platform having at least one vector component sensor fixed thereto. The instrument platform is mounted on and supported by the spherical bearing. The spherical bearing couples the instrument platform to the base assembly and allows free angular rotation of the instrument platform, within a tilt angle range. The instrument platform is bottom weighted in that it has a center of mass disposed below its center of rotation. The apparatus may include a controller that receives and/or stores data from the at least one sensor.

Abstract: Disclosed in the present invention is a multi-mode data observation method based on unmanned aerial vehicle formation for semi-airborne electromagnetic surveying. The method includes four basic formation modes: a ZX formation mode for obtaining the Z component of the response field with a high signal-to-noise ratio and the X direction gradient data of the Z component of the response field in different scales; a ZZ formation mode for obtaining the Z direction gradient data of the Z component of the response field in different scales; an XX formation mode for obtaining the X component of the response field with a high signal-to-noise ratio and the X direction gradient data of the X component of the response field in different scales; an XZ formation mode for obtaining the Z direction gradient data of the X component of the response field in different scales.

Abstract: In some examples, a sensor node comprises a sensor to measure survey data of a target structure. The sensor node receives a wireless synchronization signal, and synchronizes an operation of the sensor node based on the wireless synchronization signal.

Abstract: A method of generating a magnetic anomaly map and a system to develop a magnetic anomaly map are described. The method includes obtaining magnetic compass data recorded by two or more magnetic compasses disposed along a seismic streamer that traverses a first area and obtaining measurements from one or more navigation systems over the first area. The method also includes determining a correct position of each of the two or more magnetic compasses based on the measurements from the one or more navigation systems, and comparing the magnetic compass data with theoretical magnetic field data at the correct positions to generate a magnetic anomaly map.

Abstract: Technology for determining a geographical location is described. A sequence of magnetic field gradient measurements can be identified for specific positions on the Earth that correspond to a path traveled by a moving platform. The sequence of magnetic field gradient measurements for the path can be compared to a reference magnetic field gradient map. A trajectory derived from the reference magnetic field gradient map that correlates to the sequence of magnetic field gradient measurements can be identified. The trajectory can have known geographical coordinates. The geographical location of the moving platform can be determined based on the known geographical coordinates of the trajectory.

Abstract: A system and method for airborne geophysical exploration over the ground are disclosed. In one embodiment of the system, two towing bodies are towed behind an aircraft in flight in a vertically spaced-apart relation above a ground station. Respective magnetometer measurement instruments are located within each of the towing bodies and the ground station. Each magnetometer measurement instrument collects total field magnitude data to contribute to the magnetic vertical gradient data relative to magnetic crustal anomalies of geological origin and variations in an ambient magnetic field above the surface area of the survey. Each magnetometer measurement instrument also collects location, time, and inertial data substantially simultaneously with the total field magnitude data to provide position-correlated measurements thereof.

Abstract: An electromagnetic geophysical exploration system includes a first transmitter configured to transmit a first waveform in a first spectrum, a first receiver configured to sense signals in the first spectrum, a second transmitter configured to transmit a second waveform in a second spectrum, the second spectrum having a frequency higher than a frequency of the first spectrum, a second receiver configured to sense signals in the second spectrum, the second receiver configured to be minimum-coupled to the second transmitter, wherein a transmitter coil of the second transmitter is disposed between an inner receiver coil and an outer receiver coil of the second receiver, and the inner receiver coil and the outer receiver coil of the second receiver surround the transmitter coil of the second transmitter, and a control portion configured to control the first transmitter and the second transmitter.

Abstract: Implementations are directed to surveying equipment and/or signals at well sites using an aerial drone. In some implementations, actions include receiving data provided from the aerial drone, the data including signal measurement data, location data, and one or more of image data and video data associated with a well-site, processing the data to provide one or more of a signal survey and a well-site survey associated with the well-site, the signal survey indicating a strength of a signal at multiple locations of the well-site, the well-site survey indicating one or more pieces of equipment located at the well-site, and providing the one or more of the signal survey and the well-site survey to provide an equipment schedule, the equipment schedule identifying equipment to be installed at the well-site and, for at least one piece of equipment, a location to install the at least one piece of equipment.

Abstract: A method of migrating unmanned aerial vehicle (UAV) operations between geographic survey areas, including: uploading a first plurality of flight missions into a first UAV pod; deploying the UAV pod; autonomously launching the UAV from the UAV pod a plurality of times to perform the first plurality of flight missions; providing first survey data from the UAV to the UAV pod; autonomously migrating the UAV from the first UAV pod to a second UAV pod; receiving a second plurality of flight missions in a second UAV pod; providing the UAV with one of the second plurality of flight missions from the second UAV pod; autonomously launching the UAV from the second UAV pod a plurality of times to perform the second plurality of flight missions; and providing a second survey data from the UAV to the second UAV pod; where the autonomous migrating of the UAV to accomplish the first and second survey data happens autonomously and without active human intervention.

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: Methods and configurations are disclosed for exploiting characteristic magnetic signature of electrical power transmission and distribution lines for navigation.

Abstract: An aeromagnetic pre-processing system based on a graphic user interface (GUI) includes an input unit for inputting measured aeromagnetic data, GPS data, and reference magnetic data, a data storage unit for storing individual data, collection data, and edition data on division area data groups obtained after an investigation area is divided, a GUI providing unit for providing a GUI for data input/output, an operation unit for performing an operation to perform pre-processing for each of the division area data groups and collection and leveling of the division area data groups, and a controller for controlling the input unit, the data storage unit, the GUI providing unit, and the operation unit.

Abstract: Techniques for tracking large numbers of moving objects in an event processing system are provided. An input event stream can be received, where the events in the input event stream represent the movement of a plurality of geometries or objects. The input event stream can then be partitioned among a number of processing nodes of the event processing system, thereby enabling parallel processing of one or more continuous queries for tracking the objects. The partitioning can be performed such that each processing node is configured to track objects in a predefined spatial region, and the spatial regions for at least two nodes overlap. This overlapping window enables a single node to find, e.g., all of the objects within a particular distance of a target object, even if the target object is in the process of moving from the region of that node to the overlapping region of another node.

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: Embodiments include one or more high altitude, long endurance (HALE) unmanned aircraft (110) capable of persistent station-keeping having one or more electromagnetic (IR/Visual/RF) sensor elements or suites (112, 337) for purposes of survey and/or signal gathering. Embodiments include one or more high altitude, long endurance (HALE) unmanned aircraft (110) capable of persistent station-keeping having a directable laser (331). Embodiments include a group of four or more high altitude, long endurance (HALE) unmanned aircraft (611-614) configured as GPS repeaters.

Abstract: Methods and apparatuses for geophysical surveying are disclosed. In one embodiment, a marine vehicle may obtain magnetic measurements in a location around a drilling site. The magnetic measurements may be used to calculate a localized disturbance magnetic field resulting from, for example, solar flares. The localized disturbance magnetic field may be used to calculate a declination value and, thus, a wellbore position with improved accuracy.

Abstract: Disclosed are a portable unmanned airship for magnetic survey and a magnetic survey system using the same. The portable unmanned airship includes a fuselage using buoyancy of gas and propelled by motive power of the fuselage itself; an auto-flight unit automatically guiding the fuselage; a magnetometer disposed in the fuselage and measuring magnetic force of a stratum or a surface of the earth; a wireless communication unit transmitting magnetic data obtained by the magnetometer outside; and a control module controlling operations of the auto-flight unit and the magnetometer. With this configuration, it is possible to increase total operation time and a payload capacity of the unmanned airship.

Abstract: The present invention provides methods and apparatus for unmanned aerial vehicles (UAVs) with improved reliability. According to one aspect of the invention, interference experienced by onboard sensors from onboard electrical components is reduced. According to another aspect of the invention, user-configuration or assembly of electrical components is minimized to reduce user errors.

Abstract: The present invention provides a light weight, modular and rigid structure for supporting the transmitter loop of an airborne electromagnetic system. The airborne electromagnetic surveying system comprises a tow assembly connected to an aircraft, the tow assembly including a transmitter section comprising a transmitter coil for generating a primary electromagnetic field that induces a secondary electromagnetic field. The transmitter coil is supported by a generally rigid transmitter frame. The transmitter frame comprises a plurality of frame sections assembled in a way such that the generally rigid transmitter frame substantially retains a rigid shape during operation. The system may also include a receiver section located above the generally rigid transmitter frame in between the aircraft and the generally rigid transmitter frame for detecting the secondary electromagnetic field.

Abstract: Downhole tools and techniques acquire information regarding nearby conductors such as pipes, well casing, and conductive formations. At least some method embodiments provide a current flow along a drill string in a borehole. The current flow disperses into the surrounding formation and causes a secondary current flow in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates may be obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.

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: 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: The invention relates to a method of determining a susceptibility gradient map, the method comprising acquiring (300) a magnetic resonance k-space dataset, said dataset comprising magnetic resonance echo data, wherein a recursive iteration is used to determine the susceptibility gradient map. Further, the invention relates to a method of determining a susceptibility gradient map, the method comprising acquiring a magnetic resonance k-space dataset, said dataset comprising magnetic resonance echo data, wherein the acquired dataset comprises magnetic resonance echo data of multiple echoes with different echo times, wherein a susceptibility gradient map is determined separately for each echo time resulting in a temporary susceptibility gradient map, wherein the method further comprises calculating a total susceptibility gradient map by combining all determined temporary susceptibility gradient maps.

Abstract: A method of determining the maximum temperature undergone by a specimen of sedimentary rock during natural heating over a geological process, within the range from 60° C. to 230° C. approximately. The method includes analysis at very low temperature, down to a few kelvin, for example down to 10 kelvin, of the magnetic transitions intended to characterize an iron oxide and an iron sulfide that are formed or destroyed in the specimen by the geological heating of the sediment; and determination of the maximum temperature undergone by the specimen, using a calibration obtained by measuring the same magnetic parameters on the same sediment or on other sediments of the same nature, heated beforehand in the laboratory to known temperatures.

Abstract: A pneumatic vibration isolating suspension is disclosed for supporting a payload on a moving carrier while suppressing the transmission of vibrations in the 1 to 50 Hz band between the carrier and the payload. The disclosed invention can be deployed in the air in a towed carrier or sonde, and operated from aircraft power, making it a suitable platform for airborne geophysical instrumentation. It also has particular application to airborne electromagnetic surveying operating in the same frequency band because the sensor vibrations that result in noise created by the modulation of the sensor coupling with the earth's magnetic field are suppressed. Furthermore, the invention can be constructed from resistive composite materials and non-magnetic metals, so it can be operated without producing significant modification to the ambient electromagnetic field being measured.

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: 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 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 technique utilizes the acquisition of data from desired subterranean regions via a logging system. The logging system is constructed for use in a wellbore and comprises a transmitter module having a transmitter antenna. Additionally, the logging system utilizes a receiver module spaced from the transmitter module and having a receiver antenna. The transmitter antenna and the receiver antenna are oriented to enable sensitivity in desired directions, such as ahead of the logging system.

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 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 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: The present invention relates to a HTEM system that includes a semi-rigid bucking coil and an algorithm to determine the magnetic field B from the measured signal dB/dt. The bucking coil may be positioned in a concentric coplanar manner relative to a transmitter coil and receiver coil, in order to minimize spurious signals at the receiver coil during data acquisition time. Signals gathered by the system may be further processed by a signal processing means. Moreover, measurements performed upon data generated by the system may be performed upon the entire period of a current waveform applied to the transmitter and bucking coils.

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 apparatus for detecting a position of a component in an earth formation is disclosed. The apparatus includes: a transmitter configured to emit a first magnetic field into the earth formation and induce an electric current in the component, the transmitter having a first magnetic dipole extending in a first direction; and a receiver for detecting a second magnetic field generated by the component in response to the first magnetic field, the receiver having a second magnetic dipole extending in a second direction orthogonal to the first direction. A method and computer program product for detecting a position of a component in an earth formation is also disclosed.

Abstract: Disclosed are a portable unmanned airship for magnetic survey and a magnetic survey system using the same. The portable unmanned airship includes a fuselage using buoyancy of gas and propelled by motive power of the fuselage itself; an auto-flight unit automatically guiding the fuselage; a magnetometer disposed in the fuselage and measuring magnetic force of a stratum or a surface of the earth; a wireless communication unit transmitting magnetic data obtained by the magnetometer outside; and a control module controlling operations of the auto-flight unit and the magnetometer. With this configuration, it is possible to increase total operation time and a payload capacity of the unmanned airship.

Abstract: An apparatus, method and computer-readable medium for obtaining a resistivity image of an earth formation. The apparatus includes a downhole assembly configured to be conveyed in a borehole penetrating the earth formation; a plurality of sensor electrodes on the downhole assembly, each of the plurality of sensor electrodes having a different capacitance to a wall of the borehole; and at least one processor configured to: (i) process measurements using each of the sensor electrodes; (ii) process a subset of the measurements substantially unaffected by the different capacitances to produce an image of the borehole wall; and (iii) record the image on a suitable medium.

Abstract: A method for designing a controlled-source electromagnetic survey that will discriminate between a defined deep marginal-interest reservoir (2) and specified false positive resistivity structures of concern (3, 4, 5). A reservoir model and a false positive model are constructed for each false positive scenario. The resistivity of the false positive model may be tuned to give electromagnetic data similar enough to the reservoir model when forward modeled that any differences fall in the model null space. A null-space discriminating ratio (“NSDR”) is defined, for example as the peak normalized difference of the two related modeled electromagnetic field data sets. An area coverage display of NSDR values (6) allows determination of such additional data as may be needed to distinguish the false positive body, and a survey design is developed accordingly (7). Reduction of the number of variables affecting the area coverage displays is a key feature of the method.

Abstract: A magnetic field has a threshold that adapts in relation to a magnitude of a magnetic field signal representative of a movement of an object. A corresponding method adapts a threshold in relation to a magnitude of a magnetic field signal representative of a movement of an object.

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: The invention provides for systems and methods of enhancing crude oil recovery providing an array of electromagnetic receiver antennae arranged and operated in conjunction with an array of far field electromagnetic transmitter antennae for mapping subsurface features of a reservoir. Mapping is performed according to the relative intensities, frequencies, phase shifts, and/or other reflected signal parameters of the reflections received by the receiver antennae (relative to the transmit signals) associated with a given location or target area within a reservoir. Such mapping aids in determining an optimal location of a production well or the location of an auxiliary well relative to the production well.

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 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: A hybrid-technology metal detector, using pulse-induction and sine-wave excitation of the transmitter coil alternately, in rapid succession. The energy stored in the transmitter coil, in the pulsed mode, is used to shock-excite a high-Q circuit formed by the coil and a parallel capacitor into oscillations in the sine-wave mode. The multiplicative action of the circuit Q causes high currents to flow in the transmitter coil, causing high fluxes to be impressed on the searched area, with increased sensitivity as a result. Using a linear coil-current ramp to assess and minimize the coupling between the transmitter and receiver coils permits effective separation of the reactive and resistive components of the target signals, making accurate identification of targets possible.

Abstract: A suspension net is provided for distributing tension forces from a tow rope to an electromagnetic bird used for geophysical surveying. The suspension net allows large transmitter loop sizes, and the net structure generally avoids rope confusions that can occur during lift-up.

Abstract: The present invention relates to a HTEM system that includes a semi-rigid bucking coil and an algorithm to determine the magnetic field B from the measured signal dB/dt. The bucking coil may be positioned in a concentric coplanar manner relative to a transmitter coil and receiver coil, in order to minimize spurious signals at the receiver coil during data acquisition time. Signals gathered by the system may be further processed by a signal processing means. Moreover, measurements performed upon data generated by the system may be performed upon the entire period of a current waveform applied to the transmitter and bucking coils.

Abstract: An airborne electromagnetic survey system for conducting geological mapping is disclosed. A transmitter closed loop structure is used in the system and is designed for connection to a towing airborne vehicle. The transmitter loop structure comprises a plurality of interconnected loop segments, and transmitting means are fitted to at least one of the loop segments for generating and transmitting an earthbound primary electromagnetic field effective for geological surveying. Sensing means are fitted to the loop segments for receiving and sensing a vertical component of a secondary resulting electromagnetic field which arises from an interaction of the primary electromagnetic field with ground bodies that are traversed by the sensing means, while simultaneously nulling the primary electromagnetic field.

Abstract: A method of determining the nature of a submarine or subterranean reservoir having an electromagnetic characteristic is described. The method comprises analyzing data associated with the application of a time varying electromagnetic field from above the reservoir using a data analysis methodology that does not utilize an estimate of the reservoir's geometry in determining one or more characteristics of the reservoir.