Abstract: A metal detector employing digital means for the generation of highly quality reference signals used for transmission and demodulation and capable of continuously monitoring the parameters of the transmitting and receiving coils. Using the monitored signals and calibration of the measurements paths in both amplitude-frequency and phase-frequency, the effects of the targets and magnetic and/or conductive grounds on the transmitting and receiving coils are greatly reduced, leaving the received signals substantially free of instrumental effects. Methods of ground tracking and filtering are described to separate target information from the ground plus-target receive signals. Single-and multi-frequency operation, with or without modulation for both sinusoidal and square wave transmission, is described, as are means to detect abnormal situations and to find and operate at resonance.

Abstract: The invention relates to an apparatus and method for performing passive geophysical prospecting. More particularly, the present invention relates to an improved apparatus and method for locating and selected subsurface Earth material deposits or geologic formations bearing hydrocarbons, oil, gas, or commercially important ore deposits, precious metals, as a function of impulse discontinuities in the near surface atmosphere of the invention. A passive geophysical prospecting method and apparatus are provided. The apparatus has a magnetic component antenna for detecting electromagnetic radiation naturally emanating from the Earth's surface and an electrical signal from the detected electromagnetic radiation while traversing the Earth's surface by a vehicle traveling over land or water or in an airplane.

Abstract: An electronic component includes a semiconductor chip with a chip topside, an integrated circuit, and a chip backside. The chip backside includes a magnetic layer. The electronic component further includes a chip carrier with a magnetic layer on its carrier topside. At least one of the two magnetic layers is permanently magnetic such that the semiconductor chip is magnetically fixed on the chip carrier.

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: An array of induction magnetometers for use in airborne transient electromagnetic (ATEM) geophysical exploration is disclosed, having similar weight and external dimensions of prior art induction magnetometers but with improved signal strength, signal-to-noise ratio, higher frequency, self-resonance and bandwidth, and providing accurate and well monitored calibration.

Abstract: This invention concerns a method of making airborne geophysical measurements. Such measurements may be made from fixed or moving wing airplanes or dirigibles. The method comprises the following steps: taking first real time measurements from one, or more, geophysical instruments mounted in an aircraft to produce geophysical data related to the ground below that instrument. Taking second real time measurements from navigation and mapping instruments associated with or carried by the aircraft. Computing a background response of each geophysical instrument using the second real time measurements to take account of its time varying altitude, and the time varying topography of the ground below it. Adjusting an operating or data processing condition of each geophysical instrument using the respective background response and the instrument's attitude to enhance the performance of that instrument.

Abstract: In a magnetic resonance apparatus, the transmission coil for generating the radiofrequency excitation field is stationarily arranged. The geometry of the transmission coil is permanently prescribed. For acquiring the magnetic resonance signal, the reception arrangement includes at least one first local coil. This is secured to a movable carrier, so that it can be placed against the person from a remote position. The carrier is secured in a carrier mount arranged stationarily within the examination volume.

Abstract: An aircraft equipped for airborne vector magnetic exploration surveys comprising three magnetometers orthogonally mounted to measure the components of the earth's vector magnetic field; two rotation sensors mounted to measure the angular orientation of the aircraft; and a recording system to record the measurements of the magnetometers, and rotation sensors. The measured angular orientation is used to orientate the measured components of the earth's vector magnetic field to derive true vector aero-magnetic (VAM) data from airborne surveys. Also disclosed is a method for processing magnetic data by removing the permanent, induced, and eddy-current magnetic effects of the aircraft from the magnetic data.

Abstract: An induction logging tool is used on a MWD bottom hole assembly. Due to the finite, nonzero, conductivity of the mandrel, conventional multi frequency focusing (MFF) does not work. A correction is made to the induction logging data to give measurements simulating a perfectly conducting mandrel. MFF can then be applied to the corrected data to give formation resistivities.

Abstract: There is provided a ground sensor assembly adapted for deployment from air to a selected ground location. The ground sensor assembly comprises an aerially deployable sensor housing which has upper and lower housing ends defining a longitudinally elongated aperture therebetween. A plurality of connected sensor modules are longitudinally inserted into the aperture between the upper and lower housing ends. Furthermore, an aerodynamic module is connected to the sensor modules and is disposed adjacent the upper housing end outside the aperture. This aerodynamic module has a plurality of stabilizers which radially extend outward therefrom and form a generally parallel relationship with the upper housing end. Such stabilizers provide aerodynamic stability during the deployment of the ground sensor assembly from the air to the selected ground location.

Abstract: A method for geographical surveying includes the steps of determining an observation grid comprising observation points above a solution volume in the ground; making gravitational measurements at the observation points over a survey area; compiling a matrix having elements relating a set of gravitational accelerations and gravity gradient values at the points to the mass values for volume elements in the solution volume; and calculating the three-dimensional density distribution of the volume under the survey area based on the gravitational measurements and the inverse of the matrix. By measuring the magnetic field and gradient at the observation points, the three-dimensional magnetic susceptibility distribution of the volume under the survey area can be determined.

Abstract: A system, computer product and method for generating geophysical data is provided. At least one airborne sensor unit is provided which measures low frequency natural electromagnetic fields. Geophysical data is extrapolated from the tilt angles of the electromagnetic field by a computer running a data processing application. The system further includes a spatial attitude detection facility. The data processing application filters out distortions to the tilt angles caused by movement of the airborne sensor unit. The system further includes facilities for filtering out electronic noise.

Abstract: A airborne electromagnetic induction (EMI) detection apparatus and system. In accordance with one embodiment, the EMI detection apparatus includes a transmitter element in the form of a transmitter coil that emits a primary, multi-frequency component magnetic field which induces a secondary magnetic field in an external body. A receiver element in the form of a receiver coil is mounted in a horizontal loop-loop orientation with respect to the transmitter coil and receives the secondary magnetic field. The detection apparatus further includes a magnetic shield disposed around the receiver coil to limit the lateral footprint diameter observed by the receiving element and to shield the receiver coil from the primary magnetic field and other external electromagnetic radiation to improve the gain and resolution of the detection apparatus.

Abstract: A stable heli-borne vector platform capable of accepting a range of different sensors or instruments, particularly, but not exclusively, for the mapping and exploration of mountainous regions is described. The platform enables the arrangement of the sensors in three orthogonal directions, thus allowing the restitution of the resultant vector. The geographical referencing is provided by the use of a differential GPS receiver, whose antenna is installed on the main body of the platform. This platform distinguishes itself from its predecessors through the use of a lateral pulling axis, the use of a heavy weight placed underneath the main body, and by a perfectly symmetrical geometry in the direction of pull, thus ensuring perfect in-flight balance and stability.

Abstract: A magnetotelluric geophysical survey system used with an airborne survey bird for natural resource exploration of oil and gas, mineral deposits and aquifers. The survey system uses natural electromagnetic EM fields as an energy source. The magnetotelluric airborne survey system includes an aerodynamic airborne survey bird adapted for being towed behind a helicopter or fixed wing aircraft. The survey system can also be incorporated into a fixed wind aircraft. The survey system includes a non-conductive nose boom on the survey bird with orthogonal electric dipoles for measuring electric fields from 0.01 Hz up to 480 Hz. An angular motion detector is mounted inside the bird and used for compensating for errors caused by angular motion of the bird when in the presence of strong electric field gradients. The survey bird can use a single magnetometer or pairs of magnetometers for measuring electromagnetic gradients.

Abstract: A location system for objects having location devices (16) as a means for repeatedly interrogating the location devices on each object to provide position signals. A means (18) to detect the position signals are provided. The position of each object and the area associated with each object are determined from the position signals and stored. The system is then able to determine the relative locations of the thus determined objects and associated areas.

Abstract: In order to nullify the adverse effect of an external magnetic field on a static magnetic field generated in an MRI system, small-size coils are used to generate a compensation magnetic field. Thus, the component of the static magnetic field to be applied to a magnetic sensor is canceled. The magnetic sensor can therefore detect the external magnetic field highly precisely. A correction current proportional to the external magnetic field detected highly precisely is fed to BO correction coils. Eventually, the external magnetic field that adversely affects the static magnetic field is canceled.

Abstract: A method for geographical surveying includes the steps of determining an observation grid comprising observation points above a solution volume in the ground; making gravitational measurements at the observation points over a survey area; compiling a matrix having elements relating a set of gravitational accelerations and gravity gradient values at the points to the mass values for volume elements in the solution volume; and calculating the three-dimensional density distribution of the volume under the survey area based on the gravitational measurements and the inverse of the matrix. By measuring the magnetic field and gradient at the observation points, the three-dimensional magnetic susceptibility distribution of the volume under the survey area can be determined.

Abstract: A housing and bucking coil and receiving coil system for a helicopter towed concentric coil electromagnetic survey system that reduces micro phonic and primary field noise. The device includes an isolation housing, a bucking coil and receiving coil assembly with structural members to rigidly join the two coils together and a suspension system to suspend the joined bucking and receiving coils, in a floating manner, by bungee cords or similar non-metallic vibration dampening devices.

Abstract: The present invention is directed to a method and apparatus for measuring a magnetic field and determining whether an anomaly is present based on the magnetic field measurement and a measured ambient magnetic field. The present invention is also directed to a method and apparatus for measuring the intensity of the magnetic field by implementing operations to essentially eliminate error components that arise due to factors including offsets and gains affecting the intensity signal processing.

Abstract: The present invention provides a power frequency, i.e., time-varying, magnetic field (PF-NF) detector system for characterizing the operational condition of a remote facility responsive to time-varying magnetic fields generated by electrical transmission lines associated with the remote facility. The PF-MF detector system advantageously includes a PF-MF sensor which generates N time-varying magnetic field data sets, and a PF-MF analyzer which generates an operational condition assessment responsive to the N time-varying magnetic field data sets, wherein N is an integer greater than or equal to 1. Additionally, the PF-MF detector system includes an accumulator which stores and forwards the N time-varying magnetic field data sets to the PF-MF analyzer via a communications channel. A method for characterizing the operational condition of inaccessible electrical equipment responsive to the time-varying magnetic field generated by a transmission line are also described.

Abstract: An apparatus for reducing rotation of an article such as a bird for holding a superconducting quantum interference device for use in airborne transient electromagnetic mineral prospecting. The apparatus includes a support sphere having an inner shell and an outer shell. Liquid is contained between the inner and outer shells and a sphere has openings through which support strings project for locking to an internal point within the sphere. The strings have one end connected to an internal point within the support sphere and another end connected to a spring. The spring includes a damper for damping movement of the spring. Baffles are arranged in the cavity between the inner and outer shells in which the liquid is contained for damping movement of the liquid.

Abstract: A navigation and mobile communication satellite system including a Geo-Mobile (GEM) satellite (14) and a plurality of Global Position System (GPS) satellites (50). The GEM satellite (14) is in operative communication with at least one ground segment (12) and at least one user segment (16), and includes a GEM processor for providing communication services to the user segments (16). The GPS network is also in operative communication with at least one of the user segments (16) and at least one of the ground segments (12). The GPS network provides navigation data to the user segment (16). Each of the ground segments (12) include a gateway station (28) for receiving the navigation data and uplinking the navigation data to the GEM satellite (14) such that the navigation data is rebroadcast to the user segments (16) at a higher power than from the GPS network alone. In this manner, the GEM system provides a navigation signal at a much higher power than the present GPS system.

Abstract: A method and apparatus are provided for surveying a given region for the presence of ferromagnetic items and other sources of magnetic field disturbance on or under the ground, such as pipelines and wellheads, etc. An array of magnetic field sensors, mounted on a suitable framework, is passed over the region while the sensors emit appropriate signals, whereupon the signals are used to determine the total magnetic field and its gradients, with respect to distance, a) in the direction of movement, b) horizontally transverse to the direction of movement, and c) in the vertical direction. The total field and its gradients are interpreted to show the presence or absence of sources of magnetic field disturbance items, as well as to discriminate between various categories of such sources.

Abstract: A towed aircraft for use in an airborne electromagnetic geophysical prospecting system which includes a transmitting antenna and power generating means for powering the antenna. A bird to which is mounted a receiving antenna may be towed by the towed aircraft.

Abstract: A real time geophysical survey system and method. The system comprises a base station, one or more data acquisition vehicles, and a global positioning satellite network. The base station is provided with a computer, radio communication equipment, and means for determining from signals of the satellite network the position of the base station. The data acquisition vehicles are each provided with geophysical survey instrumentation, radio communication equipment, an acquisition vehicle positioning display, and means using signals of the satellite network to calculate at least an approximate horizontal position of the data acquisition vehicle. During a survey, by periodically polling each data acquisition vehicle, the base station determines the location of each data acquistion vehicle and accurately tracks its position, both with respect to the base station and with respect to a preselected survey pattern over the geographic area to be surveyed.

Abstract: A real time geophysical survey system and method. The system comprises a base station, one or more data acquisition vehicles, and one or more fixed reference stations. The base station is provided with a positioning system, suitable survey instrumentation, a computer, and radio communication equipment. The data acquistion vehicles are each provided with a positioning transponder, a positioning display, suitable survey instrumentation, and radio communication equipment. During a survey, by periodically polling each vehicle's positioning transponder, the base station positioning system tracks the position of each vehicle with respect to both the base station and the fixed reference stations. Data regarding each vehicle's position are then provided to the base station computer, and the base station transmits signals to the positioning display aboard each vehicle so as to guide the vehicle along a preselected survey pattern.

Abstract: Magnetic detector apparatus comprises a pair of electrically matched magnetic sensor assemblies supported at opposite ends of a titanium sensor tube of significant length. The sensor tube is supported in a liquid bath so as to resist gravitational forces tending to distort the sensor tube and thereby misalign the magnetic axes of the sensors. The excitation conductors of the sensors are connected in series with an electrically conducting path formed through the sensor tube by spider members in electrical contact with the tube interior and connected to the respective excitation conductors.

Abstract: A method of reducing magnetic data recorded at latitudes close to the magnetic equator to the equator is disclosed. The result corrects magnetic field anomalies recorded with respect to geologic anomalies to more closely reflect the shape of the geologic anomalies. In the preferred embodiment, reduction-to-the-equator is carried out in the wave number domain using an operator ##EQU1## .

Abstract: Magnetic detector apparatus comprises a pair of electrically matched magnetic sensor assemblies supported at opposite ends of a titanium sensor tube of significant length. The sensor tube is supported in a liquid bath so as to resist gravitational forces tending to distort the sensor tube and thereby misalign the magnetic axes of the sensors. The excitation conductors of the sensors are connected in series with an electrically conducting path formed through the sensor tube by spider members in electrical contact with the tube interior and connected to the respective excitation conductors.

Abstract: Method and apparatus are disclosed for airborne gravity surveying in which the airborne vehicle is stabilized with respect to speed, direction of heading and altitude, and in which the gravity meter has adequate sensitivity and signals that are recorded at a high sample rate on a magnetic tape, in which the aircraft position is computed using a multi-range navigation system that is located geodetically.

Abstract: A pair of magnetometer units symmetrically displaced from a reference measuring point along one axis and at least one magnetometer unit displaced from the reference point along a second axis perpendicular to the first axis respectively sense three and two directional field components of a magnetic source along two axes at each of the unit locations parallel to the first and second axes and a third axis perpendicular thereto at each of said pair of units. Total field strength and field gradients of the magnetic source are calculated from measurement sensor signals supplied by the magnetometer units to determine the position of the magnetic source relative to the reference point and its magnetic moments.

Abstract: An airborne system for automatically and electronically recognizing and dcting the relative presence of invariant features of a transient submarine signal occurring in the presence of signal-like noise. A plurality of comb filters receive MAD signal information in the amplitude-time domain and filter it to provide amplitude-time-frequency domain information. The primary features (positive and negative slopes) of this latter information are then abstracted, the abstracted information being utilized in a signal processor to detect and recognize the relative presence of invariant, submarine recognition features. Upon recognition, a decision thereof is routed to a visual display.