Abstract: A sea-floor electromagnetic measurement device for obtaining underwater measurements of earth formations including a central structure and arms attached to the central structure so that they can pivot relative to the central structure. An electrode is attached to the end of each of the arms or to the central structure, and/or magnetometers are attached to the arms.

Abstract: Apparatus for determining the distribution of the electric polarization of a vessel in water, comprises an array of electric potential sensors (22) which are located in the water beneath the vessel and each generates a signal corresponding to the amplitude of the electric potential at the sensor as effected by the vessel, a signal processor unit (48) and cables (42) connecting each sensor (22) to the signal processor unit (48) to deliver each respective signal to the signal processor unit, the signal processor unit (48) serving to determine the potential difference between respective pairs of sensors (22) from the respective signals they generate, and the signal processor unit (48) processing multiple such potential difference determinations to deduce the distribution of electric polarization in the vessel which would cause said electric potential at each of the electric potential sensors (22).

Abstract: A method is provided for detecting minerals and metal-containing materials which are located in sediment deposits on the sea floor and which exhibit an induced polarization response. In this method, a streamer cable is towed in the sea behind a ship. The cable has transmitters and receivers at the free end thereof and the cable is towed such that this free end is close to or trenches into the sea floor. The transmitters are used to transmit a square wave electrical current into the sediment of the sea floor while the receivers are used detect to any secondary signals produced by an induced polarization source located on or in the sea floor in response to the electrical current. The secondary signals are processed to determine measurement parameters characteristic of the source of the secondary signals so as to identify the source and using simultaneously acquired global positional data, to determine the location of the source.

Abstract: A system is provided for detecting minerals and metal-containing materials which are located in sediment deposits on the sea floor and which exhibit an induced polarization response. A streamer cable, which, in use, is towed in the sea behind a ship, includes a series of transmitters and receivers at the free end thereof. The cable is towed such that the free end is in contact with to the sea floor and the transmitters are used to transmit a square wave electrical current into the sediment there. The receivers are used to detect any secondary signals produced by an induced polarization source located on or beneath the sea floor in response to electrical current. Pre-amplifiers connected to the receivers provide noise rejection. On-board electronics process the secondary signals to determine measurement parameters characteristic of the source thereof so as to identify the source.

Abstract: Methods for testing a [A] tape carrier package (TCP) for an integrated circuit device that includes two sets of test pads. A first set of test pads are located along the outer edges of the TCP and are used to test the performance of the integrated circuit device once the TCP has been fabricated and assembled. A second set of test pads is also provided between the TCP outer leads and integrated circuit device for testing the performance of the device once the TCP has been removed from a printed circuit board.

Abstract: A probe carrying vehicle is described which has at least one probe carrier which preferably carries at least one eddy current probe and at least one magnetic field probe for ground and foreign matter detection in a search area. Spacing means which may be in the form of a bogie assembly with wheels or chains or the like are provided to maintain a spacing between the ground and the probes. The probe carrier is movable over the search area by means of a craft, to which the probe carrier is flexibly coupled by means of coupling means. The coupling means are disposed on one end of a preferably long pole, the other end of the pole being fixed rigidly to the probe carrier. The pole ensures a proper orientation of the probe relative to the ground particularly on uneven ground.

Abstract: A remotely operated submersible robot 10 is provided with two differential triaxial orthogonal dc magnetic sensing units, 1 and 2, each comprising two triaxial orthogonal dc magnetic sensors spaced at a predetermined distance apart and with their corresponding axes set in parallel; each triaxial orthogonal dc magnetic sensor incorporating three dc magnetic sensing elements sensitive only to a magnetic field in a specific axial direction and disposed such that the axial directions of respective dc magnetic sensing elements cross each other at right angles. Analog signals sent out from the differential triaxial orthogonal dc magnetic sensing units 1 and 2 are converted into digital signals by an analog-to-digital converter, and transmitted to a mother ship 20 via a tether cable 6.

Abstract: In a magnetic cartography process and apparatus, measurements are performed by magnetic field sensors placed in "fish" moved in the area to be mapped. Gradients are determined on the basis of the difference between the measurements supplied by two sensors at the same time, this applying to any pair of sensors, and/or on the basis of the difference between the measurements supplied by the same sensor at two different times, this applying to any sensor, which leads to at least one map of gradients which is broken down into a map of regional field gradients and a map of local field gradients. On the basis of the local field gradients, a determination takes place of the geological field relative to the area, or the gradients of the field and then the local field, by adding the geological field to the regional field determined on the basis of its gradients by an inversion and direct calculation method.

Abstract: A seismic cable segment is provided having a longitudinal seam for access into the seismic cable, a cable skin lock, a flotation tube for varying the buoyancy of the seismic cable, external stress members isolated from the inside of the seismic cable, and an environmentally safe gel filling the seismic cable.

Abstract: A sensor for sensing the location of objects buried in the loose sediment in the bed of the sea. A hollow, cylindrically symmetric, conductive shell is used to inject current into seawater at its tips along its axis. A sensor coil oriented along the axis ignores all magnetic fields except those along the axis, and is used to measure return signals. This is particularly useful in detecting dielectric objects buried in the sediment and in rejecting motion relative to the seabed.

Abstract: A portable underwater mount for magnetic and electric field sensors. The mount has a gimbal-like structure comprising a ball member having a mounting flange for coupling to the magnetometer. The ball member is cast from polyurethane with Teflon powder suspended therein, providing a substantially frictionless surface. The ball member is disposed over a support platform having a spherical contour so that the weighted sensor positions itself to true vertical. A collar having a lock terminating in the support platform rests over the ball member so that once the sensor is oriented to magnetic north, the lock is engaged to secure the sensor in true vertical and magnetic north positions.

Abstract: Changes in underwater sediment level in a marine environment are monitored electronically using a probe embedded in the sediment. The probe includes an electrical current source to generate an electric field extending across the sediment interface. Voltage measurements are taken at at least three sensors on the probe whose positions are known relative to the current source. The height of the sediment interface relative to the current source can then be calculated, and logged, and changes in sediment level can be monitored. The conductivities of the sediment and seawater can also be calculated by taking additional voltage measurements.

Abstract: An improved method and apparatus for electromagnetic surveying of a subterranean earth formation beneath a body of water. An electric dipole current source is towed from a survey vessel in a body of water substantially parallel to the surface of the body of water and separated from the floor of the body of water by a distance less than approximately one-quarter of the distance between the surface and the floor. Alternating electric current, preferably including a plurality of sinusoidal components, is caused to flow in the source. An array of electric dipole detectors is towed from the survey vessel substantially collinearly with the current source. Each electric dipole detector of the array is separated from the current source by a distance substantially equal to an integral number of wavelengths of electromagnetic radiation, of frequency equal to that of a sinusoidal component of the source current, propagating in the water.

Abstract: In the present invention a method and apparatus for electrical surveys of offshore metal structures includes measuring the electrical potential difference between the structure and an electrolyte, such as sea water and/or the sea bottom, in which the structure is contained. Such measurements are made at roughly approximated recorded distance locations along the structure and the approximate distance information is corrected based on periodically taken accurate distance measurements. Provision is also made to correct data for line currents in the structure, and a method is disclosed for examining the effectiveness of an electrically insulating member connected in the structure. Moreover, an improved insulated wire having minimum insulation holidays and a method for making the same are disclosed.

Abstract: This invention relates to monitoring the condition of sheathings which electrically insulate a submarine structure brought to an electrical potential differing from that of the sea water, or to monitoring the operation of the anodes if said pipeline is under cathodic protection.According to the invention one or more sets of three electrodes, which are spaced apart and aligned parallel to said pipeline, is/are displaced longitudinally above said pipeline, and the difference between the potential of the central one of said electrodes of the or each set and the algebraic sum of the potentials of the other two of said electrodes of the or each set, is measured in continuous fashion.

Abstract: The apparent electrical resistivities of various parts of a marine bottom are determined by supplying an alternating electrical current to a pair of current supply electrodes and measuring potential differences between pairs of measuring locations. The locations are on a straight line on the marine bottom. There is a fixed ratio between the distance between the locations of each pair and the distance between said pair and the pair of current supply locations. Adjoining pairs of measuring locations have a measuring location in common.A flexible cable for taking these measurements is described.The determined resistivities are subsequently compared with calculated resistivities to determine the compositions and thicknesses of the soil layers of the marine bottom.

Abstract: A method and apparatus for conducting offshore pipeline electrical surveys is characterized by initially locating and marking the pipeline, traversing the length of the pipeline towing a reference electrode in close proximity to the structure, providing a supply of wire having one end electrically and mechanically connected to the pipeline at a reference location, playing out the wire along the length of the pipeline through a distance measuring device while transporting the supply of wire and towing the reference electrode, and measuring and recording the potential difference between the reference electrode and pipe either continuously or at spaced test locations along the length of the structure.

Abstract: A marine geophysical prospecting system employs a hydrophone streamer cable containing electromagnetic field sensors, modified to be towed at a preselected distance above the sea floor by a first marine vessel senses electromagnetic energy from selected substrata beneath bodies of water. The voltage between sensors may be amplified by amplifiers in the cable or by amplifiers aboard the towing vessel. Optionally, a second similarly modified cable is preferably located above the near-bottom cable. Both cables may also contain hydrophones and/or accelerometers, as well as depth and position sensors. Optionally, a second vessel tows at least one conventional seismic source to create compressional energy which propagates downwardly through the water into the substrata beneath the body of water. At appropriate porous subsurface formations, the acoustic energy is converted to electromagnetic energy.