Abstract: An apparatus for determining the orientation of a borehole at a point along the borehole, includes a tiltmeter for measuring the inclination of the borehole relative to the vertical, a vector magnetic sensor for measuring the amplitude of the component of the Earth's magnetic field along the axis of the borehole, and means for computing the orientation of the tubular sonde from the measurements of inclination and amplitude of the component of the Earth's magnetic field aligned with axis of the sonde.

Abstract: An accelerometer comprises a chamber and a proof mass supported by an elastic element within the chamber. The elastic element is formed of fused silica. A sensor senses displacement of the proof mass. Means to inhibit interaction of water vapour with the elastic element is provided.

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: Apparatus for remotely determining the amount of current I flowing in a long, linear conductor, comprising a first sensor for measuring at a first location a magnetic field H arising due to current flow, a second sensor for measuring at a second location the same magnetic field H, a mounting mechanism for fixing the position of the first and second sensors in an unchanging, spaced-apart mutual configuration, calculating apparatus for calculating the vertical gradient H′ of the magnetic field on the basis of measurements made by the sensors, and further calculating apparatus for determining the current I on the basis of the equation I=H2/H′ where k is a constant.

Abstract: Method and apparatus for conducting regional gravity surveys, comprising a gravimeter module suspended below a helicopter and adapted to be lowered to the earth's surface for generating gravimeter readings. The gravimeter module includes an automatic reading gravimeter sensor and a mechanism for self-levelling of the sensor. A ground contact sensor is provided for determining when the gravimeter module contacts the earth's surface as a result of being lowered thereto and for determining when the gravimeter module ceases contacting the earth's surface as a result of being raised therefrom. The ground contact sensor generates a time marker indicative of these events. A GPS receiver is mounted in fixed relationship with the helicopter for generating periodic position coordinates. A system is provided for receiving and recording the subsurface gravimeter readings, the periodic position coordinates, and the time marker on a common time base.

Abstract: We have discovered that certain photoluminescent minerals of zinc, fluorine, tungsten, molybdenum, mercury and other elements which may naturally occur at the surface of the earth can be selectively detected in the presence of most other photoluminescent minerals and organic materials which are likely to occur at the earth's surface. The basis of selective detection is the discovery that the lifetimes of photoluminescent emission of materials in the latter class are much shorter than the lifetimes of photoluminescent emission of materials in the former class. This invention utilizes this discovery in the detection of minerals of uranium, zinc, lead, fluorine, tungsten, molybdenum, mercury and other elements.

Abstract: A rotating target contains an appropriately shaped section of photoelectric material which detects the position of a beam of light which is incident on the target. The position of the beam is determined in terms of its distance from the center of rotation of the target and by its angular position relative to the vertical. The vertical direction is simultaneously determined relative to the rotating target using a gravity operated reference.

Abstract: A navigational device for use by underwater swimmers and divers in which a telescopically extensible boom is releasably and pivotally attached to the swimmer or diver. A compass device such as a magnetometer or fluxgate sensor is mounted at the end of the boom and is connected to an audio signal generator so that signals are generated if the swimmer deviates to either side of a predetermined course. The swimmer or diver wears a bone conduction transducer on each side of his head, which are connected to the audio signal generator via a gating device so that he can receive an audio signal, presented selectively on either side of his head, which is indicative of deviation from his predetermined course.