Abstract: Process for real time signal processing for side-looking synthetic aperture radar systems, the signal consisting of sample sequences corresponding to given spacing gates. For each spacing gate an operation corresponding to an auto-correlation is directly performed on the radar signal, this relating to a product signal of a sample by a phase term varying quadratically with the rank of the sample, which supplies an estimate of the Fourier components of the radar image for each gate.The invention also relates to a circuit for processing the radar signal in real time for performing the aforementioned process.

Abstract: The specification discloses a method and system for determining the position of a drill bit in the earth without interrupting the drilling operations. In operation, rotation of the drill bit against the formation being drilled generates coherent acoustical signals which are recorded at the surface of the earth by a plurality of spaced detectors. The signals recorded at each of the different detectors are time shifted relative to each other. These time shifts correspond to possible locations of the drill bit within the earth and are controlled to some degree by the length of drill pipe in the borehole. After the acoustic signals are shifted in time their coherency is determined. This procedure is repeated for a number of assumed locations of the drill bit. The drill bit position is determined to be at the location having the highest coherency value.

Abstract: A method of seismic prospecting is disclosed in which the seismic source is excited in such a manner as to maximize the use of the energy generated by the seismic source. In certain cases it may be desirable to convert the received seismic signals to their frequency domain counterparts before performing subsequent processing. Such conversion may be performed using the discrete Fourier transform with the result that transformed values are obtained only at certain discrete frequencies. It may further be desirable that processing be performed only at subsets of the total set of discrete frequencies with the values at the remaining frequencies being discarded. In the practice of the present invention, source energy is generated only at those discrete frequencies at which subsequent processing is to be performed. As a result there is substantially no source energy in the transform values at the frequencies which are discarded.

Abstract: A geophone is disclosed which includes at least two transducers having axes which are perpendicular to each other for sensing vertical and horizontal in-line components of seismic waves. In one arrangement, the geophone includes a signal processor which includes active circuit elements responsive to the transducer output for suppressing ground roll components included in the transducer outputs. At least one of transducer output signals with ground roll signal components suppressed therefrom is connected to a remote location for recording. When more than one signal is to be sent from the geophone to the remote recording location, a mulliplexer is provided at the geophone for transmission of a plurality of geophone output signals to the remote location over a single transmission path, such as a dual-conductor transmission line. Analog and digital versions of the geophone are disclosed.

Abstract: The length and width of fissures in a bore hole is determined by alternately flowing liquid into and out of the formation from an isolated zone of a bore hole, at different frequencies, and measuring the dynamic pressure of the flowing fluid. The length of fissures in the isolated zone is determined from frequency peaks at high pressure to flow ratios, and the thickness of the fissures is determined from variations of pressure-flow ratios with frequency by comparison with known data. Sonde apparatus for practicing the method is also disclosed.

Abstract: An improved well logging system and method is provided for deriving and visibly displaying a recordable representation of a comprehensive lithological profile of the earth materials traversed by a borehole. In a particular form of the invention, all logging measurements are derived in digital form and on the same depth-dependent bases, such that measurements taken during one trip through the borehole may be combined or processed with other logging measurements taken during a different trip through the same borehole of interest, such that all of the measurements may then be processed at one time to derive the various lithological indications sought to be provided.An improved monitoring system and technique is further provided, such that those logging measurements and lithological relationships of interest may also be correlatively displayed on a real-time basis with respect to at least some of the logging measurements from which they are derived.

Abstract: A fixed target echo rejection circuit in a pulse Doppler radar device which uses recursion filters and which have a return loop with the feedback signal passing through a weighting multiplier. The weighting function of the recursion signal occurs when a change of the pulse repetition frequency (PRF) occurs by switching and changing the weighting factors. So as to reduce spurious signals which would occur during switching, the weighting factor switching is delayed and carried when the recursion signal passes through a zero value so as to substantially reduce the spurious signals.

Abstract: A dual mode vibrator (DMV), in its hydraulic cylinder, automatically provides a shorter stroke for higher frequencies and a longer stroke for lower frequencies. The cylinder contains a pair of sleeves, each sleeve having one diameter portion sufficient to slideably engage the piston and having a smaller diameter portion to slideably engage the piston rod. The sleeves themselves are moveable within the cylinder, such movement being effected by the application of high pressure on one end or the other. When the sleeves are moved together, the stroke is effectively shortened. When the sleeves are moved apart, the stroke is effectively lengthened.

Abstract: A medium to low PRF pulse doppler radar wherein the effect of the clutter notch filter is eliminated at times when the doppler frequency of the target approximates the doppler frequency of the clutter to continue tracking the target provided that the doppler frequency of the target and clutter are at different ranges.

Abstract: A marine seismic cable is sectionalized with the individual cable sections being joined by articulated connector assemblies which permit relative bending movement between such individual cable sections.

Abstract: A well logging method and apparatus for detecting the first arrival of an acoustic wave in a logging signal under adverse signal conditions. The received acoustic signal is amplified at a fixed gain until clipped at the largest amplitude throughout the logging procedure. This amplified signal is converted RMS to DC level signal and stored in sample and hold means for a period shortly before first arrival of the acoustic wave. The continuing DC level signal and the stored DC level signal are compared to produce a comparator output DC signal when the continuing DC signal has a certain increased magnitude. This certain increased magnitude is used to generate a pulse of given magnitude and duration that is especially suitable in digital data systems.

Abstract: An acoustic positioning system locates a marine cable at an exploration site, such cable employing a plurality of hydrophones at spaced-apart positions along the cable. A marine vessel measures water depth to the cable as the vessel passes over the cable and interrogates the hydrophones with sonar pulses along a slant range as the vessel travels in a parallel and horizontally offset path to the cable. The location of the hydrophones is determined from the recordings of water depth and slant range.

Abstract: An apparatus and method of measuring elevation of vehicles, such as radiodes, aircraft, or re-entry vehicles, is provided by identifying the specific geographic location of the vehicle in question and its difference from the geographic location of a reference station. The reference station altitude is then used as an arbitrary level to measure difference in elevation of the vehicle in question.

Abstract: The digital output telemetering system for recording seismic signals comprises, according to the invention, a seismic channels commutator connected to an instantaneous automatic gain controller whose outputs are connected to an input of an analog memory and to inputs of a decoder. The latter has its two other inputs connected to a trigger output and a calibration output, respectively, of a unit for controlling a digital-analog converter. Outputs of the decoder are respectively connected to an input of an AND gate, a reset input of a counter and a second, control, input of the analog memory whose output is connected to an analog-digital converter. The latter has its output connected to an input of a receiving register whose other inputs are respectively connected to an output of a single-digit counter and an input of the decoder. The instantaneous automatic gain controller comprises two single-digit memories connected to a second input of the analog memory and to a second input of the decoder, respectively.

Abstract: A method and apparatus for a passive station to locate itself relative to a tationary or moving transmitting station transmitting a narrow pulsed scanning beam by utilizing reception of pulses directly from the transmitting station and reception of reflected pulses from a set of scatterers. A method and means for determining a bearing from the transmitting station and a method and means for determining a range to the transmitting station is disclosed utilizing a set of differential times, the times for a pulse from the transmitting station to travel to each scatterer and then to the passive station, a set of angles lying between a line connecting the transmitting station and passive station and a set of lines connecting the transmitting station and the set of scatterers and a set of angles lying between a link connecting the passive station and the transmitting station and the set of lines connecting the passive station and the set of scatterers.

Abstract: A method for improvement of the signal-to-noise ratio of seismic data records comprising determination of the angle of incidence of acoustic waves transmitted into the earth with respect to subterranean reflecting layers which yields minimum attenuation of the acoustic wave during passage through intermediate layers is disclosed. The offset or distance between source and receiver is then selected so that the waves used to generate representations of the structure of the earth are incident on the reflector at substantially the optimal angle, thus yielding maximum signal strength, and maximizing the signal-to-noise ratio. Minimum offsets, to eliminate multiple surface/evaporite layer reflections from seismic records may be indicated as well.

Abstract: Disclosed is a method for determining the permeability of a formation which includes the steps of traversing a bore-hole with a tool having a means for transmitting low frequency acoustic energy. The transmitting means is pulsed and the acoustic energy is detected by a first wide band receiver having a frequency response of between at least 0.1k hertz and 30k hertz. The receiver is coupled to the transmitting means only by means of a cable which has a length exceeding about 5 feet and preferably a length of about 15 feet. The amplitude of tube waves detected by the receiver is determined at a plurality of locations in the bore-hole. The change of amplitude in tube waves at various of these locations provides a measure of permeability. The receiver employed preferably comprises a cylinder of piezoelectric material having end plates at the ends of the cylinder and a passageway through one of the end plates which transmits ambient but not dynamic pressure changes.

Abstract: An altitude sensing arrangement which combines the advantages of a barometric altimeter with a radar altimeter. The apparatus monitors the radar altimeter's associated radar validity signal and selects the radar altimeter's reading when the validity signal indicates a valid condition. Alternately, when the validity signal does not indicate a valid condition, the invention computes the difference in barometric altitude since the last valid radar altimeter reading and sums this difference with the last valid reading from the radar altimeter to produce a combined altitude reading.

Abstract: A method of fracturing a deep borehole to form a vertical fracture, and of determining the azimuth of the resulting fracture, comprising pumping a pressurized fracture fluid into said well through a pipe from the surface, to provide a bottom hole pressure P which is less than the normal fracturing press (NFP), and generating a series of sharp pressure pulses (SPP) of selected magnitude, such that when added to the pressure P, provide pressure peaks greater than the NFP. By providing arrays of seismic sensors at the surface and determining the direction of propagation of the seismic waves generated by the SPP, the azimuth of the fracture can be determined.

Abstract: A ranging apparatus is provided having an encoded waveform signal which is generated by completely random sequence generator without second order statistics so that the waveform signal has a remote statistical probability of being analyzed. The modulated radio frequency waveform is transmitted to an object and the reflected signal is received by the ranging apparatus which comprises a digital solid state read-write memory arranged to have information written into the memory at a fixed frequency and arranged to have the information read out of the solid state read-write memory at a variable frequency to provide the equivalent of a rotating memory. The digital logic employed in the ranging apparatus is extremely accurate and not subject to drift and changes which could occur in analog type systems. The implementation of the ranging apparatus is accomplished with economical commercially available components thus providing an improved digital ranging apparatus.