Abstract: A self-calibrating magnetic field monitor is disclosed. In one embodiment, a magnetic field sensor repeatedly generates an electronic signal related to the magnetic field. In addition, a calibration module generates a relative baseline signal based on an average value of the electronic signals for a given time period. A comparator compares the electronic signal with the relative baseline signal and generating an output signal if a difference in the comparing is greater than or equal to a threshold.

Abstract: A light grid includes pairs of transmitters and receiver units, and a programmable logic unit for signal evaluation. The analog part of the light grid includes only the reception elements and the storage capacitors for performing analog-to-digital conversion.

Abstract: A method for determining dip of rock formations penetrated by a wellbore using multiaxial induction measurements and imaging measurements made from within the wellbore includes estimating dip from the multiaxial induction measurements. Dip is also estimated from the imaging measurements. The dip is determined by combining the induction and imaging measurements.

Abstract: An underground tunnel detection system does not employ radar. Instead, an automatic frequency control is used to keep a continuous wave (CW) transmission tuned to the resonant frequency of a resonant microwave patch antenna (RMPA). Changes in loading and the bulk dielectric constant of the mixed media in front of the RMPA will affect its resonant frequency and input impedance. A significant shift in the measured input impedance is interpreted as a possible tunnel, and the phase angle of the measured input impedance tends to indicate a slightly forward or aft position relative to the detection system rolling over it on the ground surface.

Abstract: A positioning, communication, and detection system designed to provide a three dimensional location of an object, navigation tools, and bidirectional surface-to-subsurface communications, and methods of using the system. The system can include one or multiple transmitters comprising electromagnetic beacons, software defined radio receivers with an associated processing unit and data acquisition system, and magnetic antennas. The system may use theoretical calculations, scale model testing, signal processing, and sensor data.

Abstract: A highly flexible real-time metal detector platform which has a detection capability for different targets and applications, where the operator is able to alter synchronous demodulation multiplication functions to select different types or mixtures of different types to be applied to different synchronous demodulators, and also different waveforms of the said synchronous demodulation multiplication functions; examples of the different types being time-domain, square-wave, sine-wave or receive signal weighted synchronous demodulation multiplication functions. The operator can alter the fundamental frequency of the repeating switched rectangular-wave voltage sequence, and an operator may alter the waveform of the repeating switched rectangular-wave voltage sequence and corresponding synchronous demodulation multiplication functions.

Abstract: A system for detecting a buried conductor comprises a transmitter for producing an alternating test current in the buried conductor and a receiver for detecting an electromagnetic field produced by the test current in the buried conductor. A communication link is provided between the receiver and the transmitter. The receiver measures the signal to noise ratio, SNR, of the electromagnetic field produced by the test current and if the SNR is below a threshold then the receiver controls the transmitter to set frequency and/or power characteristics of the test current.

Abstract: At least one antenna array including three mutually orthogonal antennas each sharing a common center point senses an electromagnetic signal emitted by a buried object such as a utility line, pipe or sonde. A circuit at least partially mounted in a housing is connected to the array and determines a location of the buried object by measuring signal strength and field angles in three dimensions without having to align the antenna array relative to the buried object while eliminating nulls and false peaks. A graphical user interface (GUI) has user-friendly icons, symbols, menus, numbers and graphical and auditory representation of signal strength. A SEARCH view indicates signal strength by showing a rotating strength indicator, a trace mode MAP view in which line location is shown by a line that moves side-to-side, and a sonde mode MAP view in which sonde location is shown by a moving line, pole and equator.

Abstract: A spot indicating metal detector apparatus rides on a motorized platform having a rotary framework having a plurality of metal detectors mounted thereon with a plurality of metal detector coils positioned adjacent the ground below. The metal detector apparatus has a plurality of spray heads each associated with one metal detector detector coil for spraying a fluid onto the earth at the position the metal detector detects the presence of a metallic object.

Abstract: A high-Q human-portable, battery-powered self-correcting tunable resonator in a transmitter apparatus for inducing alternating currents of high quality in buried conductors to facilitate their location. The transmitter apparatus employs an FET-driven capacitive tuning circuit and a coil design that achieves high precision, high-quality transmission signals, and which is equipped with a high-voltage booster for facilitating fault-localization applications.

Abstract: An electronic metal detector having, a transmit coil arranged and adapted to transmit an alternating magnetic field associated with a reactive transmit coil voltage, the transmit coil being connected to transmit electronics arranged and adapted to generate a transmit signal, the transmit electronics having at least two power sources, a first power source and a second power source, wherein the first power source is adapted and arranged to connect to the transmit coil for at least a first period, and the second power source is adapted and arranged to connect to tie transmit coil for at least a second period, the said transmit electronics including at least one servo control negative feedback loop, a first servo control negative feedback loop, which is adapted and arranged to monitor a transmit coil current for at least part of the said first period, and to control at least part of the said transmit signal, the transmit electronics being adapted and arranged to control the transmit signal to produce the reactive

Abstract: To fully characterize the inductive response of an isolated conductive object, such as buried unexploded ordinance, one needs to measure its response to stimulation by primary magnetic fields in three linearly independent (e.g., approximately orthogonal) directions. In one embodiment this is achieved by measuring the response to magnetic fields of three independent transmitters arranged to have magnetic fields that are linearly independent. According to the apparatus and methods employing the system of this invention, multiple transmitters and receivers of known relative position and orientation on a single platform are used. In a preferred embodiment, matched sets of receiver pairs connected in gradient mode are positioned adjacent to closely spaced pairs of transmitting coils, such that a minor displacement of one or both of the receiver coil pairs relative to the paired transmitting coils will not affect the detected secondary signals emitted by a buried metallic object.

Abstract: A method is disclosed as part of an overall process in which a boring tool is moved through the ground within a given region along a particular path in an orientation which includes pitch. A locating signal is transmitted from the boring tool which signal exhibits a field defined forward point within a reference surface which field defined forward point is vertically above an inground forward point on the particular path through which the boring tool is likely to pass. The method establishes a predicted depth of the boring tool at the inground forward point by first identifying the field defined forward point. The signal strength of the locating signal is then measured at the field defined forward point as being representative of the depth of the boring tool at an inground upstream point which is the current location of the boring tool. With the boring tool at the upstream inground point, the pitch of the boring tool is determined.

Abstract: A system for detecting a buried conductor comprises a transmitter for generating a test signal in the buried conductor and a detector for detecting an electromagnetic signal resulting from the test signal flowing in the buried conductor. The transmitter comprises a waveform generator for generating a drive waveform signal, a power supply, an amplifier, connected to the power supply and the waveform generator for producing an output drive signal based on the drive waveform signal and an output circuit for acting on the output drive signal to generate an output signal having a current and a voltage. In-phase and quadrature components of the current and voltage of the output signal are fed back for controlling the amplifier.

Abstract: A portable self-standing electromagnetic (EM) field sensing locator system with attachments for finding and mapping buried objects such as utilities and with intuitive graphical user interface (GUI) displays. Accessories include a ground penetrating radar (GPR) system with a rotating Tx/Rx antenna assembly, a leak detection system, a multi-probe voltage mapping system, a man-portable laser-range finder system with embedded dipole beacon and other detachable accessory sensor systems are accepted for attachment to the locator system for simultaneous operation in cooperation with the basic locator system. The integration of the locator system with one or more additional devices, such as fault-finding, geophones and conductance sensors, facilitates the rapid detection and localization of many different types of buried objects.

Abstract: A system for detecting a buried conductor comprises a transmitter for producing an alternating test current in the buried conductor and a receiver for detecting an electromagnetic field produced by the test current in the buried conductor. A communication link is provided between the receiver and the transmitter. The test current comprises first and second components of different frequency. The receiver monitors the phase creepage of the first and second components and controls the transmitter to reset the phase difference between the first and second components as phase creepage increases.

Abstract: A wearable apparatus for detecting an underground object includes: a signal transmitter configured to transmit a predetermined signal in a predetermined direction; a reception detection sensor configured to receive a reflected wave corresponding to the transmitted signal; a wireless reception unit configured to restore the received reflected wave to a received signal; and an acknowledgement signal processing unit configured to analyze whether the underground object exists or not, based on the restored received signal, and generate first and second acknowledgement signals depending on whether the underground object exists or not.

Abstract: A service tee marker fixture comprises a disk marker and a cylindrical attachment sleeve fastened concentrically to the disk marker and constructed of a flexible material which provides a releasable friction fit with a service tee cap. For certain sleeve materials a stiffener plate is used to secure an end portion of sleeve adjacent to the disk marker. Detents are formed inside the attachment sleeve to grip matching ribs on the cap. An integrally formed inwardly-extending annular flange at an open end of the sleeve helps retain the sleeve on the cap. When installed the wire coil is horizontal and the marker shields the tee, and is further centered over a centerline of the main pipe. A novel method is also disclosed for using the service tee marker fixtures to survey and locate service line end points.

Abstract: A device rotates at least one static magnetic field about an axis, producing a rotating magnetic dipole field, and is movable in relation to the surface of the ground. The field is periodically sensed using a receiver to produce a receiver output responsive to the field. A positional relationship between the receiver and the device is monitored using the output. In one aspect, changing the positional relationship, by moving the device nearer to a boring tool which supports the receiver, causes an increase in accuracy of depth determination. In another aspect, determination of an actual overhead position of the boring tool, and its application, are described. Use of a plurality of measurements over at least one-half revolution of each magnet is disclosed. Establishing a surface radial direction toward a boring tool and resolution of multi-valued parameters is described. Calibration techniques, as well as a three transmitter configuration are also described.

Abstract: A radar device is described, in particular a hand-held short-range radar for determining the location of objects enclosed in a medium, including at least one radar sensor, which generates a first, high-frequency detection signal for penetrating a medium to be tested in such a way that information about an object enclosed in the medium can be obtained by measuring and analyzing the reflected detection signal of the radar sensor. At least one additional sensor is provided for generating at least one additional, second detection signal for obtaining information about the object enclosed in the medium. The method on which this radar instrument is based is also described.

Abstract: An electronic metal detector having, a transmit coil arranged and adapted to transmit an alternating magnetic field associated with a reactive transmit coil voltage, the transmit coil being connected to transmit electronics arranged and adapted to generate a transmit signal, the transmit electronics having at least two power sources, a first power source and a second power source, wherein the first power source is adapted and arranged to connect to the transmit coil for at least a first period, and the second power source is adapted and arranged to connect to tie transmit coil for at least a second period, the said transmit electronics including at least one servo control negative feedback loop, a first servo control negative feedback loop, which is adapted and arranged to monitor a transmit coil current for at least part of the said first period, and to control at least part of the said transmit signal, the transmit electronics being adapted and arranged to control the transmit signal to produce the reactive

Abstract: A service tee marker fixture comprises a disk marker and a cylindrical attachment sleeve fastened concentrically to the disk marker and constructed of a flexible material which provides a releasable friction fit with a service tee cap. For certain sleeve materials a stiffener plate is used to secure an end portion of sleeve adjacent to the disk marker. Detents are formed inside the attachment sleeve to grip matching ribs on the cap. An integrally formed inwardly-extending annular flange at an open end of the sleeve helps retain the sleeve on the cap. When installed the wire coil is horizontal and the marker shields the tee, and is further centered over a centerline of the main pipe. A novel method is also disclosed for using the service tee marker fixtures to survey and locate service line end points.

Abstract: At least one antenna array including three mutually orthogonal antennas each sharing a common center point senses an electromagnetic signal emitted by a buried object such as a utility line, pipe or sonde. A circuit at least partially mounted in a housing is connected to the array and determines a location of the buried object by measuring signal strength and field angles in three dimensions without having to align the antenna array relative to the buried object while eliminating nulls and false peaks. A graphical user interface (GUI) has user-friendly icons, symbols, menus, numbers and graphical and auditory representation of signal strength. A plurality of different underground objects can be simultaneously detected and their different locations can be simultaneously indicated to a user via audible sounds and/or visual images on a display.

Abstract: A method is disclosed for determining earth vertical electrical anisotropy from offshore electromagnetic survey measurements. The method requires both online and offline data, which includes at least one electromagnetic field component sensitive at least predominantly to vertical resistivity and another component sensitive at least predominantly to horizontal resistivity. Using a horizontal electric dipole source, online EZ and offline HZ measurements are preferred. For a horizontal magnetic dipole source, online HZ and offline EZ data are preferred. magnetotelluric data may be substituted for controlled source data sensitive to horizontal resistivity. Maxwell's equations are solved by forward modeling or by inversion, using resistivity models of the subsurface that are either isotropic or anisotropic.

Abstract: A sonde includes an elongate flexible ferromagnetic core and a coil surrounds an intermediate segment of the core. A housing surrounds and supports the coil. An electronic drive circuit is mounted in the housing for supplying the coil with an electric signal that will induce the core to emit electromagnetic signals at a predetermined strength and frequency that can be remotely detected. Self-contained battery powered float-type and pill-type sondes are also disclosed.

Abstract: A boring tool is moved through the ground within a region along a path from a starting point. A reference path is established. An information generating arrangement is located partially at the boring tool and partially at the locator including a transmitter for transmitting an electromagnetic signal from the boring tool and a receiver in the portable locator to generate certain information about the position of the boring tool relative to the position of the locator. The boring tool is moved in cooperation with the locator to establish a series of boring tool locations on the particular path such that each boring tool location is associated with one of a series of associated reference points on the reference path. An actual path of the boring tool is established which actual path corresponds to a particular path taken by the boring tool and a record is saved.

Abstract: An excavation apparatus for locating and separating an object from a medium comprising a handle, an excavation tool, a metal detector circuit, at least one coil connected to the metal detector circuit, and at least one output signal device connected to the metal detector circuit. The handle and the excavation tool share a unitary structure. The metal detector circuit is disposed within the handle, and has the at least one coil disposed inside of the excavation tool configured to produce a search field around the excavation tool from within the excavation tool, and the metal detector circuit is configured to notify user with the at least one output signal device when a metallic object is in proximity of the search field.

Abstract: A boring tool is moved through the ground in a region which includes at least one electrically conductive in-ground line and which is subject to static magnetic fields including the magnetic field of the earth.

Abstract: Line locator systems that fuse traditional sensors used in a combined pipe and cable locator (electromagnetic coils, magnetometers, and ground penetrating radar antennas) with low cost inertial sensors (accelerometers, gyroscopes) in a model-based approach are presented. Such systems can utilize inexpensive MEMS sensors for inertial navigation. A pseudo-inertial frame is defined that uses the centerline of the tracked utility, or an aboveground fixed object as the navigational reference. An inertial sensor correction mechanism that limits the tracking errors over time when the model is implemented in state-space form using, for example, the Extended Kalman Filter (EKF) is disclosed.

Abstract: A locate transmitter and method for performing a locate operation to detect a presence or absence of an underground facility. An applied signal is generated to be applied along the underground facility. One or more environmental conditions of an environment in which the transmitted is located are detected and compared to a target value or range of values to determine if an out-of-tolerance condition exists.

Abstract: In a locate operation to detect a presence or absence of at least one underground facility using a locate device, an applied signal is transmitted to the at least one underground facility, and/or a magnetic field emitted from the at least one underground facility is detected. Environmental information is obtained regarding at least one environmental condition of an environment in which the locate device is used, and information relating to the signal transmission, field detection and/or environmental information is logged into local memory of the locate device.

Abstract: Embodiments of the present invention provide estimates of soil moisture by measuring the change in electrical conductivity near the surface of the earth using surface-propagated electromagnetic fields. A method is provided for estimating near-surface soil moisture, including measuring signals from an electromagnetic ground wave propagating between one or more receiving element locations, determining a transfer characteristic proportional to an average electrical conductivity between pairs of locations; and determining estimated soil moisture in one or more regions derived from analyzing the determined electrical conductivity between pairs of locations and a predetermined regional relationship between electrical conductivity and soil moisture.

Abstract: A metal detector including transmit electronics having a plurality of switches for generating a repeating transmit signal cycle for transmission by a transmit coil. The repeating transmit signal cycle includes at least a high voltage period, and at least a low voltage period, the low voltage period followed by a substantially zero voltage period. The output impedance of the transmit electronics is less than three times the equivalent series resistance of the transmit coil during the low voltage period and the substantially zero voltage period.

Abstract: In a system having a boring tool and an above-ground portable locator for locating the boring tool as moved by a drill string in a region which includes an in-ground line, an apparatus is described for monitoring the positional relationship between the boring tool and the line. The apparatus includes a transmitter for generating a magnetic locating field from one of the boring tool or an underground length of the line. A receiver is carried by the boring tool if the field is generated from the line, or connected to the line if the field is generated from the boring tool, for detecting an intensity of the magnetic locating field to produce a magnetic field intensity indicative signal that is indicative of the positional relationship between the boring tool and the line. A remote display indicates the detected intensity of the magnetic locating field.

Abstract: A device rotates at least one static magnetic field about an axis, producing a rotating magnetic dipole field, and is movable in relation to the surface of the ground. The field is periodically sensed using a receiver to produce a receiver output responsive to the field. A positional relationship between the receiver and the device is monitored using the output. In one aspect, changing the positional relationship, by moving the device nearer to a boring tool which supports the receiver, causes an increase in accuracy of depth determination. In another aspect, determination of an actual overhead position of the boring tool, and its application, are described. Use of a plurality of measurements over at least one-half revolution of each magnet is disclosed. Establishing a surface radial direction toward a boring tool and resolution of multi-valued parameters is described. Calibration techniques, as well as a three transmitter configuration are also described.

Abstract: A locate device for a locate operation to detect a presence or an absence of one or more underground facilities is configured to access and display facilities map information, and/or other image information, as a visual aid to facilitate the locate operation. In various aspects, methods and apparatus relate to: selection of an appropriate “base” facilities map, or information from a database of facilities map data, relating to a given work site/dig area; selection of an appropriate pan and/or zoom (resolution) for displaying facilities map information; appropriately updating displayed facilities map information while a locate device is used during a locate operation (e.g. changing pan, zoom and/or orientation); overlaying on the displayed facilities map information locate information and/or landmark information relating to the locate operation; and storing locally on the locate device, and/or transmitting from the locate device, facilities map information and/or overlaid locate/landmark information (e.g.

Abstract: Locate information relating to use of a locate device to perform a locate operation may be acquired from one or more input devices, logged/stored in local memory of a locate device, formatted in various manners, processed and/or analyzed at the locate device itself, and/or transmitted to another device (e.g., a remote computer/server) for storage, processing and/or analysis. In one example, a locate device may include one or more environmental sensors and/or operational sensors, and the locate information may include environmental information and operational information derived from such sensors. Environmental and/or operational information may be used to control operation of the locate device, assess out-of-tolerance conditions in connection with use of the locate device, and/or provide alerts or other feedback. Additional enhancements are disclosed relating to improving the determination of a location (e.g.

Abstract: A portable self-standing electromagnetic (EM) field sensing locator system with attachments for finding and mapping buried objects such as utilities and with intuitive graphical user interface (GUI) displays. Accessories include a ground penetrating radar (GPR) system with a rotating Tx/Rx antenna assembly, a leak detection system, a multi-probe voltage mapping system, a man-portable laser-range finder system with embedded dipole beacon and other detachable accessory sensor systems are accepted for attachment to the locator system for simultaneous operation in cooperation with the basic locator system. The integration of the locator system with one or more additional devices, such as fault-finding, geophones and conductance sensors, facilitates the rapid detection and localization of many different types of buried objects.

Abstract: The invention relates to an apparatus for detecting a conductive object (5). The apparatus comprises at least one transmitting device (2), which is operative to generate a first changing magnetic flux (11, 12), and at least one receiving device (10), which is operative, in use, to receive a second changing magnetic flux (9) generated by the conductive object (5) in dependence upon the first changing magnetic flux. In addition, the at least one transmitting device and the at least one receiving device are disposed in relation to each other so as to attenuate the first changing magnetic flux (11, 12) received directly by the at least one receiving device (10) from the at least one transmitting device (2).

Abstract: A metal detector including transmit electronics having a plurality of switches for generating a repeating transmit signal cycle for transmission by a transmit coil. The repeating transmit signal cycle includes at least a high voltage period, and at least a low voltage period, the low voltage period followed by a substantially zero voltage period. The output impedance of the transmit electronics is less than three times the equivalent series resistance of the transmit coil during the low voltage period and the substantially zero voltage period.

Abstract: A method for determining the location of an underground sonde transmitter is disclosed. In some embodiments, the method includes measuring a set of complex electromagnetic field magnitude and phase strengths at one or more of positions while traversing a target sonde path at any angle using one or more electromagnetic coil sensors, modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at the one or more of positions for one or more of the electromagnetic coil sensors, the set of expected electromagnetic field values corresponding to a model for the target sonde, and estimating parameters related to the target sonde based on the residual error between the measured set of complex electromagnetic field values and the modeled set of expected complex electromagnetic field strengths, wherein a final estimated parameter set is determined after the residual error has converged to a minimum tolerance.

Abstract: A metal detector transmitting, through a transmit coil, a repeating transmit signal cycle, which includes at least one receive period and at least one non-zero transmit coil reactive voltage period; and sensing a current in the transmit coil during at least one receive period to control a magnitude and/or duration of the at least one non-zero transmit coil reactive voltage period such that the average value of the current during at least one receive period of every repeating transmit signal cycle is substantially constant, and the current during at least one receive period is substantially independent of the inductance of the transmit coil.

Abstract: The present invention provides systems and methods which can be employed to locate or detect presence of various materials, including nonferrous metals. These systems include new and useful sensors, circuits, systems and devices which power and/or interoperate with the sensors, and methods of making, operating and using such systems. Any or all of the systems, devices or processes can be combined with other systems, devices or processes disclosed.

Abstract: A device for environment detection having a first magnetic alternating field is situated in a vehicle. The device detects the at least one object in the environment of the vehicle by a second magnetic alternating field which is produced in the object as a function of the first magnetic alternating field.

Abstract: A pulse-induction type metal detector that reliably identifies ferrous and non-ferrous targets in soils with varying mineral content. The influence of the background signals from the soil is removed continuously, without the need for manual adjustment of controls by the operator, when the soil mineralization changes. The background signals are removed without affecting the sensitivity of the detector to metallic targets and the background signal removal process does not make the detector insensitive to targets whose time constant coincides with that of the soil.

Abstract: Methods and apparatus for providing on a display device an electronic rendering of a locate operation to detect a presence or an absence of an underground facility. One or more electronic detection marks are displayed in a display field of the display device, based at least in part on locate information generated by a locate device used for the locate operation. The locate device includes a receiver antenna to detect a magnetic field from the underground facility. The locate information includes magnetic field information based on the detected magnetic field, and geographic information indicating at least one location of the locate device during the locate operation. One or more characteristics of the electronic detection mark(s) is/are based on the magnetic field information, and one or more positions in the display field at which the electronic detection mark(s) is/are displayed is/are based on the geographic information.

Abstract: An electronic metal detector having, a transmit coil arranged and adapted to transmit an alternating magnetic field associated with a reactive transmit coil voltage, the transmit coil being connected to transmit electronics arranged and adapted to generate a transmit signal, the transmit electronics having at least two power sources, a first power source and a second power source, wherein the first power source is adapted and arranged to connect to the transmit coil for at least a first period, and the second power source is adapted and arranged to connect to tie transmit coil for at least a second period, the said transmit electronics including at least one servo control negative feedback loop, a first servo control negative feedback loop, which is adapted and arranged to monitor a transmit coil current for at least part of the said first period, and to control at least part of the said transmit signal, the transmit electronics being adapted and arranged to control the transmit signal to produce the reactive

Abstract: A metal detecting apparatus includes a sensor, a current signal outputting circuit, a transforming circuit, and a micro processing unit (MPU). The sensor is configured to sense metal objects in close proximity. The current signal outputting circuit is configured to generate alternative current signals. The alternative current signals are converted to digital voltage signals via the transforming circuit. The MPU is configured to obtain a specific frequency value of the alternative current signals according to the digital voltage signals. When the sensor senses a metal object in close proximity, the specific frequency value obtained by the MPU changes. The MPU is configured to determine if a metal object has been detected by determining if the obtained specific frequency value has changed.

Abstract: Multiple sources are provided for a transmitter cable for use in electromagnetic surveying. The transmitter cable includes a dipole antenna comprising a pair of spaced apart electrodes mounted on their respective cables. Two antennas may be powered from each source. Alternatively, the outputs of each source are connected to a common antenna pair. A single large power supply may be mounted on a vessel to supply power through the tow cable. Alternatively, a number of power supplies may be provided aboard the vessel, with each power supply having dedicated conductors through the tow cable to power the plurality of current sources.

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.