RU2792068C1 - Underground communication line locator - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to a technology of measurement of electrical values, in particular, to devices and methods for measurement of characteristics of an electromagnetic field. An underground communication line locator is proposed, containing a case, a probe attached to the case, while the probe includes an array of low-frequency antennas located along the probe, wherein the low-frequency antenna array defines an electromagnetic location axis of a line locator system, a real-time kinematics antenna (hereinafter – RTK) of a global navigation satellite system (hereinafter – GNSS), attached to the case, a user interface located in the case, and a processing circuit connected to the low-frequency antenna array, RTK GNSS antenna, and the user interface, wherein the case defines a location axis in a forward direction, which is perpendicular to the electromagnetic location axis, and along which a user handle is formed, and the user interface and RTK GNSS antenna are attached, wherein RTK GNSS antenna is separated from the electromagnetic location axis.

EFFECT: increase in the accuracy of determination of a location of an underground communication line.

18 cl, 9 dwg

Description

[0001] This application claims priority of U.S. Provisional Application No. 62/851,498, filed May 22, 2019, and U.S. Non-Provisional Patent Application No. 16/880,595, filed May 21, 2020, which are incorporated herein by reference in their entirety.

Technical field

[0002] Embodiments of the present invention relate to locating (locating) an underground line and, in particular, to an underground locator system with real-time kinematics and global satellite positioning.

Discussion of the Prior Art

[0003] The process of locating underground (buried) equipment (pipes and cables) using low frequency signals is well known and widely accepted as a working practice. Line locating devices typically include an array of diversity antennas that receive time-varying magnetic field signals generated by the underground equipment itself. Such signals may be the result of currents injected into the underground equipment by a separate transmitter, or inherent in the underground equipment itself, such as from power lines. An array of diversity antennas receives magnetic fields, which often have specific frequencies. The processing electronics in the line locating instrument determine the relative position of the equipment with respect to the line locating system, including depth, signal currents, and other information. The horizontal position and depth of the underground utilities may then, for example, be displayed to the user and, in some systems, recorded relative to the position of the line locator.

[0004] Increasingly, applications for line locating systems are used in utility mapping. It is desirable that such mapping of underground equipment be as accurate as possible. Therefore, there is a need to develop line locating systems with highly accurate position determination.

Brief summary of the invention

[0005] In accordance with some embodiments, an accurate (precision) line locator is provided for accurately locating an underground line. An accurate line locator, in accordance with some embodiments, includes a housing; a probe attached to the body, the probe including an array of low frequency antennas disposed along the probe, the array of low frequency antennas defining an electromagnetic location axis of the line locator system; a real-time kinematics (RTK) global navigation satellite system (GNSS) antenna attached to the housing; a user interface located in the housing; and a processing circuit associated with the low frequency antenna array, the RTK GNSS antenna, and the user interface, wherein the underground line locator determines the location data of the underground line based on the signals from the low frequency antenna array, and determines the exact position of the underground line locator from the RTK GNSS antenna.

[0006] The method for accurately determining the position of an underground line includes locating the underground line in a position with an accurate line locator, wherein the accurate line locator comprises an array of low-frequency antennas located along the probe, the array of low-frequency antennas forms an electromagnetic location axis; location of the precise line locator in the first orientation; determination and registration of location data of the line; positioning the precise line locator in a second orientation, where a real-time kinematics (RTK) global navigation satellite system (GNSS) antenna is positioned to provide an accurate position; and determining and registering the exact position with the line location data.

[0007] These and other embodiments are discussed below with reference to the following drawings.

Brief description of the drawings

[0008] FIG. 1 illustrates an accurate underground line locator in accordance with some embodiments.

[0009] FIG. 2 illustrates the operation of a fine underground line locator system using a fine line locator as shown in FIG. 1.

[0010] FIG. 3 is a block diagram illustrating the design of some embodiments of a line locator as shown in FIG. 1.

[0011] FIG. 4 illustrates a geometry illustrating fine locating position correction for fine line locator operation as shown in FIG. 1.

[0012] FIG. 5 illustrates the magnetic field declination lines of the world magnetic field model.

[0013] FIG. 6 illustrates a flowchart for operating a fine line locator system in accordance with some embodiments of the present invention.

[0014] FIG. 7A and 7B illustrate the operational orientation of the fine line locator as shown in FIG. 1.

[0015] FIG. 8 illustrates the operation of an inertial measurement unit that may be included in some line locator embodiments as shown in FIG. 1.

[0016] FIG. 9 illustrates a user interface illustrating the measurement of roll, pitch, and yaw measured in some embodiments of the fine line locator as shown in FIG. 1 which includes an inertial measurement unit.

[0017] These drawings, along with other embodiments, are discussed further below.

Detailed description

[0018] The following description sets forth specific details describing some embodiments of the present invention. However, one of skill in the art will appreciate that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are intended to be illustrative and not limiting. A person skilled in the art may implement other elements that, although not specifically described here, are within the scope and spirit of the present disclosure.

[0019] This description illustrates aspects of the invention, and the embodiments are not to be construed as limiting - the claims define the scope of protection of the invention. Various changes may be made without departing from the spirit and scope of this description and claims. In some cases, well-known structures and methods are not shown or described in detail so as not to obscure the invention.

[0020] Recent developments in satellite positioning systems or global navigation satellite system (GNSS) contribute to precision grid positioning with positioning accuracy of a few cm. In addition, real-time kinematics (RTK) can be used in combination with geo-spatial information and improve real-time position accuracy - true on-the-fly positioning with a horizontal RMS accuracy of 10 cm (actual accuracy varies across the globe, 10 cm is typical accuracy) or less.

[0021] Combining cable locating systems with GNSS to generate survey maps is common. However, these systems tend to build inaccuracies. Embodiments of the present invention solve a particular problem resulting from the deployment of a GNSS antenna on a cable locator tool. In particular, by adding RTK, the inaccuracies associated with determining the position of a locatable underground line using a GNSS-enabled locator can be reduced.

[0022] FIG. 1 shows an accurate line locator 100 or cable locator, in accordance with some embodiments. The embodiment illustrated in FIG. 1 may include a probe structure 102 that accommodates antennas for line locating. The line locating antennas are located along the length of the probe structure 102. The probe structure 102 may include any number of line location antennas that are oriented to measure magnetic fields emanating from the subsurface in multiple orthogonal dimensions and may be oriented along the probe structure 102 to measure the depth of the underground line. In some embodiments, probe structure 102 may include six (6) antennas. The first set of three antennas is positioned to measure magnetic fields in three orthogonal directions and is mounted in a first position along the probe structure 102. A second set of three antennas is positioned to measure magnetic fields in three orthogonal directions and is mounted in a second position along the probe structure 102. The probe structure 102 thus defines a location axis 114 that extends along the central axis of the first and second sets of antennas disposed in the probe structure 102. With the array of antennas configured, the time-varying magnetic field can be characterized in three dimensions, and the difference in magnetic fields at two separate positions along the location axis 114 of the probe structure 102 provides information for determining the depth and orientation of the localized underground line. Typically, the antennas placed in the probe structure 102 are designed to detect low frequency cables, which is a well known method.

[0023] Precise line locator 100 further includes a high frequency RTK GNSS antenna 108 for satellite decoding. The RTK GNSS antenna 108 is a high accuracy antenna because the requirement is to perform phase sensitive measurements for use in conjunction with RTK systems to determine accurate geographic precision measurements of the antenna 108.

[0024] FIG. 1 further shows that the fine line locator 100 includes a handle 110 that can be used by a user to hold the system 100 as the user passes the fine line locator 100 over an underground line that is being located. In addition, the fine line locator includes a user interface 104 that accepts user input and provides data to the user during use. The user interface 104 is conveniently placed in the fine line locator 100 for use by the user. Circuitry 106 may further be included in the fine line locator 100 to perform the operations of the line locator 100 .

[0025] As illustrated in the specific example shown in FIG. 1, a housing 112 is provided that is shaped for convenience and functionality. Circuit 106 and user interface 104 may be mounted in housing 112. Handle 110 may be shaped to fit housing 112. RTK GNSS antenna 108 and probe structure 102 are mounted on housing 112. Housing 112 is conveniently shaped to allow a user to manipulate precision locator 100 during holding the locator 100 over the underground line. Housing 112 defines a longitudinal axis 116 of the locator along the housing 112 between the axis 114 of the locator and the antenna 108 RTK GNSS.

[0026] FIG. 2 illustrates the functional operation of a fine line positioning system 200 that includes a fine line locator 100 in accordance with some embodiments. As shown in FIG. 2, an accurate line locator 100 is located above a buried line 206 that is buried a certain distance below the surface 208. The buried line 206 is typically associated with a transmitter 204 that injects an AC signal into line 206. In some applications, such as power lines, line 206 may carry a signal from another source. In many cases, the AC signal injected into line 206 by transmitter 204 may be of a particular frequency that is detected by fine line locator 100. Receiving antennas 202, which are housed in probe structure 102, detect the magnetic field generated by the AC signal in underground line 206. Accurate line locator 100 can, using signals from antennas 202 that result from magnetic fields generated by line 206, determine the position of line 206. relative to locator 100.

[0027] In accordance with some embodiments, the exact position of the RTK GNSS antenna 108, which is connected to the precise line locator 100, is determined by the RTK GNSS antenna 108. Therefore, once the position of the underground line 206 is determined by the fine line locator 100, the precise position of the fine line locator 100 is determined by the RTK GNSS antenna 108. Therefore, the exact geographic location of line 206 can be determined and recorded. Mapping of line 206 can be performed by pinpointing line 206 at a number of locations along line 206.

[0028] Real-time kinematics (RTK) positioning refers to a satellite navigation technique used to improve the accuracy of positioning data in the RTK antenna 108. RTK positioning uses a fixed receiver 212 that is combined with an RTK GNSS antenna 108. Each of the fixed receiver 212 and the RTK GNSS receiver 108 communicates with a plurality of global positioning satellites 210, of which satellites 210-1 to 210-N are illustrated.

[0029] As is well known, the distance to a receiver, such as a fixed receiver 212 or receiver 108, can be determined by calculating the time it takes for a signal to travel from a satellite to the receiver. This delay can be calculated based on the information carried in the satellite signal. The calculation of the distance between the receiver and a number of satellites and the known positions of the satellites provides an accurate determination of the position of the receiver. However, the accuracy that can be achieved is limited to a meter or more, depending on conditions, which may include, for example, propagation times based on atmospheric conditions or other signal interference.

[0030] RTK positioning follows the same general concept, but uses the carrier signal from each of satellites 210-1 through 210-N along with fixed receiver 212 to achieve position accuracy of 1 cm or less. In particular, RTK uses the carrier wave of the satellite signal from each of the satellites 210-1 to 210-N to update the location of the base station 212. The base station 212 determines the location correction determined by conventional methods by determining based on the phase shifts of the carrier wave, and sends the location correction into the 108 RTK GNSS receiver. Specifically, each of RTK GNSS 108 and base station 212 measures the phase difference, and RTK GNSS 108 receives the phase difference measured by base station 212 for comparison with the phase difference determined by its measurement to determine a correction.

[0031] Therefore, the RTK GNSS antenna 108 is used with a system that uses real-time kinematics methods, instead of code-based positioning in standard global positioning. RTK is a technique that uses carrier frequency based ranging and provides ranges (and hence positions) that are orders of magnitude more accurate than those available through code based positioning.

[0032] In practice, the RTK system uses a single base station receiver 212 located at a known location along with a mobile station, which in this application is the RTK antenna 108 of the precise location system 100. The base station 212 relays the carrier phase it is observing and the RTK antenna 108 compares its own phase measurements with the measurement received from the base station. This allows the RTK antenna 108 of the fine location system 100 to calculate its relative position relative to the base station 212 with high accuracy, in some cases within millimeters. The actual location is then accurate within the location accuracy of the base station 212, often within 1 centimeter ±1 ppm horizontally and within 2 centimeters ±1 ppm vertically. This results in an accuracy of ±1 cm per kilometer. In some embodiments, base station 212 may be one of the common RTK-TRIP (Internet Protocol Network Transport for Marine Services (RTCM) Network Transport) base stations. Such accuracy is very valuable when incorporating an accurate line location system 100 for mapping the location of underground utilities.

[0033] The position of the RTK GNSS antenna 108 in the locator system 100 can be very important to the operation of the accurate line locator system 100. Although the RTK GNSS antenna 108 can be mounted anywhere on the housing 112 of the fine line locator system 100, for good performance, the RTK GNSS antenna 108 can be positioned to have an unobstructed view of the sky. If the RTK GNSS antenna 108 is obstructed, it may not be possible to determine the exact location. Therefore, in many embodiments, the RTK GNSS antenna 108 is mounted at a distance R from the location axis 114.

[0034] Some existing applications of GNSS receivers involve mounting the receiver on a tall retractable mast that places the receiver above the operator's head. However, such an arrangement will not function satisfactorily in a line locating system because it is very inconvenient to handle. Although not previously used in line locating systems, RTK GNSS receivers have been used in a system such as surveying equipment. These systems use a tall retractable mast to ensure that the RTK GNSS antenna is above the head of any user. Such systems work well, but are inconvenient and impractical for use in a cable locator system.

[0035] Although placing the RTK GNSS antenna 108 at a position on the housing 112 that is directly aligned with the location axis 114 of the probe 102 (position B, indicated in FIG. 1) that is aligned with the antennas 202, this position may not be ideal. Placing the RTK GNSS antenna 108 at the position indicated by 'B' in FIG. 1 can result in a significant shadowing of the sky due to the relative position of the user, this effect is commonly referred to as ‘human shadowing’. Although impractical, position B ensures that the RTK GNSS antenna 108 is aligned on the same vertical axis as the locator's own electromagnetic axis, designated as the location axis 114 (defined by the low frequency antenna array 202), this position causes the RTK GNSS antenna 108 to be obscured, which may adversely affect the pinpointing function of the locator 100, or even render the line locator 100 inoperable as an accurate line locator.

[0036] Therefore, in embodiments according to the present disclosure, the RTK GNSS antenna 108 is placed at a location on housing 112 where it has an unobstructed view of the sky and is not likely to be obscured by a line locator 100 operator manipulating the line locator 100 with handles 110. As illustrated in FIG. 1, the RTK GNSS antenna 108 may, for example, be connected at position A of the body 112 to the fine line locator 100. Taking into account the above points, it can be concluded that the ‘A’ position is a good option and has only a minor impact on the overall ergonomics for the operation of an accurate 100 line locator. However, placing the RTK GNSS antenna 108 at position 'A' creates another error of its own, which will be discussed below. Namely, the RTK GNSS antenna 108 is offset from the electromagnetic location axis 114 of the fine line locator 100 as determined by the antennas 202 installed in the probe structure 102.

[0037] FIG. 3 illustrates an exemplary block diagram 300 illustrating a diagram 106 of a line pinpointing system 100 as shown in FIG. 1. As shown in FIG. 2, circuitry 106 includes processing circuitry 302. Processing circuitry 302 may be any combination of electronics, memories, processors, microcomputers, microcontrollers, or other devices that receives and processes data as described below. In particular, processing circuitry 302 may include at least one processor executing instructions stored in memory. The memory includes a combination of volatile and non-volatile memory that stores instructions and data that are executed to accurately locate and map one or more underground lines 206, as described further below. During mapping, the requested on-demand processing circuit 302 logs location information (depth, current, magnetic field strengths, lateral offset, etc.) from the locator and logs precise position information from the RTK GNSS antenna 108 at one or more positions along the underground line. 206 in order to maintain an accurate mapping of the location of the underground line 206. This mapping may be performed on more than one underground line to completely map the utilities in a geographic area.

[0038] As shown in FIG. 3, the processing circuit 302 receives data from the user interface 104, where the user interface 104 may be any user interface installed in the housing 112. The user interface 104 may, for example, include a display screen, which may be a touch screen, located physical buttons , speakers, microphones, and/or other devices that allow the processing circuitry 302 to provide information to the operator of the fine line locator 100 and allow the operator to enter parameters. Such parameters can be used, for example, to configure the operating parameters of the fine line locator 100 or control the display configuration. In addition, the user interface 104 may allow the user to mark the underground line and record the exact position as measured by the RTK GNSS antenna 108. In addition, the user interface 104 may include an interface with another device to transfer stored data, update instructions stored in the memory of the processing circuit 302, or perform other functions. In some embodiments, the user interface 104 may include a wireless communication interface, such as Bluetooth or another communication standard, to perform the upload and download functions of the fine line locator 100. In some embodiments, physical interfaces, such as, for example, USB interfaces, may be used to download data from or upload data to the fine line locator 100. In some embodiments, the user interface 104 may include interfaces for wireless connection to a local area network and/or may include a cellular service for communication with cloud services, for example, to display underground utilities.

[0039] Processing circuit 302 is also coupled to low frequency antenna circuit 308, which includes antennas 202. Low frequency antenna circuit 308 may include loop antennas as receive antennas 202 that are capable of measuring time-varying magnetic fields generated in an underground line. 206 as a result of transmission of signals to underground line 206 by transmitter 204 or own carried signals in underground line 206 (eg, power line signals). Processing circuitry 302 may, in some cases, provide digital signals to control the configuration of antennas 308. Low frequency antenna circuitry 308 includes circuitry for receiving signals from receive antennas 202 and providing digitized received signals to processing circuitry 302. For example, antenna circuitry 308 includes analog filters and analog-to-digital converters that are configured to provide digital signals. The antenna circuit 308 then outputs digitized signals indicative of the magnetic field strengths from each of the receive antennas 202 to the processing circuit 302 .

[0040] Auxiliary circuitry 304 may include any circuitry that is additionally used with locator 100, such as a power control circuitry, or any analog-to-digital or digital-to-analog circuitry, analog signal filtering, or other actions.

[0041] In some embodiments, processing circuitry 302 is coupled to an inertial measurement unit (IMU) 306. IMU 306 may include combinations of accelerometers, gyroscopes, and/or magnetometers that provide acceleration and attitude measurements of the fine line locator 100. In general, IMU 306 may include any number of accelerometers, gyroscopes, and/or magnetometers for measuring acceleration with respect to a set of axes relative to fine line locator 100. For example, IMU 306 may include three accelerometers arranged to measure accelerations along three orthogonal axes and three gyroscopes arranged to measure angular acceleration about each of the three orthogonal axes. In some embodiments, the IMU 306 may include magnetometers that measure magnetic fields along three orthogonal axes. Acceleration data from the IMU 306 is digitally provided to a processing circuit 302 that can determine the current orientation of the fine position sensor 100 . In some embodiments, the orientation may be defined relative to the location axis 114 and the locator axis 116.

[0042] The processing circuit 302 is also connected to the RTK GNSS antenna 108. RTK GNSS antenna 108 includes antennas and receiver circuits for receiving satellite signals from satellites 210 and antennas and receiver circuits for receiving phase data from base station 212. In some embodiments, base station 212 and RTK GNSS antenna 108 may communicate using UHF alarms. However, any communication method may be used to provide data to the RTK GNSS antenna 108 from the base station 212.

[0043] RTK techniques may include complex computation based on received signals from satellites 210 and phase data from base station 212. In some embodiments, RTK GNSS antenna 108 includes detection and processing circuitry that determines the exact location of RTK antenna 108 GNSS according to satellite signals as discussed above. In this case, the RTK GNSS antenna 108 provides accurate position data to the processing circuit 302 . In some embodiments, the RTK GNSS antenna may provide received signals from satellites 210 and phase data from base station 212 to processing circuitry 302 where the exact location of RTK GNSS antenna 108 is calculated.

[0044] FIG. 4 illustrates an accurate position measurement geometry with a specific example of the fine line locator system 100 shown in FIG. 1. FIG. 4 illustrates the orientation of the fine line locator 100 with respect to true north N and positioned so that the probe 102, which detects the magnetic axis, is vertical. In the example in FIG. 4, the precise line locator 100 is held such that the locator axis 114 is held vertically, typically above an underground line that has been located, so that the exact location of that line can be obtained using the RTK GNSS antenna 108.

[0045] As shown in FIG. 1 and 4, the R value is the distance from the locator axis 114, also referred to as the magnetic axis, to the position of the RTK GNSS antenna 108. Angle Ɵ is the angle between the longitudinal axis 116 of the locator and true north. In this example, Ɵ is a 360° bearing (eg forward direction along the longitudinal axis 116 of the locator). As discussed above, the location axis 114 is determined by the geometry of the low frequency antennas.

[0046] As shown in FIG. 4, the distance R between the axis of the RTK GNSS antenna and the location axis 114 creates an error relative to the true grid reference point, which can be at any angle relative to the orientation of the fine line locator 100. As shown in FIG. 4, the latitude error and the longitude error are determined relative to the true north direction N and the position of the RTK GNSS 108. location axis 114 along the longitudinal axis 116 of the locator, and the angle Ɵ between true north N and the locator axis Ɵ, the errors in true latitude and longitude can be calculated as follows:

Latitude error=R cosine(360-Ɵ);

Longitude error=R sine(360-Ɵ).

[0047] One solution for correcting the above errors is to measure the angle Ɵ and apply the corrections using software executing in the processing circuit 302. This solution provides an accurate and reliable way to establish the true corner reference point of the grid. In some embodiments, the IMU 306 may include a fluxgate magnetometer that may be used to measure the Earth's magnetic field, which is typically within a few degrees of true north (corner reference point). This method may work well, but cannot be considered reliable.

[0048] One problem is changing the magnetic declination. Magnetic declination refers to the angle between true north N and magnetic north, which is the local direction of the Earth's magnetic field. The magnetic declination varies considerably over the surface of the Earth, as shown in FIG. 5. FIG. 5 illustrates a Mercator map illustrating magnetic declination isogons developed by the National Oceanic and Atmospheric Administration (NOAA) with the National Geophysical Data Center (NGDC) and the Joint Institute for Environmental Research (CIRES). Contour line intervals are 2 degrees, where lines labeled "red" represent positive declinations (eastward direction), "blue" represent negative declinations (westward direction), and "green" represent zero declination lines.

[0049] In addition, local variations caused by parked vehicles and other iron structures can cause an angular measurement error of up to 180°. Embodiments of the present invention provide a simple way to solve the above problems by allowing the line locator system 100 to combine accurate communications location with centimeter precision geospatial data by using RTK with RTK GNSS antenna 108.

[0050] FIG. 6 illustrates the method of operation of an embodiment of an accurate line locator 100 for capturing and storing data relating to the position of an underground line 206 in a geographic area for generating a map. Some of the embodiments described here represent a simple but accurate method that corrects for the native errors described above. As discussed above, the localizable position is determined with respect to the electromagnetic location axis 114, which is determined by the antennas 202 in the probe 102 of the fine line locator 100. In FIG. 7A and 7B show how the fine line locator 100 may operate in various steps of the method 600 to first locate and record location data regarding the underground line 206 relative to the fine line locator 100, and then reorient the fine line locator 100 to acquire and record the exact position of the locator. 100 lines with 108 RTK GNSS antenna.

[0051] As shown in FIG. 6, in step 602, the fine line locator 100 operates as a line locator used to locate the underground line 206 using the antennas 202. The line locator 100 can accurately determine the position of the underground line 206 relative to the fine line locator 100. After the underground line 206 is located by the fine line locator 100, the line locator 100 is positioned in a first orientation 704 above the underground line 206 in step 604.

[0052] In FIG. 7A shows the orientation 704 for step 604 where the base 702 is located on the ground surface 208 and the locating axis 114 is positioned to be vertical. Orientation 704 is used to provide an accurate location of the underground line 206 with an accurate line locator 100 using antennas 202 in the probe 102. In operation, users position the base 702 of the probe 102 at ground level 208 and align the locator axis 114 vertically to eliminate any offset errors in the determination the position of the underground line 206 relative to the precise line locator 100.

[0053] Once a localizable position is determined in orientation 704, at step 606, location information is logged. Typically, logging data at this stage causes an array of electromagnetic measurements to be written to the memory of the processing circuit 302. These measurements may include, for example, the depth of the line 206, the current in the line 206 measured by the locator 100, the lateral offset indicating that the locating axis 114 is not located directly above the underground line 206, and equipment failure measurements relative to the line locating system 100. Data logging at step 606 may occur when the fine line locator 100 determines that it is in orientation 704, or when indicated on the user interface 104 by the user.

[0054] Once the location information has been registered in step 606, in step 608 the fine line locator 100 prompts the user to position the locator 100 to record accurate position data. Fig. 7B illustrates an orientation 706 that allows the position of the underground line 206 to be accurately measured using the RTK GNSS antenna 108. In orientation 706, the user is prompted to tilt the fine line locator 100 backward as shown in FIG. 7B until the RTK GNSS antenna 108 is aligned with the vertical axis 708 that extends vertically through the base 702. When the RTK GNSS antenna 108 is directly above the localizable position, the RTK geospatial position can be measured and attached to registered measurements with the location measurement data discussed above in step 610.

[0055] In orientation 706, the RTK GNSS antenna 108 and the determined localizable position are now on the same vertical line, the error caused by the offset R is eliminated. Therefore, the value of R in the above correction equations can be set to 0 in these correction equations. In other words, the GNSS RTK 108 is aligned with where the locator axis 114 was during the locating operation, and hence the R value is reduced to 0 in the correction calculation.

[0056] At 612, method 600 determines whether or not to log data for any more positions. If not, then fine line locator 600 stops at 614. If so, then fine line locator 600 moves to the next position at 616 and method 600 returns to 602. Thus, mapping the location data and fine position data for the row (1 or more) positions is stored in the memory circuit 302 processing. Each recorded data can be used to determine the exact position of the underground line 206 at each of these positions, since the geometry of the precise line locator 100 is well defined. The calculation of the exact position of the underground line 206 at each position may be performed from the logged data at a later time, or in some embodiments may be performed by processing circuit 302.

[0057] In some embodiments, an inertial measurement unit (IMU) 306 may be included. The IMU 306 may be a useful feature to provide guidance in positioning the fine line locator 100 at position 704 in FIG. 7A or 706 in FIG. 7B. In some examples, IMU 306 may include combined gyroscope and accelerometer measurements. The IMU 306, under the control of the processing circuit 302, provides real-time roll, pitch, and yaw measurements as shown in FIG. 8. In some embodiments, the update rate is typically 26 Hz (100 Hz maximum) and the measurement accuracy is typically within ±1°.

[0058] As illustrated in FIG. 8, the IMU 306 inertially measures the acceleration along the location axis 114 (Z direction), the location axis 116 in the forward direction (X direction), and the Y direction perpendicular to the Z direction and the X direction. The IMU 306 additionally measures the angular acceleration of rotation about each of the X axes, Y and Z. The IMU 306 additionally includes gyroscopes that measure the rotational acceleration around the X axis (roll Φ), the acceleration around the Y axis (pitch Ɵ) and the acceleration around the Z axis (yaw ψ). The processing circuit 302 receives acceleration data from the IMU 306 and may calculate the orientation of the fine line locator 100 .

[0059] In some embodiments, the measured angles may be linked to the locator's user interface display 104, which fits in a handle on top of the locator, as shown in FIG. 1. Therefore, it is possible to determine the exact point at which the location position and the RTK GNSS antennas are vertically collinear. The actual offset (primarily the pitch angle) is determined by the physical dimensions of the precision locator 100 and is both fixed and known.

[0060] In some embodiments, guidance during alignment may be provided on the user interface 104, as illustrated in FIG. 9. As shown in FIG. 9, the user interface 104 includes a display 902 that can show angle compensation according to user settings (off, dynamic, fixed). The display 902 currently illustrates the user's dynamic setting. When the pitch compensation is “dynamic”, then the roll and pitch are updated according to real-time measurements from the IMU 306. FIG. 9 shows the pitch and roll calculated from the readings of the 3D accelerometers (XL) on display 904, the 3D gyros (G) as indicated on display 906, and the combined pitch and roll XL&G values as indicated on display 908 as described above. In addition, the bubble level 910 demonstrates the alignment of the locator axis 114 with respect to gravity. In addition, the user interface 104 may include user input buttons 912 to control the operation of the precision locator 100. In some embodiments, the air bubble level 910 may be computer generated or be a mechanical level. An air bubble level 910 may be configured to indicate positioning in orientation 704 in FIG. 7A and subsequent positioning in orientation 706 illustrated in FIG. 7B.

[0061] Although the user interface 104 may be arranged or distributed in various ways, as shown in FIG. 9, some embodiments may include an 'air bubble level' widget 910 to alert the user that an accurate RTK alignment position has been reached. This warning also causes the exact position to be measured, allowing this data to be attached to the standard survey map data as described above. In some embodiments, the 'air bubble level' widget 910 may display the first level for alignment in orientation 704 as shown in FIG. 7A and display the second level for alignment in orientation 706 as shown in FIG. 7B.

[0062] In some embodiments, it may be determined that it is not necessary to move the locator to the exact point of collinearity. Given that the 3 roll, pitch, and yaw inertial measurements are continuously updated, and that there is a known trigonometric relationship between the locator electromagnetic axis and the RTK antenna, it can be argued that a smaller offset is adequate. Offsets from ideal positioning may be corrected by calculation in processing circuit 302 based on data from IMU 306.

[0063] The above detailed description is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Numerous variations and modifications are possible within the scope of the present invention. The present invention is set forth in the following claims.

Claims (33)

1. The locator of the line of underground utilities, containing: frame; a probe attached to the body, the probe including an array of low frequency antennas disposed along the probe, the array of low frequency antennas defining an electromagnetic location axis of the line locator system; a real-time kinematics (RTK) global navigation satellite system (GNSS) antenna attached to the housing; a user interface located in the housing; And the processing circuit associated with the array of low frequency antennas, the RTK GNSS antenna and the user interface, wherein the underground line locator is configured to determine the location data of the underground line based on signals from the array of low-frequency antennas and determine the exact position of the underground line locator from the RTK GNSS antenna, wherein the housing defines a location axis in the forward direction, which is perpendicular to the electromagnetic location axis and along which the user handle is formed and the user interface and the RTK GNSS antenna are attached, and the RTK GNSS antenna is spaced from the electromagnetic location axis. 2. An underground utility line locator according to claim 1, wherein the processing circuit records location data and the exact position of one or more underground line position points. 3. The underground utility line locator according to claim 1, wherein the underground utility line locator is configured to determine location data in a first orientation and is configured to determine an exact position in a second orientation. 4. The underground utility line locator according to claim 3, wherein the underground utility line locator is configured to achieve the first orientation when the electromagnetic location axis is aligned with the vertical line and with the probe base resting on the ground above the underground line. 5. The underground line locator of claim 4, wherein the underground line locator is configured to achieve a second orientation with the probe base remaining on the ground above the underground line and the RTK GNSS antenna is positioned along the vertical line. 6. The locator of the underground utility line according to claim 3, wherein the processing circuit is configured to execute instructions stored in the memory in order to carry out the location of the underground line using an array of low-frequency antennas; determine and register location data when the line locator is in the first orientation; And determine and record the exact position with location data. 7. The locator of the underground utility line according to claim 3, additionally including an inertial measuring unit. 8. The underground utility line locator of claim 7, wherein data from the inertial measurement unit is displayed on a user interface to facilitate placement of the line locator in the first orientation and the second orientation. 9. The underground utility line locator of claim 8, further including one or more air bubble level indicators configured to facilitate placement of the line locator in a first orientation and/or a second orientation. 10. A method for accurately determining the position of an underground line, comprising: locating the underground line in position using the locator of the line of underground utilities, while the locator of the line of underground utilities has an array of low-frequency antennas located along the probe, and the array of low-frequency antennas determines the electromagnetic location axis; location of the underground utilities line locator in the first orientation; determination and registration of line location data; positioning the underground utility line locator in a second orientation in which a real-time kinematics (RTK) global navigation satellite system (GNSS) antenna is positioned to provide an accurate position; And determination and registration of the exact position using the location data of the line. 11. The method of claim 10, further comprising generating a map of the underground line by recording the precise location position of the line at a plurality of positions. 12. The method of claim 10, wherein the probe is attached to a housing that defines a forward location axis that is perpendicular to the electromagnetic location axis and along which a user handle is formed and a user interface and an RTK GNSS antenna are attached, wherein the RTK GNSS antenna is spaced apart from the electromagnetic location axis. axes. 13. The method of claim 12, wherein the first orientation is achieved with the electromagnetic locating axis aligned with the vertical line and with the probe base resting on the ground above the underground line. 14. The method of claim 13, wherein the second orientation is achieved with the probe base remaining on the ground above the underground line and the RTK GNSS antenna positioned along the vertical line. 15. The method of claim 12, wherein locating the underground utility line locator in the first orientation includes indicating the first orientation on a user interface based on data received from the inertial measurement unit. 16. The method of claim 12, wherein locating the underground utility line locator in the second orientation includes indicating the second orientation on a user interface based on data received from the inertial measurement unit. 17. The method of claim 12, wherein locating the underground utility line locator in the first orientation includes indicating the first orientation on a user interface based on data received from the air bubble level. 18. The method of claim 12, wherein locating the underground utility line locator in the second orientation includes indicating the second orientation on a user interface based on data received from the air bubble level.

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