WO1994024584A1 - Methods of detecting location of magnetically-marked elongated buried objects - Google Patents
Methods of detecting location of magnetically-marked elongated buried objects Download PDFInfo
- Publication number
- WO1994024584A1 WO1994024584A1 PCT/US1994/003328 US9403328W WO9424584A1 WO 1994024584 A1 WO1994024584 A1 WO 1994024584A1 US 9403328 W US9403328 W US 9403328W WO 9424584 A1 WO9424584 A1 WO 9424584A1
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- WIPO (PCT)
- Prior art keywords
- marking device
- horizontal
- magnetic field
- length
- magnetic
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
Definitions
- TITLE Methods of Detecting Location of
- ferrite particles incorporated in plastic duct during manufacture are magnetized to form a helical permanent magnetic marking device having a transverse magnetic axis and having magnetic field components that vary periodically along the length of the duct.
- a magnetically marked duct buried in the ground approximately horizontally, can be located, traced, and identified by detecting periodic variations of magnetic field components above ground.
- vertical magnetic field component gradients are of the order of ⁇ 100 gammas for duct buried 4 feet deep and ⁇ 25 gammas for duct buried 6 feet deep, measured on a vertically oriented Schon ⁇ tedt GA-72CV gradiometer (marketed by the assignee of the present invention) .
- ⁇ 100 gammas is a clearly detectable signal in a magnetically clean area
- ⁇ 25 gammas is close to the level of error signals that may be encountered due to magnetic clutter at the site (e.g., magnetic rocks, magnetic construction site debris, ferrous utility pipes, steel guard rails and fences) , or magnetic clutter on the operator (e.g., zippers, shoe eyes, etc.), or due to errors in the measuring instrument itself (e.g., alignment or balance errors).
- magnetic clutter can be higher than + 100 gammas.
- One of the techniques used for reducing the effect of shallow magnetic clutter at the site is to perform detection operations with the gradiometer held up 1 foot or so above the ground surface. Because the "signature" of the magnetic clutter drops in intensity with the inverse cube of distance and the signature of a magnetically-marked duct or cable drops with the inverse square (by virtue of the inventions disclosed in the aforesaid patents) , the relative strength of the clutter is attenuated faster than that of the duct or cable. Nevertheless, the detection depth capability must be sufficient to accommodate the increased detection distance.
- the present invention provides improved sensi ⁇ tivity and improved selectivity (to discriminate against magnetic clutter) in the detection of buried magnetically-marked elongated objects.
- the invention uses a horizontal gradiometer to measure the horizontal gradient of magnetic field components produced by permanent magnet marking devices of the type disclosed in the aforesaid patents.
- Fig. 1 is a diagrammatic perspective view showing, as disclosed in the aforesaid patents, the use of a vertical gradiometer in detecting the location of a buried magnetically-marked elongated object;
- FIGs. 2-5 are diagrammatic views illustrating certain principles underlying the invention.
- Fig. 6 is a diagrammatic view illustrating a horizontal gradiometer employed in the invention
- Fig. 7 is a simplified diagram of the electrical system of the horizontal gradiometer.
- Figs. 8-11 are graphical diagrams of different magnetic field component gradients at points along the length of a helical permanent magnet marking device at different distances from a vertical gradiometer;
- Figs. 12-15 are graphical diagrams of the horizontal axial (longitudinal) magnetic field component gradient at points along the length of a helical permanent magnetic marking device at dif erent distances from a horizontal gradiometer, and also graphical diagrams of the strength of the horizontal axial magnetic field component;
- Figs. 16 and 17 are graphical diagrams of different magnetic field component gradients measured at points along a helical permanent magnet marking device at 4 feet from a horizontal gradiometer, and also graphical diagrams of the sum of different field component gradients.
- Fig. 1 illustrates diagrammatically the detection of a helical permanent magnetic marking device 10 associated with a buried elongated object 12, by means of a vertical gradiometer 14, such as the Schonstedt GA-72CV.
- the marking device 10 is shown as a strip wrapped about the elongated object 12, but if the object is a plastic duct or pipe, for example, the marking device is more commonly formed by magnetizing errite particles blended into the plastic of the duct or pipe during manufacture. It is preferred to magnetize the helical permanent magnet marking device transversely, to provide a magnetic axis in the direction of the width of the device.
- the direction of the magnetic axis changes progressively and periodical- ly along the ' length of the magnetically marked duct 12.
- the marking device thus produces magnetic field components, the magnitude and polarity of which vary periodically along the length of the duct, as illus ⁇ trated by the vertical component arrows shown in Fig. 3.
- Fig. 4 shows one-half cycle of the periodic vari ⁇ ation of the vertical component.
- Fig. 5 shows the magnetic flux emanating from the vertical component at points A and C on a magnetically marked duct 12. Above point B, the vertical component flux from points A and C forms a horizontal axial component Ha parallel to the length of the duct. Like the vertical component, the horizontal axial component Ha varies in magnitude and polarity periodically along the length of the helical magnetic marking device.
- the present invention employs a horizontal gradiometer to measure the horizontal gradient of this horizontal component and other magnetic field components, as described hereinafter.
- Fig. 6 illustrates, diagrammatically, a horizontal gradiometer 14H having sensors spaced 4 feet apart along the length of a non-magnetic support 16.
- the gradiometer is triaxial, including, mounted at each end of the support, a horizontal axial (longitudinal) sensor S A , a horizontal transverse sensor S ⁇ , and a vertical sensor S v .
- the sensors are preferably of the well-known fluxgate type, each sensor including a magnetic core, an excitation winding or wire extending longitudinally of the core, and a signal winding wound transversely around the core. See, for example, the sensors of the gradiometer (locator) disclosed in U.S. Patent No. 3,961,245 issued June 1, 1976 (incorporated herein by reference) and assigned to the assignee of the present invention.
- Fig. 7 illustrates, diagrammatically, the electrical system of a biaxial gradiometer of the type shown in Fig. 6 (without the sensors S ⁇ ) .
- Oscillations from an excitation source 18 are coupled to and excite the horizontal axial sensors S A and the vertical sensors S v .
- Outputs from the signal windings of the horizontal axial sensors are applied to a horizontal signal cir ⁇ cuit 20H (including amplifiers 22, 24, 25 and phase- sensitive detectors 26) , and outputs from the vertical sensors are applied to a similar vertical component signal circuit 20V.
- a potentiometer 28 in each circuit permits output adjustment, so that when the associated sensors are in a uniform magnetic field, the output of each circuit is nulled (zero) . Since the operating principles of fluxgate type gradiometers are well known in the art, a detailed description of the electrical system (which includes the usual power supply, filters, feedback circuits, etc.) will not be given.
- each phase sensitive detector acts like a sin ⁇ gle-pole double-throw switch operating at the second- harmonic frequency of the drive-signal (excitation) frequency.
- Proper phasing of the input signal and a reference signal from the source 18 produces a DC output proportional to the second-harmonic content of the input signal.
- the DC output is phase sensitive and directly proportional to the magnetic field along the longitudinal axis of the corresponding sensor.
- the outputs from the vertical and horizontal signal circuits which are measurements of the horizontal gradient of the respective field components, are summed in a summing circuit 30.
- a selector switch 32 provides an output from any one of the vertical, horizontal, and summing circuits to an indicator circuit (not shown) , which may include a center-zero bi-directional meter, for example, in which a needle swings in opposite directions from a center position to indicate positive and negative peaks of an output signal.
- corresponding sensors at opposite ends of the horizontal gradiometer are ideally spaced apart by a half-cycle of the periodic variation of the magnetic field components to be sensed in the measurement of horizontal gradient.
- the pitch of the helix of the marking device is 12 feet, for example, the distance between the sensors is ideally 6 feet. This makes for a rather long gradiometer, however. While it is desired to correlate the distance between corresponding sensors with a half-cycle of the pitch of the marking device, it has been found that a 4 foot sensor spacing for a 6 foot half-cycle does not detract significantly from the measurements to be performed and is more practical than a six foot spac ⁇ ing.
- Figs. 8-11 illustrate computer-generated plots of vertical gradients such as those that would be measured with a vertical gradiometer like the Schonstedt GA- 72CV, but with different orientations of sensors spaced 14 inches apart (shown symbolically in the vertical gradiometer 14) .
- the curves A, B, and C represent vertical gradients at points along a 12 foot length of a helical permanent magnet marking device having a 12 foot pitch, for 36 inch, 48 inch, 60 inch, and 72 inch distances from the center of the lower sensor of the gradiometer.
- Curves A show the vertical component vertical gradient
- curves B show the horizontal axial (longitudinal) component vertical gradient
- curves C show the horizontal transverse component vertical gradient.
- Figs. 12-15 illustrate similar plots, in which curves D show the horizontal axial component horizontal gradient measured by a horizontal gradiometer 14H, with the sensors S A spaced 48 inches apart, for the same marking device and at the same distances as Figs. 8-11, respectively (measured from the horizontal axis of the gradiometer) .
- curves E show the magnitude of the horizontal axial field component. It is apparent from a "comparison of Figs. 12-15 with Figs. 8-11, respectively, that the horizontal axial gradiometer provides three times the signal as that from the vertical gradiometer at a 4 foot distance and about four times the signal at a 6 foot distance.
- Figs. 12-15 illustrate similar plots, in which curves D show the horizontal axial component horizontal gradient measured by a horizontal gradiometer 14H, with the sensors S A spaced 48 inches apart, for the same marking device and at the same distances as Figs. 8-11, respectively (measured from the horizontal axis of the gradiometer
- FIG. 16 and 17 illustrate curves of different magnetic field component horizontal gradients actually measured by a 48 inch horizontal gradiometer at points along the length of a helical permanent magnet marking device having a 12 foot pitch, the measurements being performed at a distance of 4 feet from the marking device and parallel thereto.
- Fig. 16 shows measurements of the horizontal axial component gradient and the horizontal transverse component gradient, and also shows the sum of those measurements.
- Fig. 17 shows measurements of the horizontal axial component gradient and the vertical component gradient, as well as the sum of those measurements. In each case, the sum is higher than the individual gradients despite the fact that there is a 90 degree phase shift between the individual gradient signals in each figure.
- gradient measurements performed with one orientation of the sensors are more selective than gradient measurements performed with other orientations of the sensors (e.g., S v ) ; for other sources, the reverse may be the case.
- the ability to perform gradient measurements with different orientations of magnetic sensors provides an additional basis for detecting the location of buried magnetically-marked elongated objects, even when magnetic clutter is present.
- horizontal gradient measurements may be performed in conjunction with vertical gradient measurements (as disclosed in the aforesaid patents) to provide even greater versatility.
Abstract
A method of detecting location of a buried magnetically-marked elongated object (12) uses a horizontal gradiometer (14) for measuring the horizontal gradient of components of a magnetic field associated with the buried object (12). The object (12) is preferably provided with a helical permanent magnet marking device (10) magnetized transverse to its length to provide magnetic field components above the surface of the earth that vary periodically along the length of the device (10). The gradiometer has horizontally spaced sensors (S) and is designed to measure variations of the horizontal gradient of a vertical magnetic field component, and to measure variations of the horizontal gradient of a horizontal axial magnetic field component, as the gradiometer (14) is moved along the surface of the earth approximately parallel to the buried permanent magnet marking device (10). The measured gradient variations may be read out individually or as a sum. The method provides improved sensitivity and selectivity, which reduces errors due to magnetic clutter.
Description
TITLE: Methods of Detecting Location of
Magnetically-Marked Elongated Buried Objects
S P E C I F I C A T I O N Reference to Related Applications
The invention disclosed herein is related to the inventions of commonly owned U.S. Patent No. 5,122,750 issued June 16, 1992 and U.S. Patent No. 5,114,517 issued May 19, 1992, the disclosures of both patents being incorporated herein by reference.
Background of the Invention
The inventions disclosed in the aforesaid patents have been used successfully for detecting the location of buried fiber optic cables and ducts, for example. Typically, ferrite particles incorporated in plastic duct during manufacture are magnetized to form a helical permanent magnetic marking device having a transverse magnetic axis and having magnetic field components that vary periodically along the length of the duct. Such a magnetically marked duct, buried in the ground approximately horizontally, can be located, traced, and identified by detecting periodic variations of magnetic field components above ground. With fer-
rite fill ratios low enough to have little impact on mechanical properties and cost of the duct, vertical magnetic field component gradients are of the order of ± 100 gammas for duct buried 4 feet deep and ± 25 gammas for duct buried 6 feet deep, measured on a vertically oriented Schonεtedt GA-72CV gradiometer (marketed by the assignee of the present invention) .
While ± 100 gammas is a clearly detectable signal in a magnetically clean area, ± 25 gammas is close to the level of error signals that may be encountered due to magnetic clutter at the site (e.g., magnetic rocks, magnetic construction site debris, ferrous utility pipes, steel guard rails and fences) , or magnetic clutter on the operator (e.g., zippers, shoe eyes, etc.), or due to errors in the measuring instrument itself (e.g., alignment or balance errors). At some sites, magnetic clutter can be higher than + 100 gammas.
One of the techniques used for reducing the effect of shallow magnetic clutter at the site is to perform detection operations with the gradiometer held up 1 foot or so above the ground surface. Because the "signature" of the magnetic clutter drops in intensity with the inverse cube of distance and the signature of a magnetically-marked duct or cable drops with the inverse square (by virtue of the inventions disclosed in the aforesaid patents) , the relative strength of the clutter is attenuated faster than that of the duct or
cable. Nevertheless, the detection depth capability must be sufficient to accommodate the increased detection distance.
Brief Description of the Invention The present invention provides improved sensi¬ tivity and improved selectivity (to discriminate against magnetic clutter) in the detection of buried magnetically-marked elongated objects. The invention uses a horizontal gradiometer to measure the horizontal gradient of magnetic field components produced by permanent magnet marking devices of the type disclosed in the aforesaid patents.
Brief Description of the Drawings
The invention will be further described in conjunction with the accompanying drawings, which illustrate preferred (best mode) embodiments of the invention, and wherein:
Fig. 1 is a diagrammatic perspective view showing, as disclosed in the aforesaid patents, the use of a vertical gradiometer in detecting the location of a buried magnetically-marked elongated object;
Figs. 2-5 are diagrammatic views illustrating certain principles underlying the invention;
Fig. 6 is a diagrammatic view illustrating a horizontal gradiometer employed in the invention;
Fig. 7 is a simplified diagram of the electrical system of the horizontal gradiometer.
Figs. 8-11 are graphical diagrams of different magnetic field component gradients at points along the length of a helical permanent magnet marking device at different distances from a vertical gradiometer;
Figs. 12-15 are graphical diagrams of the horizontal axial (longitudinal) magnetic field component gradient at points along the length of a helical permanent magnetic marking device at dif erent distances from a horizontal gradiometer, and also graphical diagrams of the strength of the horizontal axial magnetic field component; and
Figs. 16 and 17 are graphical diagrams of different magnetic field component gradients measured at points along a helical permanent magnet marking device at 4 feet from a horizontal gradiometer, and also graphical diagrams of the sum of different field component gradients.
Detailed Description of Preferred Embodiments
Fig. 1 illustrates diagrammatically the detection of a helical permanent magnetic marking device 10 associated with a buried elongated object 12, by means of a vertical gradiometer 14, such as the Schonstedt GA-72CV. For purposes of illustration, the marking device 10 is shown as a strip wrapped about the elongated object 12, but if the object is a plastic
duct or pipe, for example, the marking device is more commonly formed by magnetizing errite particles blended into the plastic of the duct or pipe during manufacture. It is preferred to magnetize the helical permanent magnet marking device transversely, to provide a magnetic axis in the direction of the width of the device.
As shown by the arrows in Fig. 2, the direction of the magnetic axis changes progressively and periodical- ly along the' length of the magnetically marked duct 12. The marking device thus produces magnetic field components, the magnitude and polarity of which vary periodically along the length of the duct, as illus¬ trated by the vertical component arrows shown in Fig. 3.
Fig. 4 shows one-half cycle of the periodic vari¬ ation of the vertical component. Fig. 5 shows the magnetic flux emanating from the vertical component at points A and C on a magnetically marked duct 12. Above point B, the vertical component flux from points A and C forms a horizontal axial component Ha parallel to the length of the duct. Like the vertical component, the horizontal axial component Ha varies in magnitude and polarity periodically along the length of the helical magnetic marking device. The present invention employs a horizontal gradiometer to measure the horizontal gradient of this horizontal component and other magnetic field components, as described hereinafter.
Fig. 6 illustrates, diagrammatically, a horizontal gradiometer 14H having sensors spaced 4 feet apart along the length of a non-magnetic support 16. In the form shown, the gradiometer is triaxial, including, mounted at each end of the support, a horizontal axial (longitudinal) sensor SA, a horizontal transverse sensor Sτ, and a vertical sensor Sv. The sensors are preferably of the well-known fluxgate type, each sensor including a magnetic core, an excitation winding or wire extending longitudinally of the core, and a signal winding wound transversely around the core. See, for example, the sensors of the gradiometer (locator) disclosed in U.S. Patent No. 3,961,245 issued June 1, 1976 (incorporated herein by reference) and assigned to the assignee of the present invention. The physical construction of the gradiometer is conventional and is in accordance with practices well known in the gradiometer art, typified by the Schonstedt GA-72CV gradiometer referred to earlier. Fig. 7 illustrates, diagrammatically, the electrical system of a biaxial gradiometer of the type shown in Fig. 6 (without the sensors Sτ) . Oscillations from an excitation source 18 (including an oscillator and a power amplifier) are coupled to and excite the horizontal axial sensors SA and the vertical sensors Sv. Outputs from the signal windings of the horizontal axial sensors are applied to a horizontal signal cir¬ cuit 20H (including amplifiers 22, 24, 25 and phase-
sensitive detectors 26) , and outputs from the vertical sensors are applied to a similar vertical component signal circuit 20V. A potentiometer 28 in each circuit permits output adjustment, so that when the associated sensors are in a uniform magnetic field, the output of each circuit is nulled (zero) . Since the operating principles of fluxgate type gradiometers are well known in the art, a detailed description of the electrical system (which includes the usual power supply, filters, feedback circuits, etc.) will not be given. As is well known, each phase sensitive detector acts like a sin¬ gle-pole double-throw switch operating at the second- harmonic frequency of the drive-signal (excitation) frequency. Proper phasing of the input signal and a reference signal from the source 18 produces a DC output proportional to the second-harmonic content of the input signal. The DC output is phase sensitive and directly proportional to the magnetic field along the longitudinal axis of the corresponding sensor. The outputs from the vertical and horizontal signal circuits, which are measurements of the horizontal gradient of the respective field components, are summed in a summing circuit 30. A selector switch 32 provides an output from any one of the vertical, horizontal, and summing circuits to an indicator circuit (not shown) , which may include a center-zero bi-directional meter, for example, in which a needle swings in opposite directions from a center position to
indicate positive and negative peaks of an output signal.
As shown in Figs. 2-4, corresponding sensors at opposite ends of the horizontal gradiometer are ideally spaced apart by a half-cycle of the periodic variation of the magnetic field components to be sensed in the measurement of horizontal gradient. If the pitch of the helix of the marking device is 12 feet, for example, the distance between the sensors is ideally 6 feet. This makes for a rather long gradiometer, however. While it is desired to correlate the distance between corresponding sensors with a half-cycle of the pitch of the marking device, it has been found that a 4 foot sensor spacing for a 6 foot half-cycle does not detract significantly from the measurements to be performed and is more practical than a six foot spac¬ ing. Of course, if the pitch of the marking device is 8 feet, the 4 foot spacing corresponds exactly to a half-cycle of the pitch. Figs. 8-11 illustrate computer-generated plots of vertical gradients such as those that would be measured with a vertical gradiometer like the Schonstedt GA- 72CV, but with different orientations of sensors spaced 14 inches apart (shown symbolically in the vertical gradiometer 14) . The curves A, B, and C represent vertical gradients at points along a 12 foot length of a helical permanent magnet marking device having a 12 foot pitch, for 36 inch, 48 inch, 60 inch, and 72 inch
distances from the center of the lower sensor of the gradiometer. Curves A show the vertical component vertical gradient; curves B show the horizontal axial (longitudinal) component vertical gradient; and curves C show the horizontal transverse component vertical gradient.
Figs. 12-15 illustrate similar plots, in which curves D show the horizontal axial component horizontal gradient measured by a horizontal gradiometer 14H, with the sensors SA spaced 48 inches apart, for the same marking device and at the same distances as Figs. 8-11, respectively (measured from the horizontal axis of the gradiometer) . In Figs. 12-15 curves E show the magnitude of the horizontal axial field component. It is apparent from a "comparison of Figs. 12-15 with Figs. 8-11, respectively, that the horizontal axial gradiometer provides three times the signal as that from the vertical gradiometer at a 4 foot distance and about four times the signal at a 6 foot distance. Figs. 16 and 17 illustrate curves of different magnetic field component horizontal gradients actually measured by a 48 inch horizontal gradiometer at points along the length of a helical permanent magnet marking device having a 12 foot pitch, the measurements being performed at a distance of 4 feet from the marking device and parallel thereto. Fig. 16 shows measurements of the horizontal axial component gradient and the horizontal transverse component gradient, and
also shows the sum of those measurements. Fig. 17 shows measurements of the horizontal axial component gradient and the vertical component gradient, as well as the sum of those measurements. In each case, the sum is higher than the individual gradients despite the fact that there is a 90 degree phase shift between the individual gradient signals in each figure.
Considerable testing has been performed with different sensor orientations and with magnetic field component gradients measured vertically and horizontally. The tests were performed to determine sensitivity as well as selectivity (discrimination against magnetic clutter) . Substantial improvements in sensitivity resulting from measurements of horizontal axial and vertical magnetic field component gradients with a horizontal gradiometer were apparent from the test results. It was also determined that horizontal axial component gradients measured with a horizontal gradiometer produce the highest level of confidence (selectivity) generally in detecting the location of buried magnetically marked elongated objects accompanied by magnetic clutter. It was found, however, that the selectivity depends somewhat upon the source of the magnetic clutter. For certain sources of magnetic#clutter, gradient measurements performed with one orientation of the sensors (e.g., SA) are more selective than gradient measurements performed with other orientations of the
sensors (e.g., Sv) ; for other sources, the reverse may be the case. The ability to perform gradient measurements with different orientations of magnetic sensors provides an additional basis for detecting the location of buried magnetically-marked elongated objects, even when magnetic clutter is present. Moreover, horizontal gradient measurements may be performed in conjunction with vertical gradient measurements (as disclosed in the aforesaid patents) to provide even greater versatility.
While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims.
Claims
The Invention Claimed Is: 1. A method of detecting location of an elongated permanent magnet marking device buried beneath the surface of the earth approximately horizontally and magnetized so as to provide a magnetic field component that varies in magnitude periodically along the length of the device, comprising detecting periodic variations of the magnetic field component by moving a horizontal magnetic gradiometer along the surface of the earth substantially parallel to the marking device, so as to measure variations of the horizontal gradient of the magnetic field component.
2. A method of detecting location of an elongated object buried beneath the surface of the earth, com- prising burying with said object an elongated permanent magnet marking device with its length extending along the length of the object and magnetized transverse to its length to provide a magnetic axis that is substantially transverse to the length of the marking device and the direction of which varies progressively and periodically along the length of the marking device, so as to provide above the surface of the earth a magnetic field having a vertical component, the magnitude and polarity of which vary periodically along the length of the marking device, and a horizontal component along the length of the marking device, the magnitude and polarity of which vary periodically along the length of the marking device, and detecting periodic variations of the horizontal gradient of at least one of said components by moving along the surface of the earth substantially parallel to the marking device a horizontal magnetic gradiometer having magnetic sensors spaced apart a predetermined distance and oriented so as to be sensitive to a magnetic field component to be sensed.
3. A method in accordance with Claim 2, wherein periodic variations of the horizontal gradients of both of said components are detected.
4. A method in accordance with Claim 3, wherein the distance between the sensors is correlated with the periodicity of said magnetic field components.
5. A method in accordance with Claim 3, wherein signals produced by the detecting of the periodic variations of both of said gradients are summed.
6. A method in accordance with Claim 2, wherein the distance between the sensors is correlated with the periodicity of the magnetic field components.
7. A method in accordance with Claim 2, wherein the marking device is formed as a helix. 14
1 8. A method in accordance with Claim 7, wherein
2 the pitch of the helix is about 12 feet and the
3 magnetic sensors are spaced apart about 4 feet.
1 9. A method in accordance with Claim 7, wherein
2 the pitch of the helix is about 8 feet and the magnetic
3 sensors are spaced apart about 4 feet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU66984/94A AU6698494A (en) | 1993-04-20 | 1994-03-28 | Methods of detecting location of magnetically-marked elongated buried objects |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US4806893A | 1993-04-20 | 1993-04-20 | |
| US08/048,068 | 1993-04-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1994024584A1 true WO1994024584A1 (en) | 1994-10-27 |
Family
ID=21952569
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1994/003328 WO1994024584A1 (en) | 1993-04-20 | 1994-03-28 | Methods of detecting location of magnetically-marked elongated buried objects |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU6698494A (en) |
| WO (1) | WO1994024584A1 (en) |
Cited By (10)
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| DE19648120A1 (en) * | 1996-03-26 | 1997-10-02 | Vallon Gmbh | Underground object locating method |
| DE19641196A1 (en) * | 1996-09-24 | 1998-04-02 | Andreas Dr Fischer | Detection method for metal object e.g. bomb in ground |
| US8903643B2 (en) | 2007-03-13 | 2014-12-02 | Certusview Technologies, Llc | Hand-held marking apparatus with location tracking system and methods for logging geographic location of same |
| US8965700B2 (en) | 2008-10-02 | 2015-02-24 | Certusview Technologies, Llc | Methods and apparatus for generating an electronic record of environmental landmarks based on marking device actuations |
| US9085007B2 (en) | 2006-08-16 | 2015-07-21 | SeeScan, Inc. | Marking paint applicator for portable locator |
| US9086277B2 (en) | 2007-03-13 | 2015-07-21 | Certusview Technologies, Llc | Electronically controlled marking apparatus and methods |
| US9097522B2 (en) | 2009-08-20 | 2015-08-04 | Certusview Technologies, Llc | Methods and marking devices with mechanisms for indicating and/or detecting marking material color |
| US9185176B2 (en) | 2009-02-11 | 2015-11-10 | Certusview Technologies, Llc | Methods and apparatus for managing locate and/or marking operations |
| US9542863B2 (en) | 2008-10-02 | 2017-01-10 | Certusview Technologies, Llc | Methods and apparatus for generating output data streams relating to underground utility marking operations |
| US10105723B1 (en) | 2016-06-14 | 2018-10-23 | SeeScan, Inc. | Trackable dipole devices, methods, and systems for use with marking paint sticks |
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|---|---|
| AU6698494A (en) | 1994-11-08 |
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