CA2178332A1 - Sensor system for detecting, locating and identifying metal objects - Google Patents
Sensor system for detecting, locating and identifying metal objectsInfo
- Publication number
- CA2178332A1 CA2178332A1 CA 2178332 CA2178332A CA2178332A1 CA 2178332 A1 CA2178332 A1 CA 2178332A1 CA 2178332 CA2178332 CA 2178332 CA 2178332 A CA2178332 A CA 2178332A CA 2178332 A1 CA2178332 A1 CA 2178332A1
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- CA
- Canada
- Prior art keywords
- sensor system
- foregoing
- sensor
- gradient
- objects
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- 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
- G01V3/10—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 using induction coils
- G01V3/104—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 using induction coils using several coupled or uncoupled coils
- G01V3/105—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 using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
- G01V3/107—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 using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops using compensating coil or loop arrangements
-
- 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
- G01V3/15—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat
Abstract
The invention relates to a high-resolution sensor system for detecting, locating and identifying metal objects beneath the earth's surface. It comprises at least one active gradient metal detector.
Description
Specification Sensor System for Detection, Location, and Identification of Metallic Objects The invention relates to a sensor system for electronic detection of metallic objects, located beneath the surface of the ground.
Metallic objects beneath the surface of the ground can be for example military and industrial contaminant residues that pose a high risk to persons and the environment.
To avert this danger, according to the prior art sites that are affected are searched by hand with metal detectors and all of the objects found are dug up. In addition to hazardous objects, frequently a large number of nonhazardous metallic objects are in the soil, such as nails, cans, and lids, which cannot be distinguished from nonhazardous objects by using conventional metal detectors. Therefore, according to the prior art, all objects that are found must be dug up, although the overwhelming majority are not hazardous and could remain in the ground. In many contaminated sites, on the average only one hazardous object requiring removal is found among approximately 1000 metallic objects. The resultant alarm rate in such cases leads to a thousand times the excavation time by comparison with the ideal case, in which it is precisely the single hazardous object that is found and excavated.
Since all objects contain a minimum quantity of metal, there is a serious problem in distinguishing hazardous objects from nonhazardous ones using magnetic measurements.
Particularly difficult conditions exist when the hazardous objects are very small, and these objects can also be located in the immediate vicinity of other, large objects.
-Hence the goal of the invention is to provide a sensor system with which the lateral and vertical resolution of conventional metal detectors and magnetic field probes can be considerably improved.
This goal is achieved with a sensor system according to Claim 1. Advantageous embodiments of the invention are the subjects of additional claims.
The sensor system according to the invention comprises at least one sensor module with at least one active-gradient metal detector. The active-gradient metal detector comprises at least one gradient coil and an exciter coi]..
Gradient coils and exciter coils are preferably in a rigid configuration.
In one especially advantageous embodiment, a gradient metal detector comprises two gradient coils located orthogonally with respect to one another. Such a metal detector is termed a double-gradient metal detector in the following.
A much higher resolution is obtained with the sensor system according to the invention than with the known sensor systems. In order to utilize the increased resolution fully, the sensor signals are advantageous]y evaluated with a higher dynamic range of 22 bits corresponding to 130 dB.
In one advantageous embodiment, a signal analysis or a model calculation is also performed to reconstruct the measurement signals. In the model calculation, the three-dimensional positions of objects, their shapes and sizes, and their electrical and magnetic material parameters are determined.
From these calculated data on depth, size, shape, and material of the metallic objects, the sensor system -according to the invention performs a classification of the found objects which permits the important decision to be made as to which objects are not hazardous or can simply be left in the ground.
The invention will now be described in greater detail with reference to the figures.
Figure 1 is a schematic diagram of an active metal detector according to the prior art;
Figure 2 is a schematic diagram of an active-gradient metal detector, as used in the sensor system according to the invention;
Figure 3 shows the typical signal shape of a metal detector with diameter D that belongs to the prior art, while passing over a metal sphere;
Figure 4 shows the typical signal shape of an active-gradient metal detector with diameter D when passing over a metal sphere;
Figure 5 is a schematic diagram of an active double-gradient metal detector as used in the invention;
Figure 6 is a sensor module in a linear two-dimensional array arrangement with double-gradient metal detectors and three-axis flux gate magnetometers;
Figure 7 is a circular arrangement of the sensors in Fiqure 6;
Figure 8 is an embodiment of the sensor system according to the invention;
igure 9 is an embodiment of a sensor module according t:o the invention;
igure 10 is a hand-carried embodiment of the sensor system according to the invention;
igures 11 to 13 show examples of evaluation of sensor data.
1. Magnetic Sensory Analysis In order to record the magnetic image of the site to be investigated, both active sensors (metal detectors and/or induction coil sensors) as well as additionally passive sensors (magnetic field probes) are used.
(a) Metal Detectors Gradient metal detectors are used as metal detectors. They differ from conventional metal detectors (Figure 1) in that the pickup coil is divided into two coils connected back to back (coil pair) (Figure 2) and used to measure a field gradient component. A coil pair of this type is termed a gradient coil in this application. The measurement signals from a conventional metal detector and a gradient metal detector for a metal sphere are compared in Figures 3 and 4.
The signal strength is the same for the two versions, but in the gradient metal detector the half-value width of the signals is cut in half and hence the lateral resolution is halved to the size of half the diameter of the exciter coil.
The advantage of improving the resolution however is only utilized fully if the field gradient is measured in both horizontal directions. This means that a second pickup coil pair oriented in the measurement plane perpendicularly to the first coil pair must be provided and used for measurement as well (Figure 5). The two pickup coil pairs are then arranged in the shape of a cloverleaf. This double-gradient metal detector is operated by a common excitjer coil. This arrangement is termed a hardware gradiometer in the following.
By computer differentiation of the measured values obtained by two-dimensional scanning with a conventional meta]
detector, the same gradient components are calculated that a double-gradient metal detector measures. The difference between this "software gradiometer" and the "hardware gradiometer" consists in the fact that in the hardware gradiometer, coherent noise signals are immediately eliminated by simultaneous creation of a differential, which is not the case in the software gradiometer. The signa]
noise is therefore higher in the latter.1 In addition, the measurement grid must be made finer for the software gradiometer. The measurements therefore necessarily take longer. The hardware gradiometer used in the sensor system according to the invention therefore permits higher search efficiency. To eliminate interference, caused for examp]e by paramagnetic or damp soils, a multifrequency method is employed.
(b) Maqnetic Field Probes In addition to the abovementioned gradient metal detectors, a sensor module can also include passive magnetic field probes.
In order to obtain a two-dimensional image of the magnetic field o~ a site as simply as possible, absolute field measuring instruments such as proton resonance magnetometers are usually employed in geophysical measurements. The lSic, not "signal/noise ratio." WJG
, measurement results of these magnetometers are independent of the position of the measuring instruments in space and the measured values are therefore independent of twisting and tilting. However, they have the disadvantage that their measurement frequency range is limited to a maximum of 1 Hz.
During the magnetic investigation of a site with high resolution however, high measurement frequencies above 100 Hz are required so that the measuring time falls within realistic limits.
In one advantageous embodiment of the invention, therefore, three-axis flux gate magnetometers are used. They allow measurement frequencies up to 1 kHz. In a calibration procedure, the individual sensitivities of the three magnetometers are determined. With their aid, the absolute value of the magnetic field is determined by calculation from the individual measured values. This part of the sensor system according to the invention is a rapid absolute value measuring device. The dynamic range and linearity of the flux gate magnetometer permit field resolutions of less than 1 nT.
Natural and human-produced magnetic noise in the frequency band up to 100 Hz is several 100 nT depending on the environment. In order to eliminate this noise and the Earth's magnetic field, which is always superimposed on the measurement fields, an additional reference magnetometer must be installed in addition to the magnetometers already mentioned. The absolute value of the magnetic field is formed for the reference magnetometer as well. The difference between the squares and the measurement results of the measuring magnetometer and the reference magnetometer are then:
~S2 = (Sl + Bl + r) 2 - (S2 + B2 r) 2 = (Sl + S2 + Bl + B2 + 2 r) (Sl - S2 + Bl B~) l, S2 = magnetic fields to be measured at the positions of the magnetometer Bl, B2 Earth's magnetic field at the positions of the magnetometer r = noise.
When the reference magnetometer is placed so that S2 _ O and Bl _ B2 - B~, we then have, because Be ~ r and Be ~ Sl, ~S2 = e Be Sl = const-Sl Thus a signal is obtained that is proportional to the magnetic field to be measured, thus eliminating the noise.
(c) Multisensor System To increase the search efficiency, in other words the area searched per hour, a plurality of double-gradient metal detectors (Figure 5) and magnetic field probes can be integrated into the device. The sensors can then be arranged in a two-dimensional linear arrangement (Figure 6) or on a disk (Figure 7), rigidly and/or movably with respect to one another.
(d) Improvement of Resolution The multisensor system can be moved to improve position resolution as a whole. Permissible types of movement include for example oscillations in three dimensions, and rotations.
-This motion can be controlled and/or measured by sensors.
(e) Decouplinq of Metal Detectors Metal detectors influence one another through their magnetic alternating fields. Decoupling ensures that a metal detector will not (or to only a slight degree) measure the magnetic field of the adjacent metal detector.
Decoupling of metal detectors can be achieved by a geometric arrangement, e.g. a certain minimum distance, by time-division multiplex and/or frequency-division multiplex operation, and by a different choice of operating frequencies.
Metallic objects beneath the surface of the ground can be for example military and industrial contaminant residues that pose a high risk to persons and the environment.
To avert this danger, according to the prior art sites that are affected are searched by hand with metal detectors and all of the objects found are dug up. In addition to hazardous objects, frequently a large number of nonhazardous metallic objects are in the soil, such as nails, cans, and lids, which cannot be distinguished from nonhazardous objects by using conventional metal detectors. Therefore, according to the prior art, all objects that are found must be dug up, although the overwhelming majority are not hazardous and could remain in the ground. In many contaminated sites, on the average only one hazardous object requiring removal is found among approximately 1000 metallic objects. The resultant alarm rate in such cases leads to a thousand times the excavation time by comparison with the ideal case, in which it is precisely the single hazardous object that is found and excavated.
Since all objects contain a minimum quantity of metal, there is a serious problem in distinguishing hazardous objects from nonhazardous ones using magnetic measurements.
Particularly difficult conditions exist when the hazardous objects are very small, and these objects can also be located in the immediate vicinity of other, large objects.
-Hence the goal of the invention is to provide a sensor system with which the lateral and vertical resolution of conventional metal detectors and magnetic field probes can be considerably improved.
This goal is achieved with a sensor system according to Claim 1. Advantageous embodiments of the invention are the subjects of additional claims.
The sensor system according to the invention comprises at least one sensor module with at least one active-gradient metal detector. The active-gradient metal detector comprises at least one gradient coil and an exciter coi]..
Gradient coils and exciter coils are preferably in a rigid configuration.
In one especially advantageous embodiment, a gradient metal detector comprises two gradient coils located orthogonally with respect to one another. Such a metal detector is termed a double-gradient metal detector in the following.
A much higher resolution is obtained with the sensor system according to the invention than with the known sensor systems. In order to utilize the increased resolution fully, the sensor signals are advantageous]y evaluated with a higher dynamic range of 22 bits corresponding to 130 dB.
In one advantageous embodiment, a signal analysis or a model calculation is also performed to reconstruct the measurement signals. In the model calculation, the three-dimensional positions of objects, their shapes and sizes, and their electrical and magnetic material parameters are determined.
From these calculated data on depth, size, shape, and material of the metallic objects, the sensor system -according to the invention performs a classification of the found objects which permits the important decision to be made as to which objects are not hazardous or can simply be left in the ground.
The invention will now be described in greater detail with reference to the figures.
Figure 1 is a schematic diagram of an active metal detector according to the prior art;
Figure 2 is a schematic diagram of an active-gradient metal detector, as used in the sensor system according to the invention;
Figure 3 shows the typical signal shape of a metal detector with diameter D that belongs to the prior art, while passing over a metal sphere;
Figure 4 shows the typical signal shape of an active-gradient metal detector with diameter D when passing over a metal sphere;
Figure 5 is a schematic diagram of an active double-gradient metal detector as used in the invention;
Figure 6 is a sensor module in a linear two-dimensional array arrangement with double-gradient metal detectors and three-axis flux gate magnetometers;
Figure 7 is a circular arrangement of the sensors in Fiqure 6;
Figure 8 is an embodiment of the sensor system according to the invention;
igure 9 is an embodiment of a sensor module according t:o the invention;
igure 10 is a hand-carried embodiment of the sensor system according to the invention;
igures 11 to 13 show examples of evaluation of sensor data.
1. Magnetic Sensory Analysis In order to record the magnetic image of the site to be investigated, both active sensors (metal detectors and/or induction coil sensors) as well as additionally passive sensors (magnetic field probes) are used.
(a) Metal Detectors Gradient metal detectors are used as metal detectors. They differ from conventional metal detectors (Figure 1) in that the pickup coil is divided into two coils connected back to back (coil pair) (Figure 2) and used to measure a field gradient component. A coil pair of this type is termed a gradient coil in this application. The measurement signals from a conventional metal detector and a gradient metal detector for a metal sphere are compared in Figures 3 and 4.
The signal strength is the same for the two versions, but in the gradient metal detector the half-value width of the signals is cut in half and hence the lateral resolution is halved to the size of half the diameter of the exciter coil.
The advantage of improving the resolution however is only utilized fully if the field gradient is measured in both horizontal directions. This means that a second pickup coil pair oriented in the measurement plane perpendicularly to the first coil pair must be provided and used for measurement as well (Figure 5). The two pickup coil pairs are then arranged in the shape of a cloverleaf. This double-gradient metal detector is operated by a common excitjer coil. This arrangement is termed a hardware gradiometer in the following.
By computer differentiation of the measured values obtained by two-dimensional scanning with a conventional meta]
detector, the same gradient components are calculated that a double-gradient metal detector measures. The difference between this "software gradiometer" and the "hardware gradiometer" consists in the fact that in the hardware gradiometer, coherent noise signals are immediately eliminated by simultaneous creation of a differential, which is not the case in the software gradiometer. The signa]
noise is therefore higher in the latter.1 In addition, the measurement grid must be made finer for the software gradiometer. The measurements therefore necessarily take longer. The hardware gradiometer used in the sensor system according to the invention therefore permits higher search efficiency. To eliminate interference, caused for examp]e by paramagnetic or damp soils, a multifrequency method is employed.
(b) Maqnetic Field Probes In addition to the abovementioned gradient metal detectors, a sensor module can also include passive magnetic field probes.
In order to obtain a two-dimensional image of the magnetic field o~ a site as simply as possible, absolute field measuring instruments such as proton resonance magnetometers are usually employed in geophysical measurements. The lSic, not "signal/noise ratio." WJG
, measurement results of these magnetometers are independent of the position of the measuring instruments in space and the measured values are therefore independent of twisting and tilting. However, they have the disadvantage that their measurement frequency range is limited to a maximum of 1 Hz.
During the magnetic investigation of a site with high resolution however, high measurement frequencies above 100 Hz are required so that the measuring time falls within realistic limits.
In one advantageous embodiment of the invention, therefore, three-axis flux gate magnetometers are used. They allow measurement frequencies up to 1 kHz. In a calibration procedure, the individual sensitivities of the three magnetometers are determined. With their aid, the absolute value of the magnetic field is determined by calculation from the individual measured values. This part of the sensor system according to the invention is a rapid absolute value measuring device. The dynamic range and linearity of the flux gate magnetometer permit field resolutions of less than 1 nT.
Natural and human-produced magnetic noise in the frequency band up to 100 Hz is several 100 nT depending on the environment. In order to eliminate this noise and the Earth's magnetic field, which is always superimposed on the measurement fields, an additional reference magnetometer must be installed in addition to the magnetometers already mentioned. The absolute value of the magnetic field is formed for the reference magnetometer as well. The difference between the squares and the measurement results of the measuring magnetometer and the reference magnetometer are then:
~S2 = (Sl + Bl + r) 2 - (S2 + B2 r) 2 = (Sl + S2 + Bl + B2 + 2 r) (Sl - S2 + Bl B~) l, S2 = magnetic fields to be measured at the positions of the magnetometer Bl, B2 Earth's magnetic field at the positions of the magnetometer r = noise.
When the reference magnetometer is placed so that S2 _ O and Bl _ B2 - B~, we then have, because Be ~ r and Be ~ Sl, ~S2 = e Be Sl = const-Sl Thus a signal is obtained that is proportional to the magnetic field to be measured, thus eliminating the noise.
(c) Multisensor System To increase the search efficiency, in other words the area searched per hour, a plurality of double-gradient metal detectors (Figure 5) and magnetic field probes can be integrated into the device. The sensors can then be arranged in a two-dimensional linear arrangement (Figure 6) or on a disk (Figure 7), rigidly and/or movably with respect to one another.
(d) Improvement of Resolution The multisensor system can be moved to improve position resolution as a whole. Permissible types of movement include for example oscillations in three dimensions, and rotations.
-This motion can be controlled and/or measured by sensors.
(e) Decouplinq of Metal Detectors Metal detectors influence one another through their magnetic alternating fields. Decoupling ensures that a metal detector will not (or to only a slight degree) measure the magnetic field of the adjacent metal detector.
Decoupling of metal detectors can be achieved by a geometric arrangement, e.g. a certain minimum distance, by time-division multiplex and/or frequency-division multiplex operation, and by a different choice of operating frequencies.
2. Sensor Module In one advantageous embodiment, the sensor system according to the invention (Figure 8) comprises one or more rotating sensor modules (Figure 9). The sensor module shown in Figure 9 contains as essential components at least one active metal detector 2, 4 and at least one passive magnetic field sensor 14. Movable parts are shown shaded.
The active metal detectors in this case are preferably double-gradient metal detectors. These consist of two gradiometers arranged orthogonally with respect to one another, which are both located in a field of an exciting coil, which is operated at at least two different exciting frequencies (Figure 5).
The passive magnetic field sensor 14 is calibrated with a reference magnetometer 16 (Figure 8) in such fashion that the terrestrial field noise is removed from its measurement signal.
The measurement data from the sensors, together with data from a synchro-transmitter 10 and a displacement sensor 8 (displacement sensor 8 measures the position of the system relative to a reference point) the measurement data of the sensors are prepared by a measured value recording2 6, and transmitted over a transmission line 12 to a central control and processing unit, for example a central computer 18 located on or in a vehicle 20. There the data from the various sensor modules are stored, processed, evaluated, and shown on a display.
The search with the sensor system according to the invention involves an operator observing the high-resolution two-dimensional image of the ground on the monitor of the central computer. He therefore gets a view of the magnetic image of the objects located beneath the surface of the ground. Recognition of objects can be performed interactively by the operator himself or automatically by an image processing program. When an object has been recognized, a computer evaluation of the measurement data is performed to determine the depth, shape, and material, and then to classify the object.
The location of the found objects is plotted on a chart prepared in real time and marked on the ground by a marking device.
The active metal detectors in this case are preferably double-gradient metal detectors. These consist of two gradiometers arranged orthogonally with respect to one another, which are both located in a field of an exciting coil, which is operated at at least two different exciting frequencies (Figure 5).
The passive magnetic field sensor 14 is calibrated with a reference magnetometer 16 (Figure 8) in such fashion that the terrestrial field noise is removed from its measurement signal.
The measurement data from the sensors, together with data from a synchro-transmitter 10 and a displacement sensor 8 (displacement sensor 8 measures the position of the system relative to a reference point) the measurement data of the sensors are prepared by a measured value recording2 6, and transmitted over a transmission line 12 to a central control and processing unit, for example a central computer 18 located on or in a vehicle 20. There the data from the various sensor modules are stored, processed, evaluated, and shown on a display.
The search with the sensor system according to the invention involves an operator observing the high-resolution two-dimensional image of the ground on the monitor of the central computer. He therefore gets a view of the magnetic image of the objects located beneath the surface of the ground. Recognition of objects can be performed interactively by the operator himself or automatically by an image processing program. When an object has been recognized, a computer evaluation of the measurement data is performed to determine the depth, shape, and material, and then to classify the object.
The location of the found objects is plotted on a chart prepared in real time and marked on the ground by a marking device.
3. System The design of the sensor system according to the invention shown in Figure 8 will now be described in greater detail:
2Sic. German = Messwerterfassung. A measured value logger, which may have been meant, would be Messwerterfassungsgerat. WJG
"
(a) Confiquration The system is modular in design and consists of one or more modules (Figure 9), with the modules being connected permanently with one another but movable individually, or connected completely rigidly with one another.
Possible System Configurations:
1.) The sensor module as well as equipment to evaluate and display the sensor signals (e.g. front-end processor, central computer, screen, etc.) are integrated into a compact unit and mounted on wheels or a skid. They are either manually operated by an operator (pushed) or pushed or pulled by a vehicle (powered).
2.) The sensor module as well as devices for evaluating and displaying sensor signals (e.g.front-end processor, central computer, screen, etc.) are mounted on a powered carrier vehicle. The carrier vehicle can be a land vehicle or an aircraft, for example a dirigible3.
An air cushion vehicle is also possible.
3.) In an especially advantageous embodiment, the sensor system can be made in the form of a manual device carried by an operator over the ground to be investigated. Any movements of the manual device are possible. For example the operator, as he walks forward, can make oscillating movements transverse]y with respect to his direction of movement, in order to scan the site to be investigated as quickly and completely as possible. The fact that the device has 3Sic. A dirigible is a rigid airship, while blimps are more common today; perhaps this was meant. WJG
21 7~332 -no mechanical contact with the ground imposes particular requirements on position determination.
Advantageously, the following means for position determination are suitable for this hand-carried device:
- Satellite-supported GPS sensors in conjunction with a directional gyro and acceleration sensors and/or speed sensors;
- A two-dimensional ultrasonic system that cooperates with a correlation computer;
- A laser tracking system;
- A two-dimensional laser Doppler sensor system;
- A two-dimensional cable system.
The coordinates determined can be corrected by a calibration measurement, with the locations being measured with respect to a reference point.
An example of such a manual device is shown in Figure 10. It comprises a sensor module 22 with at least one gradient metal detector, advantageously a double-gradient metal detector. Sensor module 22 is preferably connected immovably with frame 32 of the device. A position sensor 26 is also located on frame 32 of the device.
The device also comprises a power supply 30 as well as a computer 28 with a screen, advantageously designed as a flat screen, with which the sensor data, together with the position data, can be processed and displayed -as a two-dimensional image of the site to be investigated (especially in real time~. With a marking device 24, for example a sprayer, the location of the found objects in the site can be marked.
2Sic. German = Messwerterfassung. A measured value logger, which may have been meant, would be Messwerterfassungsgerat. WJG
"
(a) Confiquration The system is modular in design and consists of one or more modules (Figure 9), with the modules being connected permanently with one another but movable individually, or connected completely rigidly with one another.
Possible System Configurations:
1.) The sensor module as well as equipment to evaluate and display the sensor signals (e.g. front-end processor, central computer, screen, etc.) are integrated into a compact unit and mounted on wheels or a skid. They are either manually operated by an operator (pushed) or pushed or pulled by a vehicle (powered).
2.) The sensor module as well as devices for evaluating and displaying sensor signals (e.g.front-end processor, central computer, screen, etc.) are mounted on a powered carrier vehicle. The carrier vehicle can be a land vehicle or an aircraft, for example a dirigible3.
An air cushion vehicle is also possible.
3.) In an especially advantageous embodiment, the sensor system can be made in the form of a manual device carried by an operator over the ground to be investigated. Any movements of the manual device are possible. For example the operator, as he walks forward, can make oscillating movements transverse]y with respect to his direction of movement, in order to scan the site to be investigated as quickly and completely as possible. The fact that the device has 3Sic. A dirigible is a rigid airship, while blimps are more common today; perhaps this was meant. WJG
21 7~332 -no mechanical contact with the ground imposes particular requirements on position determination.
Advantageously, the following means for position determination are suitable for this hand-carried device:
- Satellite-supported GPS sensors in conjunction with a directional gyro and acceleration sensors and/or speed sensors;
- A two-dimensional ultrasonic system that cooperates with a correlation computer;
- A laser tracking system;
- A two-dimensional laser Doppler sensor system;
- A two-dimensional cable system.
The coordinates determined can be corrected by a calibration measurement, with the locations being measured with respect to a reference point.
An example of such a manual device is shown in Figure 10. It comprises a sensor module 22 with at least one gradient metal detector, advantageously a double-gradient metal detector. Sensor module 22 is preferably connected immovably with frame 32 of the device. A position sensor 26 is also located on frame 32 of the device.
The device also comprises a power supply 30 as well as a computer 28 with a screen, advantageously designed as a flat screen, with which the sensor data, together with the position data, can be processed and displayed -as a two-dimensional image of the site to be investigated (especially in real time~. With a marking device 24, for example a sprayer, the location of the found objects in the site can be marked.
4) In addition to the embodiments of ~he sensor system described under 1.), 2.), and 3.), a remote control point can be provided which is connected with the sensor system by optical, electrical, or electromechanical digital data transmission. It includes means for supplying power to the sensor system as well as an especially powerful computer with display means, and in one advantageous embodiment it can access external databases. As a result, an evaluation with higher accuracy is possible. The results of the evaluation can be transferred to the individual sensor system or systems.
Position and location measurement can be located both in the sensor module itself or at the control point. This can be accomplished by distance measurement on the ground, optically with laser trackers for example, or electromagnetically using satellite-supported navigation with differential formation.
(b) Decoupling Metal Detectors in the System As in the case of magnetic sensory analysis (l.e), the metal detectors must be decoupled in the system. The same remedies as in (l.e) can be used for this purpose. In general, the arrangement of the sensors in the system is selected in such fashion that the distances of the sensors from objects which negatively influence the sensor function (e.g. other sensors, metallic parts on the complete system) remain constant over time. With rotating sensors, this can be achieved for example by synchronizing the movement of the sensors.
(c) Adaptive Resolution Control If the operator of the system or an evaluation unit detects an object, the rate of movement of the system is reduced.
By virtue of the lower speed, measured values can be collected with a higher density so that the measurement resolution increases. With the higher measurement point density in a two-dimensional grid, the fine resolution of the magnetic signals can be increased by subsequent data processing. Three-dimensional separation of small and large objects is thus improved.
4. Display of Measurement Data and Evaluation The measured values from the double-gradient metal detectors (Figure 5) were pre-processed and color-coded in a two-dimensional image of the scanned site. Additional displays, isolines for example, are possible. The measured data from the magnetic field probes can be displayed in the same image with different color coding. As a result, objects with and without their own magnetic fields can be distinguished from one another in the image.
The color coding can be adjusted to the measuring situation by the operator. The measured values are fed to an evaluating computer. Objects that are recognized are displayed.
If the metallic volume of the object is sufficient, an eddy current distribution can be calculated. The shape, size, and depth as well as the position of the object can be determined from this. In the case of nonmagnetic objects, -their conductivity is calculated, while the magnetic moment is determined for magnetic objects.
!
Identification of the discovered objects can be performed with the aid of the object parameters determined (shape, volume, and electrical conductivity). The characteristic data of anticipated object are stored in a database. A
suitable computer program offers the operator of the devlce suggestions for identification.
In one especially advantageous embodiment, the data are evaluated using the following method:
An active double-gradient metal detector (Figure 5), when moving over a metallic object, delivers an absolute-value signal whose phase angle with respect to the exciting voltage depends on the material of the metal and the frequency of the exciting voltage. In this manner, metals such as brass, iron, copper, or aluminum can be distinguished regardless of their shape and size.
In practice, however, a background signal from the ground often prevents recognition of materials. By using a double-gradient metal detector, which is excited at one frequency, but especially advantageously at several frequencies, these difficulties can be overcome. The measured values from such a double-gradient metal detector are linked as point data sets with frequency-dependent absolute values and phases with the corresponding position coordinates of the metal detector by a computer to a data field that is multidimensional with respect to the exciting frequencies, said field being capable of being differentiated as a function of the position coordinates.
-A data set at a three-dimensional point in space P(x,y) within the site to be investigated, during operation of the exciting coil of the metal detector at two frequencies v"
V2 ~ contains the following components:
Amount and phase at exciting frequency v Phase and phase at exciting frequency v2 If the exciting coil of the metal detector is operated at more than two frequencies, i.e. at N frequencies, the stated two-dimensional measurement data set expands accordingly to an N-dimensional data set.
Since the signals of the two orthogonal gradiometer coils of the double-gradient metal detector tFigure 5) enter a single component, spatially two-dimensional information about the existing magnetic field is contained therein.
To obtain further information, the individual components of the measurement data set can also be linked with one another.
From the differentials and differential quotients of the absolute values and phase values of adjacent data sets (derivation according to the local coordinates) of the entire measurement data field, the location, depth, volume, and structure of the materials and a classification of hidden metallic objects can be obtained. Differential formation thus results directly in suppression of the background and noise signals.
Advantageously, the results of differential formation can be assigned to a gray scale value or color scale and displayed (advantageously in real time) displayed as a two-dimensional representation on a computer monitor. The areas between the -individual calculated points of the two-dimensional display can advantageously be filled by interpolated gray or color values.
The method will now be described in greater detail with reference to Figures 11 to 13. In Figure 11, at the upper right, the structure of an N-dimensional measurement data set (i.e. measurement at N different frequencies) is shown for a specific location.
At the upper left, a grid composed of individual locations is shown, with a measurement data set measured at each of these points being associated with these locations.
At the bottom left, the result of gradient formation by differential formation between the measurement data sets at adjacent locations is shown, and (for reasons of clarity) for only one fixed frequency vi. A vector which is shown corresponds to the vectorial difference of the data set at exciting frequency vi at one location and to the data set at the exciting frequency vi at an adjacent location.
The absolute value of the vectors shown is normalized to the unit value.
In Figure 12, several examples are shown for the alignment of the gradient vectors for certain materials and shapes of detected objects.
The sketch at the upper left shows the gradient vectors for a punctiform and ferromagnetic object. The vectors all point to a single point which is thus recognized as the center of the object. At the upper right, the gradient vectors determined for a punctiform paramagnetic object are shown. The vectors in this case point away from the object.
-At the bottom left and right, two examples of detection of elongate objects are shown. The gradient vectors are each shown at one edge of the object. In the case of a ferromagnetic object (left), the gradients point toward the edge, while in a paramagnetic object (right) the gradients point away from the edge.
Finally, Figure 13 shows several concrete examples of the evaluation of measurement signals for three different objects (lines 1 to 3).
The middle column shows the unit vector field of the gradients at a fixed exciting frequency, as already described in Figures 11 and 12. The first column shows the scalar field of the absolute values of the corresponding measurement data sets at the same exciting frequency. The values between the measured points are interpolated. The absolute values are assigned to a color scale so that different absolute values or intervals correspond to different color values. The third column shows the final result of evaluation.
The top line shows the evaluation for a simple object (punctiform). The vectors here all point in the direction of a single point. The absolute values in this color coding form concentric circles around this point. Thus, this central point can be recognized and labeled as the position of the object.
The middle line shows the evaluation for a composite object (a plurality of punctiform objects). The gradient vectors here point toward several points. The color coding of the absolute values exhibits a corresponding symmetry.
The evaluation for a complex (distributed) object is shown on the bottom line. It is evident that the gradients here point both to a single central point, and in this example also show a characteristic reversal of direction along a closed, roughly circular line. Together with the color-coded image of the absolute values shown, it indicates a distributed object whose center is established and mar]ced by the central point addressed and which is delimited by the abovementioned closed line.
The components of the data field can be processed and evaluated in the manner described for each individual exciting frequency. From a comparison of the values at different exciting frequencies, the material (e.g. copper, brass, aluminum, iron, nickel, precious metals) can be identified. The physical basis for this is the fact that the signal received from an object changes with the exciting frequency in a typical manner that depends on the type of material. By using a plurality of suitable frequencies, one thus obtains information about the nature of the material of objects concealed in the soil, which clearly characterizes them and makes it possible to distinguish them.
Advantageously, a database may be available for example in which a characteristic frequency dependence is stored for a large number of materials and objects. By comparing the measured values with the contents of the database, an identification can be obtained.
With measurement at different exciting frequencies, moreover, disturbances caused by the low conductivity of damp soil can be eliminated. The sensitivity of the system is considerably increased.
In summary, high-resolution magnetic measurement of the upper layers of the soil, real-time display on a map of the measured values obtained, real-time marking on the ground of the positions of objects found, and classification of the objects found can all be achieved. Classification allows a significant decrease in the number of objects that need to be dug up. The time and cost of cleaning up the soil as well as the risk to personnel in charge of cleanup are considerably reduced.
List of Reference Numerals Used in Figures 8, 9, and 10:
2 and 4 Double gradiometer (rotating) 6 Measured value acquisition and transmission (rotating) 8 Rotary transducer to detect vehicle position (rigid) Rotary transducer for determining position of sensor module (rotating) 12 Optical data transmission and supply (rigid and rotating) 14 Passive magnetic field sensor (rotating) 16 Reference magnetic field sensor (rigid) 18 Central computer Vehicle 22 Gradient metal detector 24 Marking device, sprayer 26 Position sensor 28 Computer with flat screen Power supply 32 Instrument rack
Position and location measurement can be located both in the sensor module itself or at the control point. This can be accomplished by distance measurement on the ground, optically with laser trackers for example, or electromagnetically using satellite-supported navigation with differential formation.
(b) Decoupling Metal Detectors in the System As in the case of magnetic sensory analysis (l.e), the metal detectors must be decoupled in the system. The same remedies as in (l.e) can be used for this purpose. In general, the arrangement of the sensors in the system is selected in such fashion that the distances of the sensors from objects which negatively influence the sensor function (e.g. other sensors, metallic parts on the complete system) remain constant over time. With rotating sensors, this can be achieved for example by synchronizing the movement of the sensors.
(c) Adaptive Resolution Control If the operator of the system or an evaluation unit detects an object, the rate of movement of the system is reduced.
By virtue of the lower speed, measured values can be collected with a higher density so that the measurement resolution increases. With the higher measurement point density in a two-dimensional grid, the fine resolution of the magnetic signals can be increased by subsequent data processing. Three-dimensional separation of small and large objects is thus improved.
4. Display of Measurement Data and Evaluation The measured values from the double-gradient metal detectors (Figure 5) were pre-processed and color-coded in a two-dimensional image of the scanned site. Additional displays, isolines for example, are possible. The measured data from the magnetic field probes can be displayed in the same image with different color coding. As a result, objects with and without their own magnetic fields can be distinguished from one another in the image.
The color coding can be adjusted to the measuring situation by the operator. The measured values are fed to an evaluating computer. Objects that are recognized are displayed.
If the metallic volume of the object is sufficient, an eddy current distribution can be calculated. The shape, size, and depth as well as the position of the object can be determined from this. In the case of nonmagnetic objects, -their conductivity is calculated, while the magnetic moment is determined for magnetic objects.
!
Identification of the discovered objects can be performed with the aid of the object parameters determined (shape, volume, and electrical conductivity). The characteristic data of anticipated object are stored in a database. A
suitable computer program offers the operator of the devlce suggestions for identification.
In one especially advantageous embodiment, the data are evaluated using the following method:
An active double-gradient metal detector (Figure 5), when moving over a metallic object, delivers an absolute-value signal whose phase angle with respect to the exciting voltage depends on the material of the metal and the frequency of the exciting voltage. In this manner, metals such as brass, iron, copper, or aluminum can be distinguished regardless of their shape and size.
In practice, however, a background signal from the ground often prevents recognition of materials. By using a double-gradient metal detector, which is excited at one frequency, but especially advantageously at several frequencies, these difficulties can be overcome. The measured values from such a double-gradient metal detector are linked as point data sets with frequency-dependent absolute values and phases with the corresponding position coordinates of the metal detector by a computer to a data field that is multidimensional with respect to the exciting frequencies, said field being capable of being differentiated as a function of the position coordinates.
-A data set at a three-dimensional point in space P(x,y) within the site to be investigated, during operation of the exciting coil of the metal detector at two frequencies v"
V2 ~ contains the following components:
Amount and phase at exciting frequency v Phase and phase at exciting frequency v2 If the exciting coil of the metal detector is operated at more than two frequencies, i.e. at N frequencies, the stated two-dimensional measurement data set expands accordingly to an N-dimensional data set.
Since the signals of the two orthogonal gradiometer coils of the double-gradient metal detector tFigure 5) enter a single component, spatially two-dimensional information about the existing magnetic field is contained therein.
To obtain further information, the individual components of the measurement data set can also be linked with one another.
From the differentials and differential quotients of the absolute values and phase values of adjacent data sets (derivation according to the local coordinates) of the entire measurement data field, the location, depth, volume, and structure of the materials and a classification of hidden metallic objects can be obtained. Differential formation thus results directly in suppression of the background and noise signals.
Advantageously, the results of differential formation can be assigned to a gray scale value or color scale and displayed (advantageously in real time) displayed as a two-dimensional representation on a computer monitor. The areas between the -individual calculated points of the two-dimensional display can advantageously be filled by interpolated gray or color values.
The method will now be described in greater detail with reference to Figures 11 to 13. In Figure 11, at the upper right, the structure of an N-dimensional measurement data set (i.e. measurement at N different frequencies) is shown for a specific location.
At the upper left, a grid composed of individual locations is shown, with a measurement data set measured at each of these points being associated with these locations.
At the bottom left, the result of gradient formation by differential formation between the measurement data sets at adjacent locations is shown, and (for reasons of clarity) for only one fixed frequency vi. A vector which is shown corresponds to the vectorial difference of the data set at exciting frequency vi at one location and to the data set at the exciting frequency vi at an adjacent location.
The absolute value of the vectors shown is normalized to the unit value.
In Figure 12, several examples are shown for the alignment of the gradient vectors for certain materials and shapes of detected objects.
The sketch at the upper left shows the gradient vectors for a punctiform and ferromagnetic object. The vectors all point to a single point which is thus recognized as the center of the object. At the upper right, the gradient vectors determined for a punctiform paramagnetic object are shown. The vectors in this case point away from the object.
-At the bottom left and right, two examples of detection of elongate objects are shown. The gradient vectors are each shown at one edge of the object. In the case of a ferromagnetic object (left), the gradients point toward the edge, while in a paramagnetic object (right) the gradients point away from the edge.
Finally, Figure 13 shows several concrete examples of the evaluation of measurement signals for three different objects (lines 1 to 3).
The middle column shows the unit vector field of the gradients at a fixed exciting frequency, as already described in Figures 11 and 12. The first column shows the scalar field of the absolute values of the corresponding measurement data sets at the same exciting frequency. The values between the measured points are interpolated. The absolute values are assigned to a color scale so that different absolute values or intervals correspond to different color values. The third column shows the final result of evaluation.
The top line shows the evaluation for a simple object (punctiform). The vectors here all point in the direction of a single point. The absolute values in this color coding form concentric circles around this point. Thus, this central point can be recognized and labeled as the position of the object.
The middle line shows the evaluation for a composite object (a plurality of punctiform objects). The gradient vectors here point toward several points. The color coding of the absolute values exhibits a corresponding symmetry.
The evaluation for a complex (distributed) object is shown on the bottom line. It is evident that the gradients here point both to a single central point, and in this example also show a characteristic reversal of direction along a closed, roughly circular line. Together with the color-coded image of the absolute values shown, it indicates a distributed object whose center is established and mar]ced by the central point addressed and which is delimited by the abovementioned closed line.
The components of the data field can be processed and evaluated in the manner described for each individual exciting frequency. From a comparison of the values at different exciting frequencies, the material (e.g. copper, brass, aluminum, iron, nickel, precious metals) can be identified. The physical basis for this is the fact that the signal received from an object changes with the exciting frequency in a typical manner that depends on the type of material. By using a plurality of suitable frequencies, one thus obtains information about the nature of the material of objects concealed in the soil, which clearly characterizes them and makes it possible to distinguish them.
Advantageously, a database may be available for example in which a characteristic frequency dependence is stored for a large number of materials and objects. By comparing the measured values with the contents of the database, an identification can be obtained.
With measurement at different exciting frequencies, moreover, disturbances caused by the low conductivity of damp soil can be eliminated. The sensitivity of the system is considerably increased.
In summary, high-resolution magnetic measurement of the upper layers of the soil, real-time display on a map of the measured values obtained, real-time marking on the ground of the positions of objects found, and classification of the objects found can all be achieved. Classification allows a significant decrease in the number of objects that need to be dug up. The time and cost of cleaning up the soil as well as the risk to personnel in charge of cleanup are considerably reduced.
List of Reference Numerals Used in Figures 8, 9, and 10:
2 and 4 Double gradiometer (rotating) 6 Measured value acquisition and transmission (rotating) 8 Rotary transducer to detect vehicle position (rigid) Rotary transducer for determining position of sensor module (rotating) 12 Optical data transmission and supply (rigid and rotating) 14 Passive magnetic field sensor (rotating) 16 Reference magnetic field sensor (rigid) 18 Central computer Vehicle 22 Gradient metal detector 24 Marking device, sprayer 26 Position sensor 28 Computer with flat screen Power supply 32 Instrument rack
Claims (38)
1. Sensor system for detection, location, and identification of metallic objects located beneath the surface of the ground, characterized in that it comprises at least one sensor module with at least one active-gradient metal detector, with the gradient metal detector comprising at least one gradient coil and one exciting coil.
2. Sensor system according to Claim 1 characterized in that the gradient metal detector comprises two gradient coils orthogonal to one another (double-gradient metal detector).
3. Sensor system according to Claim 1 or 2 characterized in that it comprises at least one rotating sensor module.
4. Sensor system according to one of the foregoing claims characterized in that the exciting coil is operated at two frequencies.
5. Sensor; system according to one of the foregoing claims characterized in that, in order to increase position resolution, a sensor module comprises two active-gradient metal detectors, with the corresponding exciter coils being operated at different frequencies.
6. Sensor system according to one of the foregoing claims characterized in that the active-gradient metal detectors are operated in time-division multiplex or in frequency-division multiplex to reduce mutual interference.
7. Sensor system according to one of the foregoing claims characterized in that the active-gradient metal detectors are operated with shielding to reduce mutual interference.
8. Sensor system according to one of the foregoing claims characterized in that the active-gradient metal detectors maintain a certain minimum spacing to reduce mutual interference.
9. Sensor system according to one of Claims 2 to 8 characterized in that two active-gradient metal detectors move synchronously on a circular path diametrally opposite one another and unchangeably with respect to one another, to reduce mutual interference.
10. Sensor system according to one of the foregoing claims characterized in that the sensor module contains at least one additional passive magnetic field probe.
11. Sensor system according to one of the foregoing claims characterized in that measurement resolution is adjusted adaptively as a function of signal magnitude by changing the measuring grid.
12. Sensor system according to one of the foregoing claims characterized in that the sensor system is moved by a vehicle or carried by hand over the surface of the ground.
13. Sensor system according to one of the foregoing claims characterized in that position determination means are provided for the sensor system and/or an individual sensor.
14. Sensor system according to one of the foregoing claims characterized in that the position determination means comprise a differential global positioning system (DGPS).
15. Sensor system according to Claim 15 characterized in that the position determination means additionally comprise a directional gyro and acceleration sensors and/or speed sensors.
16. Sensor system according to one of the foregoing claims characterized in that the position determination means comprise a location-dependent laser tracking system.
17. Sensor system according to one of the foregoing claims characterized in that the position determination means comprise a two-dimensional ultrasound system that cooperates with a correlation computer.
18. Sensor system according to one of the foregoing claims characterized in that the position determination means comprise a two-dimensional laser Doppler sensor system.
19. Sensor system according to one of the foregoing claims characterized in that the position determination means comprise rotation sensors and/or displacement sensors.
20. Sensor system according to one of the foregoing claims characterized in that the location of the sensor system is determined on the basis of a reference point.
21. Sensor system according to one of the foregoing claims characterized in that the measurement data from the magnetic field sensors and the position determination means are pre-processed.
22. Sensor system according to one of the foregoing claims characterized in that a central computer is provided which prepares a two-dimensional image of the investigated surface of the ground, preferably in real time, based on the data from the magnetic field sensors and the position data from the sensor system.
23. Sensor system according to Claim 22 characterized in that a screen is provided to display the two-dimensional image of the investigated area of the ground.
24. Sensor system according to Claim 23 characterized in that the measurement data from the active and passive magnetic field sensors are converted into color values and the color values are displayed on the screen to reflect positions.
25. Sensor system according to one of the foregoing claims characterized in that the position-dependent magnetic moment, magnetization, and/or reversible magnetization are calculated from the measurement data.
26. Sensor system according to one of the foregoing claims characterized in that the measurement data are evaluated in terms of absolute value and phase.
27. Sensor system according to one of the foregoing claims characterized in that the location, depth, size, shape, and/or material of metallic objects are calculated from the measurement data.
28. Sensor system according to one of the foregoing claims characterized in that the objects are classified on the basis of calculated data on size, shape, and material.
29. Sensor system according to one of the foregoing claims characterized in that identification is calculated for certain classifications of objects.
30. Sensor system according to Claim 29 characterized in that the classified/identified objects are mapped as a function of location.
31. Sensor system according to one of the foregoing claims characterized in that means are provided to label the location where found, classifications, and identifications on the screen, in the color printout, and on the ground.
32. Sensor system according to Claim 31 characterized in that means are provided to indicate the classification of objects on the ground by using colored markings.
33. Sensor system according to one of the foregoing claims characterized in that the data are transmitted electro-optically from the individual sensor modules to the central computer.
34. Method for the detection, location, and identification of metallic objects beneath the surface of the ground, characterized in that the measurement signals, differing in absolute value and phase, from a double-gradient metal detector excited at one or more frequencies are linked to a data field as a function of the actual position coordinates of the double-gradient metal detector.
35. Method according to Claim 34 characterized in that an image and/or a position determination for metallic objects concealed beneath the surface is generated by differential formation or formation of differential quotients between data sets of adjacent position coordinates.
36. Method according to Claim 35 characterized in that a gray value scale or a color scale is assigned to the differential values or the absolute values of the differential quotients or the amounts of the data sets.
37. Method according to one of the Claims 34 to 36 characterized in that the material of which the metallic objects are composed is determined from the characteristic change in the data sets as a function of the exciting frequency.
38. Method according to one of the foregoing Claims 34 to 37 characterized in that the sensor signals are evaluated with a dynamic range of 22 bits corresponding to 130 dB.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4436078.9 | 1994-10-10 | ||
| DE19944436078 DE4436078A1 (en) | 1994-10-10 | 1994-10-10 | High resolution imaging sensor system for detection, location and identification of metallic objects |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2178332A1 true CA2178332A1 (en) | 1996-04-18 |
Family
ID=6530329
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2178332 Abandoned CA2178332A1 (en) | 1994-10-10 | 1995-10-09 | Sensor system for detecting, locating and identifying metal objects |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0733218A1 (en) |
| CA (1) | CA2178332A1 (en) |
| DE (1) | DE4436078A1 (en) |
| WO (1) | WO1996011414A1 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140132269A1 (en) * | 2011-11-14 | 2014-05-15 | Mark S. Olsson | Multi-frequency locating systems and methods |
| US20140132270A1 (en) * | 2011-11-14 | 2014-05-15 | Mark S. Olsson | Quad-gradient coils for use in locating systems |
| US9103939B2 (en) | 2011-06-07 | 2015-08-11 | Hilti Aktiengesellschaft | Method and device for detecting a conductive object |
| US9488747B2 (en) | 2012-03-23 | 2016-11-08 | Seesoon, Inc. | Gradient antenna coils and arrays for use in locating systems |
| WO2017205958A1 (en) * | 2015-06-02 | 2017-12-07 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
| US20220291412A1 (en) * | 2021-03-12 | 2022-09-15 | Christopher Frank Eckman | Metal detecting sensor array for discriminating between different objects |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5842986A (en) | 1995-08-16 | 1998-12-01 | Proton Sciences Corp. | Ferromagnetic foreign body screening method and apparatus |
| US7047059B2 (en) | 1998-08-18 | 2006-05-16 | Quantum Magnetics, Inc | Simplified water-bag technique for magnetic susceptibility measurements on the human body and other specimens |
| US6965792B2 (en) | 1996-06-25 | 2005-11-15 | Mednovus, Inc. | Susceptometers for foreign body detection |
| US6496713B2 (en) | 1996-06-25 | 2002-12-17 | Mednovus, Inc. | Ferromagnetic foreign body detection with background canceling |
| DE19648834A1 (en) * | 1996-11-26 | 1998-05-28 | Foerster Inst Dr Friedrich | Method for operating and evaluating signals from an eddy current probe and device for carrying out the method |
| DE19648833A1 (en) * | 1996-11-26 | 1998-05-28 | Foerster Inst Dr Friedrich | Method and device for locating and identifying search objects hidden in the ground, in particular plastic mines |
| DE19652977C1 (en) * | 1996-12-19 | 1998-04-30 | Vallon Gmbh | Buried object locating device for ferromagnetic, plastics or metallic objects |
| DE29717370U1 (en) * | 1997-09-29 | 1998-01-08 | Ebinger Klaus | Probe arrangement |
| GB9813889D0 (en) * | 1998-06-27 | 1998-08-26 | Secr Defence | Apparatus for detecting metals |
| SE511951C2 (en) * | 1998-09-29 | 1999-12-20 | Saab Ab | Mine clearance Robot |
| DE10104924B4 (en) * | 2001-01-30 | 2004-09-30 | Mit Gmbh Magnetic Imaging Tools | Mobile measuring device and method for the spatially resolved determination of magnetic and / or electrical parameters of bodies embedded in liquids or solid substances |
| US6525539B2 (en) * | 2001-03-15 | 2003-02-25 | Witten Technologies Inc. | Apparatus and method for locating subsurface objects in conductive soils by measurements of magnetic fields by induced currents with an array of multiple receivers |
| GB0124887D0 (en) | 2001-10-17 | 2001-12-05 | Qinetiq Ltd | Metal detection apparatus |
| EP1828811A2 (en) * | 2004-12-20 | 2007-09-05 | Andrä, Wilfried | Assembly and method for locating magnetic objects or objects that can be magnetised |
| DE102009042616A1 (en) | 2009-09-23 | 2011-03-24 | Christoph Rohe | Handleable device for detecting metallic objects located in a substrate, in particular a wall or the like |
| DE102012218174A1 (en) | 2012-10-05 | 2014-04-10 | Robert Bosch Gmbh | Location device for determining an object depth |
| DE102015206275A1 (en) * | 2015-03-18 | 2016-09-22 | Gerd Reime | System, method and computer program for the mobile provision of data of hidden objects |
| DE102016108988B4 (en) * | 2016-05-13 | 2019-05-29 | Heinrich Hirdes Gmbh | Method and device for finding electrically conductive objects under a ground surface |
| DE102017210672A1 (en) * | 2017-06-23 | 2018-12-27 | Heinrich Hirdes Gmbh | Method for measuring a coverage of a line and device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3826973A (en) * | 1973-01-10 | 1974-07-30 | Benson R | Electromagnetic gradiometer |
| US3875497A (en) * | 1973-12-26 | 1975-04-01 | Seatrek Ltd | Waterborne magnetic anomaly detection system and apparatus |
| US4021725A (en) * | 1976-03-05 | 1977-05-03 | The United States Of America As Represented By The Secretary Of The Navy | Mobile mine detection system having plural color display |
| US4727329A (en) * | 1986-02-19 | 1988-02-23 | Atlantic Richfield Company | Method and system for measuring displacement of buried fluid transmission pipelines |
| DE3619308C1 (en) * | 1986-06-07 | 1991-08-29 | Klaus Ebinger | Probe for a metal detector |
| DE4242541C2 (en) * | 1992-12-16 | 1996-03-28 | Tzn Forschung & Entwicklung | Device for locating ammunition located below the earth's surface |
-
1994
- 1994-10-10 DE DE19944436078 patent/DE4436078A1/en not_active Withdrawn
-
1995
- 1995-10-09 EP EP95934044A patent/EP0733218A1/en not_active Withdrawn
- 1995-10-09 CA CA 2178332 patent/CA2178332A1/en not_active Abandoned
- 1995-10-09 WO PCT/DE1995/001375 patent/WO1996011414A1/en not_active Application Discontinuation
Cited By (11)
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|---|---|---|---|---|
| US9103939B2 (en) | 2011-06-07 | 2015-08-11 | Hilti Aktiengesellschaft | Method and device for detecting a conductive object |
| US20140132269A1 (en) * | 2011-11-14 | 2014-05-15 | Mark S. Olsson | Multi-frequency locating systems and methods |
| US20140132270A1 (en) * | 2011-11-14 | 2014-05-15 | Mark S. Olsson | Quad-gradient coils for use in locating systems |
| US9638824B2 (en) | 2011-11-14 | 2017-05-02 | SeeScan, Inc. | Quad-gradient coils for use in locating systems |
| US9927545B2 (en) * | 2011-11-14 | 2018-03-27 | SeeScan, Inc. | Multi-frequency locating system and methods |
| US9488747B2 (en) | 2012-03-23 | 2016-11-08 | Seesoon, Inc. | Gradient antenna coils and arrays for use in locating systems |
| US10031253B2 (en) | 2012-03-23 | 2018-07-24 | SeeScan, Inc. | Gradient antenna coils and arrays for use in locating systems |
| US10989830B1 (en) | 2012-03-23 | 2021-04-27 | SeeScan, Inc. | Utility locator apparatus and systems |
| WO2017205958A1 (en) * | 2015-06-02 | 2017-12-07 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
| US10274630B2 (en) | 2015-06-02 | 2019-04-30 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
| US20220291412A1 (en) * | 2021-03-12 | 2022-09-15 | Christopher Frank Eckman | Metal detecting sensor array for discriminating between different objects |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1996011414A1 (en) | 1996-04-18 |
| DE4436078A1 (en) | 1996-04-11 |
| EP0733218A1 (en) | 1996-09-25 |
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