JPH1183421A - Measuring method for depth of underground buried object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring depth of a buried object by accurately detecting the position of the object buried in the underground such as a gas pipe and a water pipe, that is, position on the corresponding to the position of the object buried in the underground. SOLUTION: This detection system consists of a transmitting antenna coil 3, which is a movable means to generate electromagnetic wave and generates electromagnetic wave with directivity, and a receiving antenna coil, which is a movable means to recognize a signal output and can detect the electromagnetic wave with directivity generated from an information display 1. It is structured by a combination of a calibration curve found by measuring in advance a relation between a signal output value and a burying depth and the information display 1 or by a combination of at least two information displays 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the indication of the position of underground objects such as land, roads and buried pipes, and various kinds of information on the site. It can be used for surveying-related systems such as measurement of the depth of a buried object at a specified location.

[0002]

2. Description of the Related Art As a method for detecting the position of an underground object such as a gas pipe or a water pipe, Japanese Patent Publication No. Hei 7-86533 discloses that a current is applied to a conductive underground object by electromagnetic induction. There has been proposed a method of detecting the position of an underground object by detecting a generated magnetic field.

In this technique, in a method of detecting the position of an underground object, a transmitter variably configures a magnetic flux linkage state with respect to an underground object, measures a magnetic field distribution by a receiver,
While detecting the deviation of this and the prescribed cylindrical magnetic field distribution, the state of the magnetic flux linkage is changed, and the transmitter is adjusted so as to minimize this deviation. It detects the position of an object.

[0004]

When following this method,
Limited to the identification of metal pipes such as water pipes or gas pipes,
There is a difficulty that cannot be detected when the material of the pipe is PVC or the like. Further, when measuring the magnetic field distribution, the detection area of the magnetic sensor has an extension, so that it is not always possible to specify the position with high accuracy and to measure the depth of the buried object.

The present invention has been made in view of the above points, and the present invention provides a method for measuring the depth of an underground buried object which was not a function of the system in the conventional method of detecting the position of an underground buried object. It is intended to do so. Of course, the ground surface corresponding position corresponding to the position of the underground object is detected with high accuracy,
A detection method having distinctiveness is also provided.

[0006]

In order to achieve the above-mentioned object, an electromagnetic wave generated from an antenna of a transmitter has a direction, and an electromagnetic wave generated from an information display has a direction. Paying attention to the fact that the amplitude corresponds to the detection distance, the present inventors have made intensive studies on measuring the depth of a buried object, and as a result, have reached the present invention.

That is, the present invention provides a movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in the vertical direction on the surface of the earth, and a response to the electromagnetic wave from the means (1) by electromagnetic induction of the electromagnetic wave. An information display (2) that generates a signal having a vertical directivity on the surface embedded in the ground, and a signal generated from the display (2) is detected to recognize each signal output, and is movable. Recognizing means (3)
By moving the means (1) and the means (3) in the horizontal direction along the ground surface, the means (3) obtains a signal output value in the vertical direction on the ground surface at each position of the movement of the means (1). Based on the maximum value of the signal output value at each of the positions, the surface burying position corresponding to the underground burying position of the information display (2) is specified, and the signal output maximum value of the recognizing means (3) and the burying depth are identified. And a method for measuring the depth of a buried object based on a calibration curve obtained by previously measuring the relationship between the depth and the depth of the buried object. (Hereinafter referred to as the first invention)

Alternatively, a movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in a direction parallel to and / or perpendicular to the surface of the earth, and responding by electromagnetic induction of the electromagnetic wave from the means (1); An information display (2) buried in the ground and generating a signal formed in the in-plane direction by signals having a plurality of directivities in a plane parallel to the ground;
Movable recognizing means (3) for detecting signals generated from the display (2) and recognizing respective signal outputs, for generating electromagnetic waves having directivity in the vertical direction on the ground surface. By moving (1) and (3) in the horizontal direction along the ground surface, the means (3) obtains a signal output value in the horizontal direction on the ground surface at each position of the movement of the means (1). Means for specifying the ground buried position corresponding to the ground buried position of the information display (2) when the signal output value of the position becomes a minimum value, and generating an electromagnetic wave having directivity in a direction parallel to the ground surface. The depth of the buried object is obtained by using a calibration curve obtained by measuring in advance the relationship between the signal output value of (1) and the signal output value of the means (3) and the signal output value of the recognizing means (3) at the ground buried position and the burial depth. To measure the depth of underground objects It is intended to provide. (Hereinafter referred to as the second invention)

Specifically, in the first invention, for example, the signal output of the electromagnetic wave generated from the information display has at least one directivity, and is selected from the following information display or one directivity. It can be obtained by combining at least two information indicators from the following information indicators having only the following information indicators.

On the other hand, in the second invention, for example, the signal output of the electromagnetic wave generated from the information display device has at least two directivities and has only one of the following information display devices selected from the following or only one directivity. The following information indicators can be obtained by combining at least two information indicators.

(A) LC resonance circuit marker. (B) An electromagnetic induction type marker composed of a semiconductor memory element, a communication / memory control element, and a frequency transmission / reception element and recorded with position information and the like. (C) A magnetic pattern corresponding to a bias magnetic field mechanically resonates with a magnetized bias magnetic field generating element at a specific frequency in an incident alternating magnetic field of a fluctuating frequency to change a magnetic flux density or a magnetic permeability. A marker in which a specific frequency at which a magnetic flux density or a magnetic permeability changes is generated as position information or the like, wherein the highly permeable metal is laminated so as to be able to resonate mechanically.

[0012]

Next, the operation of the present invention will be described with reference to FIGS. 1 and 2 and FIGS. 3 and 4 showing the basic concept. 1 and 2 are diagrams showing the basic concept of the first invention for measuring the depth of a buried object using an information display device having only one directivity, and FIG. 3 and FIG. It is the figure which showed the basic concept of 2 inventions. In the figure, reference numeral 1 denotes an information display, reference numeral 2 denotes a ground surface, and reference numeral 3 denotes a transmission antenna coil as an example of an electromagnetic wave generating means.

[0013] The shape of the transmitting antenna coil for generating an electromagnetic wave having directivity is preferably a loop antenna, and particularly preferably a copper wire or the like wound one or more turns in a circular or rectangular shape. The electromagnetic wave generated from the transmitting antenna coil is
In the near field, the impedance is low, the magnetic vector is dominant, and the energy is composed of a magnetic field component and a slight electric field component. The directivity of electromagnetic waves is particularly high at frequencies higher than the microwave range, but when penetrating deep into soil containing moisture, long-wave electromagnetic waves are preferred.

Here, the operation will be specifically described with respect to the magnetic field component of an electromagnetic wave, that is, an AC magnetic field. A magnetic flux line of an AC magnetic field, which is an example of an electromagnetic wave having a directivity in the vertical direction on the surface of the earth and emitted from the electromagnetic wave generating means, is represented by a solid line arrow, and is indicated by reference numeral 4. X indicates when the directivity of the information display 1 is perpendicular to the ground, and Y indicates when it is parallel to the ground.

Reference numeral 5 denotes a magnetic flux line generated by the information display in response to an electromagnetic wave emitted from the transmitting antenna coil, which is indicated by a dotted arrow. Reference numeral 6 denotes a receiving antenna coil as an example of a recognition unit that detects a signal emitted from an information display and recognizes the signal as a signal output. The shape of the receiving antenna coil that receives an electromagnetic wave having directivity is a loop antenna. Preferably, a coil or a center feed loop coil in which a copper wire or the like is wound in a circular or rectangular shape one or more turns concentrically with the transmitting antenna coil.

FIGS. 1 and 2 show that an information display device having a single directivity is embedded in the ground so as to have a directivity in a vertical direction.
The figure shows a transmitting coil as an electromagnetic wave generating means and a receiving coil as a signal output recognizing means which are placed in contact with each other after moving parallel to the ground.

In FIG. 1, a vector component of the magnetic flux lines generated from the transmission coil in the ground and in the vertical direction gives magnetic energy to the information display, and the position corresponding to the ground surface of the information display coincides with the center position of the transmission coil. Sometimes the strongest yet stable magnetic energy is applied. As the position of the information indicator shifts away from the center position of the transmitting coil and moves away, the applied magnetic energy becomes weaker.

The information display generates a magnetic flux line having a vertical directivity on the ground in response to the applied magnetic energy, and is detected by the receiving coil as shown in FIG. The current generated when the magnetic flux lines are cut by the receiving coil from the information display unit flows the strongest when the position of the information display unit matches the position of the center of the receiving coil. As the position shifts and moves away, the flowing current becomes weaker.

Therefore, with the maximum value of the current flowing through the receiving coil, the center position of the transmitting coil and the center of the receiving coil is a place where the position corresponding to the ground surface of the information display unit coincides.

The magnitude of the magnetic field applied to the information display at this time is given by the following equation. Here, in order to simplify the model, calculation is performed in the case of a loop transmission coil.

[0021]

[Formula 1] Hd = nｎIA / 2π (r ² + d ² ) ^3/2 (1)

In the equation (1), n is the number of turns of the coil, I is the current flowing through the coil, A is the area of the coil, r is the radius of the coil, d is the distance between the center of the coil and the information display. Is shown. Therefore, the magnitude of the magnetic field applied to the information display is determined unitarily with respect to the distance d.
The magnetic energy applied to the information display is reduced.

An information display to which magnetic energy has been applied has a magnetic moment, and generates a magnetic flux from the moment. This magnetic moment is proportional to the applied magnetic field,
The magnitude of the voltage generated in the loop receiving coil is given by the following equation.

[0024]

[Formula 2] V = μ ₀ · f · M · Hr (2)

Here, in equation (2), μ ₀ is the magnetic permeability of vacuum, f is the frequency generated by the information display, M is the magnitude of the magnetic moment of the information display, and Hr is the current of 1 A to the receiving coil. This indicates the magnitude of the magnetic field generated when flowing. Therefore, when a constant current flows through the transmission coil and a magnetic field is applied to the information display, the current flowing through the reception coil is determined unitarily with respect to the distance d.

Therefore, if the magnitude of the voltage generated in the receiving coil is measured in advance with respect to the distance d, that is, the depth at which the information display device is buried, and a calibration curve is created, the information display device can be used underground or the like. When buried in, the depth can be measured.

Here, since equation (2) shows the result of calculation in free space, in practice, soil, hydrous sand containing salt,
It is needless to say that it is preferable to compensate for the difference in magnetic permeability of rocks and the like.

FIGS. 3 and 4 show that an information display device having a single directivity is embedded parallel to the ground with directivity.
A transmitting coil as an electromagnetic wave generating means and a receiving coil as a signal output recognizing means, which are installed in vertical contact with the ground, are shown.

In FIG. 3, a vector component of a magnetic flux line generated from a transmission coil in a direction parallel to the ground gives magnetic energy to an information display unit having a directivity Y, and a directivity is provided at a center position of a portion of the transmission coil in contact with the ground surface. When the position of the information display of Y coincides, and the direction of the directivity of the transmission coil coincides with the direction of the directivity of the information display, magnetic energy is applied most strongly. As the position of the information indicator shifts away from the center of the part of the transmitting coil that touches the ground,
Alternatively, as the angle between the direction of the directivity of the transmission coil and the direction of the direction of the information display approaches 90 °, the applied magnetic energy decreases.

The information indicator of directivity Y generates a magnetic flux line having directivity parallel to the surface of the earth in accordance with the applied magnetic energy, and is detected by the receiving coil as shown in FIG. . The current generated when the magnetic flux lines from the directivity Y information display are cut by the receiving coil is such that the position of the directivity Y information display coincides with the center position of the portion of the receiving coil in contact with the ground, and the transmission coil The current value flowing when the direction of the directivity of the information display and the direction of the directivity of the information display coincide with each other shows a maximum. As the position of the information indicator shifts away from the center position of the part of the receiving coil that touches the ground surface, or
As the angle between the direction of the directivity of the transmitting coil and the direction of the directivity of the information display approaches 90 °, the current gradually decreases.

Therefore, with the local maximum value of the current flowing through the receiving coil, the center position of the portion where the transmitting coil and the receiving coil are in contact with the ground surface is the position where the information display device corresponds to the ground surface.

The magnitude of the magnetic field applied to the information display at this time is given by the following equation. For simplicity of the model, the transmitting and receiving coils are rectangular here, and the calculation is performed by approximating a straight line current in contact with the ground surface.

[0033]

Hd = n · I / 2πd (3)

Here, in equation (3), n is the number of turns of the coil, I is the current flowing through the coil, and d is the distance between the ground and the information display. Therefore, the magnitude of the magnetic field applied to the information display is determined unitarily with respect to the distance d. As the distance d increases, the magnetic energy applied to the information display decreases. An information display to which magnetic energy is applied has a magnetic moment, and generates a magnetic flux from the moment.
This magnetic moment is proportional to the applied magnetic field, and the magnitude of the voltage generated in the rectangular receiving coil is given by the equation having the same configuration as equation (2).

Therefore, a constant current is applied to the transmitting coil,
When a magnetic field is applied to the information display, the current flowing through the receiving coil is determined unitarily with respect to the distance d.

Therefore, if the magnitude of the voltage generated in the receiving coil is measured in advance with respect to the distance d, that is, the depth at which the information display is buried, and a calibration curve is created, the information display can be used underground or the like. When buried in, the depth can be measured.

However, when the direction of the directivity of the transmitting / receiving coil and the direction of the directivity of the information display unit exactly match, reproducibility can be obtained with respect to the calibration curve. Has a problem that reproducibility cannot be obtained.

Here, if at least two or more directivities are provided to the information display so that the same level of magnetic moment is generated in the directivity direction of the transmitting and receiving coils in a plane parallel to the ground surface, the transmitting and receiving coils have a directivity. A constant voltage can be obtained with respect to the burying depth regardless of the directional direction and the directional direction of the information display. As an example, FIG. 5 shows a positional relationship between an information display having two directivities and a transmitting and receiving coil, and shows a case where two information displays having only one directivity are used in combination for convenience. . The two directivities of this information display are orthogonal to each other. The magnetic field H of the transmitting / receiving coil at this time
The vector component of the magnetic moment of the information display in the directivity direction is expressed by the following equation (4). If one of the directivity of the information display and the angle of the coil is θ,

[0039]

[Equation 4] _{M X = M 1 COSθ + M} 2 SINθ (4)

Here, in the equation (4), 0 ° <θ <90 °.
_Let M _{X be} the vector sum of the directivity directions of the transmitting and receiving coils of the two magnetic moments. Assuming that the magnitudes of the two magnetic moments are the same, if M ₁ = M ₂ = M

[0041]

[Equation 5] _{M X = M √2 SIN (θ} + 45 °) (5)

The next, the size of the M _X is in the range of 1～√2. Since the magnitude of the magnetic field applied to the information display decreases at a level of 1 / d with respect to the distance, the magnitude of this range falls within the error range, and the magnitude of the magnetic moment is almost constant with respect to the burial depth. .

Further, this information display has an advantage that the position can be accurately detected. This will be described with reference to FIGS.

FIGS. 6 and 7 show a state in which an information display device having a single directivity is embedded with a directivity Y parallel to the ground surface, and the transmitting coil and the receiving coil move parallel to the ground surface (thick). (Dotted arrow).

In FIG. 6, the vector component of the magnetic flux lines generated from the transmission coil in the direction parallel to the ground surface gives magnetic energy to the information indicator of directivity Y, and the information indicator of directivity Y is located at the center of the transmission coil. When the position of the transmission coil coincides, the weakest magnetic energy is applied, and as the position of the information indicator shifts away from the center position of the transmission coil and moves away, the applied magnetic energy increases and the transmission coil line It increases most in the vicinity and then gradually decreases.

The information display of the directivity Y generates magnetic flux lines having directivity parallel to the surface of the earth in accordance with the applied magnetic energy, and is detected by the receiving coil as shown in FIG. . The current generated when the magnetic flux lines from the information indicator of the directivity Y are cut by the receiving coil is such that the current flowing when the position of the information indicator matches the center position of the receiving coil is minimal, The current flowing increases as the position of the information display device shifts away from the center position, shows a maximum current value near the line of the transmission coil, and then gradually decreases.

Therefore, the point where the value of the current flowing through the receiving coil shows the minimum value is the position corresponding to the ground surface of the embedded information display. In the case of the present invention, the information display device has at least two directivities so that the same level of dipole moment is generated in any direction on a plane parallel to the ground surface. On the other hand, the center point of the donut-shaped signal output is the ground-corresponding position of the embedded information display.

Next, the information display (3) used in the present invention will be described. As this indicator (3),
As described above, as described above, a marker having only one directivity and a marker having two or more directivities can be used.

(A) LC resonance circuit marker. (B) An electromagnetic induction type marker composed of a semiconductor memory element, a communication / memory control element, and a frequency transmission / reception element and recorded with position information and the like. (C) A magnetic pattern corresponding to a bias magnetic field mechanically resonates with a magnetized bias magnetic field generating element at a specific frequency in an incident alternating magnetic field of a fluctuating frequency to change a magnetic flux density or a magnetic permeability. A marker in which a specific frequency at which a magnetic flux density or a magnetic permeability changes is generated as position information or the like, wherein the highly permeable metal is laminated so as to be able to resonate mechanically.

As the information display, a marker constituted by an electric resonance circuit such as an LC resonance circuit or a crystal resonance circuit can be used. The LC resonance circuit is a circuit system including a coil and a capacitor, and the direction perpendicular to the coil surface becomes directivity.

Alternatively, a marker using an electromagnetic induction type non-contact communication medium can be used. That is, a marker having a non-contact transmission and reception function and including a semiconductor memory element, a communication control unit, and a memory control unit can be used. The communication medium is an induction electromagnetic field of several hundred KHz or less, and coils are used for transmission and reception functions. The direction perpendicular to the coil plane becomes the directivity.

Alternatively, the magnetic pattern corresponding to the bias magnetic field mechanically resonates with the magnetized bias magnetic field generating element at a specific frequency in the incident alternating magnetic field having a variable frequency,
Magnetic flux density or magnetic permeability changes, high magnetic permeability metal having magnetostriction is laminated so that it can resonate mechanically, and a specific frequency at which magnetic flux density or magnetic permeability changes is generated as position information or the like. Magnetic markers can be used. In particular, the highly permeable metal having magnetostriction is preferably in a strip shape, and when the magnetic pattern is magnetized in the long side direction of the strip, the long side direction becomes directivity. Therefore, by combining magnetic markers having different mechanical resonance frequencies, it can be used as the information display of the present invention.

As described above, the information display can combine the same type of markers. Although the magnetic marker is electrically equivalent to the LC resonance circuit, the frequency band of the resonance frequency is low for most of the markers of the LC resonance circuit, from the long wave to the medium wave, and the frequency of the magnetic marker is lower than the microwave. Considering that electromagnetic waves penetrate through water-containing layers such as puddles and fallen leaves when soil is assumed, long waves to medium waves are preferable, and magnetic markers are excellent.

Although a marker using a non-contact communication medium of the electromagnetic induction type uses a long wave to a medium wave, a marker having a power source such as a battery lacks permanence when buried in the soil. Have a problem. Those that do not have a power supply have a shorter reading distance than a magnetic marker that is identified by the presence or absence of a resonance frequency because the carrier is modulated to carry information, and are also more expensive than a magnetic marker.

The information display may be combined with different types of markers in order to add an information amount. For example, a magnetic marker and a marker of an LC resonance circuit can be combined. It is also possible to combine a marker of the LC resonance circuit with a marker using an electromagnetic induction type non-contact communication medium. Alternatively, a magnetic marker and a marker using a non-contact communication medium of an electromagnetic induction type can be combined.

Regardless of the LC resonance circuit or the non-contact communication medium of the electromagnetic induction type, when the transmitting and receiving coils are brought close to the coils having different directivities, unnecessary electromagnetic induction between the coils is caused, which causes noise. Combinations with magnetic markers that are not required are preferred.

Regardless of whether the information display is formed by combining two or more markers having only one directivity or the information display is formed by using one marker having two or more directivities, Even in the case of (1), it is optimal to use the magnetic marker (C).

Here, the most preferred magnetic marker (C)
The description of the information display body using is described below.

The feature of this magnetic marker is that, with respect to a fluctuating incident AC magnetic field, the frequency for forming a magnetic field is gradually changed from a low frequency to a high frequency or from a high frequency to a low frequency. Alternatively, in a state where a magnetic pattern corresponding to a bias magnetic field is magnetized in a magnetic field generating element with respect to an alternating magnetic field of white noise having a burst frequency of all frequencies, at least one predetermined frequency at which a magnetic flux density or a magnetic permeability changes is used. The point is that it is generated and responded to as an identification signal.

Since no bias magnetic field is generated when the magnetic field generating element is not magnetized, an output signal based on a predetermined frequency at which the magnetic flux density or the magnetic permeability changes with respect to the fluctuating incident alternating magnetic field is based on the magnetostriction. It does not occur from highly magnetically permeable metals having properties.

The structure of the magnetic marker will be described with reference to FIG. 8, which is an example. A magnetic pattern corresponding to a bias magnetic field mechanically resonates with a magnetized bias magnetic field generating element 21 at a specific frequency in an incident alternating magnetic field of a fluctuating frequency to change a magnetic flux density or a magnetic permeability. The magnetically permeable metal 22 is laminated so that it can resonate mechanically.

As the bias magnetic field generating element 21, a flat hard magnetic material strip having a higher coercive force than the highly permeable metal 22 can be used. In particular,
A thin body of a ferromagnetic material such as SAE1095 steel, baicaloy, anochrome, stainless steel, nickel, ferrite, and soft iron can be used. Alternatively, a housing made of a molded product into which iron oxide-based magnetic powder such as barium ferrite is kneaded can be used.

Alternatively, the saturation magnetic flux density in the binder is 70 em
A dried coating film formed by dispersing magnetic powder of u / g or more may be used. Alternatively, even if a material other than the above is used, a material in which a bias magnetic field intensity generated when a magnetic pattern is magnetized on the bias magnetic element 21 causes magnetostriction of the highly permeable metal 22 having magnetostriction can be used. .

As the non-magnetic casing 23, any of those made of known and commonly used synthetic resins can be used. For example, polystyrene, polymethyl methacrylate, ABS, vinyl chloride, polyethylene, polypropylene, polycarbonate, PET, PBT, PPS, etc. Is raised.

A predetermined frequency at which the magnetically permeable metal 22 having magnetostriction mechanically resonates and the magnetic flux density and the magnetic permeability rapidly change is specific to the length of the metal. Defined

[0066]

Equation 6 fn = n / 2Lｎ (D / ρ) (6)

In the formula (6), n is an integer and L is metal 2
The length of 2, D is the Young's modulus of the metal, and ρ is the density of the metal.

As the metal 22 which is provided with a bias magnetic field and which responds to an alternating magnetic field having a predetermined frequency among externally applied fluctuating frequencies, a highly permeable metal material having magnetostriction is used. Can be used, and the magnetostriction is 1
A ferromagnetic metal having a content of 5 ppm or more is preferable, and a material having the above-mentioned magnetic permeability of 100 or more is more preferable. Specifically, for example, when the maximum magnetic field strength is 0.25 Oe at 1 kHz, it is particularly preferable that the strength be 1000 or more.

As such a metal 22, an amorphous metal manufactured by Allied Signal Co., Ltd., for example, Metoglass “2605”
SC "," 2605CO "," 2826MB ", amorphous metal" VIROVAC40 "manufactured by Vacuum Schmelz
40 "and the like.

The shape of the metal 22 is not particularly limited, and may be a deformed plate such as a trapezoid, a parallelogram, a hexagon, or the like.
There are long and narrow strips such as strips and wires.
The latter strip shape is preferred.

In order to reduce the influence of the demagnetizing field and the non-linear vibration caused by the shape, a rectangular shape is preferable.
In order to obtain the vibration direction of only the long side, it is preferable that the ratio of the long side to the short side is 15 or more.

Further, by combining metals 22 having long sides having different lengths, the capacity of marker identification is greatly improved. Incidentally, the shape of the metal shown in the figure is a strip shape. The thickness is 15 to 35 μm
It is preferred that

In actually using the marker,
As described above, a bias magnetic field is applied to the metal 22 from the magnetic field generating element 21. When the magnetic field generating element 21 is a permanent magnet that is magnetized in advance, the magnetic field generating element 21 may be used as it is. However, when the magnetic field generating element 21 is not magnetized, for example, the magnetic field generating element 21 may be magnetized so as to be divided at equal intervals. And a bias magnetic field is generated. Note that it is preferable to select a bias magnetic field having an optimum intensity so that the mechanical resonance of the metal 22 becomes as large as possible.

The information display device used in the first invention can be used as it is by protecting the marker with water, acid, salt and the like.

The information display used in the second invention is prepared by combining two or more markers so as to have at least two directivities so that the same level of dipole moment is generated in the plane. It is preferable to use a vessel.

More specifically, as shown in FIG. 9, it is preferable that the number of magnetic markers 20 be at least two and each resonate at the same frequency. When N, the marker is 90 ° / N
It is preferable that they are combined so that they are adjacent to each other at an angle of. When buried underground, it is preferable that these magnetic markers are parallel to the ground surface and on the same plane.

At the time of assembling the magnetic marker, the marker may be buried in the ground so that the assembling form can be maintained. However, in order to maintain the assembling form, the magnetic marker is fixed with a publicly known adhesive or adhesive. Protection such as water resistance, acid resistance, and salt water resistance may be provided.

Examples of the adhesive include a vinyl chloride-propionic acid copolymer, a rubber-based resin, a cyanoacrylate resin, a cellulose-based resin, an ionomer resin, a polyolefin-based resin, and a polyurethane resin. Examples of the material include vinyl chloride resin, vinyl acetate resin, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, vinyl chloride / propionic acid copolymer, rubber resin, acrylic copolymer resin, cyano resin Examples include acrylate resin, cellulose resin, ionomer resin, polyolefin resin, polyurethane resin, polyester resin, polyamide resin, acrylonitrile butadiene resin, natural rubber, rosin and the like.

Alternatively, a housing 31 that can maintain the assembled form may be formed. For example, after incorporating a magnetic marker into a shallow draw forming material of a predetermined form of a known and commonly used resin film and a lid material, the sealing may be performed by impulse sealing, ultrasonic fusion, or high frequency welding.

Materials usable as the resin film include, for example, polyethylene film, polypropylene film, polyvinyl chloride film, polyvinylidene chloride film, polyethylene naphthalate film, polyvinyl alcohol film, polyethylene terephthalate (P
ET) plastic films or sheets comprising films, polycarbonate films, nylon films, polystyrene films, ethylene vinyl acetate copolymer films, ethylene vinyl copolymer films, etc .; or non-magnetic metals such as aluminum; paper, impregnated paper; A composite made of each material can be mentioned, and other materials can be used without particular limitation as long as they have the necessary strength, configuration, and the like.

Alternatively, the housing 31 may be formed by molding a predetermined form using a known and commonly used resin, and the magnetic marker 20 may be incorporated. An existing plastic stake or the like can be used as the appearance of the housing. As the resin, for example, polystyrene, polymethyl methacrylate, ABS, vinyl chloride, polyethylene, polypropylene, polycarbonate, PET, PBT, PPS and the like can be used.

According to the method of the present invention, a directional electromagnetic wave is generated from a transmitting antenna coil, which is a movable electromagnetic wave generating means, while a directional electromagnetic wave is generated from an information display. If a known and conventional detection system consisting of a receiving antenna coil is used as a movable signal output recognizing means that can detect the signal output, information is displayed based on a calibration curve obtained by previously measuring the relationship between the signal output value and the burial depth. It is possible to detect the burial depth of the vessel.

At this time, in the first invention, if the signal output of the information display device buried in the ground is measured so that the electromagnetic wave of the display device is parallel to the directivity of the electromagnetic wave generated from the transmission coil, What is necessary is just to detect the burying depth of the information display device based on a calibration curve obtained by measuring the relationship between the signal output value and the burying depth in advance.

In the second invention, at least two electromagnetic moments are generated so that the electromagnetic wave of the information display device generates the same level of magnetic moment in the direction of directivity of the transmitting / receiving coil in a plane parallel to the ground.
By measuring the signal output of an information display buried underground with more than one directivity, the information display based on the calibration curve obtained by measuring the relationship between the signal output value and the burial depth in advance What is necessary is just to detect the burial depth of the vessel.

As described above, the method of measuring the buried depth of the information display device of the present invention is as follows.

A movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in the vertical direction on the ground surface, and a ground surface buried in the ground which responds by electromagnetic induction of the electromagnetic wave from the means (1). An information display (2) for generating a signal having a vertical directivity, and a movable recognition means (3) for detecting a signal generated from the display (2) and recognizing each signal output. By moving the means (1) and the means (3) in the horizontal direction along the surface of the ground, the means (3) allows a signal in a vertical direction on the ground surface at each position of the movement of the means (1). An output value is obtained, and a ground surface buried position corresponding to the underground buried position of the information display (2) is specified based on the position where the signal output value of each position becomes the maximum value, and the signal output maximum of the recognizing means (3) is determined. Measure the relationship between the value and the burial depth in advance. Measuring the depth of the buried object based on a calibration curve obtained, the depth measuring method of underground buried object.

Alternatively, a movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in a direction parallel to the ground surface and / or in a vertical direction, and responding by electromagnetic induction of electromagnetic waves from the means (1). An information display (2) buried in the ground and generating a signal formed in the in-plane direction by signals having a plurality of directivities in a plane parallel to the ground;
Movable recognizing means (3) for detecting signals generated from the display (2) and recognizing respective signal outputs, for generating electromagnetic waves having directivity in the vertical direction on the ground surface. By moving (1) and (3) in the horizontal direction along the ground surface, the means (3) obtains a signal output value in the horizontal direction on the ground surface at each position of the movement of the means (1). Means for specifying the ground buried position corresponding to the ground buried position of the information display (2) when the signal output value of the position becomes a minimum value, and generating an electromagnetic wave having directivity in a direction parallel to the ground surface. The depth of the buried object is obtained by using a calibration curve obtained by measuring in advance the relationship between the signal output value of (1) and the signal output value of the means (3) and the signal output value of the recognizing means (3) at the ground buried position and the burial depth. For measuring the depth of underground objects.

The information display device (2) electrically resonates at a predetermined frequency in the information display device (A) exemplified above in accordance with each directivity generated from the means (1).
The information display (B) has a carrier, or the information display (C) resonates mechanically and responds by changing the magnetic flux density and the magnetic permeability.

Further, the most preferable method of measuring the depth of the underground object using the most preferable information indicator as the magnetic marker (C) is as follows.

A movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in a direction parallel to and / or perpendicular to the ground surface, and a bias magnetic field generating element in which a magnetic pattern corresponding to the bias magnetic field is magnetized The magnetic flux density is a layer of magnetically permeable, highly permeable metal that resonates mechanically at a specific frequency in an incident alternating magnetic field at a frequency that changes and changes in magnetic flux density or magnetic permeability. Alternatively, an information display device (2) that generates a signal formed in a direction parallel to the ground by a plurality of signals having a plurality of directivities in a plane parallel to the ground, wherein a specific frequency at which the magnetic permeability changes is generated as position information or the like. ), And the signal generated from the display (2) is detected to recognize each signal output.
Moving means (1) and (3) for generating electromagnetic waves having directivity in the vertical direction on the ground surface, and moving the recognition means (3) in the horizontal direction along the ground surface, In 3), at each position of the movement of the means (1), a signal output value in the horizontal direction on the ground surface is obtained, and when the signal output value at each position becomes a minimum value, the information display (2) is buried underground. A signal output value by means (1) and means (3) for generating an electromagnetic wave having directivity in a direction parallel to the ground by specifying a ground buried position corresponding to the position, and a recognition means (3) for the ground buried position. An underground buried object depth measuring method for measuring the depth of a buried object using a calibration curve obtained by previously measuring a relationship between a signal output value and a buried depth.

The above means (1) and (3) and means for identifying a magnetic marker resonating at a predetermined frequency are included.
As the detection device that embodies the identification of the magnetic marker, a known device can be used. An AC magnetic field whose frequency fluctuates is generated by the magnetic field generating means and applied to the detection area (1).

Such a device is disclosed in Japanese Patent Application Laid-Open No. Sho 62-67.
No. 485, JP-A-62-67486, JP-A-62-6
9183, JP-A-62-69184, JP-A-62-69184
No. 90039 and other publications.

In the present invention, in order to increase the accuracy of detection and identification, the synchronization between the generated AC magnetic field and the detection signal may be adjusted. The frequency can be varied from small to large, large to small, or
White noise including bursty broadband frequencies may be used.

FIG. 10 shows that the electromagnetic wave of the information display device has at least two directivities such that the same level of magnetic moment is generated in the direction of the directivity of the transmitting and receiving coils in a plane parallel to the ground. An example of a method for measuring the buried depth by measuring the signal output of an information display buried therein has been described.

First, the apparatus 100 is an example of an incident AC magnetic field generating means (2), and includes an oscillator 101 for generating a sine wave signal whose frequency can be swept, an output amplifier 102 for amplifying the sine wave signal, and an amplifier. And an excitation coil 103 capable of applying an alternating magnetic field to the metal of the magnetic marker in the information display.

The device 200 is an example of the detecting means (4), and detects the frequency at which the detecting coil 201 coaxially arranged inside the exciting coil 103 and the magnetic marker in the information display unit mechanically resonate and responds. It comprises a device 202 capable of measuring the amplitude of a signal, for example, a spectrum analyzer or the like, and a buried depth measuring device 203 for calculating a buried depth based on a calibration curve obtained by measuring the relationship between the amplitude and the buried depth in advance. .

The magnetic field generating element of the magnetic marker is magnetized using, for example, a magnetic encoder or the like, and has a predetermined magnetic pattern corresponding to a target bias magnetic field. Among the fluctuating frequencies in the incident AC magnetic field, resonance occurs at the frequency of the above equation (1) according to the magnetic pattern.

Therefore, when the frequency of the incident AC magnetic field is swept in the detection area where the marker whose magnetic pattern is magnetized is present, a characteristic signal is generated. This is because when an alternating magnetic field and a bias magnetic field generated by a magnetic field generating element in which a magnetic pattern is magnetized are introduced into a metal exhibiting magnetostriction, energy is alternately stored in magnetic energy and mechanical energy according to the frequency of the alternating magnetic field. Because it is released. The stored and released magnetic energy is greatest at the material's mechanical resonance frequency.

Due to the accumulation and release of the energy, a current is induced in, for example, a detection coil, which is one component of the depth measuring means (4), through a change in the magnetic permeability, ie, the magnetic flux density, of the magnetostrictive metal. Therefore, the output signal induced in the detection coil 201, that is, the amplitude of a specific frequency component is checked, the calculated value is compared with a previously obtained calibration curve, and the buried depth can be specified.

In the case of the device shown as an example, it is desirable that the excitation frequency of the oscillator 101 and the detection band of the detection coil 201 be in the range of 10 kHz to 5 MHz. The intensity of the AC magnetic field generated in the exciting coil 103 is 1
The magnetic field of this level does not erase or attenuate the magnetic pattern magnetized by the bias magnetic field generating element.

According to the method of measuring the burial depth of an underground buried object of the present invention, not only can the burial depth of the information display device be specified with extremely high precision, but also information on the ground surface position can be provided. .

[0102]

The present invention will be described in more detail with reference to the following examples. A 30-μm-thick Fe—Ni—Mo—B-based “Metgrass 2826 MB” (manufactured by Allied Signal Inc.) was cut into a rectangle having a width of 4 mm and a length of 75 mm to prepare a magnetostrictive metal strip.

Next, a non-magnetic casing 23 made of a polycarbonate material having the shape shown in FIG. 8 was prepared, and the strip of the magnetostrictive metal was stored in the groove of the non-magnetic casing.

Using a metal magnetic powder “HJ-8” (manufactured by Dowa Mining Co., Ltd.) having a coercive force of 1550 Oersted and a saturation magnetic flux density of 120 emu / g, a PET film having a thickness of 30 μm and having a magnetic coating film of 30 μm was used. The non-magnetic support is cut out along the orientation direction into a strip having a width of 10 mm and a length of 85 mm, and the film surface is adhered so that the PET film surface having a thickness of 50 μm faces the strip of the magnetostrictive metal. Three magnetic markers in which a magnetic pattern corresponding to a bias magnetic field was not magnetized yet were formed by attaching the magnetic pattern corresponding to a bias magnetic field to a non-magnetic housing in which a strip of magnetostrictive metal was stored using an agent.

One of the magnetic markers is a magnetic encoder which applies a rectangular wave pattern at intervals of 75/4 mm by a magnetic encoder so that a fourth harmonic is generated in the vertical direction on the ground surface when an excitation magnetic field is applied. The magnetization was performed so that the magnetization of the sample was saturated. On the other two markers, rectangular wave patterns are provided at 75/5 mm intervals by a magnetic encoder so that fifth-order harmonics are generated in a direction parallel to the ground when receiving an exciting magnetic field.
The coating was magnetized so that the magnetization of the magnetic layer was saturated.

Next, as shown in FIG. 9, a + -shaped shallow-drawn 250 μm-thick Barex tray 24 (manufactured by Mitsui Toatsu Co., Ltd.) and a lid 25 were prepared. In the groove of the tray, two magnetic markers that generate the fifth harmonic that is parallel to the surface of the ground are stored. After the lid is covered with a lid material, the periphery of the tray is fused with a high-frequency welder, and an information display (A ) Got.

Further, as shown in FIG. 11, a tray 24 and a lid 25 of I-shaped shallow drawn 250 μm thick barex (manufactured by Mitsui Toatsu Co., Ltd.) were prepared. In the groove of the tray, a magnetic marker that generates the fourth harmonic in the vertical direction is stored on the surface of the ground, and after covering with a lid material, the periphery of the tray is fused with a high-frequency welder to display the information display (B). Obtained.

Next, as shown in FIG. 10, a vertical information display (B) and a horizontal information display (A) are displayed on the ground surface.
A system for detecting a signal output resonating at a predetermined frequency corresponding to the above, that is, an amplitude, was created. Information display (A),
(B) FIGS. 1 and 2, FIG. 3 and FIG.
, And the amplitude value when the distance between the coil and the information display was changed was measured to prepare a calibration curve.

An exciting coil was prepared by winding a copper wire having a diameter of 2 mm twice around a rectangular core having a length of 300 mm. Then, the length of each piece is 1 m in a rectangular core having a length of 300 mm.
A coil was prepared by winding a 20-m copper wire 20 times and used as a detection coil. An integrated transmission / reception coil was prepared such that the excitation coil and the detection coil were coaxially flush with each other.

Next, the frequency band is changed from 80 kHz to 160 kHz.
A pulse-shaped transmission current having a frequency of 5.4 A and an effective current of 5.4 A can be added, and 89 kHz, 4
120 kHz corresponding to the fifth harmonic, 148 kHz corresponding to the fifth harmonic,... 290 corresponding to the tenth harmonic
At kHz, a sensing device was created which, when an excitation magnetic field was applied to the magnetic marker, provided the signal output, or amplitude, of each harmonic of the magnetic marker.

As signal processing, when the signal outputs of the sampling frequency are arranged in the order of magnitude, the (number of sampling frequencies + 1) th signal output is treated as a noise level, and the ratio between the signal output of the sampling frequency and the noise level is determined. In the case of three or more, it is determined that the signal is recognized as a signal from a magnetic marker. Next, the ratio between the signal output at a predetermined frequency whose directivity is perpendicular to the ground surface and the signal output at a predetermined frequency whose directivity is parallel to the ground surface can be calculated.

In the case of this embodiment, 1 corresponding to the fourth harmonic
The signal output of 20 kHz becomes a signal output of a predetermined frequency whose directivity is vertical to the surface of the ground, and corresponds to the fifth harmonic.
48 kHz is a signal output of a predetermined frequency whose directivity is parallel to the ground surface. The noise level is the third signal output when the signal output of the frequency to be sampled is arranged in order of magnitude.

Next, the information display (B) created in the present embodiment is set so that its upper end is 10 cm, 20 cm and 30 cm above the ground surface.
cm, and the signal output of the fourth harmonic at the surface burial point corresponding to the underground burial position was measured.
FIG. 12 shows the measurement results and the calibration curve.

Further, the information display (A) prepared in this embodiment is arranged such that its upper end is 10 cm, 15 cm, 20 cm above the ground surface.
buried parallel to the surface to a depth of 25 cm
The signal output of the fifth harmonic was measured by moving the coil parallel to the ground surface at a position 0.5 m away from the ground surface burial point corresponding to the underground burying position. FIG. 13 shows the measurement results.

Next, at the ground burial point corresponding to the ground burial position, which is the minimum value of the signal output, in the range in which the coil is turned 90 ° around the center of one side of the coil toward the vertical with respect to the ground surface. The signal output was measured. FIG. 14 shows the result. FIG. 12 shows a result obtained by comparing the measurement result at this arbitrary angle with the calibration curve.

From this result, it can be seen that, in the case of the present embodiment, the depth of the buried object of the information display is detected with an accuracy within ± several centimeters.

In the case of the conventional general marker, it was only possible to specify the buried position of the underground object corresponding to the surface of the ground, but as shown in FIGS. The burial depth is detected with an accuracy within ± several centimeters.

[0118]

According to the first aspect of the present invention, an electromagnetic wave generating means having a directivity in the vertical direction on the ground surface, and a movable signal output recognizing means using an information display having a directivity on the ground surface are provided. In combination, the recognition means is moved along the surface of the ground, and a calibration curve obtained by previously measuring the relationship between the signal output maximum value of the recognition means and the burial depth is also used. This has a particularly remarkable effect that the object depth can be measured. Moreover, in this case, the ground surface corresponding position of the buried position can be specified with relatively high accuracy.

According to the second aspect of the present invention, the information display which generates a signal formed in the in-plane direction by a plurality of signals having directivity in a plane parallel to the ground is used.
It can be buried more easily than the information display device used in the present invention, and a particularly remarkable effect that the position corresponding to the ground surface of the buried position can be accurately specified with particularly high accuracy is further added.

Further, it has a contactless transmission and reception function,
If a marker composed of a semiconductor memory element, a communication control unit and a memory control unit is installed in a direction perpendicular to the surface of the earth, information on a position requiring a considerable data capacity,
For example, latitude, longitude, address, and the like can be incorporated.

[Brief description of the drawings]

FIG. 1 is a basic concept of the first invention showing a state in which an information display device having a single directivity is embedded in the ground so as to have directivity vertically and a transmission coil is installed in parallel with the ground. FIG.

FIG. 2 is a basic concept of the first invention showing a state in which an information display device having a single directivity is buried in the ground so as to have directivity vertically and a receiving coil is installed in parallel with the ground. FIG.

FIG. 3 is a basic concept of the second invention showing a state in which an information display device having a single directivity is embedded with directivity parallel to the ground, and a transmitting coil is installed at right angles to the ground. FIG.

FIG. 4 is a basic concept of the second invention showing a state in which an information display device having a single directivity is embedded with directivity parallel to the ground, and a receiving coil is installed at right angles to the ground. FIG.

FIG. 5 shows the relationship between the direction of the vector of the magnetic moment vector of the two information indicators which are buried parallel to the ground with directivity and are orthogonal to each other, and the direction of the vector of the magnetic field generated from the transmitting coil. FIG.

FIG. 6 is a second diagram showing a state in which an information display device having a single directivity is embedded with directivity parallel to the ground and the transmission coil moves parallel to the ground (thick dotted arrow). FIG. 1 is a schematic explanatory view showing a basic concept of the invention.

FIG. 7 shows a second state in which an information display device having a single directivity is embedded with directivity parallel to the ground, and the receiving coil moves parallel to the ground (thick dotted arrow). FIG. 1 is a schematic explanatory view showing a basic concept of the invention.

FIG. 8 is a diagram illustrating an example of a configuration of a magnetic marker.

FIG. 9 shows a 250 μm cross-shaped shallow aperture made in the example.
FIG. 2 is a configuration diagram of an information display device embedded with a tray and a cover material of Thick Barex (manufactured by Mitsui Toatsu Co., Ltd.).

10 is buried in the ground with at least two or more directivities so that the electromagnetic wave of the information display device generates the same level of magnetic moment in the directivity direction of the transmitting and receiving coil in a plane parallel to the ground surface. FIG. 5 is a schematic explanatory view showing an example of a method for measuring a signal output of a displayed information display device to measure a buried depth.

FIG. 11 shows a 250 μm I-shaped shallow aperture made in Example.
FIG. 3 is a configuration diagram of an information display device embedded with a tray of a m-thick Barex (manufactured by Mitsui Toatsu Co., Ltd.) and a cover material.

FIG. 12 is a diagram showing a comparison between a measurement result of a signal output of a predetermined frequency whose directivity is perpendicular to the ground surface and a signal output of a predetermined frequency whose directivity is parallel to the ground surface and a calibration curve thereof.

FIG. 13 is a diagram illustrating a result of measuring a signal output of a predetermined frequency whose directivity is parallel to the ground surface when the transmitting / receiving coil is moved in parallel with the ground surface.

FIG. 14 shows a result of measuring a signal output at a predetermined frequency in which a transmitting and receiving coil is installed at a position corresponding to the ground surface of the information display device at a right angle to the ground surface, and the directivity in the rotation direction is parallel to the ground surface. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Information display 2 Ground surface 3 Transmitting antenna coil 4 Magnetic flux line of an alternating magnetic field generated from a transmitting antenna coil 5 Magnetic flux line generated from an information display 6 Receiving antenna coil X The directivity of the information display indicates a state of being perpendicular to the ground. . Y Indicates a state where the directivity of the information display is parallel to the ground. M1, M2 Vector of magnetic moment of information display H Vector of magnetic field generated from transmission coil θ Angle between vector of magnetic field generated from transmission coil and magnetic moment vector of information display 20 Information display 21 Bias magnetic field generating element Reference Signs List 22 Highly permeable metal having magnetostriction 31 Housing 100 Example of device of incident AC magnetic field generating means (2) 101 Oscillator for generating sine wave signal 102 Output amplifier 103 Exciting coil 200 Example of device of detecting means (4) 201 Detection coil 201 202 Apparatus capable of detecting the frequency of resonance and measuring the amplitude of a response signal 203 Embedding calculating the embedding depth based on a calibration curve obtained by measuring the relationship between the amplitude of the response signal and the embedding depth in advance Depth measuring device

Continued on the front page (72) Inventor Shigeru Tonaki 1434-2 Matsudo, Matsudo-shi, Chiba Prefecture Sun Heights B IG1 Room 302

Claims (4)

[Claims] 1. A movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in the vertical direction on the ground surface, and responding by electromagnetic induction of electromagnetic waves from said means (1).
An information display (2) for generating a signal having a directivity perpendicular to the surface of the ground buried in the ground, and detecting a signal generated from the display (2) to recognize each signal output;
Moving means (3), said means (1)
And moving the means (3) in the horizontal direction along the surface of the ground to obtain a signal output value in the vertical direction on the ground surface at each position of the movement of the means (1) by the means (3). Based on the maximum value of the signal output value, the surface burial position corresponding to the underground burial position of the information display (2) is specified, and the relationship between the signal output maximum value of the recognition means (3) and the burial depth is determined in advance. An underground buried object depth measurement method that measures the depth of a buried object based on a calibration curve obtained by measurement. 2. An information display (2) mechanically resonates with a bias magnetic field generating element in which a magnetic pattern corresponding to a bias magnetic field is magnetized at a specific frequency in an incident alternating magnetic field of a fluctuating frequency, and a magnetic flux density or permeability changes were as high permeability metal having a magnetostrictive are stacked so as to be able to mechanically resonate, occur in the position information of the specific frequency magnetic flux density or permeability varies marker The method for measuring the depth of an underground buried object according to claim 1, wherein: 3. A movable electromagnetic wave generating means (1) for generating an electromagnetic wave having directivity in a direction parallel to the ground surface and / or in a vertical direction, and responding by electromagnetic induction of electromagnetic waves from the means (1). An information display (2) that is buried in the ground and generates a signal formed in the in-plane direction by signals having a plurality of directivities in a plane parallel to the ground, and a signal generated from the display (2) And a movable recognizing means (3) for recognizing the respective signal outputs. The means (1) and (3) for generating electromagnetic waves having directivity in the vertical direction on the ground are provided on the ground. In the horizontal direction, the signal output value in the horizontal direction on the ground surface at each position of the movement of the means (1) is obtained by the means (3), and the signal output value at each position becomes a minimum value. However, the information display ( The signal output value by means (1) and means (3) for generating an electromagnetic wave having directivity in a direction parallel to the ground surface by specifying the ground surface buried position corresponding to the ground buried position of 2) and the ground surface buried position An underground buried object depth measuring method for measuring the depth of a buried object using a calibration curve obtained by previously measuring the relationship between the signal output value of the recognition means (3) and the buried depth. 4. The information display device (2) mechanically resonates at a specific frequency in an incident alternating magnetic field of a variable frequency with a bias magnetic field generating element in which a magnetic pattern corresponding to a bias magnetic field is magnetized, and or permeability changes, high permeability metal having a magnetostrictive are stacked so as to be able to mechanically resonate and to occur in the position information of the specific frequency magnetic flux density or permeability changes 4. The method for measuring the depth of an underground object according to claim 3, wherein the marker is a marker for generating a signal formed in an in-plane direction by signals having a plurality of directivities in a plane parallel to the ground surface.