JPH077072B2 - Method and device for detecting buried piping system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is for detecting the configuration of an electrically conductive piping system buried in the ground, such as a gas pipe, a water pipe, a power cable or a telephone cable. And a device therefor.

(Prior Art) A conventional method for detecting the position of an electrically conductive buried pipe, buried cable, or the like (hereinafter generically referred to as a buried pipe) buried in the ground, that is, the position directly above and the buried depth. For this reason, the magnetic detection method is often used because it is simple and has relatively high detection accuracy and can be applied to various places. In such a magnetic detection method, the method most often used is to apply an alternating current to the buried pipe and detect from the distribution of the magnetic field created by this alternating current on the ground surface.In this case, the alternating current is applied to the buried pipe. There are a direct method in which an alternating current source is directly connected and flowing, and an indirect method in which an induction current is generated in a buried pipe by utilizing electromagnetic induction.

The conventional method will be briefly described with reference to the accompanying drawings. First, in the method shown in FIG. 7, a pair of magnetic sensors S1 and S2 having similar magnetic detection characteristics are arranged so that their detection directions are parallel to each other. Then, the detector L that is integrally formed with a fixed distance d is used. According to this method, the magnetic field components in the horizontal direction are detected by the magnetic sensors S1 and S2 while moving the detector L along the ground surface E, and the position where the detected magnetic field becomes maximum is the position directly above the buried pipe P. Judgment, and then from the outputs B1 and B2 of the magnetic sensors S1 and S2, the buried depth r1
Is calculated. However, C is a constant.

r1 = d × B2 / (B1-B2) Next, the method shown in FIG. 8 uses a detector L'provided with a single magnetic sensor S. This method is similar to the above-mentioned method. While moving the detector L ′ along the ground surface E, the magnetic sensor S detects the horizontal magnetic field component, and after determining that the position where the detected magnetic field is maximum is the position directly above the buried pipe P, The detector L'is further moved until the output of the sensor S becomes half of the maximum detection output, and the moving distance is detected as the embedding depth r1. It is shown by the following equation that the horizontal magnetic field component B3 at a point horizontally separated by the embedding depth r1 from the position just above is half of the maximum detection magnetic field B1 at the position just above.

Since the latter method uses a single magnetic sensor, it has the advantage of not causing an error due to the difference in the characteristics of the pair of magnetic sensors, unlike the former method, but it has a maximum magnetic field in order to obtain the burial depth. The sensor has to be moved again after the detection, which has a drawback that the measurement operation is complicated.

(Problems to be Solved by the Invention) In the conventional method described above, for a piping system that spreads two-dimensionally or three-dimensionally, in each case, every point While measuring the magnetic field, it is assumed that the buried pipe exists alone in a straight line, and that the magnetic field created around it has a cylindrical distribution. It is detecting.
However, in the actual piping system, it is rare that the buried pipe exists alone in a straight line.Therefore, there is a branch pipe, and it is raised or lowered to avoid other buried pipes. It composes a complicated piping system, and the distribution of the magnetic field is complicated in such a piping system.Therefore, the detection error of the position directly above the buried pipe becomes large, and the There is a problem that the error in the calculation of the burial depth on the premise of detection also becomes large, and the operator cannot know the degree of the error.

The present invention aims to solve the above problems.

(Means for Solving Problems) The structure of the present invention will be described with reference to FIGS. 1 to 6 corresponding to the embodiments. First, the method described in claim 1 is In the method of detecting the piping system by a magnetic field created on the ground surface by directly or indirectly applying an alternating current to the buried piping system having electrical conductivity, on a plane parallel to the ground surface of the magnetic field. Is measured as a component in which the two axes are in the directions of three orthogonal axes on the plane, and the piping system is detected from the plane distribution of at least one of these components.

Next, the method described in item 2 is the same as the method described in item 1,
The pipe is detected as a series of a plurality of positions where the absolute value becomes maximum in the plane distribution of the magnetic field component in the axial direction orthogonal to the pipe on a plane parallel to the ground surface.

Next, the method described in item 3 is the same as the method described in item 1,
In the plane distribution of the magnetic field component in the axial direction orthogonal to the plane parallel to the surface of the earth, the pipe is detected as a series of a plurality of positions where the absolute value becomes minimum.

Next, the method described in item 4 is the same as the method described in item 1,
The presence or absence of paired maximum positions in the plane distribution of the magnetic field component in the axial direction parallel to the pipe on the plane parallel to the ground surface detects the rising or falling portion of the pipe.

Next, the method described in paragraph 5 is a method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field created on the ground surface. In, the distribution of the magnetic field on a plane parallel to the surface of the earth is measured at least for each component in the directions of two orthogonal axes on the plane, and the absolute value becomes maximum in each of the plane distribution of each magnetic field component. As a series of a plurality of positions, a main pipe and a branch pipe branching from the main pipe are detected, and an intersection of the series is detected as a branch position.

Next, the method described in item 6 is a method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field generated on the ground surface. In the above, the distribution of the magnetic field on a plane parallel to the surface of the earth is measured at least for each of the components in the directions of two orthogonal axes on the plane, and among these, in the plane distribution of the magnetic field component in the axial direction orthogonal to the pipe. The pipe is detected as a series of a plurality of positions where the absolute value becomes maximum, and the rise of the pipe is caused by the existence of the maximum regions forming a pair on both sides of the pipe in the plane distribution of the magnetic field component in the axial direction parallel to the pipe. Or detect the falling edge,
Further, at the corresponding position of the portion, whether the portion is rising or falling is specified by the magnitude of the magnetic field of the area in the plane distribution of the magnetic field component in the axial direction orthogonal to the pipe, as compared with the surrounding area. It is a thing.

Next, the method described in item 7 is a method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field generated on the ground surface. , The distribution of the magnetic field on a plane parallel to the surface of the earth is 2
The axes are measured as components in the directions of three orthogonal axes on the plane, and the plane distribution of at least one of these components is calculated as a theoretical magnetic field which is considered to be created on the ground surface by the current model flowing in the assumed piping system. By comparing with the corresponding plane distribution, the structure of the assumed piping system is verified.

Next, the method described in item 8 is a method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field created on the ground surface. , The distribution of the magnetic field on a plane parallel to the surface of the earth is 2
The axes are measured as components in the directions of three orthogonal axes on the plane, and the plane distribution of at least one of these components is calculated as a theoretical magnetic field which is considered to be created on the ground surface by the current model flowing in the assumed piping system. Corresponding to the current model by comparing with the corresponding plane distribution, modifying the parameters of the assumed current model so that its squared residual is minimized, and making the squared residual less than or equal to a preset value. It detects the piping system of the configuration.

Next, in the method described in the ninth item, in the method described in the first item, the fifth item, or the sixth item, the plane distribution of the magnetic field components is such that magnetic field sensors having corresponding detection axes are arranged vertically and horizontally on the plane. It is something that can be measured.

Next, the method described in the tenth item is the method described in the first item, the fifth item, or the sixth item, wherein the plane distribution of the magnetic field component is obtained by arranging a plurality of magnetic field sensors having corresponding detection axes. Is measured in the direction perpendicular to the row direction.

Next, the method according to the eleventh aspect is the method according to the first, fifth or sixth aspect, wherein the plane distribution of the magnetic field component is obtained by planarizing a single or a small number of magnetic sensors having corresponding detection axes. The measurement is performed by vertically and horizontally scanning the above.

Next, the method described in paragraph 12 is a method in which an alternating current is directly or indirectly applied to an electrically conductive piping system buried in the ground, and the magnetic field produced by the alternating current is distributed on a plane parallel to the ground. To
2 axes are measured on the plane as components in 3 orthogonal directions,
In a device for detecting the piping system from the plane distribution of at least one of these components, a plurality of magnetic sensors whose detection axes are oriented in the direction of the magnetic field component of the measurement object are made parallel to the ground surface. Sensor units arranged in a row as described above, moving means for moving the sensor units in a direction perpendicular to the direction in which the magnetic sensors are arranged so as to be parallel to the ground surface, and the movement amount of the moving means. Of the magnetic field component from the movement amount detecting means for detecting the movement, the output of the magnetic sensor in the sensor unit, and the output of the movement amount detecting means, and the data processing means for deriving the piping system from the detected plane distribution. And display means for displaying the derivation result.

(Operation and Embodiment) The operation of the present invention as described above will be described below with reference to the drawings corresponding to the embodiment.

FIG. 1 schematically shows an actual piping system for gas, water, etc., (a) shows a branch pipe 1b for supply from a main pipe 1a buried along a road etc. to each home. 3 is a plan view showing the piping system used. The branch angle of the branch pipe 1b with respect to the main pipe 1a is normally a right angle as shown in the figure. Also, (b) is a portion that is raised as shown by a solid line in the figure or lowered as shown by a chain double-dashed line in order to avoid the existing pipe 2 when the pipe 1c is newly installed. That is, it is a side view showing a piping system having a rising portion 3a or a falling portion 3b.

In the present invention, for example, as shown in the drawing, an alternating current source 4 is connected between an appropriate place of the piping system and the ground, or by utilizing electromagnetic induction, an alternating current is caused to flow through the above-mentioned piping system, which is the earth surface 5. The distribution of the magnetic field created above is measured on a plane parallel to the ground surface 5. Such distribution is measured as a component in which two axes are in directions of three orthogonal axes on the plane. The X-, Y-, and Z-axis methods shown in FIGS. 1A and 1B correspond to the orthogonal triaxial directions. 1 (a) and 1 (b), the X and Y axes are on the plane, and in FIG. 1 (a), the X and Y axes are the branch pipes 1b and 1b, respectively.
It corresponds to the direction of the main pipe 1a. Also, in (b), the Y axis corresponds to the direction of the pipe 1c.

FIGS. 2 (a), (b) and FIGS. 3 (a), (b) show the magnetic field components in the X-axis and Y-axis directions in the piping system of FIGS. 1 (a) and (b), respectively. The plane distribution is represented by isomagnetic field curves in which the positions of the same magnetic field strength are connected. Also, the numbers in the figure represent the magnetic field strength, and the-sign indicates that the phase of the magnetic field is opposite to the magnetic field at the reference point.

First, in the piping system of FIG. 1 (a), the plane distribution of the magnetic field component in the X-axis direction, that is, in the direction orthogonal to the main pipe 1a, is indicated by diagonal lines in the drawing, as shown in FIG. 2 (a). The distribution in which the absolute value is maximum at the position directly above the main pipe 1a, and the plane distribution of the magnetic field component in the Y-axis direction, that is, in the direction parallel to the main pipe 1a is shown in FIG. 2 (b). As described above, the distribution is such that the absolute value becomes maximum at the position directly above the branch pipe 1b, which is indicated by the diagonal lines in the figure. In this way, since the main pipe 1a and the branch pipe 1b are orthogonal to each other, it is possible to independently detect the magnetic field created by the current flowing through them.

Therefore, it is possible to detect the presence of the branch pipe 1b in the pipe system from the pattern of the plane distribution of the magnetic field components in each of the orthogonal X-axis and Y-axis directions. It can be seen that, by connecting a plurality of positions at which the value becomes maximum by connecting by calculation or the like, the positions directly above both the main pipe 1a and the branch pipe 1b which are orthogonal to each other can be detected, and the intersection point can be detected as the branch position 6. In addition, the planar distribution of the magnetic field component in the Z-axis direction has a distribution in which the absolute value becomes a minimum at the position immediately above the main pipe 1a and the branch pipe 1b, so that a plurality of positions where the absolute value becomes a minimum are connected. Thus, the position directly above both the main pipe 1a and the branch pipe 1b and the branch position 6 can be detected.

Next, in the piping system of FIG. 1 (b), the plane distribution of the magnetic field component in the X-axis direction shown in FIG. The distribution has a distribution in which the absolute value is maximum at the position where the magnetic field exists, and a region 7a having a larger magnetic field than the surroundings exists near Y = 0m corresponding to the rising portion 3a. This is because the horizontal portion 8a of the rising portion 3a is close to the surface of the earth 5, and in the case of the falling portion 3b as indicated by the chain double-dashed line in the figure, on the contrary, the magnetic field is smaller than the surrounding area.

Further, in the plane distribution of the magnetic field component in the Y-axis direction shown in FIG. 3 (b), in the vicinity of Y = 0 m corresponding to the rising portion 3a, the regions 7b having the maximum absolute value are paired on both sides of the pipe 1c. The distribution will exist. This corresponds to the magnetic field component produced by the current flowing in the vertical portion 9 of the rising portion 3a. In the illustrated structure, there are a pair of vertical portions 9 and 9 ', so that the region 7b has two pairs. .

As described above, in the piping system having the rising portion 3a or the falling portion 3b, in the plane distribution of the magnetic field component in the axial direction parallel to the pipe 1c, the regions 7b in which the absolute value becomes maximum on both sides of the pipe 1c are provided. Since it has a very characteristic pattern that it exists as a pair, by detecting such a pattern, along with the position of the pipe 1c in this pipe system, the presence of the rising portion 3a or the rising portion 3b and The position can be accurately detected, and in the plane distribution of the magnetic field component in the axial direction orthogonal to the pipe 1c, the rising portion
Whether the region 8a corresponding to the rising portion 3b or the rising portion 3b is the rising portion 3a or the rising portion 3b can be easily specified by the magnitude of the magnetic field compared with the surroundings.

As described above, by measuring the magnetic field component in each direction as a plane distribution, it is not configured only by the linear pipe 1c (1a), there is a branch pipe 1b in it, the rising portion 3a and Even in a complicated piping system in which the falling portion 3b exists, these positions, that is, the position directly above can be accurately detected. The depth can be derived accurately by the same method as the conventional one.

The invention described above is to detect and derive the above-mentioned characteristic patterns appearing when those constituent elements are present from the planar distribution of the measured magnetic field components, and this method ( (Referred to as the pattern method)
Can be applied to the case where the components of the piping system to be detected are limited to, for example, the pipe, the branch pipe, and the rising portion or the falling portion, and such operation is performed by the data processing device using a computer or the like. Automation is also easy.

With respect to the above method, the method described below detects the entire piping system configuration without limiting the components of the piping system to be detected. That is, this method first assumes the overall configuration of the piping system by means of piping diagrams and measurements in advance, and the theoretical model of the planar distribution of the magnetic field that is thought to be created on the surface of the ground by the model of the current flowing through the piping system of such assumed configuration. Can be verified with the planar distribution of the magnetic field obtained by the measurement for each magnetic field component in the corresponding direction to verify the assumed configuration of the piping system. That is, it is judged whether or not the characteristic patterns such as the maximum areas and the numbers in the respective plane distributions match, and if they match, it is considered that the assumed piping system configuration is correct and the detection Is to do.

Further, the following method corresponds the theoretical plane distribution of the magnetic field that is considered to be created on the ground by the current model flowing in the piping system of the configuration assumed above, and the plane distribution of the magnetic field obtained by the measurement. By comparing for each magnetic field component of the direction, the parameter of the assumed current model is corrected so that its squared residual is minimized, and by making the squared residual less than or equal to a preset value, the current model This method (referred to as the minimum residual method) is used to detect the piping system as a corresponding configuration.
In this case, the position directly above the component of the piping system and the position where it is buried can be detected accurately at the same time. In the above method, the squared residual Re is defined by the following equation.

Re ＝ Σ {(Bxm-Bxc) ² + (Bym-Byc) ² + (Bzm-Bzc) ² }, where Bxm, Bym, and Bzm are the X, Y, and Z axial components of the measured magnetic field, respectively. Bxc, Byc and Bzc are the theoretical magnetic field X,
It is a component in the Y and Z axis directions. And Σ means to take the sum of all the measured points. The above operations for modifying the parameters of the current model include various least squares methods such as Newton's method and other iterative methods. The method of can be applied.

The method of assuming the configuration of the piping system may be performed by the operator based on the piping diagram or the measurement in advance, or occurs by accumulating various piping system patterns in the storage means of the data processing device, The data processing device may select the one having the best feature match from among them, and make a substantial assumption.

The following table shows an example of the detection result of the piping system to which the method of the present invention, that is, the above-described pattern method and minimum residual method is applied. The true value in the table indicates the position and the burial depth of the branch pipe actually measured by excavation. The embedding depth in the pattern method is derived assuming a cylindrical magnetic field as in the conventional case. The square of the difference between the theoretical magnetic field component distribution obtained by calculation from the current model flowing in the pipe and the actually measured magnetic field component distribution created based on the derivation result is the squared residual, and this square root, that is, the deviation Is described in the table.

As can be seen from the table, the detection result obtained by applying the minimum residual method is closer to the true value in any of the items than that obtained by the pattern method. This is because, as described above, the minimum residual method corrects the parameters of the current model so as to reduce the deviation and detects the piping system as a configuration corresponding to the current model. In this way, the minimum residual method has a derivation result that is closer to the true value than the pattern method,
That is, although the accuracy is high, the required time is long, and it is preferable to use these methods properly according to various conditions such as required accuracy.

In the method described above, in the directions of the three orthogonal axes,
Measure the plane distribution of the magnetic field component in any one direction,
Although it is possible to detect the minimum required source, it goes without saying that the more directions in which measurement is performed, the more reliable and highly accurate detection can be performed.

The plane distribution of the magnetic field component is measured, for example, by arranging magnetic sensors having corresponding detection axes vertically and horizontally on a plane, or by arranging a plurality of magnetic sensors having corresponding detection axes in a row. It can be performed by moving in a direction perpendicular to the row direction, or by scanning a single or a small number of magnetic sensors having corresponding detection axes vertically and horizontally on a plane.

The method of (1) allows the fastest measurement because it does not need to move the magnetic sensor at all, but it has the advantage and disadvantage that the device becomes very large, and the method of (2) has the minimum number of magnetic sensors. Therefore, it is economical, but there is a trade-off that it takes too long to move.

A specific example of an apparatus to which the following method is applied will be described with reference to FIGS.

FIG. 4 shows a general view of the apparatus. Reference numeral 10 is the apparatus main body and 11 is a sensor unit. The device main body 10 is configured to be movable by moving means such as wheels 12, and is configured to be manually moved by using a handle 13 provided on the upper part or automatically moved by an electric motor or the like. The sensor unit 11 is provided in the device body 10 so as to be parallel to the ground surface.
A plurality of magnetic sensors 14 each having a detection axis provided in the direction of the magnetic field component to be measured are stored in the column 11 so as to be parallel to the ground surface 5. The magnetic sensor 14 shown in FIG. 5 (a) has all three directions of orthogonal three axes, that is, X, Y,
It has a detection axis in the Z-axis direction. Of course, in some cases, a magnetic sensor having only a detection axis in some of these three orthogonal directions, for example, a detection axis in the directions of the X and Y axes may be used. Then, a plurality of the magnetic sensors 14 are stored in the sensor unit 11 in a row so that they are parallel to the ground surface 5 as shown in FIG. Further, the apparatus body 10 is provided with a movement amount detecting means 15 such as an encoder which is interlocked with the wheels 12 and the like, and the movement amount detecting means 15 detects the movement amount of the apparatus body 10. The apparatus main body 10 detects the plane distribution of the magnetic field component from the movement amount detecting means 15 and the outputs of the plurality of magnetic sensors 14 in the sensor unit 11, and the data processing means 16 derives the piping system from the detected plane distribution. And a display means 17 for displaying the derivation result. The data processing means 16 shown in FIG. 6 includes a multiplexer 18 for time-divisionally inputting outputs corresponding to each axial direction of the plurality of magnetic sensors 14, and an A / D converter 19 connected to the output of the multiplexer 18. The A / D
The CPU 20 calculates the plane distribution of the magnetic field component from the digital output of the converter 19 and the output of the movement amount detecting means 15, and the output is displayed on the display means 17 such as a CRT. As the display mode of the display means 17, in addition to the above-mentioned equal magnetic field curve, three-dimensional display of the absolute value of the magnetic field strength and other suitable display can be applied.

In such a configuration, the above-described detection can be performed by moving the apparatus main body 10 on the ground surface along the pipe estimated based on the description of the piping diagram, etc. The necessary information of can be obtained from the display means 17.

In addition, although the case where the present invention is simply used for the detection of the piping system is described above, the present invention is not limited to the simple detection of the piping system as described above, and the above-mentioned measurement of the planar distribution of the magnetic field is performed. The measurement results are recorded and saved as appropriate over time, and the changes over time in the planar distribution are monitored to be used for monitoring the condition of buried pipes such as the condition of the insulating film on the pipes. Is something that can be done. That is,
When a defect occurs in the insulating film of the pipe, the current flowing in the buried pipe leaks from here and changes the plane distribution of the magnetic field.By analyzing this change, it is possible to detect the occurrence of such a defect. You can do it.

(Effect of the Invention) As described above, the present invention detects an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detects the piping system by a magnetic field generated on the ground surface. In the method described above, the distribution of the magnetic field on a plane parallel to the surface of the earth is measured as a component with two axes in the directions of three orthogonal axes on the plane, and the piping system is determined from the plane distribution of at least one of these components. Since it is detected, by applying the above-mentioned pattern method and the minimum residual method, it is not composed of only linear pipes,
Even in a complicated piping system that has a branch pipe or a rising portion and a falling portion, it is possible to accurately detect these positions, that is, the position directly above and the buried depth. It has an effect. Therefore, when the present invention is applied, it becomes possible to improve the efficiency of excavation work for a buried pipe such as a gas pipe or a water pipe, and at the same time prevent accidents due to damage to the buried pipe due to erroneous excavation. It has a great effect on safety and economy. The present invention not only detects the piping system in this way,
By performing the above-mentioned measurement of the plane distribution of the magnetic field at appropriate time intervals, recording and saving the measurement results, and monitoring the change over time of the plane distribution, the situation such as the condition of the insulating film on the pipe can be buried. There is an effect that it can be used for monitoring the condition of piping.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and a side view schematically showing the configuration of the piping system, and FIGS. 2 (a) and (b) and FIGS. 3 (a) and 3 (b). 3A and 3B show the planar distributions of the magnetic field components in the X-axis and Y-axis directions in the piping system of FIGS. 1A and 1B, respectively, by the uniform magnetic field curves in which the positions of the same magnetic field strength are connected. . FIG. 4 is an explanatory perspective view showing an example of a configuration of an apparatus for carrying out the present invention, and FIG. 5 (a) is an explanatory perspective view showing an example of a magnetic sensor alone applied to the apparatus of FIG. 4B is an explanatory plan view showing an example of an arrangement method of a plurality of magnetic sensors in the sensor unit of the apparatus shown in FIG. FIG. 6 is a system explanatory view showing one row of the magnetic field measuring system in the present invention. Further, FIG. 7 (a),
(B), FIG. 8 (a), (b) is an explanatory view showing a conventional buried pipe detection method. Reference numeral 1a ... main pipe, 1b ... branch pipe, 1c ... piping, 2 ... existing pipe, 3a ... rising part, 3b ... falling part, 4 ... AC current source, 5 ... ground surface, 6 …… Branch position,
7a, 7b ... area, 8a ... horizontal part, 9,9 '... vertical part, 10 ... device body, 11 ... sensor unit, 12 ... wheels, 13 ... handle, 14 ... magnetic sensor, 15 …… Movement detection means, 16 …… Data processing means, 17 …… Display means, 18 ……
Multiplexer, 19 ... A / D converter, 20 ... CPU.

Claims (12)

[Claims] 1. A method for detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground and detecting the piping system by a magnetic field generated on the surface of the earth. It is characterized in that the distribution of the magnetic field on a plane parallel to the surface of the earth is measured as a component of two triaxial directions orthogonal to the plane, and the piping system is detected from the plane distribution of at least one of these components. Detection method for buried piping system 2. The method according to claim 1, wherein a plurality of positions having a maximum absolute value in a plane distribution of a magnetic field component in an axial direction orthogonal to the pipe on a plane parallel to the ground surface are connected. Detection method for buried piping system characterized by detecting piping 3. In the method according to claim 1, in the plane distribution of the magnetic field component in the axial direction orthogonal to the plane parallel to the ground surface,
A method for detecting a buried piping system characterized by detecting piping as a series of multiple positions where the absolute value is minimal. 4. The method according to claim 1, wherein the rising of the pipe is caused by the existence of a pair of maximal positions in the plane distribution of the magnetic field component in the axial direction parallel to the pipe on the plane parallel to the ground surface. Alternatively, a method for detecting a buried piping system characterized by detecting a falling portion 5. A method for detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field generated on the surface of the earth. The distribution of the magnetic field on a plane parallel to the ground surface is measured at least for each component in the directions of two orthogonal axes on the plane, and a plurality of positions in which the absolute value becomes maximum in each plane distribution of each magnetic field component are connected. Detecting a main pipe and a branch pipe branching from the main pipe, and detecting an intersection point between them as a branch position. 6. A method for detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field generated on the surface of the earth, the method comprising: The distribution of the magnetic field on a plane parallel to the surface of the earth is measured at least for each of the components in the two orthogonal axis directions on the plane, and the absolute value is maximized in the planar distribution of the magnetic field component in the axial direction orthogonal to the pipe. The pipe is detected as a series of a plurality of positions, and due to the existence of maximum regions forming a pair on both sides of the pipe in the plane distribution of the magnetic field component in the axial direction parallel to the pipe, the rising or falling portion of the pipe is detected. Further, at the corresponding position of the portion, whether the portion rises or falls depending on the magnitude of the magnetic field in the area in the plane distribution of the magnetic field component in the axial direction orthogonal to the pipe, compared with the surrounding area. Characterized by identifying Method of detecting buried piping system to 7. A method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground, and detecting the piping system by a magnetic field generated on the surface of the earth. A model of current flowing through a piping system having a configuration in which the distribution of a magnetic field on a plane parallel to the ground surface is measured as components of two triaxial directions on the plane, and the plane distribution of at least one of these components is assumed. Is detected on the surface of the earth by comparing with a corresponding plane distribution of the theoretical magnetic field to verify the configuration of the assumed pipe system, and a method for detecting an embedded pipe system. 8. A method of detecting an alternating current directly or indirectly through an electrically conductive piping system buried in the ground and detecting the piping system by a magnetic field generated on the surface of the earth. A model of current flowing through a piping system having a configuration in which the distribution of a magnetic field on a plane parallel to the ground surface is measured as components of two triaxial directions on the plane, and the plane distribution of at least one of these components is assumed. Is compared with the corresponding plane distribution of the theoretical magnetic field that is considered to be created on the ground surface, the parameters of the assumed current model are modified so that the squared residual is minimized, and the squared residual is preset. A method for detecting a buried piping system, characterized in that the piping system is detected as a configuration corresponding to the current model by setting the value to a value or less. 9. The method according to claim 1, 5, 6, 7, or 8, wherein the plane distribution of the magnetic field component is such that a magnetic field sensor having a corresponding detection axis is placed on a plane. A method for detecting a buried piping system, which is characterized by arranging vertically and horizontally. 10. The method according to claim 1, 5, 6, 7, or 8, wherein the plane distribution of the magnetic field component is such that a plurality of magnetic field sensors having corresponding detection axes are arranged in a row. Detecting a buried piping system, characterized by moving it in a direction perpendicular to the row 11. The method according to claim 1, 5, 6, 7, or 8, wherein the plane distribution of the magnetic field component is a single or a small number of magnetic fields having corresponding detection axes. A method for detecting a buried piping system characterized by scanning the sensor horizontally and vertically on a plane for measurement 12. An alternating current is directly or indirectly applied to an electrically conductive piping system buried in the ground, and the distribution of a magnetic field generated on the ground surface on a plane parallel to the ground surface is represented by two axes. In a device for measuring the components in the directions of three orthogonal axes on the plane and detecting the piping system from the plane distribution of at least one of these components, a plurality of detection axes are oriented in the direction of the magnetic field component to be measured. And a sensor unit in which the magnetic sensors of the above are stored in a row so that they are parallel to the ground surface, and a right angle to the row direction of the magnetic sensors so that the sensor unit is parallel to the ground surface. The moving means for moving in the direction of, the moving amount detecting means for detecting the moving amount of the moving means, the output of the magnetic sensor in the sensor unit, and the output of the moving amount detecting means detect the planar distribution of the magnetic field component. Then
Detecting device for buried piping system, comprising data processing means for deriving the piping system from the detected plane distribution and display means for displaying the derivation result