JP3038423B2 - How to detect buried objects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an object buried in the ground or a structure using electromagnetic waves, and more particularly to a method of detecting a buried object on a ground surface or a structure surface. The present invention relates to a method of detecting a buried object that can notify a measurer of the presence of the buried object in real time by a buzzer, sound, a lamp, or the like without measuring the moving distance of the antenna when moving the object along the object.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing an example of an apparatus to which this kind of conventional method for detecting a buried object is applied. This apparatus detects an object buried underground using an electromagnetic wave method. is there. FIG. 10 is a diagram showing an underground section observation pattern showing the detection result of this device. The operation of the conventional device will be described with reference to FIGS. That is, in FIG. 9, a pulse of several nsec as a time width is transmitted from the transmitter 1 to the transmitting antenna 2. Here, the pulse signal is converted into an electromagnetic wave by the transmitting antenna 2 and radiated into the ground. The radiated electromagnetic wave propagates through the ground and is reflected at a location having an electrical property different from that of the surrounding medium. The reflected electromagnetic wave is received by the receiving antenna 3 and converted into an electric signal by the receiver 4. In the actual measurement, the antennas 2 and 3 and the distance detection unit 9 are moved using the moving wheels 10 in the direction of the arrow in the figure. Then, the above-described transmission and reception processes are performed for each prescribed antenna moving distance D0 (for example, 2 cm), and a plurality of reception signals are recorded. The antenna moving distance D0 is calculated by the distance detecting unit 9 from the rotation angle of the moving wheel 10. The plurality of received signals are color-modulated for each magnitude of the amplitude value in the arithmetic unit 6 and then arranged two-dimensionally to obtain the signals shown in FIG.
The observation pattern of the underground cross section shown in FIG.

That is, FIG. 10A shows the above-described underground cross-section observation pattern displayed on the display unit 8.
FIG. 2B shows a reception signal received when the antenna is positioned above a buried pipe which is a buried object. In FIG. 10A, a time position where the absolute value of the amplitude value of the received signal is equal to or greater than the specified value A is indicated by oblique lines. The pattern 21 in the figure corresponds to a reflected wave from the ground surface. Here, since the electromagnetic wave radiated from the antenna spreads at a certain angle, the reflection pattern from the receiving antenna has a hyperbolic shape like the pattern 31 in the figure, and the actual position of the buried pipe is the position of the apex of the hyperbola. Becomes Therefore, the buried pipe can be detected by recognizing the hyperbolic shape in the underground section observation pattern.

Conventionally, in order to recognize this hyperbolic shape,
Recognition processing is mainly performed by the synthetic aperture method. That is, since this hyperbolic shape depends on the propagation speed of the electromagnetic wave in the ground, the hyperbolic shape is theoretically calculated assuming the propagation speed, and the theoretical curve and the actually observed hyperbolic shape, that is, the shape of the pattern 31 By performing matching with the above, the hyperbolic shape in the underground section observation pattern is recognized.

[0005]

However, the calculation of the synthetic aperture processing requires an antenna moving distance. The moving distance of the antenna is calculated from the rotation angle of the moving wheel.If the moving surface of the antenna is soft such as sand, or if the surface has irregularities such as unpaved parts, There was a problem that the moving distance could not be calculated, and therefore the accurate position of the buried pipe could not be detected. Furthermore, since the antenna is moved by the moving wheels, there is a disadvantage that the device becomes large as a whole and it becomes difficult to search in a narrow place. Further, in image processing such as synthetic aperture processing, it is not possible to determine the presence of a detected object at every moment when a sensor (antenna) is moved like a so-called metal detector.
That is, the position of the buried object is calculated based on a plurality of received signals received at the time when the movement of the antenna for several meters has been completed. Therefore, it is necessary to actually determine which point on the ground surface the calculated buried object position corresponds to on the actual ground surface by actually measuring from the antenna movement start point, for example, depending on the measurement place such as a place with a lot of traffic. However, there is a problem that the work of distance measurement becomes difficult. Further, in the synthetic aperture processing, there is a problem that the calculation requires a great deal of time, and the hardware configuration for realizing the calculation is complicated and the apparatus becomes large.

Accordingly, an object of the present invention is to detect a buried object without using a synthetic aperture process that requires an antenna moving distance.

[0007]

SUMMARY OF THE INVENTION In order to solve such a problem, the present invention receives a reflected wave not at every moving distance of the antenna but at a certain time and differentiates the amplitude value of the received signal. Focusing on the time position where the differential value becomes zero, the amplitude value is normalized to "1", "-1", "0", and the standard value is "1" for two signals received continuously. Alternatively, the relevance of coordinates "-1" is checked, the change in propagation time between the coordinates determined to be relevant is calculated, the result is added and stored on an addition value map, and the value is calculated. This is a method for notifying the operator of the presence of a buried object and its buried position when the value of 以上 exceeds a specified value.

[0008]

Therefore, according to the present invention, the presence and position of the buried object can be notified to the operator in real time at the time when the operator moves the antenna, so that the skill of the operator is not required. In addition, there is no need to measure the antenna moving distance and it is not necessary to keep the moving speed of the antenna constant, making it easy to detect embedded objects even when the antenna moving surface is soft or uneven. it can. Also,
Since it is not necessary to measure the moving distance of the antenna, there is no need for a moving wheel, so that the entire antenna can be reduced in size and detection in a narrow place becomes possible. Further, since there is no need to perform a huge amount of data processing unlike the conventional synthetic aperture method processing, the configuration of the apparatus can be simplified.

[0009]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an apparatus to which a method for detecting a buried object according to the present invention is applied. In the figure,
The same parts as those of the conventional apparatus of FIG. That is, the apparatus of the embodiment shown in FIG. 1 eliminates the need for the distance detection unit and the moving wheel, which are conventionally required, and additionally includes the time counter 5 and the buzzer 7. FIG. 2 is a flowchart showing the operation of this embodiment, and FIG. 3 is an explanatory diagram showing an example in which the amplitude of a signal received by the above-mentioned device is normalized to "1", "-1", and "0". FIG. 4A is a diagram showing a data map in which standardized received signals are arranged two-dimensionally, and FIG. 4B is a diagram showing a standard value of "1" for two consecutively received signals.
Alternatively, FIG. 4C is a diagram illustrating an addition value map for storing a difference in propagation time between coordinates determined to be related, and FIG.
FIG. 5 is a diagram showing the relationship between the value of the added value and the volume of the buzzer sounding, FIG. 6 is a diagram showing the relative positional relationship between the buzzer sound and the antenna and the buried object, and FIG. FIG. 8 is a diagram showing an example of application of the apparatus of the above embodiment.

Next, the operation of the apparatus according to the embodiment will be described in detail with reference to the flow chart of FIG. 2 and the drawings of FIGS. In the present embodiment, a buried pipe 30 buried in the ground will be described as an example. First, step S
At T1, a reflected wave from the buried pipe 30 is received. That is, in this case, first, a pulse of several nsec as a time width is transmitted from the transmitter 1 to the transmitting antenna 2 installed on the ground surface 20. Here, the pulse signal is converted into an electromagnetic wave by the transmitting antenna 2 and radiated into the ground. The emitted electromagnetic wave propagates in the ground and is reflected by the buried pipe 30. The reflected electromagnetic wave is received by the receiving antenna 3 in accordance with the timing of the signal sent from the time counter 5 and converted into an electric signal by the receiver 4 to obtain a received signal shown in FIG. Note that FIG.
(A) shows an example of the received signal as a digital signal.

Next, at step ST2, the amplitude value of the above-mentioned received signal is normalized to "1", "-1", and "0".
That is, at the time position where the differential value of the received signal becomes zero (the position where the amplitude value becomes locally maximum and minimum), if the sign of the amplitude of the original received signal at that time position is plus, it is set to “1”. , Negative values are normalized to “−1”, and amplitude values at other time positions are normalized to “0”. At this time, in order to remove the influence of noise, if the absolute value of the original amplitude value is smaller than the specified value B, the amplitude value is set to “0” at all time positions. FIG. 3B shows the result of this normalization.

Next, the processing operations in steps ST3 and ST4 are the same as those in steps ST1 and ST2. Next, in step ST5, a data map is created in which two-dimensionally arranged results of the standardized results of the two continuously received signals are created. One example of this is shown in FIG. The data map shown in FIG. 3C is a data map of the standardized signal shown in FIG. 3B, and a dotted portion in the cell in the figure is set to "1". , The hatched part is “-
1 ".

Here, for convenience of explanation, FIG.
4 shows an example of a data map of one received signal. In FIG. 4A, the vertical axis is the propagation time, and each cell is a sampling point of the received signal. Here, 51, 52, 61,
62, 71 to 73, 81 to 83, and 91 indicate respective coordinate numbers of each sampling point. The numbers on the horizontal axis are the numbers indicating the reception order of the reflected waves. Hereinafter, assuming that this number is n, each vertical line in FIG. 4 corresponding to this number n is called n-line data. Here, assuming that the timing sent from the time counter 5 is 1 second, each received signal is received every 1 second. Therefore, FIG.
The three-line data in (a) is a signal received three seconds after the start of reception, and corresponds to a signal received immediately above the buried pipe 30. Note that the three-line data in FIG. 4A corresponds to FIG. 3C. In this embodiment, when two consecutively received signals are one-line data and two-line data, the standard values “1” and “−1” included in each line data are focused on. The following line drawing tracking / addition processing is performed.

Here, the coordinate 71 whose standard value is "1" will be described as an example with reference to FIG. FIG. 4 (b)
FIG. 5 is an enlarged view of the vicinity of a coordinate 71 in FIG. 4A for explaining a tracking process. As shown in FIG. 4B, a range of a certain specified value SA (hereinafter, referred to as a center) around a coordinate 100 of two-line data at the same propagation time position as the coordinate 71.
(Search range). If coordinates having the same standard value “1” as the coordinates 71 exist in the search range, it is determined that both are related. Therefore, in this case, it is determined that the coordinates 71 and the coordinates 72 are related. Such a process 1
This is performed for all coordinates whose standard values of the line data are “1” and “−1”. As a result, in FIG.
1 and coordinate 52, coordinate 61 and coordinate 62, coordinate 71 and coordinate 7
2, and the coordinates 81 and 82 are determined to be related,
It is determined that the coordinates 91 are not relevant. Such a process is called a line drawing tracking process.

Next, in step ST6, the following processing is executed for each set of coordinates determined to be relevant after the line drawing tracking processing. Here, a set of coordinates 71 and coordinates 72 will be described as an example. First, the electromagnetic wave propagation time T71 at the coordinate 71
And the difference between the electromagnetic wave propagation time T72 at the coordinates 72 (T71−T
72) (in this embodiment, the difference value is 2 nsec).
Is). Next, an addition value map having a coordinate system similar to that of FIG. 4A is created as shown in FIG. Here, the coordinates 51 shown in FIG. 4A and the coordinates 510 shown in FIG. 4C are defined as being in the same coordinate system.

Next, FIG. 4 corresponding to the coordinates 72 in FIG.
The calculated difference value is stored in the coordinate 720 of (c). Further, the sum of the value already stored at the coordinates 710 (in this case, “0”) and the value stored at the coordinates 720 is calculated, and the result is stored in the coordinates 720 again as an added value. FIG. 4C shows values in which the numbers shown in the squares are stored. Such processing is performed for all sets of coordinates determined to be relevant. Since the propagation time between the coordinates 51 and the coordinates 52 is zero, the value stored in the coordinates 520 in FIG. 4C is zero (0).

Next, at step ST7, if the stored added value exceeds the specified value SH in any of the added value maps shown in FIG. 4C, the buzzer sounds at a volume proportional to the magnitude of the added value. Ring 7 The relationship between the buzzer volume and the magnitude of the added value is shown in FIG. It should be noted that the notification can be made by an audio signal or a lamp instead of the volume of the buzzer 7.

Next, in step ST8, it is determined that the measurement has been completed, and if the measurement has not been completed, step ST3 is performed again.
To receive the reflected wave. This received signal is 3 in this case.
This is the signal received second, and corresponds to the three-line data in FIG. Therefore, this time, the two line data for the continuously received signals described in step ST5 are the three-line data and the four-line data in FIG. 4A. Thus, the above-mentioned step ST3
Steps ST7 to ST7 are repeated while moving the antenna. As a result, the vertex coordinates 7 of the convex image in the data map of FIG.
3,83 (corresponding to the vertex coordinates of the hyperbola shown in FIG. 10)
730, 8 of the added value map of FIG.
At 30, the addition value becomes maximum.

In step ST9, the burial depth of the buried pipe 30 is calculated and displayed. Here, FIG. 6 shows the relative positional relationship between the antenna, the buried pipe, and the buzzer sound. That is, the center of the moving range in which the buzzer is sounding by moving the antenna is the horizontal position of the buried pipe. In the present embodiment, when the prescribed value SH is set to “3”, 3
The addition value is the specified value SH at the coordinates 730 of the line data.
Buzzer 7 sounds at this position. Assuming that the propagation time of the coordinate 730 at which the addition value is maximum in the addition value map of FIG. 4C is T, the relative permittivity in the ground is εs, and the speed of the electromagnetic wave in free space is C, the burying depth L is It can be calculated by the formula.

L = TC / 2 (εs) ^1/2

In this way, the buried depth of the buried pipe can be measured without requiring the moving distance of the antenna. As described above, various effects can be expected by using the detection method of the present invention as described below. That is, conventionally, in order to increase the calculation accuracy of the synthetic aperture processing, it has generally been necessary to perform background removal for removing the ground surface reflected wave as preprocessing, but according to the present invention, the set of coordinates 51 and 52 is used. As can be seen, the addition value at the coordinate position of the ground surface reflected wave is zero, so that it is not affected by the reflected wave, so that the above pre-processing becomes unnecessary.

When the operator receives a reflected wave at a constant time interval while moving the antenna at a certain constant speed, the antenna may not move at a constant speed depending on the ground surface condition. In that case, the hyperbolic shape, which is the group of reflected waves from the buried pipe that is observed, does not have a smooth shape as shown in FIGS. 7B and 7C. Therefore, the conventional synthetic aperture processing recognizes this shape. Can not do it. In contrast, the present invention can automatically recognize this shape.

In addition, since the operator can move the antenna along the surface of the measurement location and simultaneously inform the operator of the position of the buried object by sounding a buzzer or the like, the operator does not need to be skilled. Further, it is not necessary to perform a complicated operation of calculating the buried position of the buried object from the underground cross-section observation pattern and then measuring it again to measure the actual horizontal position of the buried object as in the related art.

Further, since it is not necessary to measure the moving distance of the antenna, even if there are irregularities on the antenna moving surface at the measuring point or if the surface is soft like mud, the measurement is not affected. Further, even if the moving speed of the antenna changes, the measurement is not affected.

As described above, various effects can be expected by using the detection method of the present invention, and it is particularly effective in measurement in a dangerous place for an operator to measure or in a place where the state of the antenna moving surface is poor. For example, as shown in FIG. 8, by inserting an antenna into a digging trench while digging with a digging machine such as a backbow in road construction, a buried object that cannot be detected by measurement from the ground surface can be easily obtained. It is possible to detect and prevent a buried object damage accident caused by an excavating machine.

[0026]

As described above, according to the present invention, the reflected wave is received not at every moving distance of the antenna but at certain times and the amplitude value of the received signal is differentiated, and the time position at which the differentiated value becomes zero is obtained. Focusing on, the amplitude values are "1", "-1",
The relationship between coordinates whose standard values are "1" or "-1" is checked for two signals received after normalization to "0", and the coordinates determined to be related are determined. Calculate the change in propagation time, add the result to the added value map, and store it. If the value exceeds the specified value, notify the operator of the presence of the buried object and its buried position. It was done. As a result, at the same time as the operator moves the antenna along the surface of the measurement location, the position of the buried object can be notified to the operator by sounding a buzzer or the like, so that the skill of the operator is not required. In addition, a complicated operation of actually measuring the horizontal position of the buried object by actually measuring the embedment position read from the cross-sectional observation pattern and measuring the actual horizontal position of the buried object is not required, thereby improving work efficiency. Also, since it is not necessary to measure the moving distance of the antenna and it is not necessary to keep the moving speed of the antenna constant, it is easy to detect embedded objects even when the antenna moving surface is soft or uneven. Can be. In addition, since it is not necessary to measure the moving distance of the antenna, a moving wheel is not required, so that the entire antenna can be reduced in size and detection in a narrow place becomes possible. Further, since there is no need to perform a huge amount of arithmetic processing unlike the conventional synthetic aperture method processing, the configuration of the apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an apparatus to which a method for detecting a buried object according to the present invention is applied.

FIG. 2 is a flowchart showing the operation of the above device.

FIG. 3 shows an example in which the amplitude of a received signal is “1”,
It is explanatory drawing which shows the example normalized to "-1" and "0".

FIG. 4 shows a data map [FIG.
(A)], a relationship between coordinates [FIG. 4 (b)], and an added value map [FIG. 4 (c)].

FIG. 5 is a diagram showing a relationship between an added value and a volume of a sounding buzzer in the device.

FIG. 6 is a diagram showing a relative positional relationship between a buzzer sound and an antenna and a buried object in the device.

FIG. 7 is a diagram showing a hyperbolic shape obtained when the antenna movement distances are different in the above device.

FIG. 8 is a diagram showing an application example of the above device.

FIG. 9 is a block diagram of an apparatus to which a conventional embedded object detection method is applied.

FIG. 10 is a diagram showing an example of an underground cross-section pattern displayed on a display unit of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmitting antenna 3 Receiving antenna 4 Receiver 5 Time counter 6 Operation part 7 Buzzer 8 Display part 20 Ground surface 30 Buried pipe

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Masuda 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-4-161883 (JP, A) JP-A-Hei 4-55787 (JP, A) JP-A-1-280277 (JP, A) JP-A-1-2744093 (JP, A) JP-A-63-281086 (JP, A) (58) Fields investigated (Int. G01S ^7/ 00-7/42 G01S 13/00-13/95 G01V 3/12

Claims (1)

(57) [Claims] 1. An electromagnetic wave transmitted from an antenna installed on a ground surface or a structure surface to a ground surface or a structure surface, and an electromagnetic wave reflected by an object existing in the ground or a structure is received by the antenna again. In the method of detecting a buried object for detecting an object existing in the ground or in a structure, a step of receiving a reflected wave at certain time intervals while moving an antenna to obtain a received signal; A value is calculated and the amplitude of the received signal at the time position where the differential value is zero is set to “1” when the sign of the amplitude of the received signal at the time position is plus, to “−1” when the sign is minus, Normalizing the amplitude value at other time positions to “0”; creating a data map in which the normalized results of two consecutively received signals are arranged two-dimensionally and received first did Examine the relationship between the coordinates having the values of "1" and "-1" indicating the code of the line data which is the standard value of the received signal and the coordinates of the line data which is the standard value of the next received signal. A relevance determining step, and calculating a difference between propagation times of electromagnetic waves on the respective coordinates in a set of coordinates determined to be relevant in the relevancy determining step, and using the difference value in the same coordinate system as the data map. A storage step of storing the coordinates of the added value map as coordinates, and a step of notifying when the value stored in the added value map exceeds a prescribed value in the storing step, while repeatedly moving the antenna, and The center position of the antenna movement position at the time when the value stored in the addition value map exceeds a prescribed value is determined as the horizontal position of the buried object, and the addition value corresponding to this center position is determined. Method of detecting buried objects, characterized in that so as to calculate the depth of the buried object from the electromagnetic wave propagation time Tsu coordinate having a value exceeding the specified value of the flop.