JPS63305278A - System for searching underground buried object - Google Patents

Abstract

PURPOSE:To omit another measuring work for obtaining the dielectric constant of soil, by determining the dielectric constant of the soil for correction in geology and the like based on the sharpness of an object spot on image data. CONSTITUTION:A monocycle pulse is transmitted from a transmitting antenna 4, with the transmitting antenna 4 and a receiving antenna 5 being moved. The reflected wave is received with the receiving antenna 5. Thus reflected wave profile data at a specified underground cross sectional unit are collected. The reflected-wave profile data are inputted into a receiver 6. The reflected- wave profile data undergo synthetic aperture processing, and image data are obtained. The dielectric constant of soil for correction in geology and the like is determined based on the sharpness of an object spot on the obtained image data.

Description

[Detailed description of the invention] [Industrial field of application] This invention provides an underground object exploration method using a synthetic aperture method;
In particular, it concerns the determination of the dielectric constant of the soil in which the target is buried.

[Conventional technology]

Figure 3 shows, for example, the conventional underground buried object exploration method shown in the paper ``Underground exploration using electromagnetic wave reflection method (Part 2)'' on pages 59 to 60 of the Proceedings of the Japan Society for Physical Exploration in October 1981. FIG. In the figure, 1 is a target such as a pipe, 2 is the soil where this target 1 is buried, 3 is a transmitter, and 4
is a transmitting antenna connected to this transmitter 3 and emits a pulse signal from the transmitter 3 as an electromagnetic wave into the soil 2, and 5 is a receiver that receives reflected waves of the electromagnetic waves emitted from this transmitting antenna 4 by the target object 1. The distance between the antenna and the transmitting antenna 4 can be adjusted as appropriate, and 6 is a receiver connected to the receiving antenna 5.

Next, the operation will be explained. First, the interval between the transmitting antenna 4 and the receiving antenna 5 is adjusted to Y, and the transmitter 3 sends out, for example, a monocycle pulse. This monocycle pulse is emitted from the transmitting antenna 4 as an electromagnetic wave within ±2, and the reflected wave from the target object 1 is transmitted to the receiving antenna 5.
The monocycle pulse is received by the receiver 6 and sent to the receiver 6, and the time T1 from transmission to reception of this monocycle pulse is measured. next,
After moving the receiving antenna 5 to a position separated by Y2 from the transmitting antenna 4, the time T2 from transmission to reception of the monocycle pulse is measured in the same manner.

Here, the burial depth of target 1 is R1, and the relative dielectric constant of soil 2 is ε3.
Then, there is a relationship between the time T from signal transmission to reception and the interval Y between both antennas 4.5. Here, C
is the speed of light.

Therefore, by substituting the measurement time T, , T, for T and the set interval Y + , T z for Y and solving the simultaneous equations with ε1 and R as unknowns, we can obtain the relative dielectric constant ε5 of ±2. You can ask for it.

Apart from such measurement of the relative dielectric constant ε8, the transmitting antenna 4 and the receiving antenna 5 are moved perpendicularly to the arrangement direction while keeping the spacing fixed, and monocycle pulses are transmitted and received in units of ground planes. Collect reflected wave profile data of , and perform synthetic aperture processing on the reflected wave profile data using the relative permittivity ε, to obtain time scale image data, and perform geological correction using the above-mentioned relative permittivity ε3. The time scale is converted into a length scale, and an exploration image output of the target object 1 buried in the soil 2 is obtained from this image data.

[Problem that the invention seeks to solve]

Since the conventional underground object exploration method is configured as described above, the measurement of the relative dielectric constant of the soil in which the target is buried is performed as a completely separate task from the measurement for collecting reflected wave profile data. Furthermore, it is necessary to support the transmitting antenna and the receiving antenna so that the mutual spacing thereof can be adjusted, resulting in problems such as a complicated support structure.

This invention was made in order to solve the above-mentioned problems, and it is possible to measure the relative permittivity for geological correction etc. and collect reflected wave profile data in the same measurement operation, and also to The purpose of this invention is to obtain an underground object exploration method that allows the mutual spacing of receiving antennas to be fixed and the supporting structure to be simplified.

[Means for solving problems]

The underground buried object exploration method according to the present invention detects the envelope of the collected reflected wave profile data to create profile data based on the reflected wave envelope, and converts the profile data based on the reflected wave envelope into a temporary relative dielectric Synthetic aperture processing is performed while changing the set value of the ratio in predetermined steps to obtain each image data, and the relative permittivity of the soil in which the target is buried is adjusted to the sharpness of the target spot on each image data. The decision shall be made based on the

[Effect]

The underground buried object exploration method in this invention performs synthetic aperture processing on reflected wave profile data for each temporary dielectric constant that changes sequentially in predetermined steps, and detects target spots on the obtained image data. By determining the relative permittivity of the soil in which the target is buried from the sharpness, there is no need for special measurement work to determine the relative permittivity of the soil in which the target is buried, and the mutual spacing between the transmitting and receiving antennas can be reduced. This eliminates the need for adjustment of The dielectric constant becomes more accurate.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, STI is a step of detecting the envelope of reflected wave profile data and creating profile data based on the reflected wave envelope, and ST2 is a step of performing synthetic aperture processing on the profile data based on the obtained reflected wave envelope following step STI. A step of obtaining image data, Sr3 is a step of calculating a focus evaluation function A (ε) for evaluating the sharpness of a target spot on the obtained image data following step ST2, and Sr1 is a focus evaluation following step ST3. A step of plotting the calculated value of the function A(ε), Sr5 is a step of increasing the temporary dielectric constant ε by a predetermined step Δε following step ST4, Sr6 is a step of end detection following step ST5, and Sr7 is a step of step ST6. This is the step of determining the relative permittivity ε5 following step ST6, and from the branch of step ST6, the process returns to step ST2.

Further, 10 is reflected wave profile data used for envelope detection in step STI, 11 is ``profile data based on reflected wave envelope used in synthetic aperture processing,''
12 is image data obtained by the synthetic aperture processing,
13 is the focus evaluation function A (ε
) is a plot of calculated values.

Next, the operation will be explained. First, reflected wave profile data 10 for each ground plane is collected. FIG. 2 is an explanatory diagram for explaining the collection of reflected wave profile data, and in the figure, numerals 1 to 6 correspond to the conventional ones indicated by the same reference numerals in FIG. 3. The mutual spacing between the transmitting antenna 4 and the receiving antenna 5 is fixed at a predetermined value y, and the transmitting antenna 4 and the receiving antenna 5 are moved at a constant pitch in the direction indicated by an arrow X perpendicular to the direction in which both the antennas 4 and 5 are arranged. Each time it moves, for example, a monocycle pulse is emitted from the transmitting antenna 4, and its reflected wave is received by the receiving antenna 5.

Therefore, the reflected wave from the target object 1 returns in the shortest time when both the antennas 4 and 5 are directly above the target object 1, and when the antennas 4 and 5 deviate from this, the time becomes longer depending on the amount of the deviation. That is, the depth of target 1 is R1, the distance between both antennas 4°5 is y, and target l is
Let ε1 be the relative dielectric constant of ±2 where is buried, and C be the speed of light.
Then, there is the following relationship between the distance X from directly above the target object 1 to the line connecting both antennas 4 and 5 (hereinafter referred to as antenna position) and the time t until the reflected wave returns. This equation can be transformed into , which is a hyperbola with a vertex of (however, the negative region of the time axis is not considered) and an asymptote of . The reflected wave profile data indicated by 10 in FIG. 1 is for the case where there are two buried targets 1, and a waveform due to direct coupling from the transmitting antenna 4 to the receiving antenna 5 appears on the upper side.

Therefore, if the reflected wave profile data for each ground plane obtained in this way is subjected to synthetic aperture processing and the corresponding hyperbola data for each target l is accumulated at its apex,
Image data in which a target spot exists at the position of target 1 is obtained. However, the synthetic aperture process requires an actual dielectric constant ε of ±2.

Furthermore, the image data obtained is on a time scale, and as mentioned above, the hyperbola created by the reflected wave of target 1 changes its apex and asymptote depending on the dielectric constant ε3 of soil 2. Therefore, in order to obtain length scale image data, the relative dielectric constant ε of ±2 where target 1 is buried is required.
5, it is necessary to perform geological correction processing on time-scale image data.

To this end, first, in step STI, the envelope of each reflected wave of the reflected wave profile data 10 is determined, and profile data 11 based on the reflected wave envelope is created. Here, the envelope of the reflected wave can be obtained by, for example, differentiating the reflected wave, squaring the differential data and the raw reflected wave data, and taking the square root of the sum.

Next, in step ST2, the profile data 11 is subjected to synthetic aperture processing using the above-mentioned reflected wave envelope using the initially set temporary dielectric constant ε to obtain image data 12. Here, if this temporary relative permittivity ε is far from the actual relative permittivity ε5 of ±2, the shape of the hyperbola will be greatly different, and even if synthetic aperture processing is performed, there will be a slight difference at the apex. Only partial data can be accumulated, and the height of the target spot on the image data 12 will be extremely low, but if the temporary relative permittivity ε approaches the actual relative permittivity ε of ±2, it will have a hyperbolic shape. gradually become closer to each other, and when they become equal, the shapes of the hyperbolas match, and a large portion of data is accumulated at the apex, forming an extremely high target spot on the image data 12.

In step ST3, in order to evaluate the acuity of these target spots, the base area Si at a predetermined level of the target spot and the height Hi are calculated from the predetermined level, and the value of the ratio of the two is calculated for all the corresponding target spots. The value of the focus evaluation function defined by A(ε)=Σ(Si/Old) i=1 at the dielectric constant ε of the plate is calculated and plotted in step ST4. In step ST5, the temporary relative permittivity ε
Step S while increasing by a predetermined step Δε
The above-described process is repeated until the end is detected at T6, for example, until the temporary dielectric constant ε reaches a predetermined value.

When the end of step ST6 is detected, step ST7 searches for the minimum value of the focus evaluation function A(ε) plotted in step ST4 shown at 13 in FIG. Let the value of be the dielectric constant ε3 of the soil 2 in which the target 1 is buried. The relative dielectric constant ε of the soil 2 obtained in this way is used in the synthetic aperture processing of the reflected wave profile data to obtain the exploration image output to obtain image data on a time scale, and is also used for geological correction. It is used to convert the scale of image data obtained on a time scale to a length scale.

In the above embodiment, the sharpness of the target spot on the image data is evaluated based on the ratio of the cross-sectional area and height of the target spot at a predetermined level. Other methods, such as one in which data is normalized by the height of the spot and evaluated by its volume, may be used, and the same effect as in the above embodiment can be achieved.

° [Effects of the Invention] As described above, according to the present invention, the relative permittivity of soil for geological correction etc. is determined by a profile based on the reflected wave envelope for each temporary relative permittivity that is successively set in predetermined steps. Since the configuration is configured to determine the sharpness of the target spot on the image data obtained by performing synthetic aperture processing of the data, in order to obtain the relative permittivity for geological correction etc., the reflected wave profile data Not only does it eliminate the need for measurement work separate from the measurement work for collection, the relative dielectric constant of the soil obtained is highly accurate, and the mutual spacing between the transmitting and receiving antennas is fixed, making it easier to support their support structure. This has the effect of simplifying the process.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing an underground object exploration method according to an embodiment of the present invention, Fig. 2 is an explanatory diagram for explaining the collection of reflected wave profile data, and Fig. 3 is a conventional underground object exploration method. It is an explanatory diagram showing a method. 1 is the target, 2 is the soil where the target 1 is buried, 3 is the transmitter, 4 is the transmitting antenna, 5 is the receiving antenna, and 6 is the receiver. In addition, the same reference numerals or corresponding parts are shown in the figures.

Claims (1)

[Claims] A transmitting antenna and a receiving antenna arranged at a predetermined interval are provided, and while both the antennas are moved along the ground surface at a constant pitch substantially perpendicular to the direction in which they are arranged, a signal is transmitted from the transmitting antenna toward the ground. The reflected wave of the pulse signal is received by the receiving antenna, and the obtained reflected wave profile data for each ground plane is subjected to synthetic aperture processing to obtain an exploration image output of the target buried underground. In the buried object exploration method, the envelope of each reflected wave of the reflected wave profile data is determined, profile data based on the reflected wave envelope is created, and the temporary relative permittivity is sequentially set while changing in predetermined steps. , performs synthetic aperture processing on the profile data using the reflected wave envelope for each set value of the temporary dielectric constant, and determines whether the target object is buried based on the sharpness of the target spot on the obtained image data. An underground object exploration method characterized by determining the dielectric constant of the soil.