JP2012198082A - Ground monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground monitoring system capable of monitoring the ground in real time and estimating a position of a ground deformation by highly accurately detecting the ground deformation.SOLUTION: A ground monitoring system 1 to preliminarily obtain landslide information comprises: ground observation means 2 which is arranged on a surface of the ground and has a hexagonal shape; GPS receivers 3 installed at each point 2A to 2G on the ground observation means 2; and a computer device 8 to determine presence or absence of ground deformation. The ground observation means 2 has: an observation point 2G which is arranged at a center of the hexagonal shape and has a light source 21 as well as an illumination meter 22; and light relay points 2A to 2F which are arranged at each apex of the hexagonal shape and transfer received light from the light source. The observation point 2A and the light relay points 2A to 2F are connected by optical fiber cables 4 to 6. The computer device 8 has: a first determination section to determine the presence or the absence of the ground deformation; and a second determination section to determine whether or not a scale of the ground deformation determined by the first determination section is large.

Description

  The present invention relates to a ground monitoring system.

  For construction and civil engineering work, it is necessary to maintain and manage slopes such as slopes properly for safety. For this reason, various protective works and countermeasure work, or measures such as installing a disaster prevention monitoring system that can predict the collapse of slopes are being taken.

  As such a disaster prevention monitoring system, a system in which a disaster prevention net knitted with optical fiber cables is stretched on a collapse site such as a slope is proposed (for example, see Patent Document 1). In this system, when the fiber optic cable is subjected to stress such as tension or bending due to the movement of the rock on the slope, the amount of light transmitted through the fiber optic cable decreases to the specified value or less, so by monitoring the amount of decrease, You can know the signs of collapse in advance.

In addition, there is known a system for laying a single optical fiber cable in a lattice shape and measuring the settlement and elevation of the ground (see, for example, Patent Document 2).
In general, when land subsidence or landslide occurs, ground subsidence or landslide does not occur suddenly, and ground shaking in units of millimeters may be measured before land subsidence or landslide occurs. Therefore, as in Patent Document 1 or 2, an optical fiber cable can be stretched at a place where a collapse is likely to be foreseen, so that a major disaster can be prevented in advance or at a minimum.

  As another disaster prevention distribution system, a system in which a plurality of GPS receivers are arranged on a slope and the state of the slope is monitored in real time is known (for example, see Patent Document 3).

JP-A-10-11777 Japanese Patent Laid-Open No. 2003-232631 Japanese Patent No. 3742346

  However, in the disaster prevention monitoring system described in Patent Document 1, the slope cannot be monitored in real time because the sign of the collapse is known only when the amount of light transmitted through the optical fiber cable decreases below a specified value. Furthermore, in this system, since the disaster prevention net is an optical fiber cable knitted vertically and horizontally, there is also a problem that it is impossible to identify where the signs of the collapse of the stretched disaster prevention net are present.

  In addition, the system described in Patent Document 2 has a problem that the installation of the optical fiber cable is complicated and the cost is high, and the measurement accuracy is lowered because one long optical fiber cable is used. Furthermore, in the disaster prevention delivery system described in Patent Document 3, since the position information of the slope is obtained based on the radio wave from the GPS satellite, the slope change cannot be measured with millimeter-order accuracy. It is difficult to grasp the stage where slight fluctuation occurs, that is, the initial stage of the sign of collapse.

  Accordingly, an object of the present invention is to provide a ground monitoring system capable of monitoring the ground in real time, detecting ground fluctuation with high accuracy, and estimating the position of the fluctuation.

In order to solve the above-mentioned problem, the ground monitoring system according to claim 1 of the present invention is a ground monitoring system for observing changes in the ground and obtaining in advance landslide information on the ground,
A ground observation means arranged on the ground surface of the ground, a position measurement means for measuring the position of the ground observation means arranged on the ground surface, and a determination means for determining the presence or absence of the fluctuation of the ground,
The ground observation means has a polygonal shape, an observation point that is arranged inside the polygon and has a light source and a light amount measuring device, and an optical relay point that is arranged at each vertex of the polygon,
The observation point and each optical repeater point are an optical path for the outward path that guides light from the light source of the observation point to the optical repeater point, and an optical path for the return path that guides light from the optical repeater point to the light quantity measuring device of the observation point Connected with
The optical relay points are connected by a relay optical line arranged on each side of the polygon,
Each optical relay point forwards the light from the forward optical line to one of the relay optical lines, and forwards the light from the other relay optical line to the return optical line. And an optical transmitter for the return path,
The position measuring means includes a GPS receiver provided at the observation point, and a GPS receiver provided at each optical relay point,
The determination means compares the light amount from each light relay point measured by the light amount measuring device, and if this difference is not less than a predetermined value, the triangular area surrounded by the light path that minimizes the light amount Alternatively, a first determination unit that determines that there is ground fluctuation in the vicinity of the triangle area, and the GPS receiver measures the positions of the observation point and the two light relay points at the apex of the triangle area, and the triangle. And a second determination unit that calculates the area of the region and determines that the ground variation determined by the first determination unit is large if the time displacement of the area of the triangular region is equal to or greater than a threshold value. It is a thing.

Further, the ground monitoring system according to claim 2 of the present invention is the ground monitoring system according to claim 1, wherein another ground observation means is arranged in the ground below the ground observation means arranged on the ground surface. ,
The ground observation means arranged on the ground surface and the ground observation means arranged in the ground are substantially parallel.

Furthermore, the ground monitoring system according to claim 3 of the present invention is the ground monitoring system according to claim 1 or 2, wherein the polygon is a hexagon.
A ground monitoring system according to claim 4 of the present invention is the ground monitoring system according to any one of claims 1 to 3, for observing the ground at an observation point provided with a GPS receiver. A camera is provided.

  According to the above ground monitoring system, the ground can be monitored in real time by using GPS, the ground fluctuation can be detected with high accuracy by providing the optical line, and there are a plurality of light paths guided by the optical line. Thus, the position of the ground fluctuation can be estimated.

1 is a conceptual diagram of a ground monitoring system according to an embodiment of the present invention. It is a cross-sectional perspective view of the observation point and one optical relay point in the ground monitoring system. It is a block diagram of the computer apparatus in the ground monitoring system. It is a layout of units in the ground monitoring system according to Embodiment 1 of the present invention. It is a conceptual diagram of the ground monitoring system which concerns on Example 2 of this invention. It is the arrangement | positioning figure of the unit in the ground monitoring system which concerns on Example 3 of this invention.

Hereinafter, a ground monitoring system according to an embodiment of the present invention will be described with reference to the drawings.
The ground monitoring system according to the embodiment of the present invention uses a GPS (Global Positioning System) and an optical fiber cable (an example of an optical line) to detect ground fluctuations in real time with high accuracy. The position of the fluctuation is estimated. The purpose of the ground monitoring system is to detect ground changes and prevent damage caused by landslides.

  Briefly describing the use of the GPS, a real-time kinematic (hereinafter referred to as RTK) method capable of measuring with accuracy of a centimeter while ensuring real-time properties is used. The RTK method is a relative positioning method in which the position of a GPS receiver installation point is measured using data from a GPS reference station whose position is known. Specifically, the RTK method is a dynamic interference positioning method. According to the RTK method, highly accurate measurement can be performed by measuring the phase of a carrier wave from a GPS satellite.

First, the overall configuration of the ground monitoring system will be described.
As shown in FIG. 1, the ground monitoring system 1 includes a ground observation means 2 that is arranged on a ground to be observed and includes observation points 2G and six optical relay points 2A to 2F, and these observation points 2G and 6. Optical fiber cables (detailed connection will be described later) 4 to 6 for connecting the optical relay points 2A to 2F, and GPS receivers (position measuring means) provided at the observation point 2G and the optical relay points 2A to 2F, respectively. 3), a GPS reference station 7 which is provided at a stable point (a point sufficiently away from the ground) and is not affected by the ground fluctuation, and the presence or absence of the ground fluctuation. And a computer device 8 (which is an example of a determination unit). The ground observation means 2 and the optical fiber cables 4 to 6 are arranged on the ground surface (precisely, directly below the ground surface shown in FIG. 2).

  The arrangement of the observation point 2G and the six optical relay points 2A to 2F will be described with reference to FIG. 1. The six optical relay points 2A to 2F are arranged at positions corresponding to the vertices of the hexagon. The point 2G is arranged at a position corresponding to the approximate center of the hexagon. That is, the ground observation means 2 is hexagonal, and the observation point 2G is arranged inside the hexagon. The observation point 2G and the six optical relay points 2A to 2F are connected in a straight line by an outward optical fiber cable 4 and an outward optical fiber cable 5, respectively. Further, the optical relay points 2A to 2F are linearly connected by a relay optical fiber cable 6 disposed at a position corresponding to each side of the hexagon.

  Here, as shown in FIG. 2, the observation point 2G includes a light source 21 that transmits light to the optical relay points 2A to 2F via the outward optical fiber cable 4, and an outward path from the optical relay points 2A to 2F. And an illuminance meter (an example of a light amount measuring device) 22 that measures the illuminance (an example of the amount of light) of light received via the optical fiber cable 5. Although not shown, the illuminometer 22 is connected to the same number of sensors as the outward optical fiber cable 5, that is, six sensors. These sensors directly receive the light whose illuminance is to be measured, and are connected to the end of each forward path optical fiber cable 5 on the observation point 2G side. Each of the optical relay points 2A to 2F includes a forward optical splitter (which is an example of a forward optical transmitter) 24 that transfers light from the forward optical fiber cable 4 to one of the relay optical fiber cables 6, and the other. And a return optical splitter (which is an example of a return optical transfer device) 25 that transfers light from the relay optical fiber cable 6 to the forward optical fiber cable 5. Therefore, the outward optical fiber cable 4 guides light from the light source 21 to the optical relay points 2A to 2F, and the outward optical fiber cable 5 guides light from the optical relay points 2A to 2F to the illuminometer 22. The relay optical fiber cable 6 guides light from the optical relay point 2A to another optical relay point 2B adjacent to the optical relay point 2A. Further, as shown in FIG. 1, the light from the light source 21 at the observation point 2G is transmitted to the optical relay point 2A via the forward optical fiber cable 4, and is adjacent by the forward optical splitter 24 at the optical relay point 2A. It is transferred to another optical relay point 2B, and transferred to the illuminometer (precisely a sensor) 22 at the observation point 2G by the return optical splitter 25 of the other optical relay point 2B. That is, the light path of the light source 21 draws a triangle, and this triangle is the observation point 2G (corresponding to the first vertex of the triangle) and the forward optical fiber cable 4 (corresponding to the first side). Optical relay point 2A (corresponding to the second vertex), optical fiber cable for relay 6 (corresponding to the second side), and another adjacent optical relay point 2B (corresponding to the third vertex), forward path Optical fiber cable 5 (corresponding to the third side) and observation point 2G. For this reason, in the ground monitoring system 1 as a whole, there are as many light paths as the number of the optical relay points 2A to 2F, that is, six.

  Next, the configuration of the computer device 8 will be described with reference to FIG. 3. This computer device 8 is used to detect changes in the ground where the ground observation means (observation point 2G and the six optical relay points 2A to 2F) 2 are arranged. A first determination unit 10 that determines presence / absence and a second determination unit 15 that determines whether the ground fluctuation is large-scale are included.

  The first determination unit 10 includes an input unit 11 to which carrier wave data from the GPS receiver 3 and the GPS reference station 7 and illuminance data measured by the illuminometer 22 are input, and the six input units input to the input unit 11. The light amount comparison unit 12 that compares each illuminance data of the light path, and if the difference between the maximum value and the minimum value of the illuminance data compared by the light amount comparison unit 12 is greater than or equal to a predetermined value, it is determined that there is a change in the ground. The first detection unit 13 and a first output unit 14 that outputs data on the presence or absence of ground change determined by the first detection unit 13 to a transmitter (described later) T. The second determination unit 15 includes a position measurement unit 16 that measures the positions of the observation point 2G and the six optical relay points 2A to 2F by the RTK method based on the carrier wave data input to the input unit 11, and the position measurement unit 16 An area calculation unit 17 that calculates the area of each triangular region drawn by the six light paths based on the positions of the observation point 2G and the six optical relay points 2A to 2F measured by the position measurement unit 16, and a first detection A second detector 18 for determining whether the ground fluctuation is large or not based on the temporal displacement of the area of the triangular area when the part 13 determines that there is ground fluctuation; and the second detector 18 includes a second output unit 19 that outputs data obtained as a result of determining that the ground fluctuation is large-scale to the transmitter T.

  Here, the input unit 11 of the first determination unit 10 includes carrier wave data from the GPS receivers 3 provided at the observation point 2G and the six optical relay points 2A to 2F, carrier wave data from the GPS reference station 7, and The illuminance data measured by the illuminometer 22 through the six light paths are input. The light amount comparison unit 12 compares the six illuminance data input to the input unit 11 and extracts the maximum value and the minimum value. Further, the first detection unit 13 calculates the difference between the maximum value and the minimum value extracted by the light amount comparison unit 12, and if this difference is greater than or equal to a predetermined value, the light path where the illuminance data is the minimum value is calculated. It is determined that there is a change in the ground in the triangle area to be drawn or in the vicinity of the triangle area. This predetermined value needs to have a range that can absorb at least the measurement error of the illuminance. If the predetermined value is set to a large value, the probability of erroneous determination due to the measurement error of the illuminometer 22 is reduced. Even a slight fluctuation of the signal is detected. Specifically, it is preferable to set the predetermined value to a value that allows the first detection unit 13 to detect ground fluctuations in the millimeter order.

On the other hand, the position measurement unit 16 of the second determination unit 15 uses the RTK method based on the carrier wave data from the GPS receiver 3 and the GPS reference station 7 input to the input unit 11, and the observation point 2G and the six optical relay points 2A. The position of ~ 2F is measured in real time. In addition, the area calculation unit 17 calculates the area of each triangular area drawn by the six light paths based on the positions of the observation point 2G and the six optical relay points 2A to 2F measured by the position measurement unit 16 in real time. Is calculated by Further, when the first detection unit 13 determines that there is a ground change, the second detection unit 18 extracts from the area calculation unit 17 the area of the triangular region that is determined to have the ground change. Then, the time displacement of the area is calculated, and if the time displacement of the area of the triangular region is equal to or greater than the threshold value, it is determined that the ground fluctuation is large. Since this threshold value needs a range that can absorb the measurement error of the position by the RTK method, it is set to, for example, 6 to 15 cm ² (when the length of the optical fiber cables 4 to 6 is about 30 m).

  As shown in FIG. 3, the transmitter T is an apparatus that is provided in the computer device 8 and converts an electrical signal that is data from the first output unit 14 and the second output unit 19 into an optical signal. . This optical signal is transmitted to the receiver R of the user who uses the ground monitoring system 1 through the optical communication network N. The receiver R is a device that converts an optical signal received from the transmitter T via the optical communication network N into an electrical signal, and transmits the electrical signal to the user's personal computer P provided therewith. The personal computer P displays the data that is the electrical signal.

Hereinafter, preparation for using the ground monitoring system 1 will be described.
First, as shown in FIGS. 1 and 2, a GPS receiver 3G for an observation point 2G is installed near the center of the ground to be monitored such as a slope, and a light source is provided as an observation point 2G directly below the GPS receiver 3G. 21 and the illuminance meter 22 are embedded. Then, the GPS receivers 3A to 3F for the optical relay points 2A to 2F are installed on the ground surface at positions corresponding to the vertices of the hexagon centered on the observation point 2G, and directly below these GPS receivers 3A to 3F. The forward optical splitter 24 and the backward optical splitter 25 are embedded as the optical relay points 2A to 2F, respectively. Next, the light source 21 at the observation point 2G and the forward optical splitter 24 at each of the optical relay points 2A to 2F are connected in a straight line by the outward optical fiber cable 4, and the backward optical splitter at each of the optical relay points 2A to 2F. 25 and an illuminometer (precisely a sensor) 22 at the observation point 2G are connected in a straight line by an optical fiber cable 5 for the forward path. On the other hand, the forward optical splitter 24 at the optical repeater point 2A and the return optical splitter 25 at another adjacent optical repeater point 2B are connected in a straight line by the optical fiber cable 6 for relay.

Next, a method for using the ground monitoring system 1 will be described.
By activating the light source 21 at the observation point 2G, the light from the light source 21 is transmitted to the optical relay point 2A, and transferred to another adjacent optical relay point 2B by the forward optical splitter 24 of the optical relay point 2A. Then, the light is transferred to the illuminometer (precisely sensor) 22 at the observation point 2G by the return optical splitter 25 at the other optical relay point 2B. The illuminance of this light is measured by the illuminometer 22, and the measured illuminance data is input to the input unit 11 of the computer device 8. Similarly, the illuminance of light passing through other light paths is also measured by the illuminance meter 22, and these illuminance data are also input to the input unit 11. The input six illuminance data are compared by the light quantity comparison unit 12 and the maximum value and the minimum value are extracted. The difference between the extracted maximum value and the minimum value is calculated by the first detection unit 13, and if this difference is equal to or greater than a predetermined value, the triangular area drawn by the light path where the illuminance data becomes the minimum value or the triangular area It is determined that there is a change in the ground in the vicinity. Then, data on the presence or absence of ground fluctuation is output to the transmitter T by the first output unit 14.

  On the other hand, carrier wave data is input to the input unit 11 of the computer device 8 from the GPS receiver 3 and the GPS reference station 7. Based on these carrier wave data, the position measuring unit 16 measures the positions of the observation point 2G and the six optical relay points 2A to 2F in real time by the RTK method. Based on the measured positions of the observation point 2G and the six optical relay points 2A to 2F, the area calculation unit 17 calculates the area of each triangular region drawn by the six light paths in real time. Among the calculated areas of the six triangular areas, the second detector 18 calculates the time displacement of the area of the triangular area determined by the first detector 13 as having ground fluctuation, and the time displacement. If is greater than or equal to the threshold value, it is determined that the ground fluctuation is large. Then, data obtained as a result of determining that the ground fluctuation is large is output to the transmitter T by the second output unit 19.

  The data from the first output unit 14 and the second output unit 19 output to the transmitter T is transmitted to the user's personal computer P via the optical communication network N and the receiver R and displayed.

  As described above, the ground monitoring system 1 can detect ground fluctuations with millimeter-order accuracy by using the optical fiber cables 4 to 6, and has six light paths to reduce the ground fluctuations. The position can be estimated.

  Further, since the six triangular areas share the observation point 2G as a vertex (the first vertex) and form one hexagon, the triangular area is a substantially equilateral triangle. For this reason, the lengths of the outgoing optical fiber cable 4 and the outgoing optical fiber cable 5 are substantially the same as the length of the relay optical fiber cable 6, so that each decrease in the illuminance of light passing through these optical fiber cables 4 to 6 is achieved. Are substantially the same, and the detection accuracy of ground fluctuation can be further increased.

  Hereinafter, a ground monitoring system according to a plurality of examples showing the above embodiment more specifically will be described. In addition, about the structure same as the said embodiment, description is abbreviate | omitted using the same code | symbol.

  As shown in FIG. 4, the ground monitoring system according to Example 1 includes ground observation means (observation point 2G and six optical relay points 2A to 2F) 2, a GPS receiver 3, and an optical fiber described in the above embodiment. The unit 30 including the cables 4 to 6 is arranged on a steep slope such as a mountain slope.

  Even the ground monitoring system according to the first embodiment has the same effects as the ground monitoring system 1 according to the above embodiment.

  In the ground monitoring system 1 according to the above embodiment, the ground observation means 2 and the optical fiber cables 4 to 6 are arranged on the ground surface (more precisely, directly below the ground surface), but the ground monitoring system 51 according to the second embodiment. As shown in FIG. 5, another ground observation means 52 and optical fiber cables 54 to 56 are arranged in the ground below the ground observation means 2 and the optical fiber cables 4 to 6 arranged on the ground surface. It is.

  The ground observation means 52 arranged in the ground has a hexagonal shape as well as the ground observation means 2 arranged on the ground surface, and is arranged inside the hexagon to provide a light source and an illuminometer (not shown). Observation point 52G and optical relay points 52A to 52F arranged at each vertex of the hexagon. Further, the connection of the observation point 52G and the optical relay points 52A to 52F by the optical fiber cables 54 to 56 disposed in the ground is the connection of the observation point 2G and the optical relay points 2A to 2F by the optical fiber cables 4 to 6 disposed on the ground surface. Same as connection. Further, the observation point 52G and the six optical relay points 52A to 52F in the ground are arranged at positions corresponding to the observation point 2G and the six optical relay points 2A to 2F on the ground surface. That is, the distance between the observation point 2G on the ground surface and the observation point 52G in the ground is equal to the distance between each light relay point 2A-2F on the ground surface and each light relay point 52A-52F in the ground, in other words, on the ground surface. The disposed ground observation means 2 and the ground observation means 52 disposed in the ground are substantially parallel.

  As described above, since the ground monitoring system 51 according to the second embodiment includes the ground observation means 52 not only on the ground surface but also in the ground, even if a ground change occurs in the ground, the ground Fluctuations can be detected.

  Although the ground monitoring system according to the first embodiment includes only one unit 30 including the ground observation means 2, the GPS receiver 3, and the optical fiber cables 4 to 6 arranged on the ground surface as shown in FIG. The ground monitoring system according to the third embodiment includes a plurality of units 30 as shown in FIG.

  In the ground monitoring system 61 according to the third embodiment, the units 30 are arranged with the closest relay optical fiber cables 6 parallel to each other. In other words, the units 30 are arranged in a honeycomb shape on the ground. . The interval between the two optical fiber cables for relay 6 is set to a distance shorter than the length of the optical fiber cable for relay 6, and specifically, set to about 2 to 3 meters.

  As described above, the ground monitoring system 61 according to the third embodiment monitors a wide range of ground without extending the light path, that is, without lowering the detection accuracy, because a plurality of the units 30 are arranged. Can do.

  By the way, in the said embodiment and Examples 1-3, although the ground observation means 2 and 52 demonstrated as a hexagon shape, it is not limited to this shape, Polygon shape, ie, N is a natural number of 3 or more. Any N-angle shape may be used. In this case, the number of the optical relay points and the numbers of the forward optical fiber cable 4, the forward optical fiber cable 5, and the relay optical fiber cable 6 are N and N, respectively.

  Although not described in the above embodiment and Examples 1 to 3, a video camera (an example of a camera) for photographing the ground is provided at the observation point 2G where the GPS receiver 3G is provided. Also good. By adopting a configuration in which the moving image data of the ground photographed by the video camera is transmitted to the user's personal computer P via the computer device 8, the user can grasp the state of the ground with the moving image in real time. it can.

DESCRIPTION OF SYMBOLS 1 Ground monitoring system 2 Ground observation means 2A-2F Optical relay point 2G Observation point 3 GPS receiver 4 Outgoing optical fiber cable 5 Return optical fiber cable 6 Repeating optical fiber cable 7 GPS reference station 8 Computer apparatus 10 1st determination part 15 2nd Determination unit 21 Light source 22 Illuminometer 24 Outbound optical splitter 25 Inbound optical splitter 30 Unit T Transmitter N Optical communication network R Receiver

Claims (4)

A ground monitoring system for observing changes in the ground and obtaining in advance landslide information on the ground,
A ground observation means arranged on the ground surface of the ground, a position measurement means for measuring the position of the ground observation means arranged on the ground surface, and a determination means for determining the presence or absence of the fluctuation of the ground,
The ground observation means has a polygonal shape, an observation point that is arranged inside the polygon and has a light source and a light amount measuring device, and an optical relay point that is arranged at each vertex of the polygon,
The observation point and each optical repeater point are an optical path for the outward path that guides light from the light source of the observation point to the optical repeater point, and an optical path for the return path that guides light from the optical repeater point to the light quantity measuring device of the observation point Connected with
The optical relay points are connected by a relay optical line arranged on each side of the polygon,
Each optical relay point forwards the light from the forward optical line to one of the relay optical lines, and forwards the light from the other relay optical line to the return optical line. And an optical transmitter for the return path,
The position measuring means includes a GPS receiver provided at the observation point, and a GPS receiver provided at each optical relay point,
The determination means compares the light amount from each light relay point measured by the light amount measuring device, and there is a change in the ground in or near the triangular region surrounded by the light path where the light amount is minimum. A first determination unit that determines that there is an observation point, and each position of the observation point and the two light relay points at the apex of the triangular region is measured by the GPS receiver to calculate the area of the triangular region and A ground monitoring system comprising: a second determination unit that determines that the variation of the ground determined by the first determination unit is large if the time displacement of the area is equal to or greater than a threshold value. Place other ground observation means in the ground below the ground observation means placed on the ground surface,
2. The ground monitoring system according to claim 1, wherein the ground observation means arranged on the ground surface and the ground observation means arranged in the ground are substantially parallel.   The ground monitoring system according to claim 1 or 2, wherein the polygon is a hexagon. The ground monitoring system according to any one of claims 1 to 3, wherein a camera for observing the ground is provided at an observation point provided with a GPS receiver.

Images