JP2019158656A - Method for detecting moisture state of soil and detection system - Google Patents

Abstract

To provide a technique for measuring a moisture distribution in a predetermined area.SOLUTION: The method for examining the state of soil includes the steps of: intermittently irradiating the soil in a predetermined target area with a plurality of light beams having different wavelengths; detecting a plurality of light beams reflected by the soil in the predetermined target area; and calculating an index related to a relative moisture amount based on the intensity of reflected light of the light beams for each point irradiated with the plurality of light beams.SELECTED DRAWING: Figure 7

Description

  This disclosure relates to a method for examining the state of the ground, and more specifically to a method for examining a relative moisture content distribution in a predetermined area.

  Regarding a technique for measuring the amount of moisture contained in an object, for example, Japanese Patent Laid-Open No. 2000-146634 (Patent Document 1) states that “two types of monochromatic light having different wavelengths are guided by an irradiation light guide and the measurement member Irradiate the surface, calculate the reflection absorbance difference between two wavelengths (ΔAλ) or the reflection absorbance ratio between two wavelengths (Aλ ′) between the reflected absorbance at a certain wavelength and the reflected absorbance at 1350 nm or less, and store it in advance. A moisture measurement method for calculating the moisture content of the measurement member from the relationship between the reflected absorbance difference or the reflected absorbance ratio and the moisture content is disclosed (see “Summary”).

JP 2000-146834 A

  In certain aspects, moisture distribution in a predetermined area may be required. For example, when predicting sediment-related disasters in mountainous areas, moisture distribution on slopes may be required.

  However, the technique disclosed in Patent Document 1 is based on the premise that the moisture content of materials such as plant fibers, synthetic fibers, and foods is measured (see paragraph [0021]), and is a technique for measuring moisture distribution in a predetermined area. is not. Therefore, a technique for measuring the moisture distribution in a predetermined area is required.

  This indication is made in order to solve the above problems, and the objective in a certain situation is to provide the technique which measures the moisture distribution of a predetermined area.

  According to an embodiment, a method for detecting ground moisture status is provided. The method includes intermittently irradiating a plurality of light beams having different wavelengths to the ground of the measurement target area, detecting a plurality of light beams reflected by the ground of the measurement target area, and the plurality of light beams. And calculating a relative water content index for each point based on the reflected light intensity of the plurality of light beams.

  A method according to an embodiment can output a relative moisture distribution in a given area. Therefore, the user can evaluate the state of the ground based on the moisture distribution.

  The above and other objects, features, aspects and advantages of the disclosed technical features will become apparent from the following detailed description of the invention which is to be understood in connection with the accompanying drawings.

It is a figure for demonstrating the technical idea about the method of investigating the state of the ground. 1 is a block diagram illustrating an example of a configuration of an aircraft 100. FIG. It is a figure showing an example of composition of irradiation device 250. FIG. 3 is a diagram illustrating a flight path 410 of the aircraft 100. FIG. 3 is a diagram illustrating an example of a data structure of measurement data 500 acquired by an aircraft 100. FIG. 25 is a block diagram illustrating an example of a configuration of a computer 600. It is a flowchart showing an example of the process which produces the relative moisture distribution figure of a measurement object area. It is an example of the moisture distribution map 810 created by CPU610. It is an example of the synthetic | combination figure 830 output by CPU610. It is a figure for demonstrating the judgment method of the presence or absence of a landslide. It is the figure which added the underground structure to FIG.10 (B). It is a composite diagram 1100 in which a moisture distribution map, a topographic map, and a specific resistance distribution map are superimposed.

  Hereinafter, embodiments of this technical idea will be described in detail with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Each embodiment and each modified example described below may be selectively combined as appropriate.

[Technology]
FIG. 1 is a diagram for explaining a technical idea about a method for examining a ground state. FIG. 1A shows a state in which the aircraft 100 is examining the state of the ground 110. FIG. 1B shows the relative moisture distribution of the ground 110.

  The aircraft 100 flies in the measurement target area while irradiating the points 111, 112, 113,... In other words, the aircraft 100 flies while intermittently irradiating the ground 110 with a plurality of light beams.

  In the example shown in FIG. 1, the aircraft 100 emits light beams LP and LN having different wavelengths. As an example, the light beam LP is set to the wavelength of the water absorption band (for example, 1450 nm), and the light beam LN is set to the wavelength of the water non-absorption band (for example, 1064 nm). Preferably, the wavelengths of the light beam LP and the light beam LN are set to wavelengths that have little influence on the human eye (so-called eye-safe wavelengths).

  The aircraft 100 detects the reflected light intensity of the light beam reflected by the ground 110 at each point where the light beam is irradiated.

  The aircraft 100 acquires position information at the timing when a plurality of light beams are emitted. The aircraft 100 stores the reflected light intensities of the light beam LP and the light beam LN in a storage device in association with the position information. The stored information (hereinafter also referred to as “measurement data”) is output to a computer 600 described later.

  Based on the measurement data, the computer 600 determines an index (hereinafter referred to as “moisture index”) for the relative amount of water based on the reflected light intensity of the plurality of light beams for each point irradiated with the plurality of light beams LP and LN. Say). A method for calculating the moisture index will be described later. The moisture index is used to determine a relative moisture content such as which location has a larger moisture content by comparing the moisture index at a certain point with the moisture index at another point. That is, the moisture index does not represent an absolute moisture content (moisture content).

  The computer 600 creates a moisture distribution map on the surface of the ground 110 in the measurement target area based on the moisture index and position information calculated for each point. The computer 600 outputs the created moisture distribution map to the display 640. In the example shown in FIG. 1B, the darker the hatched portion, the higher the amount of water, and the thinner the hatched portion, the lower the amount of water.

  According to the above, the method according to the embodiment can output a relative moisture distribution map of the ground surface in the measurement target area. Therefore, for example, the user can determine whether there is a risk of landslide on the slope by looking at the moisture distribution on the slope. Hereinafter, the configuration and processing necessary for creating a moisture distribution map on the ground surface will be specifically described.

[Aircraft 100]
FIG. 2 is a block diagram illustrating an example of the configuration of aircraft 100. The aircraft 100 includes a central processor unit (CPU) 210, a read only memory (ROM) 220, a random access memory (RAM) 230, a timer 240, an irradiation device 250, a detector 260, a global navigation satellite (GNSS). System) receiver 270 and IMU (Inertial Measurement Unit) 280.

  CPU 210 controls the operation of aircraft 100 by executing a control program (not shown) stored in ROM 220. The RAM 230 functions as a working memory for the CPU 210. The RAM 230 stores measurement data and a control program. The timer 240 is composed of a crystal resonator or the like, and is configured to be able to measure time. The irradiation device 250 intermittently irradiates the ground with a plurality of light beams having different wavelengths. The detector 260 detects a plurality of light rays reflected by the ground and outputs the detection result to the CPU 210. The detector 260 may include a detector for detecting the light beam LP and a detector for detecting the light beam LN (that is, a plurality of detectors having different frequency characteristics), or one detection. Each of the plurality of light beams may be detected by a detector. A GNSS (Global Navigation Satellite System) receiver 270 receives a GPS signal emitted from a GPS satellite and outputs a reception result to the CPU 210. IMU 280 detects the attitude of aircraft 100 and outputs the detection result to CPU 210.

  In the example illustrated in FIG. 1, the aircraft 100 is a helicopter, but the aircraft 100 is not limited to a helicopter. For example, the aircraft 100 may include an aircraft having an engine such as an airplane or a helicopter, an aircraft having no engine such as a balloon, a flying object, or any other object that moves in the air. The flying object may include, for example, a rocket, a drone (unmanned aircraft), a flying object operated by a radio control, and the like.

  The light emitted from the irradiation device 250 is reflected not only by the ground but also by trees or the like provided on the ground. Therefore, in an embodiment, the detector 260 is configured to be able to detect a light beam (last pulse) reflected by the ground. The CPU 210 measures the time (hereinafter also referred to as “TOF (Time Of Flight)”) from when the irradiation device 250 irradiates a light beam until the last pulse corresponding to the light beam is detected by the timer 240.

  FIG. 3 is a diagram illustrating an example of the configuration of the irradiation apparatus 250. The irradiation device 250 includes a laser 310, a laser 320, and a beam splitter 330. In certain aspects, laser 310 and laser 320 may be fiber lasers. In one aspect, the beam splitter 330 can be a half mirror. Note that the irradiation device 250 may further include another optical element (for example, a lens).

  Although an infrared camera or a multispectral sensor can be used as the measurement device, the measurement device may measure trees on the ground. On the other hand, it is possible for the laser to pass through trees and the like to reach the ground by reducing the diameter of the light beam.

  Therefore, the aircraft 100 can calculate an accurate moisture distribution by employing a laser.

  The laser 310 irradiates the light beam LP intermittently. The laser 320 irradiates the light beam LN intermittently. The beam splitter 330 is disposed so that the incident angle of the light beam LP is 45 degrees, and is disposed so that the incident angle of the light beam LN is 135 degrees. Further, the beam splitter 330 is disposed so that the incident points of the light beam LP and the light beam LN are the same. As a result, the light beam LP and the light beam LN that have passed through the beam splitter 330 are coaxially irradiated onto the ground. In addition, the CPU 210 synchronizes the irradiation timings of the lasers 310 and 320.

  If the light beam LP and the light beam LN are emitted from different axes, the light beam is not irradiated to the same point due to the shaking of the aircraft 100 in flight and the uneven ground surface. In such a case, the calculation accuracy of the moisture index described later is lowered. On the other hand, the irradiation apparatus 250 according to an embodiment irradiates the light beam LP and the light beam LN coaxially and synchronously. Therefore, the irradiation device 250 can irradiate these light rays at the same point regardless of the vibration of the aircraft 100 and the ground surface shape. Therefore, the method according to an embodiment can improve the calculation accuracy of the moisture index. In other embodiments, the irradiation device 250 may irradiate the light beam LP and the light beam LN with different axes or without synchronization.

  In addition, the structure of the irradiation apparatus 250 is not restricted to the example shown by FIG. For example, the light beam LP and the light beam LN may be irradiated coaxially by using a prism instead of the beam splitter 330.

  As another example, the irradiation apparatus 250 may irradiate light beams having two different wavelengths coaxially by a multiplexer. As yet another example, the irradiation device 250 has one laser, splits the light beam emitted from the laser into two by a splitter, converts the wavelength of one light beam by a filter or the like, and converts the other light beam to the other light beam. You may irradiate coaxially and synchronously with one light ray by delaying.

  As yet another example, the irradiation device 250 has one laser, and converts the wavelengths of the light beams from the outer periphery of the light beams emitted from the laser by a filter or the like, thereby coaxially combining two light beams having different wavelengths. And you may irradiate synchronously.

  As yet another example, the irradiation device 250 may irradiate a plurality of light beams having different wavelengths coaxially and synchronously by adopting an oscillation laser with one chip having a plurality of wavelengths.

[measurement data]
Next, data acquired by the aircraft 100 will be described.

  FIG. 4 is a diagram representing flight path 410 of aircraft 100. FIG. 5 is a diagram illustrating an example of a data structure of measurement data 500 acquired by aircraft 100.

  In the example shown in FIG. 4, the aircraft 100 flies along a flight path 410 in a mountainous area. At this time, the aircraft 100 flies over the measurement target area while intermittently irradiating the light beam LP and the light beam LN from the irradiation device 250. As an example, the CPU 210 controls the irradiation timing of the irradiation apparatus 250 so that the interval between the irradiation points adjacent to each other is a predetermined distance (for example, 50 cm). In the example shown in FIG. 5, the CPU 210 irradiates the points P1, P2, P3,... On the flight path 410 with the light beam LP and the light beam LN.

  In addition, in this example, in order to simplify description, although the case where it measures by irradiating light beam LP and LN intermittently for every point is demonstrated, it is not restricted to this system in particular. The light beams LP and LN may be irradiated to a predetermined area (surface), and the reflected light reflected from the irradiated area may be measured. Further, it is possible to irradiate the light beams LP and LN continuously without the necessity of intermittent irradiation.

  CPU 210 detects the reflected light intensities of light beam LP and light beam LN reflected by the ground based on the output of detector 260.

  Further, the CPU 210 calculates the position in the geographic coordinate system of each point irradiated with the light beam based on the outputs of the GNSS receiver 270 and the IMU 280. The geographic coordinate system functions as a coordinate system for representing points on the earth, and is represented by longitude and latitude as an example.

  The CPU 210 further measures the TOF until the last pulse of the light beam LN at each point is detected by the timer 240.

  In an embodiment, the CPU 210 associates geographic coordinates (E, N), reflected light intensity (LP, LN), and TOF (T) with each other at each point P1, P2, P3,. , And stored in the RAM 230 as measurement data 500.

  Computer 600 acquires measurement data 500 from aircraft 100 by wired or wireless communication. Based on the measurement data 500, the computer 600 creates a relative moisture distribution map of the measurement target area corresponding to the flight path 410.

[Computer 600]
FIG. 6 is a block diagram illustrating an example of the configuration of the computer 600. The computer 600 includes a CPU 610, a ROM 620, a RAM 630, and a display 640.

  CPU 610 controls the operation of computer 600. The RAM 630 functions as a working memory for the CPU 610. The RAM 630 stores measurement data 500. In addition, the computer 600 may include an input device (for example, a keyboard and a mouse) for receiving input from the user, a communication device that can communicate with an external device (the aircraft 100), and the like.

[Creation of moisture distribution map]
FIG. 7 is a flowchart showing an example of processing for creating a relative moisture distribution map of the measurement target area. Each process shown in FIG. 7 can be realized by the CPU 610 executing a control program (not shown) stored in the ROM 620.

  In step S710, CPU 610 acquires measurement data 500 directly from aircraft 100 via a communication device or indirectly (for example, via a server). There are various methods of acquisition, and the method is not limited.

  In step S720, CPU 610 calculates a moisture index at the point for each point P1, P2, P3,... Irradiated with the light, based on the reflected light intensity of light beam LP and light beam LN.

  In an embodiment, the CPU 610 calculates a value obtained by subtracting the reflected light intensity of the light beam LP from the reflected light intensity of the light beam LN as a moisture index.

  In another embodiment, the CPU 610 calculates a value obtained by dividing the reflected light intensity of the light beam LN by the reflected light intensity of the light beam LP (that is, the ratio between the two) as a moisture index.

  In step S730, CPU 610 creates a moisture distribution map of the ground surface in the measurement target area based on the moisture index calculated for each point.

  FIG. 8 is an example of a moisture distribution diagram 810 created by the CPU 610. This moisture distribution diagram 810 represents that the moisture content of the darker color portion is higher than the moisture content of the lighter color portion.

Note that the moisture distribution diagram is an enlarged view of a part of the measurement target area.
The user can grasp the relative moisture content by looking at the moisture distribution diagram.

  In step S740, CPU 610 calculates the altitude (the height of the ground) for each point based on the TOF included in measurement data 500.

  In step S750, CPU 610 creates a digital elevation model (DEM: Digital Elevation Model) based on the calculated elevation. For example, it is possible to create a topographic map based on DEM as shown in FIG.

  In step S760, CPU 610 outputs a composite diagram 830 obtained by superimposing the created moisture distribution map and the topographic map to display 640.

FIG. 9 is an example of the composite diagram 830 output by the CPU 610.
As an example, the CPU 610 outputs a composite diagram 830 shown in FIG. 9 in which the moisture distribution map and the topographic map are superimposed on the display 640.

  At this time, the CPU 610 may set the color of the moisture distribution map to a color different from the color of the topographic map. Thereby, the user can easily distinguish the moisture distribution map and the topographic map. In other embodiments, the CPU 610 may output the composite diagram 830 to a medium such as paper instead of the display 640.

  In another aspect, the CPU 610 may be configured to superimpose the ortho image of the measurement target area and the moisture distribution diagram 810 and output the superimposed image to the display 640. In such a case, the aircraft 100 may further include a camera (not shown) for photographing the measurement target area.

  Thus, the method according to the embodiment can output a relative moisture distribution map in the measurement target area. The user can make various considerations by looking at the moisture distribution diagram. As an example, the user can specify a place where a landslide may occur in the measurement target area with reference to the moisture distribution diagram.

  FIG. 10 is a diagram for explaining a method for determining whether or not there is a landslide. FIG. 10A shows a slope with a low possibility of landslide. FIG. 10B shows a slope where landslide is likely to occur.

  In FIG. 10, the moisture content in the portion where the hatching density is high indicates that the moisture content in the portion where the density is low is higher. In the example shown in FIG. 10 (A), the moisture content on the slope surface increases uniformly as the altitude decreases. Such moisture distribution appears, for example, several days after raining.

  On the other hand, in the example shown in FIG. 10B, the moisture content on the slope surface does not increase uniformly as the altitude decreases. Specifically, the moisture content of the area 910 is higher than the moisture content of the area 920 whose altitude is lower than that of the area 910. This phenomenon may indicate that a crack has occurred in the basement of the region 910, and spring water is generated through the crack. In such a case, the region 910 and the region 930 on the upper side of the region 910 are easily collapsed.

  The user can identify a place where a landslide is likely to occur in the measurement target area by finding a non-uniform moisture distribution as shown in FIG.

  As another example, the user can specify a location where water leaks from a river bank, that is, a deterioration site of the bank, based on a moisture distribution diagram. As yet another example, the user can specify a portion where groundwater is springed based on the moisture distribution diagram.

  In the above example, the computer 600 displays the moisture distribution map on the display 640, and the user makes some judgment while viewing the moisture distribution map. In another embodiment, the computer 600 may be configured to identify a region that satisfies a predetermined condition in the measurement target area based on the moisture distribution diagram.

  As an example, the computer 600 has a learning model that has been machine-learned based on a plurality of composite maps (a map in which a topographic map and a moisture distribution map are superimposed) before and after landslides occur. Based on the learning model, the CPU 210 determines an area where a sediment disaster is likely to occur in the generated composite diagram. CPU610 changes the display mode of the said area | region and another area | region. For example, the CPU 610 classifies the possibility of a landslide disaster into three stages and displays them on the display 640 in different colors. According to this configuration, the user can identify a place where a landslide may occur by looking at the composite drawing at a glance.

[Other configurations]
(Display method)
By the way, whether or not there is a possibility of landslide may be determined not by the moisture distribution on the ground surface but by other parameters.

  FIG. 11 is a diagram in which an underground structure is added to FIG. As described above, in the areas 910 and 930 shown in FIG. 10B, landslide may occur from the viewpoint of moisture distribution. However, there may be a case where the water content in the region 910 is temporarily high due to factors other than spring water (that is, there is no fear of landslides).

  Therefore, the computer 600 according to an embodiment displays on the display 640 the results of other parameters that affect the landslide in the measurement target area. Thereby, the user can improve the prediction accuracy of the landslide.

  In the example shown in FIG. 11, a cavity 1010 exists in the basement of the regions 910 and 930. As described above, the regions 910 and 930 including many voids in the basement are easily collapsed.

  It is known that the specific resistance of the ground varies depending on its composition and water content. For example, the specific resistance of a region with many voids or a region with cavities is high. In other words, it is possible to estimate the ground structure by investigating the underground resistivity distribution. Therefore, aircraft 100 according to an embodiment measures a moisture index and a specific resistance in the measurement target area.

  As an example, the aircraft 100 employs a so-called airborne electromagnetic survey method to measure the specific resistance. More specifically, the aircraft 100 flies while suspending a bird (not shown) that houses a transmission coil and a reception coil. The aircraft 100 flies in the air at a constant speed and a constant altitude, transmits electromagnetic waves at a preset time interval, and searches each point by observing electromagnetic waves having the same frequency as the electromagnetic waves with a receiving coil. The aircraft 100 stores the position in the geographic coordinate system and the specific resistance in the RAM 230 in association with each other. The aircraft 100 can control the exploration depth of the specific resistance by manipulating the frequency of the electromagnetic wave.

  The computer 600 acquires measurement data of specific resistance in the measurement target area directly or indirectly from the aircraft 100. In an embodiment, the computer 600 superimposes and outputs the moisture distribution map of the measurement target area and the specific resistance distribution map of the measurement target area.

  FIG. 12 shows a composite diagram 1100 in which a moisture distribution map, a topographic map, and a specific resistance distribution map are superimposed. In the example shown in FIG. 12, specific resistance contour lines (specific resistance distribution diagrams) connecting portions having the same specific resistance in the measurement target area are superimposed and displayed.

  The user can identify a candidate for a place where landslides are likely to occur in the measurement target area by looking at the topographic map and the moisture distribution map of the composite diagram 1100 and finding an uneven moisture distribution on the slope. Further, the user can determine a place having a high specific resistance among candidates for a place where landslide is likely to occur as a place where the possibility of landslide is high. Thus, according to the display method according to an embodiment, the user can increase the prediction accuracy of the landslide.

  In another aspect, aircraft 100 obtains specific resistance at different depths (for example, about 1 m20 cm at risk of surface layer collapse and about 10 m at risk of deep layer collapse) by electromagnetic waves of a plurality of frequencies. May be. In such a case, the computer 600 may change the exploration depth of the resistivity distribution map displayed on the display 640 based on the user input.

  In some cases, measurement data of specific resistance in the measurement target area already exists. In such a case, the computer 600 may create a specific resistance distribution map based on already existing measurement data instead of the specific resistance measurement data (specific resistance contour) acquired by the aircraft 100.

(Number of rays)
In the above embodiment, the irradiation device 250 irradiates the light beam LP set to the wavelength of the water absorption band and the light beam LN set to the wavelength of the water non-absorption band one by one at the measurement point. However, the number of light rays to be irradiated is not limited to two. For example, in an embodiment, the irradiation device 250 may irradiate one light beam LP and two light beams LN having different wavelengths. In such a case, the CPU 610 can use the average value or the total value of the reflected light intensities of the two light beams LN for calculating the moisture index. According to the configuration, the calculation accuracy of the moisture index can be improved.

[Constitution]
The technical features disclosed above can be summarized as follows.

  (Configuration 1) According to an embodiment, a method for detecting a moisture state of a ground is provided. The method includes intermittently irradiating the ground of the measurement target area with a plurality of light beams having different wavelengths (for example, the light beam LP and the light beam LN), detecting a plurality of light beams reflected by the ground, Calculating a moisture index (an index related to the relative moisture content) based on the reflected light intensity of the plurality of rays for each spot irradiated with the light beam (S720).

(Configuration 2) Irradiating a plurality of light beams includes irradiating a plurality of light beams coaxially.
(Configuration 3) Irradiating a plurality of light beams includes irradiating a plurality of light beams simultaneously.

  (Configuration 4) The plurality of light beams include a light beam LP having a wavelength in the water absorption band and a light beam LN having a wavelength in the water non-absorption band. The method further includes a step of detecting a time (TOF) from when the light beam LN is irradiated until the reflected light of the light beam LN is detected, and a step of generating a DEM based on the TOF (S750).

(Configuration 5) The method further includes a step of measuring a specific resistance in a predetermined area.
(Configuration 6) The method further includes a step (S760) of outputting a relative moisture amount distribution map in a predetermined area based on the index calculated for each point.

  (Structure 7) The step of outputting the moisture content distribution map includes superimposing and outputting the moisture content distribution map and ground height information (DEM) in a predetermined area.

  (Structure 8) The step of outputting the moisture distribution diagram includes superimposing and outputting the moisture distribution diagram and the specific resistance diagram of a predetermined area.

  (Structure 9) The step of outputting the moisture amount distribution chart includes specifying a region satisfying a predetermined condition in the predetermined area based on the distribution of the index of the predetermined area, and displaying the region satisfying the condition And changing the display mode of the area that does not satisfy the condition.

  (Configuration 10) In an embodiment, a detection system for detecting the moisture state of the ground in the measurement target area is provided. This detection system includes an irradiation unit (for example, an irradiation device 250) for intermittently irradiating the ground of the measurement target area with a plurality of light beams having different wavelengths, and a detection unit for detecting the plurality of light beams reflected by the ground. (For example, the detector 260) and a calculation unit (for example, the CPU 210 or the CPU 610) for calculating an index relating to the relative amount of water based on the reflected light intensity of the plurality of light beams for each point irradiated with the plurality of light beams. ).

  The various processes described above are realized by the CPU, but are not limited thereto. These various functions include at least one semiconductor integrated circuit such as a processor, at least one application specific integrated circuit (ASIC), at least one DSP (Digital Signal Processor), and at least one FPGA (Field Programmable). Gate Array), and / or other circuits having arithmetic functions.

  These circuits can perform the various processes described above by reading one or more instructions from at least one tangible readable medium.

  Such media take the form of magnetic media (eg, hard disk), optical media (eg, compact disc (CD), DVD), volatile memory, any type of memory such as non-volatile memory, etc. The form is not limited.

  Volatile memory can include DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory). The non-volatile memory can include ROM and NVRAM.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Aircraft, 110 Ground, 220, 620 ROM, 230, 630 RAM, 240 Timer, 250 Irradiation device, 260 Detector, 270 GNSS receiver, 310, 320 Laser, 330 Beam splitter, 410 Flight path, 500 Measurement data, 600 Computer, 640 display, 810 moisture distribution diagram, 830, 1100 composite, 910, 920, 930 region, 1010 cavity, LN, LP light.

CPU 210 controls the operation of aircraft 100 by executing a control program (not shown) stored in ROM 220. The RAM 230 functions as a working memory for the CPU 210. RAM230 stores the measurement data. The timer 240 is composed of a crystal resonator or the like, and is configured to be able to measure time. The irradiation device 250 intermittently irradiates the ground with a plurality of light beams having different wavelengths. The detector 260 detects a plurality of light rays reflected by the ground and outputs the detection result to the CPU 210. The detector 260 may include a detector for detecting the light beam LP and a detector for detecting the light beam LN (that is, a plurality of detectors having different frequency characteristics), or one detection. Each of the plurality of light beams may be detected by a detector. A GNSS (Global Navigation Satellite System) receiver 270 receives a GPS signal emitted from a GPS satellite and outputs a reception result to the CPU 210. IMU 280 detects the attitude of aircraft 100 and outputs the detection result to CPU 210.

Claims (10)

A method for detecting the moisture state of the ground,
Intermittently irradiating the ground of the measurement area with a plurality of light beams having different wavelengths;
Detecting the plurality of light rays reflected by the ground;
Calculating a relative water content index for each spot irradiated with the plurality of light rays based on the reflected light intensity of the plurality of light rays.   The method of claim 1, wherein irradiating the plurality of rays comprises irradiating the plurality of rays coaxially.   The method according to claim 1 or 2, wherein irradiating the plurality of light beams includes irradiating the ground with the plurality of light beams simultaneously. The plurality of light beams include a first light beam having a first wavelength and a second light beam having a second wavelength that has a lower water absorption rate than the first wavelength.
The method according to any one of claims 1 to 3, further comprising a step of detecting a time from when the second light beam is irradiated to when a reflected light of the second light beam is detected.   The method according to claim 1, further comprising measuring a specific resistance of the measurement target area.   The method according to any one of claims 1 to 5, further comprising a step of outputting a relative water content distribution map in the measurement target area based on an index calculated for each point.   The step of outputting the moisture content distribution map includes superimposing and outputting the moisture content distribution map and ground height information in the measurement target area. The method described.   The method according to claim 6 or 7, wherein the step of outputting the moisture content distribution diagram includes superimposing and outputting the moisture content distribution diagram and the specific resistance diagram of the measurement target area. The step of outputting the moisture content distribution chart includes:
Identifying a region that satisfies a predetermined condition in the measurement target area based on the distribution of the index of the measurement target area;
The method according to claim 6, comprising differentiating a display mode of an area that satisfies the condition and a display mode of an area that does not satisfy the condition. An irradiation unit for intermittently irradiating a plurality of light beams having different wavelengths to the ground of the measurement target area;
A detection unit for detecting the plurality of light beams reflected by the ground;
A detection system comprising: a calculation unit for calculating an index related to a relative moisture content based on the reflected light intensity of the plurality of light beams for each point irradiated with the plurality of light beams.