Embankment monitoring device, embankment monitoring method, and program

Abstract

Provided are an embankment monitoring device, an embankment monitoring method, and a program capable of improving embankment candidate region detection capabilities. An optical image acquisition unit of the embankment monitoring device acquires first and second optical images resulting from the ground surface in an observation target region being surveyed during first and second periods. An NDVI change region extraction unit extracts an NDVI change region from a comparison image of first and second NDVI images generated from the first and second optical images. A SAR image acquisition unit acquires first and second SAR images resulting from the ground surface in the observation target region being surveyed during the first and second periods. A reflection intensity change region extraction unit extracts a reflection intensity change region from a comparison image of first and second reflection intensity images generated from the first and second SAR images. A deforested region extraction unit extracts a deforested region on the basis of the result of comparing the NDVI change region and the reflection intensity change region. An embankment candidate region extraction unit extracts an embankment candidate region established in the deforested region.

Description

Embankment monitoring device, embankment monitoring method and program

[0001] The present invention relates to an embankment monitoring device, an embankment monitoring method, and a program.

[0002] Illegal embankments are being built without prior approval, causing landslides. Currently, local governments conduct on-site surveys to investigate embankments, but this is expensive. Therefore, there is a need for technology to detect embankments without relying on human labor.

[0003] Patent Document 1 discloses a technology for estimating changes in the earth's surface based on difference values ​​between a digital elevation model (DEM) generated by airborne radar surveying and a digital surface model (DSM).

[0004] Japanese Patent Application Laid-Open No. 2016-085145

[0005] Detecting candidate areas for newly constructed embankments (hereinafter referred to as embankment candidate areas) requires first detecting areas where forests have been cut down (hereinafter referred to as deforestation areas). The technology disclosed in Patent Document 1 can be used to detect deforestation areas. However, this technology has low detection power for deforestation areas. Specifically, this technology has low detection power for deforestation areas in areas where the trees are spaced apart and tree canopy elevation data cannot be obtained, and in areas where low-rise trees grow and the difference between DEM and DSM is unclear, and in these areas, this technology has low detection power for deforestation areas. Therefore, this technology has a problem in that its low detection power for deforestation areas results in low detection power for embankment candidate areas.

[0006] In consideration of such issues, the present disclosure aims to provide an embankment monitoring device, an embankment monitoring method, and a program that can improve the detection ability of embankment candidate areas.

[0007] The embankment monitoring device of the present disclosure includes an optical image acquisition unit that acquires a first optical image of the ground surface of an observation target area obtained by surveying the ground surface during a first period using an optical sensor and a second optical image that is surveyed during a second period after the first period; an NDVI change area extraction unit that generates a first NDVI (Normalized Difference Vegetation Index) image from the first optical image, generates a second NDVI image from the second optical image, compares the first NDVI image with the second NDVI image, extracts an NDVI change area in the compared images where the NDVI value has changed, and extracts position coordinates of the NDVI change area; and an SAR image acquisition unit that acquires a first SAR image of the ground surface of the observation target area obtained by surveying the ground surface during the first period using a SAR (Synthetic Aperture Radar) and a second SAR image that is surveyed during the second period. the first SAR image and the second SAR image, and extracts a reflection intensity change area that is an area where the reflection intensity has changed within the compared images, and extracts position coordinates of the reflection intensity change area; a deforestation area extraction unit that compares the position coordinates of the NDVI change area with the position coordinates of the reflection intensity change area, and extracts position coordinates of a deforestation area that is an area in the observation area where forests have been cut down between the first period and the second period based on the result of the comparison; and an embankment candidate area extraction unit that extracts position coordinates of an embankment candidate area that is an area where an embankment has been newly constructed between the first period and the second period based on the position coordinates of the deforestation area.

[0008] The embankment monitoring method of the present disclosure includes a computer: acquiring a first optical image of the ground surface of an observation target area obtained by surveying the ground surface by an optical sensor during a first period and a second optical image obtained by surveying the ground surface during a second period after the first period; generating a first NDVI image from the first optical image; generating a second NDVI image from the second optical image; comparing the first NDVI image with the second NDVI image; extracting an NDVI change area, which is an area where the NDVI value has changed, from the compared images; and extracting position coordinates of the NDVI change area; acquiring a first SAR image of the ground surface of the observation target area obtained by surveying the ground surface by SAR during the first period and a second SAR image obtained by surveying the ground surface during the second period; A first reflection intensity image is generated from the first SAR image, a second reflection intensity image is generated from the second SAR image, the first reflection intensity image is compared with the second reflection intensity image, a reflection intensity change area is extracted, which is an area where the reflection intensity has changed in the compared images, and the position coordinates of the reflection intensity change area are extracted, the position coordinates of the NDVI change area are compared with the position coordinates of the reflection intensity change area, and based on the result of the comparison, the position coordinates of a deforestation area, which is an area in the observation area where forests have been cut down between the first period and the second period, are extracted, and based on the position coordinates of the deforestation area, the position coordinates of a potential embankment area, which is a candidate area for a new embankment constructed in the observation area between the first period and the second period, are extracted.

[0009] The program disclosed herein includes: acquiring a first optical image of the earth's surface in an observation target area obtained by surveying the earth's surface in a first period using an optical sensor and a second optical image obtained by surveying the earth's surface in a second period after the first period; generating a first NDVI image from the first optical image; generating a second NDVI image from the second optical image; comparing the first NDVI image with the second NDVI image; extracting an NDVI change area in the compared images where the NDVI value has changed; and extracting position coordinates of the NDVI change area; acquiring a first SAR image of the earth's surface in the observation target area obtained by surveying the earth's surface in the first period using SAR and a second SAR image obtained by surveying the earth's surface in the second period; The computer is caused to execute the following processes: generate a first reflection intensity image from the first SAR image, generate a second reflection intensity image from the second SAR image, compare the first reflection intensity image with the second reflection intensity image, extract a reflection intensity change area, which is an area where reflection intensity has changed in the compared images, and extract position coordinates of the reflection intensity change area; compare the position coordinates of the NDVI change area with the position coordinates of the reflection intensity change area, and based on the result of the comparison, extract position coordinates of a deforestation area, which is an area in the observation area where forests were cut down between the first period and the second period; and extract position coordinates of an embankment candidate area, which is a candidate area for embankment newly constructed in the observation area between the first period and the second period, based on the position coordinates of the deforestation area.

[0010] The present disclosure makes it possible to provide an embankment monitoring device, an embankment monitoring method, and a program that can improve the detection ability of embankment candidate areas.

[0011] FIG. 1 is a block diagram showing an example of the configuration of an embankment monitoring device 10 according to the present disclosure. FIG. 1 is a diagram showing an example of the configuration of an embankment monitoring system 2 according to the present disclosure. FIG. 2 is a block diagram showing an example of the configuration of an embankment monitoring device 20 according to the present disclosure. FIG. 3 is a flowchart showing an example of the operation of an embankment monitoring device 20 according to the present disclosure. FIG. 4 is a block diagram showing an example of the configuration of an embankment monitoring device 30 according to the present disclosure. FIG. 5 is a flowchart showing an example of the operation of an embankment monitoring device 30 according to the present disclosure. FIG. 6 is a block diagram showing an example of the configuration of an embankment monitoring device 40 according to the present disclosure. FIG. 7 is a flowchart showing an example of the operation of an embankment monitoring device 40 according to the present disclosure. FIG. 8 is a block diagram showing an example of the configuration of an embankment monitoring device 50 according to the present disclosure. FIG. 9 is a flowchart showing an example of the operation of an embankment monitoring device 50 according to the present disclosure. FIG. 10 is a block diagram showing an example of the configuration of a computer 500 according to the present disclosure.

[0012] The present invention will be described below through embodiments of the invention, but the invention according to the claims is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential means for solving the problems. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In each drawing, the same elements are assigned the same reference numerals, and duplicate explanations are omitted as necessary.

[0013] First Embodiment First, the configuration of an embankment monitoring device 10 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing an example of the configuration of an embankment monitoring device 10 according to the present disclosure.

[0014] As shown in Figure 1, the embankment monitoring device 10 includes an optical image acquisition unit 11, an NDVI (Normalized Difference Vegetation Index) changed area extraction unit 12, a SAR (Synthetic Aperture Radar) image acquisition unit 13, a reflection intensity changed area extraction unit 14, a deforestation area extraction unit 15, and an embankment candidate area extraction unit 16.

[0015] The optical image acquisition unit 11 acquires a first optical image of the earth's surface in an observation target area measured by an optical sensor during a first period and a second optical image measured during a second period after the first period. The NDVI change area extraction unit 12 generates a first NDVI image from the first optical image and generates a second NDVI image from the second optical image. The NDVI image is an image showing the distribution of NDVI values. The NDVI change area extraction unit 12 compares the first NDVI image with the second NDVI image, extracts areas in the compared images where the NDVI value has changed (hereinafter referred to as NDVI change areas), and extracts position coordinates of the NDVI change areas.

[0016] The SAR image acquisition unit 13 acquires a first SAR image obtained by surveying the earth's surface of the observation target area using SAR during a first period and a second SAR image obtained by surveying the earth's surface during a second period. The reflection intensity change area extraction unit 14 generates a first reflection intensity image from the first SAR image and a second reflection intensity image from the second SAR image. The reflection intensity image is an image showing the distribution of reflection intensity. The reflection intensity indicates the amplitude of the reflected wave of the microwave irradiated to the earth's surface by the SAR. The first reflection intensity image and the second reflection intensity image are compared, and areas where the reflection intensity changes within the compared images (hereinafter referred to as reflection intensity change areas) are extracted, and the position coordinates of the reflection intensity change areas are extracted.

[0017] The deforestation area extraction unit 15 compares the position coordinates of the NDVI change area with the position coordinates of the reflection intensity change area, and based on the comparison result, extracts the position coordinates of an area in the observation area where forests were cut down between the first and second time periods (hereinafter referred to as the deforestation area).The embankment candidate area extraction unit 16 extracts the position coordinates of a candidate area for embankment newly constructed between the first and second time periods in the observation area (hereinafter referred to as the embankment candidate area) based on the position coordinates of the deforestation area.

[0018] The embankment monitoring device 10 according to the first embodiment extracts candidate deforestation areas not only from NDVI images taken at different times but also from reflection intensity images taken at different times. The embankment monitoring device 10 then compares these images to extract the deforestation areas. Even if an area that is not actually a deforestation area is mistakenly extracted as a candidate deforestation area from the NDVI image, the embankment monitoring device 10 can prevent this error by comparing it with the candidate deforestation area extracted from the reflection intensity image. Therefore, the embankment monitoring device 20 can improve its ability to detect deforestation areas. Therefore, the embankment monitoring device 20 can improve its ability to detect candidate embankment areas.

[0019] Furthermore, by using NDVI images and reflection intensity images, the embankment monitoring device 10 can detect deforestation areas even in areas where the trees are spaced apart and tree canopy elevation data cannot be obtained, or where low-lying trees grow and the difference between DEM and DSM is unclear. The embankment monitoring device 10 can also automatically detect potential embankment areas, thereby reducing the personnel costs required for monitoring potential embankment areas.

[0020] Second Embodiment Next, the configuration of an embankment monitoring system 2 according to a second embodiment will be described with reference to Fig. 2. The embankment monitoring system 2 is a specific embodiment of the embankment monitoring device 10 according to the first embodiment.

[0021] Fig. 2 is a diagram showing an example of the configuration of an embankment monitoring system 2 according to the present disclosure. As shown in Fig. 2, the embankment monitoring system 2 includes an optical satellite 101A, a SAR satellite 101B, an antenna 102A, an antenna 102B, a receiving device 103, a recording device 104, an embankment monitoring device 20, and a display device.

[0022] The optical satellite 101A is equipped with an optical sensor. The optical satellite 101A receives sunlight reflected from the surface of the observation target area A10 using the onboard optical sensor. The optical satellite 101A generates optical images of the surface of the observation target area A10 measured from the received optical information. The optical satellite 101A also generates optical images of the observation target area A10 at different time periods. The optical satellite 101A sequentially transmits the generated optical images of the observation target area A10 to the antenna 102A.

[0023] The SAR satellite 101B is equipped with a SAR. The SAR satellite 101B irradiates microwaves from the onboard SAR onto the surface of the Earth in the observation target area A10 and receives the reflected waves. The SAR satellite 101B generates a SAR image of the Earth's surface in the observation target area A10 by surveying the surface of the Earth from information on the received reflected waves. The SAR image is a complex image that shows the distribution of reflection intensity and phase. The reflection intensity indicates the amplitude of the reflected waves of the microwaves irradiated onto the Earth's surface by the SAR. The phase indicates the phase of the reflected waves of the microwaves irradiated onto the Earth's surface by the SAR. The SAR satellite 101B also generates SAR images of the observation target area A10 for different time periods. The SAR satellite 101B sequentially transmits the generated SAR images of the observation target area A10 to the antenna 102B.

[0024] The optical image and the SAR image may include information about the position of the observation target area A10, information about the positions of the optical satellite 101A and the SAR satellite 101B, and information about the time of measurement of the image. Furthermore, the optical satellite 101A and the SAR satellite 101B may be flying objects such as artificial satellites, aircraft, or drones.

[0025] The antenna 102A receives optical images from the optical satellite 101A and supplies the received optical images to the receiving device 103. The antenna 102B receives SAR images and supplies the received SAR images to the receiving device 103. The receiving device 103 performs processing such as demodulation on the optical images received from the antenna 102A and the SAR images received from the antenna 102B, and supplies the images to the recording device 104.

[0026] The recording device 104 has a recording medium such as a solid state drive (SSD), a hard disk, or a magnetic tape. The recording device 104 sequentially and readably records the optical images and SAR images received from the receiving device 103. The recording device 104 stores optical images measured over multiple different time periods and SAR images measured over multiple different time periods. The recording device 104 may also be cloud storage. The recording device 104 is communicatively connected to the embankment monitoring device 20 and supplies predetermined optical images and predetermined SAR images to the embankment monitoring device 20 in response to a request from the embankment monitoring device 20.

[0027] The display device 105 is, for example, a display. The display device 105 displays each piece of information generated by the embankment monitoring device 20.

[0028] Next, the configuration of an embankment monitoring device 20 according to a second embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the configuration of an embankment monitoring device 20 according to the present disclosure. As shown in Fig. 3, the embankment monitoring device 20 is, for example, a server. The embankment monitoring device 20 includes an optical image acquisition unit 21, an NDVI changed area extraction unit 22, an SAR image acquisition unit 23, a reflection intensity changed area extraction unit 24, a deforestation area extraction unit 25, an elevation change detection unit 26, and an embankment candidate area extraction unit 27.

[0029] The optical image acquisition unit 21 acquires, from the recording device 104, a first optical image obtained by surveying the ground surface of the observation target area A10 during a first period, and a second optical image obtained by surveying the ground surface of the observation target area A10 during a second period that follows the first period. The length of the nth period (n is a natural number) is, for example, about one to two months. The optical images may be obtained by surveying the ground surface at any time within the nth period. The interval between the nth period and the n+1th period is, for example, about one year.

[0030] The NDVI-changed region extraction unit 22 generates a first NDVI image from the first optical image and generates a second NDVI image from the second optical image. Specifically, the NDVI-changed region extraction unit 22 calculates a first NDVI value from the first optical image and calculates a second NDVI value from the second optical image. The NDVI-changed region extraction unit 22 generates the first NDVI image from the first NDVI value and generates the second NDVI image from the second NDVI value. The NDVI images are images that show the distribution of NDVI values.

[0031] NDVI is an index that was devised to utilize the characteristics of light reflection by plants to grasp the state of vegetation using satellite data and a simple calculation formula, and is an index that represents the amount and vitality of plants. The NDVI value is given by the following formula (1).

[0032]

[0033] NIR represents the reflectance of near-infrared light in the optical image. RED represents the reflectance of red light in the optical image. NDVI is expressed as a normalized value between -1 and 1. The closer the NDVI value is to -1, the poorer the vegetation is, and the closer the NDVI value is to 1, the better the vegetation is. A group of pixels in an NDVI image where the NDVI is equal to or greater than a predetermined threshold may be determined to be an area where vegetation is observed.

[0034] The NDVI-changed region extraction unit 22 then compares the first NDVI image with the second NDVI image and extracts a region in the compared images where the NDVI value has changed (NDVI-changed region). Specifically, the NDVI-changed region extraction unit 22 compares the first NDVI image with the second NDVI image and extracts a group of pixels in the compared images where the NDVI value has decreased by a predetermined threshold or more as an NDVI-changed region. This is because the NDVI value decreases in regions where forests have been cut down (i.e., regions where trees have been removed from the ground). The NDVI-changed region extraction unit 22 then extracts the position coordinates of the NDVI-changed region. The position coordinates are position coordinates in the compared images and position coordinates in real space (e.g., latitude and longitude).

[0035] The SAR image acquisition unit 23 acquires from the recording device 104 a first SAR image obtained by surveying the ground surface of the observation target area A10 during a first period, and a second SAR image obtained by surveying the ground surface of the observation target area A10 during a second period.

[0036] The reflection intensity change area extraction unit 24 generates a first reflection intensity image from the first SAR image and a second reflection intensity image from the second SAR image. The reflection intensity image is an image showing the distribution of reflection intensity. The reflection intensity indicates the amplitude of the reflected waves of the microwaves irradiated onto the Earth's surface by the SAR satellite 101B. In areas of smooth ground such as bare ground in the reflection intensity image, the reflection intensity tends to be low (they tend to appear dark in the image). This is because the reflected waves do not return to the SAR satellite 101B from smooth ground such as bare ground. On the other hand, in areas of rough ground such as forests and cities in the reflection intensity image, the reflection intensity tends to be high (they tend to appear bright in the image). This is because the reflected waves partially return to the SAR satellite 101B from rough ground such as forests and cities.

[0037] The reflection intensity change region extraction unit 24 compares the first reflection intensity image with the second reflection intensity image and extracts regions in the compared images where the reflection intensity has changed (reflection intensity change regions). Specifically, the reflection intensity change region extraction unit 24 compares the first reflection intensity image with the second reflection intensity image and extracts, as reflection intensity change regions, groups of pixels in the compared images where the reflection intensity has decreased by a predetermined threshold or more. This is because reflection intensity decreases in areas where forests have been cut down (i.e., areas where trees have been removed from the ground). The reflection intensity change region extraction unit 24 then extracts the position coordinates of the reflection intensity change regions. The position coordinates are position coordinates in the compared images and position coordinates in real space.

[0038] The deforestation area extraction unit 25 compares the position coordinates of the NDVI change area with the position coordinates of the intensity change area, and extracts the position coordinates of an area (deforestation area) in the observation area A10 where forests were cut down between the first time period and the second time period based on the comparison result. Specifically, the deforestation area extraction unit 25 compares the NDVI image in which the NDVI change area is extracted with the reflection intensity image in which the reflection intensity change area is extracted. The deforestation area extraction unit 25 extracts, as the deforestation area, an area in the compared image where the NDVI change area and the reflection intensity change area coincide. Note that the deforestation area extraction unit 25 may extract the deforestation area by comparing the position coordinates in real space of the NDVI change area with the position coordinates in real space of the reflection intensity change area. The deforestation area extraction unit 25 then extracts the position coordinates of the deforestation area. The position coordinates are the position coordinates in the compared image and the position coordinates in real space.

[0039] The elevation change detection unit 26 generates a first phase image from the first SAR image and a second phase image from the second SAR image. The phase image is an image showing the distribution of phases. The phase indicates the phase of the reflected waves of the microwaves irradiated onto the Earth's surface by the SAR satellite 101B. The distance from the SAR satellite 101B to the Earth's surface can be calculated from the phase information. The elevation change detection unit 26 calculates the elevation for each position coordinate in the deforestation area during a first period from the first phase image. The elevation change detection unit 26 calculates the elevation for each position coordinate in the deforestation area during a second period from the second phase image. The elevation change detection unit 26 then detects the amount of elevation change for each position coordinate in the deforestation area that occurred between the first and second periods. Note that the elevation for each position coordinate in the first and second periods may be corrected using a DEM (Digital Elevation Model) from the Geospatial Information Authority of Japan. Furthermore, the altitude change detection unit 26 may detect the amount of altitude change for each position coordinate not only in the deforestation area but also in the vicinity of the deforestation area (i.e., an area within a predetermined range from the periphery of the deforestation area).

[0040] The embankment candidate area extraction unit 27 extracts embankment candidate areas that have been newly constructed between the first and second time periods in the observation target area A10 based on the amount of elevation change for each position coordinate in the deforestation area. For example, the embankment candidate area extraction unit 27 determines as an embankment candidate area an area in the deforestation area where the amount of elevation change for each position coordinate between the first and second time periods is equal to or greater than a predetermined threshold. The embankment candidate area extraction unit 27 then extracts the position coordinates and the amount of embankment for each position coordinate in the embankment candidate area. The position coordinates are the position coordinates in the image (e.g., the second optical image) and the position coordinates in real space. The amount of embankment is the amount of elevation change in the embankment candidate area, which is the height of the embankment.

[0041] The embankment candidate area extraction unit 27 may calculate the area of ​​the embankment candidate area based on the position coordinates of the embankment candidate area. Furthermore, the embankment candidate area extraction unit 27 may further extract the scale of the embankment in the embankment candidate area based on the amount of embankment for each position coordinate of the embankment candidate area and the area of ​​the embankment candidate area. The scale of the embankment may be expressed, for example, as a level.

[0042] Furthermore, the embankment monitoring device 20 of this embodiment is not limited to extracting the position coordinates of candidate embankment areas constructed between the first period and the second period, but may also extract the position coordinates of candidate embankment areas constructed between the nth period (n is a natural number) and the n+1th period, which is after the nth period, in chronological order.

[0043] Next, an example of the operation of the embankment monitoring device 20 according to the second embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing an example of the operation of the embankment monitoring device 20 according to the present disclosure.

[0044] 4, in step S201, the optical image acquisition unit 21 of the embankment monitoring device 20 acquires first and second optical images of the ground surface of the observation target area A10, which are acquired during a first period and a second period subsequent to the first period, from the recording device 104. The recording device 104 stores optical images acquired during a plurality of different periods by the optical satellite 101A.

[0045] Next, in step S202, the NDVI-changed region extracting unit 22 generates a first NDVI image and a second NDVI image from the first optical image and the second optical image, respectively.

[0046] Next, in step S203, the NDVI change region extraction unit 22 compares the first NDVI image with the second NDVI image, extracts an NDVI change region in the compared images, and extracts the position coordinates of the NDVI change region.

[0047] Next, in step S204, the SAR image acquisition unit 23 acquires a first SAR image and a second SAR image of the earth's surface in the observation target area A10 photographed in a first period and a second period, respectively, from the recording device 104. The recording device 104 stores SAR images measured by the SAR satellite 101B in a plurality of different periods.

[0048] Next, in step S205, the reflection intensity varying region extracting unit 24 generates a first reflection intensity image and a second reflection intensity image from the first SAR image and the second SAR image.

[0049] Next, in step S206, the reflection intensity changing region extraction unit 24 compares the first reflection intensity image with the second reflection intensity image, extracts a reflection intensity changing region in the compared images, and extracts the position coordinates of the reflection intensity changing region. Next, in step S207, the deforestation region extraction unit 25 compares the position coordinates of the NDVI changing region with the position coordinates of the reflection intensity changing region, and extracts the position coordinates of the deforestation region based on the comparison result.

[0050] Next, in step S208, the elevation change detection unit 26 detects the amount of elevation change that occurred for each position coordinate in the deforestation area between the first and second periods. Next, in step S209, the embankment candidate area extraction unit 27 extracts the position coordinates and amount of embankment candidate areas that were newly constructed between the first and second periods based on the amount of elevation change for each position coordinate.

[0051] As described above, the embankment monitoring device 20 according to the second embodiment achieves the same effects as the embankment monitoring device 10 according to the first embodiment. Furthermore, the embankment monitoring device 20 detects the amount of elevation change that occurred in the extracted deforestation area between the first and second periods, and extracts the position coordinates of the embankment candidate area and the amount of embankment for each position coordinate based on the amount of elevation change. Therefore, the embankment monitoring device 20 only needs to detect the amount of elevation change for the deforestation area, and can extract the embankment candidate area efficiently and accurately. Furthermore, the embankment monitoring device 20 can automatically extract the position coordinates of the embankment candidate area and the amount of embankment for each position coordinate, thereby reducing labor costs.

[0052] Third Embodiment Next, the configuration of an embankment monitoring system 3 (not shown) according to a third embodiment will be described with reference to FIGS. 2, 3 and 5. FIG.

[0053] Compared to the embankment monitoring system 2 according to the second embodiment (see FIG. 2), the embankment monitoring system 3 includes an embankment monitoring device 30 instead of the embankment monitoring device 20. The embankment monitoring device 30 can improve the ability to detect deforestation areas compared to the embankment monitoring device 20. FIG. 5 is a block diagram showing an example of the configuration of the embankment monitoring device 30 according to the present disclosure. As shown in FIG. 5, the embankment monitoring device 30 further includes a coherence change area extraction unit 31 in addition to the components of the embankment monitoring device 20 (see FIG. 3). Furthermore, the SAR image acquisition unit 23 and the deforestation area extraction unit 25 further include the following functions.

[0054] The SAR image acquisition unit 23 acquires a first SAR image obtained by surveying the ground surface of the observation target area A10 during a first period and a second SAR image obtained by surveying the ground surface of the observation target area A10 during a second period. Furthermore, the SAR image acquisition unit 23 acquires a third SAR image obtained by surveying the ground surface of the observation target area A10 during a third period prior to the first period.

[0055] The coherence change region extraction unit 31 generates a first coherence image, which is the distribution of coherence between the third SAR image and the first SAR image, and generates a second coherence image, which is the distribution of coherence between the first SAR image and the second SAR image. The coherence image indicates the distribution of coherence between multiple SAR images. In other words, the coherence indicates the degree of interference between reflected waves received by the SAR satellite 101B over multiple different time periods. When the shapes (e.g., intensity or phase) of the reflected waves are similar, the degree of interference is high, and when the shapes of the reflected waves are different, the degree of interference is low.

[0056] The coherence change region extraction unit 31 compares the first coherence image with the second coherence image and extracts a region in the compared images where coherence has changed (hereinafter referred to as a coherence change region). Specifically, the coherence change region extraction unit 31 compares the first coherence image with the second coherence image and extracts a region in the compared images where coherence has decreased by a predetermined threshold or more as a coherence change region. This is because if an event occurs on the ground surface between the first time period and the second time period, such as forest cutting (i.e., the trees are left bare), the coherence will be low in the region where the event occurred. The coherence change region extraction unit 31 then extracts the position coordinates of the coherence change region. The position coordinates are position coordinates in the compared images and position coordinates in real space.

[0057] The deforestation area extraction unit 25 extracts the position coordinates of the deforestation area based on the position coordinates of the NDVI change area extracted by the NDVI change area extraction unit 22, the position coordinates of the reflection intensity change area extracted by the reflection intensity change area extraction unit 24, and the position coordinates of the coherence change area extracted by the coherence change area extraction unit 31. Specifically, the deforestation area extraction unit 25 compares the NDVI image from which the NDVI change area is extracted, the reflection intensity image from which the reflection intensity change area is extracted, and the coherence image from which the coherence change area is extracted. The deforestation area extraction unit 25 extracts, as the deforestation area, an area in the compared images where the position coordinates of the NDVI change area, the reflection intensity change area, and the coherence change area match. Note that the deforestation area extraction unit 25 may also compare the position coordinates in real space between the NDVI change area, the reflection intensity change area, and the coherence change area and extract the deforestation area based on the comparison result. In this case, the deforestation area extraction unit 25 extracts, as the deforestation area, an area where the position coordinates in real space match between the NDVI change area, the reflection intensity change area, and the coherence image.

[0058] Next, the operation of the embankment monitoring device 30 according to the third embodiment will be described with reference to Fig. 4 and Fig. 6. Fig. 6 is a flowchart showing an example of the operation of the embankment monitoring device 30 according to the present disclosure.

[0059] As shown in Fig. 6, the embankment monitoring device 30 performs the above-mentioned processes of steps S201 to S206 (see Fig. 4). After the process of step S206, the embankment monitoring device 30 performs the processes of steps S301 to S303 instead of the process of step S207.

[0060] In step S301, the coherence change region extraction unit 31 generates a first coherence image and a second coherence image from the first SAR image and the second SAR image, respectively. In step S302, the coherence change region extraction unit 31 compares the first coherence image and the second coherence image, extracts a coherence change region in the compared images, and extracts the position coordinates of the coherence change region. In step S303, the deforestation region extraction unit 25 compares the position coordinates of the NDVI change region, the position coordinates of the reflectance intensity change region, and the position coordinates of the coherence change region, and extracts the position coordinates of the deforestation region based on the comparison result.

[0061] Thereafter, the embankment monitoring device 30 proceeds to the processing of step S208 (see FIG. 4) and performs the processing of steps S208 to S209.

[0062] As described above, the embankment monitoring device 30 according to the third embodiment achieves the same effects as the embankment monitoring device 20 according to the second embodiment. Furthermore, the embankment monitoring device 30 extracts deforestation areas using coherence images in addition to NDVI images and reflection intensity images. Therefore, the embankment monitoring device 30 can further improve its ability to detect deforestation areas.

[0063] Fourth Embodiment Next, the configuration of an embankment monitoring system 4 (not shown) according to a fourth embodiment will be described with reference to FIGS. 2, 3 and 7. FIG.

[0064] Compared to the components of the embankment monitoring system 2 according to the second embodiment (see FIG. 2), the embankment monitoring system 4 includes an embankment monitoring device 40 instead of the embankment monitoring device 20. The embankment monitoring device 40 can improve the ability to detect deforestation areas compared to the embankment monitoring device 20. FIG. 7 is a block diagram showing an example of the configuration of the embankment monitoring device 40 according to the present disclosure. As shown in FIG. 7, the embankment monitoring device 40 further includes a road map acquisition unit 41 in addition to the components of the embankment monitoring device 20 (see FIG. 3). Furthermore, the deforestation area extraction unit 25 further includes the following functions.

[0065] In the above-described second embodiment, the deforestation area extraction unit 25 compares the position coordinates of the NDVI change area and the position coordinates of the reflection intensity change area, and extracts the position coordinates of the deforestation area between the first period and the second period in the observation area A10 based on the comparison result.

[0066] In this embodiment, the road map acquisition unit 41 acquires a road map for the second time period. The road map includes information on the real-world position coordinates (e.g., latitude and longitude) of each road. The roads are roads defined by laws such as the Road Act, and include public roads such as national highways, prefectural roads, municipal roads, and expressways.

[0067] The deforestation area extraction unit 25 further extracts deforestation areas that are within a predetermined range of the road from the deforestation area based on the position coordinates of the deforestation area extracted by the deforestation area extraction unit 25 and the position coordinates of each road included in the road map.

[0068] Next, the operation of the embankment monitoring device 40 according to the fourth embodiment will be described with reference to Fig. 4 and Fig. 8. Fig. 8 is a flowchart showing an example of the operation of the embankment monitoring device 40 according to the present disclosure.

[0069] As shown in Fig. 8, the embankment monitoring device 40 performs the above-mentioned processes of steps S201 to S207 (see Fig. 4). After the process of step S207, the embankment monitoring device 40 performs the processes of steps S401 to S402.

[0070] In step S401, the road map acquisition unit 41 of the embankment monitoring device 40 acquires a road map for the second period including the position coordinates of roads. Next, in step S402, the deforestation area extraction unit 25 further extracts at least one deforestation area that is within a predetermined range from the deforestation area based on the position coordinates of the deforestation area extracted in step S207 and the position coordinates of the roads included in the road map.

[0071] Thereafter, the embankment monitoring device 40 proceeds to the processing of step S208 (see FIG. 4) and performs the processing of steps S208 to S209.

[0072] As described above, the embankment monitoring device 40 according to the fourth embodiment achieves the same effects as the embankment monitoring device 20 according to the second embodiment. Furthermore, it is conceivable that vehicles such as tractors will visit deforestation areas to transport tools for cutting down trees or to transport cut forests. Because it is difficult for such vehicles to travel far from well-maintained roads, deforestation areas are inevitably located near roads. The embankment monitoring device 40 determines that an area within a predetermined range from a road in the observation target area A10 is a deforestation area. Therefore, the embankment monitoring device 40 can further improve its ability to detect deforestation areas.

[0073] Fifth Embodiment Next, the configuration of an embankment monitoring system 5 (not shown) according to a fifth embodiment will be described with reference to FIGS. 2, 3 and 9. FIG.

[0074] Compared to the embankment monitoring system 2 according to the second embodiment (see FIG. 2), the embankment monitoring system 5 includes an embankment monitoring device 50 instead of the embankment monitoring device 20. Compared to the embankment monitoring device 20, the embankment monitoring device 50 can further detect candidate areas for illegal embankments (hereinafter, "illegal embankment candidate areas") from among candidate embankment areas.

[0075] Fig. 9 is a block diagram showing an example of the configuration of an embankment monitoring device 50 according to the present disclosure. As shown in Fig. 9, the embankment monitoring device 50 further includes a registered embankment area storage unit 51 and an illegal embankment candidate area extraction unit 52 in addition to the components of the embankment monitoring device 20 (see Fig. 3).

[0076] The registered embankment area storage unit 51 stores information on the position coordinates of areas registered as legitimate embankments (hereinafter referred to as registered embankment areas) and the amount of embankment for each position coordinate.

[0077] In the second embodiment described above, the embankment candidate area extraction unit 27 extracts the position coordinates of the embankment candidate area and the embankment volume for each position coordinate. In this embodiment, the illegal embankment candidate area extraction unit 52 acquires the position coordinates of the registered embankment area and the embankment volume for each position coordinate from the registered embankment area storage unit 51. The illegal embankment candidate area extraction unit 52 compares the position coordinates of the embankment candidate area with the position coordinates of the registered embankment area and extracts the illegal embankment candidate area from the embankment candidate area based on the comparison result. Specifically, the illegal embankment candidate area extraction unit 52 determines whether the position coordinates of the embankment candidate area match the position coordinates of the registered embankment area. If it determines that they do not match, the illegal embankment candidate area extraction unit 52 extracts, as the illegal embankment candidate area, the areas within the embankment candidate area whose position coordinates do not match those of the registered embankment area.

[0078] Furthermore, the illegal banking candidate area extraction unit 52 compares the fill volume for each position coordinate of the banking candidate area with the fill volume for each position coordinate of the registered banking area, and extracts illegal banking candidate areas from among the banking candidate areas based on the comparison result. Specifically, the illegal banking candidate area extraction unit 52 determines whether the fill volume of the banking candidate area matches the fill volume of the registered banking area. If it is determined that they do not match, the illegal banking candidate area extraction unit 52 extracts as illegal banking candidate areas any area within the banking candidate area whose fill volume does not match that of the registered banking area.

[0079] The illegal fill candidate area extraction unit 52 extracts the illegal fill candidate area by either or both of the above-mentioned methods of checking the position coordinates and checking the fill volume of the illegal fill candidate area.The illegal fill candidate area extraction unit 52 then extracts the position coordinates of the illegal fill candidate area in real space.

[0080] Next, the operation of the embankment monitoring device 50 according to the fifth embodiment will be described with reference to Fig. 4 and Fig. 10. Fig. 10 is a flowchart showing an example of the operation of the embankment monitoring device 50 according to the present disclosure.

[0081] 10, the embankment monitoring device 50 performs the above-mentioned processes of steps S201 to S209 (see FIG. 4). After the process of step S209, the embankment monitoring device 50 performs the processes of steps S501 to S502.

[0082] First, in step S501, the illegal embankment candidate area extraction unit 52 of the embankment monitoring device 50 acquires the position coordinates of the registered embankment area and the embankment volume for each position coordinate from the registered embankment area storage unit 51. Next, in step S502, the illegal embankment candidate area extraction unit 52 compares the position coordinates of the embankment candidate area with the position coordinates of the registered embankment area.

[0083] Next, in step S503, the illegal fill area candidate extraction unit 52 compares the fill volume for each position coordinate of the fill area candidate with the fill volume for each position coordinate of the registered fill area. Next, in step S504, the illegal fill area candidate extraction unit 52 extracts illegal fill area candidate from the fill area candidate based on the comparison result, and extracts the position coordinates of the illegal fill area candidate and the fill volume for each position coordinate. For example, the illegal fill area candidate extraction unit 52 extracts as an illegal fill area candidate any area within the fill area candidate whose position coordinates and the fill volume for each position coordinate do not match those of the registered fill area.

[0084] As described above, the embankment monitoring device 50 according to the fifth embodiment achieves the same effects as the embankment monitoring device 20 according to the second embodiment. Furthermore, the embankment monitoring device 50 can automatically detect potential areas of illegal embankment from among potential embankment areas using the position information and embankment volume information of registered embankment areas. Compared to manually monitoring potential areas of illegal embankment, the embankment monitoring device 50 can reduce costs and improve monitoring efficiency.

[0085] <Example of Hardware Configuration> Each functional component of the embankment monitoring device 10 according to the above-described embodiment, and each device of the embankment monitoring systems 2 to 5 (e.g., embankment monitoring device 20 to embankment monitoring device 50) may be realized by hardware that realizes each functional component (e.g., a hardwired electronic circuit, etc.), or may be realized by a combination of hardware and software (e.g., a combination of an electronic circuit and a program that controls it, etc.). Below, a case where each functional component of the above-described devices is realized by a combination of hardware and software will be further described.

[0086] FIG. 11 is a block diagram showing an example of the hardware configuration of a computer 500 according to an embodiment. The functional components of the embankment monitoring device 10 and each device of the embankment monitoring systems 2 to 5 (e.g., embankment monitoring device 20 to embankment monitoring device 50) can all be realized by a computer 500 having the hardware configuration shown in FIG. 11. The computer 500 may be a portable computer such as a smartphone or tablet terminal, or a stationary computer such as a PC (personal computer). The computer 500 may be a dedicated computer or a general-purpose computer. For example, by installing a predetermined application on the computer 500, the computer 500 can be given desired functions.

[0087] The computer 500 has a bus 501, a processor 502, a memory 503, a storage device 504, an input / output interface (I / F) 505, and a network interface (I / F) 506. The bus 501 is a data transmission path for the processor 502, the memory 503, the storage device 504, the input / output interface 505, and the network interface 506 to transmit and receive data to and from each other. However, the method of connecting the processor 502 and the like to each other is not limited to bus connection.

[0088] The processor 502 is one of various processors, such as a central processing unit (CPU), a graphics processing unit (GPU), or a field-programmable gate array (FPGA). The memory 503 is a main storage device realized using a random access memory (RAM) or the like. The storage device 504 is an auxiliary storage device realized using a hard disk, a solid state drive (SSD), a memory card, a read only memory (ROM), or the like.

[0089] The input / output interface 505 is an interface for connecting the computer 500 to an input / output device. For example, the input / output interface 505 is connected to an input device such as a keyboard and an output device such as a display device.

[0090] The network interface 506 is an interface for connecting the computer 500 to a network. This network may be a LAN (Local Area Network) or a WAN (Wide Area Network).

[0091] The storage device 504 stores programs for realizing desired functions. For example, the storage device 504 of the computer 500 stores programs for realizing each function. The processor 502 reads the programs into the memory 503 and executes them to realize each function.

[0092] These programs include instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The programs may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0093] The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, one or more of the features disclosed in the second to fifth embodiments may be combined.

[0094] Some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes: (Supplementary Note 1) An optical image acquisition unit that acquires a first optical image of the earth's surface in an observation target area measured by an optical sensor in a first period and a second optical image measured in a second period after the first period, an NDVI change region extraction unit that generates a first NDVI (Normalized Difference Vegetation Index) image from the first optical image, generates a second NDVI image from the second optical image, compares the first NDVI image with the second NDVI image, extracts an NDVI change region in the compared images where the NDVI value has changed, and extracts position coordinates of the NDVI change region, an SAR image acquisition unit that acquires a first SAR image of the earth's surface in the observation target area measured by a SAR in the first period and a second SAR image measured in the second period, an embankment monitoring device comprising: a reflection intensity change region extraction unit that generates a first reflection intensity image from the first SAR image, generates a second reflection intensity image from the second SAR image, compares the first reflection intensity image with the second reflection intensity image, extracts reflection intensity change regions that are regions where reflection intensity has changed in the compared images, and extracts position coordinates of the reflection intensity change regions; a deforestation region extraction unit that compares the position coordinates of the NDVI change regions with the position coordinates of the reflection intensity change regions and extracts position coordinates of deforestation regions that are regions in the observation target area where forests have been cut down between the first period and the second period based on the result of the comparison; and an embankment candidate region extraction unit that extracts position coordinates of embankment candidate regions that are candidate regions for embankments that have been newly constructed in the observation target area between the first period and the second period, based on the position coordinates of the deforestation regions.(Supplementary Note 2) The embankment monitoring device according to Supplementary Note 1 further comprises an elevation change detection unit that generates a first phase image from the first SAR image, calculates an elevation for each position coordinate of the observation area during the first period based on the first phase image, generates a second phase image from the second SAR image, calculates an elevation for each position coordinate of the observation area during the second period based on the second phase image, and detects an amount of change in elevation for each position coordinate in the deforestation area between the first period and the second period, and the embankment candidate area extraction unit extracts the position coordinates of the embankment candidate area based on the amount of change in elevation for each position coordinate in the deforestation area. (Supplementary Note 3) The embankment monitoring device according to Supplementary Note 1, wherein the SAR image acquisition unit further acquires a third SAR image in which the surface of the observation target area is surveyed in a third period prior to the first period; the embankment monitoring device further comprises a coherence change region extraction unit that generates a first coherence image which is a distribution of coherence between the third SAR image and the first SAR image, generates a second coherence image which is a distribution of coherence between the first SAR image and the second SAR image, compares the first coherence image with the second coherence image, extracts a coherence change region which is a region in the compared images where coherence has changed, and extracts position coordinates of the coherence change region; and the deforestation region extraction unit extracts position coordinates of the deforestation region based on the position coordinates of the NDVI change region and the position coordinates of the reflection intensity change region, and further the position coordinates of the coherence change region. (Appendix 4) The embankment monitoring device described in Appendix 1 further comprises a road map acquisition unit that acquires a road map for the second period including the position coordinates of roads, and the deforestation area extraction unit further extracts the position coordinates of deforestation areas within a predetermined range of the roads based on the position coordinates of the extracted deforestation areas and the position coordinates of roads included in the road map.(Supplementary Note 5) The embankment monitoring device according to Supplementary Note 1, further comprising: a storage unit that stores position coordinates of registered embankment areas, which are areas that are registered as legitimate embankments; and an illegal embankment candidate area extraction unit that compares the position coordinates of the embankment candidate areas with the position coordinates of the registered embankment areas and extracts illegal embankment candidate areas, which are candidate areas for illegal embankments, from among the embankment candidate areas based on the result of the comparison. (Supplementary Note 6) The embankment monitoring device according to Supplementary Note 2, wherein the embankment candidate area extraction unit further extracts the amount of embankment for each position coordinate in the embankment candidate area based on the amount of elevation change for each position coordinate. (Supplementary Note 7) The embankment monitoring device according to Supplementary Note 6, further comprising: a storage unit that stores position coordinates of registered embankment areas and the amount of embankment for each position coordinate of the registered embankment area, in association with each other; and an illegal embankment candidate area extraction unit that compares the position coordinates of the embankment candidate area with the position coordinates of the registered embankment area, and compares the amount of embankment for each position coordinate of the embankment candidate area with the amount of embankment for each position coordinate of the registered embankment area, and extracts illegal embankment candidate areas that are candidate areas for illegal embankments from among the embankment candidate areas based on the results of the comparison. (Supplementary Note 8) The embankment monitoring device according to Supplementary Note 6, wherein the embankment candidate area extraction unit calculates the area of ​​the embankment candidate area based on the position coordinates of the embankment candidate area, and further extracts the scale of embankment in the embankment candidate area based on the amount of embankment for each position coordinate of the embankment candidate area and the area of ​​the embankment candidate area. (Supplementary Note 9) The embankment monitoring device according to Supplementary Note 2, wherein the embankment candidate area extraction unit determines, as the embankment candidate area, an area in the deforestation area where an amount of elevation change for each of the position coordinates is equal to or greater than a predetermined threshold.(Supplementary Note 10) A computer acquires a first optical image of the earth's surface in an observation area measured by an optical sensor in a first period and a second optical image measured in a second period after the first period, generates a first NDVI image from the first optical image, generates a second NDVI image from the second optical image, compares the first NDVI image with the second NDVI image, extracts an NDVI change area in the compared images where the NDVI value has changed, and extracts position coordinates of the NDVI change area, acquires a first SAR image of the earth's surface in the observation area measured by SAR in the first period and a second SAR image measured in the second period, an embankment monitoring method comprising: generating a first reflection intensity image from the first SAR image; generating a second reflection intensity image from the second SAR image; comparing the first reflection intensity image with the second reflection intensity image; extracting a reflection intensity change region, which is a region where reflection intensity has changed in the compared images; extracting position coordinates of the reflection intensity change region; comparing the position coordinates of the NDVI change region with the position coordinates of the reflection intensity change region; extracting position coordinates of a deforestation region, which is a region in the observation area where forests have been cut down between the first period and the second period, based on the result of the comparison; and extracting position coordinates of an embankment candidate region, which is a candidate region for an embankment newly constructed in the observation area between the first period and the second period, based on the position coordinates of the deforestation region. (Supplementary Note 11) The embankment monitoring method according to Supplementary Note 10, wherein the computer generates a first phase image from the first SAR image, calculates the elevation for each position coordinate of the observation area during the first period based on the first phase image, generates a second phase image from the second SAR image, calculates the elevation for each position coordinate of the observation area during the second period based on the second phase image, detects an amount of elevation change for each position coordinate in the deforestation area between the first period and the second period, and extracts the position coordinates of the embankment candidate area based on the amount of elevation change for each position coordinate in the deforestation area.(Supplementary Note 12) The embankment monitoring method according to Supplementary Note 10, wherein the computer further acquires a third SAR image in which the surface of the observation target area is surveyed during a third period prior to the first period, generates a first coherence image which is a distribution of coherence between the third SAR image and the first SAR image, generates a second coherence image which is a distribution of coherence between the first SAR image and the second SAR image, compares the first coherence image with the second coherence image, extracts a coherence change region which is a region in which coherence has changed within the compared images, and extracts position coordinates of the coherence change region, and extracts position coordinates of the deforestation region based on the position coordinates of the NDVI change region and the position coordinates of the reflection intensity change region, and further the position coordinates of the coherence change region. (Supplementary Note 13) The embankment monitoring method according to Supplementary Note 10, wherein the computer acquires a road map for the second period including position coordinates of roads, and further extracts position coordinates of deforestation areas within a predetermined range from the road based on the position coordinates of the extracted deforestation area and the position coordinates of roads included in the road map. (Supplementary Note 14) The embankment monitoring method according to Supplementary Note 10, wherein the computer stores position coordinates of registered embankment areas which are areas registered as legitimate embankments, compares the position coordinates of the embankment candidate areas with the position coordinates of the registered embankment areas, and extracts illegal embankment candidate areas which are candidate areas for illegal embankments from among the embankment candidate areas based on the result of the comparison. (Supplementary Note 15) The embankment monitoring method according to Supplementary Note 11, wherein the computer further extracts the amount of embankment for each position coordinate in the embankment candidate area based on the amount of elevation change for each position coordinate. (Appendix 16) An embankment monitoring method as set forth in Appendix 15, wherein the computer: stores the position coordinates of registered embankment areas in association with the amount of embankment for each position coordinate of the registered embankment area; compares the position coordinates of the candidate embankment areas with the position coordinates of the registered embankment areas; and compares the amount of embankment for each position coordinate of the candidate embankment areas with the amount of embankment for each position coordinate of the registered embankment areas; and extracts illegal embankment candidate areas, which are candidate areas for illegal embankments, from the candidate embankment areas based on the results of the comparison.(Supplementary Note 17) The embankment monitoring method according to Supplementary Note 15, wherein the computer calculates an area of ​​the embankment candidate area based on position coordinates of the embankment candidate area, and further extracts the scale of the embankment in the embankment candidate area based on the amount of embankment for each position coordinate of the embankment candidate area and the area of ​​the embankment candidate area. (Supplementary Note 18) The embankment monitoring method according to Supplementary Note 11, wherein the computer determines, as the embankment candidate area, an area in the deforestation area where the amount of elevation change for each position coordinate is equal to or greater than a predetermined threshold. (Supplementary Note 19) A method for detecting an NDVI change in an observation target area includes: acquiring a first optical image obtained by surveying the surface of the earth in a first period using an optical sensor; and acquiring a second optical image obtained by surveying the surface of the earth in a second period after the first period; generating a first NDVI image from the first optical image; generating a second NDVI image from the second optical image; comparing the first NDVI image with the second NDVI image; extracting an NDVI change area in the compared images where the NDVI value has changed; and extracting position coordinates of the NDVI change area; acquiring a first SAR image obtained by surveying the surface of the observation target area using SAR in the first period and a second SAR image obtained by surveying the surface of the earth in the observation target area in the second period; A program that causes a computer to execute processes to generate a first reflection intensity image from the first SAR image, generate a second reflection intensity image from the second SAR image, compare the first reflection intensity image with the second reflection intensity image, extract a reflection intensity change region, which is a region where reflection intensity has changed in the compared images, and extract position coordinates of the reflection intensity change region, compare the position coordinates of the NDVI change region with the position coordinates of the reflection intensity change region, and extract position coordinates of a deforestation region, which is a region in the observation area where forests have been cut down between the first period and the second period, based on the position coordinates of the deforestation region, and extract position coordinates of an embankment candidate region, which is a candidate region for new embankment construction in the observation area between the first period and the second period, based on the position coordinates of the deforestation region.(Supplementary Note 20) The program described in Supplementary Note 19 further causes a computer to execute the following processes: generate a first phase image from the first SAR image; calculate the elevation for each position coordinate of the observation area during the first period based on the first phase image; generate a second phase image from the second SAR image; calculate the elevation for each position coordinate of the observation area during the second period based on the second phase image; detect an amount of elevation change for each position coordinate in the deforestation area between the first period and the second period; and extract the position coordinates of the embankment candidate area based on the amount of elevation change for each position coordinate in the deforestation area. (Supplementary Note 21) The program according to Supplementary Note 19, further causing a computer to execute the following processes: acquire a third SAR image in which the surface of the observation target area is surveyed in a third period prior to the first period; generate a first coherence image which is a distribution of coherence between the third SAR image and the first SAR image; generate a second coherence image which is a distribution of coherence between the first SAR image and the second SAR image; compare the first coherence image with the second coherence image; extract a coherence change region which is a region in the compared images where coherence has changed; and extract position coordinates of the coherence change region; and extract position coordinates of the deforestation region based on the position coordinates of the NDVI change region, the position coordinates of the reflection intensity change region, and further the position coordinates of the coherence change region. (Supplementary Note 22) The program according to Supplementary Note 19, which causes the computer to further execute a process of acquiring a road map for the second period including position coordinates of roads, and further extracting position coordinates of deforestation areas within a predetermined range from the road based on the position coordinates of the extracted deforestation area and the position coordinates of roads included in the road map. (Supplementary Note 23) The program according to Supplementary Note 19, which causes the computer to further execute a process of storing position coordinates of registered embankment areas which are areas to be registered as legitimate embankments, comparing the position coordinates of the embankment candidate areas with the position coordinates of the registered embankment areas, and extracting illegal embankment candidate areas which are candidate areas for illegal embankments based on the result of the comparison.(Supplementary Note 24) The program according to Supplementary Note 20, which causes the computer to further execute a process of extracting a fill volume for each position coordinate in the embankment candidate area based on the amount of elevation change for each position coordinate. (Supplementary Note 25) The program according to Supplementary Note 24, which causes the computer to further execute a process of storing position coordinates of registered embankment areas and the fill volume for each position coordinate of the registered embankment area in association with each other, comparing the position coordinates of the embankment candidate area with the position coordinates of the registered embankment area, and comparing the fill volume for each position coordinate of the embankment candidate area with the fill volume for each position coordinate of the registered embankment area, and extracting illegal embankment candidate areas that are candidate areas for illegal embankment from among the embankment candidate areas based on the results of the comparison. (Supplementary Note 26) The program according to Supplementary Note 24, which causes the computer to further execute a process of calculating the area of ​​the embankment candidate area based on the position coordinates of the embankment candidate area, and further extracting the scale of embankment in the embankment candidate area based on the amount of embankment for each position coordinate of the embankment candidate area and the area of ​​the embankment candidate area. (Supplementary Note 27) The program according to Supplementary Note 20, further causing the computer to execute a process of determining, as the banking candidate area, an area in the deforestation area where the amount of elevation change for each of the position coordinates is equal to or greater than a predetermined threshold.

[0095] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0096] This application claims priority based on Japanese Patent Application No. 2024-088727, filed May 31, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0097] 2, 3, 4, 5 Embankment monitoring system 10, 20, 30, 40, 50 Embankment monitoring device 11, 21 Optical image acquisition unit 12, 22 NDVI change area extraction unit 13, 23 SAR image acquisition unit 14, 24 Reflection intensity change area extraction unit 15, 25 Deforestation area extraction unit 16, 27 Embankment candidate area extraction unit 26 Elevation change detection unit 31 Coherence change area extraction unit 41 Road map acquisition unit 51 Registered embankment area storage unit 52 Illegal embankment candidate area extraction unit 101A Optical satellite 101B SAR satellite 102A Antenna 102B Antenna 103 Receiving device 104 Recording device 105 Display device 500 Computer 501 Bus 502 Processor 503 Memory 504 Storage device 505 Input / output interface (I / F) 506 Network interface (I / F)

Claims

1. An optical image acquisition unit that acquires a first optical image of the earth's surface in the observation target area measured by an optical sensor during a first period and a second optical image measured during a second period after the first period; an NDVI change area extraction unit that generates a first NDVI (Normalized Difference Vegetation Index) image from the first optical image, generates a second NDVI image from the second optical image, compares the first NDVI image with the second NDVI image, extracts an NDVI change area in the compared images where the NDVI value has changed, and extracts the position coordinates of the NDVI change area; and an SAR image acquisition unit that acquires a first SAR image of the earth's surface in the observation target area measured by SAR during the first period and a second SAR image measured during the second period. an embankment monitoring device comprising: a reflection intensity change region extraction unit that generates a first reflection intensity image from the first SAR image, generates a second reflection intensity image from the second SAR image, compares the first reflection intensity image with the second reflection intensity image, extracts reflection intensity change regions that are regions where reflection intensity has changed in the compared images, and extracts position coordinates of the reflection intensity change regions; a deforestation region extraction unit that compares the position coordinates of the NDVI change regions with the position coordinates of the reflection intensity change regions and extracts position coordinates of deforestation regions that are regions in the observation target area where forests have been cut down between the first period and the second period based on the result of the comparison; and an embankment candidate region extraction unit that extracts position coordinates of embankment candidate regions that are candidate regions for embankments that have been newly constructed in the observation target area between the first period and the second period, based on the position coordinates of the deforestation regions.

2. An embankment monitoring device as described in claim 1, further comprising an elevation change detection unit that generates a first phase image from the first SAR image, calculates the elevation for each position coordinate of the observation area during the first period based on the first phase image, generates a second phase image from the second SAR image, calculates the elevation for each position coordinate of the observation area during the second period based on the second phase image, and detects the amount of change in elevation for each position coordinate in the deforestation area between the first period and the second period, and wherein the embankment candidate area extraction unit extracts the position coordinates of the embankment candidate area based on the amount of change in elevation for each position coordinate in the deforestation area.

3. The embankment monitoring device according to claim 1, wherein the SAR image acquisition unit further acquires a third SAR image in which the surface of the observation area is surveyed during a third period prior to the first period; the embankment monitoring device further comprises a coherence change area extraction unit that generates a first coherence image which is the distribution of coherence between the third SAR image and the first SAR image, generates a second coherence image which is the distribution of coherence between the first SAR image and the second SAR image, compares the first coherence image with the second coherence image, extracts coherence change areas which are areas in the compared images where coherence has changed, and extracts the position coordinates of the coherence change areas; and the deforestation area extraction unit extracts the position coordinates of the deforestation area based on the position coordinates of the NDVI change area and the position coordinates of the reflection intensity change area, and further the position coordinates of the coherence change area.

4. An embankment monitoring device as described in claim 1, further comprising a road map acquisition unit that acquires a road map for the second period including the position coordinates of roads, and the deforestation area extraction unit further extracts the position coordinates of deforestation areas within a predetermined range of the roads based on the position coordinates of the extracted deforestation areas and the position coordinates of roads included in the road map.

5. An embankment monitoring device as described in claim 1, further comprising: a memory unit that stores the position coordinates of registered embankment areas, which are areas that are registered as legitimate embankments; and an illegal embankment candidate area extraction unit that compares the position coordinates of the embankment candidate areas with the position coordinates of the registered embankment areas and extracts illegal embankment candidate areas, which are candidate areas for illegal embankments, from among the embankment candidate areas based on the result of the comparison.

6. An embankment monitoring device according to claim 2, wherein the embankment candidate area extraction unit further extracts the amount of embankment for each position coordinate in the embankment candidate area based on the amount of elevation change for each position coordinate.

7. An embankment monitoring device as claimed in claim 6, further comprising: a memory unit that stores the position coordinates of registered embankment areas and the amount of embankment for each position coordinate of the registered embankment areas in correspondence with each other; and an illegal embankment candidate area extraction unit that compares the position coordinates of the embankment candidate areas with the position coordinates of the registered embankment areas and compares the amount of embankment for each position coordinate of the embankment candidate areas with the amount of embankment for each position coordinate of the registered embankment areas, and extracts illegal embankment candidate areas that are candidate areas for illegal embankments from among the embankment candidate areas based on the results of the comparison.

8. An embankment monitoring device as described in claim 6, wherein the embankment candidate area extraction unit calculates the area of ​​the embankment candidate area based on the position coordinates of the embankment candidate area, and further extracts the scale of the embankment in the embankment candidate area based on the amount of embankment for each position coordinate of the embankment candidate area and the area of ​​the embankment candidate area.

9. An embankment monitoring device as described in claim 2, wherein the embankment candidate area extraction unit determines an area in the deforestation area where the amount of elevation change for each position coordinate is equal to or greater than a predetermined threshold as the embankment candidate area.

10. A computer acquires a first optical image of the earth's surface in an observation area measured by an optical sensor during a first period and a second optical image measured during a second period after the first period, generates a first NDVI image from the first optical image, generates a second NDVI image from the second optical image, compares the first NDVI image with the second NDVI image, extracts an NDVI change area in the compared images where the NDVI value has changed, and extracts the position coordinates of the NDVI change area, acquires a first SAR image of the earth's surface in the observation area measured by SAR during the first period and a second SAR image measured during the second period, an embankment monitoring method comprising: generating a first reflection intensity image from the first SAR image; generating a second reflection intensity image from the second SAR image; comparing the first reflection intensity image with the second reflection intensity image; extracting a reflection intensity change region, which is a region where reflection intensity has changed in the compared images; extracting position coordinates of the reflection intensity change region; comparing the position coordinates of the NDVI change region with the position coordinates of the reflection intensity change region; extracting position coordinates of a deforestation region, which is a region in the observation area where forests have been cut down between the first period and the second period, based on the result of the comparison; and extracting position coordinates of an embankment candidate region, which is a candidate region for an embankment newly constructed in the observation area between the first period and the second period, based on the position coordinates of the deforestation region.

11. Obtaining a first optical image of the earth's surface in an observation area measured by an optical sensor in a first period and a second optical image measured in a second period after the first period, generating a first NDVI image from the first optical image, generating a second NDVI image from the second optical image, comparing the first NDVI image with the second NDVI image, extracting an NDVI change area in the compared images where the NDVI value has changed, and extracting the position coordinates of the NDVI change area, obtaining a first SAR image of the earth's surface in the observation area measured by SAR in the first period and a second SAR image measured in the second period, A program that causes a computer to execute processes to generate a first reflection intensity image from the first SAR image, generate a second reflection intensity image from the second SAR image, compare the first reflection intensity image with the second reflection intensity image, extract a reflection intensity change region, which is a region where reflection intensity has changed in the compared images, and extract position coordinates of the reflection intensity change region, compare the position coordinates of the NDVI change region with the position coordinates of the reflection intensity change region, and extract position coordinates of a deforestation region, which is a region in the observation area where forests have been cut down between the first period and the second period, based on the position coordinates of the deforestation region, and extract position coordinates of an embankment candidate region, which is a candidate region for new embankment construction in the observation area between the first period and the second period, based on the position coordinates of the deforestation region.

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