Radar image display control device and radar image display control method

Abstract

This radar image display control device comprises: a luminance difference calculation unit (13) that compares radar images of two periods in pixel units to generate a luminance difference image indicating a luminance difference in each pixel; a coherence calculation unit (14) that compares the radar images of the two periods in pixel units to generate a correlation image indicating coherence; an artificial object extraction unit (15) that generates an artificial object image on the basis of geographical information of a target region; a synthesis processing unit (16) that allocates a color element corresponding to the luminance difference to each pixel of the luminance difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of an artificial object to each pixel of the artificial object image such that the color elements become different from one another, thereby generating a synthetic image; and a display control unit (17) that, on the basis of the synthetic image, causes change information to be displayed in a form that enables the identification of the presence or absence of the luminance difference, the level of the coherence, and the presence of the artificial object.

Description

Radar image display control device and radar image display control method

[0001] The present disclosure relates to a radar image display control device and a radar image display control method.

[0002] Conventionally, there has been known a technique for observing changes in land or buildings that are an observation target based on radar images obtained from a radar device. For example, Patent Document 1 discloses a technique for calculating a plurality of characteristic values ​​that represent the state of the ground surface that is the observation target from a plurality of radar image data of the same observation target acquired at different times, extracting a change candidate region for each calculated characteristic value, and extracting a change region of the observation target from the change candidate region using a threshold, an extraction condition, and a discriminant function.

[0003] Japanese Patent Application Laid-Open No. 2008-46107

[0004] For example, in the event of a disaster occurring at an observed object, it would be useful to have a technology that can estimate the basis for changes, such as the circumstances under which the observed object changed or did not change. By estimating the basis for changes, such as the circumstances under which the observed object changed or did not change, a user can determine, for example, whether or not relief is required. However, there has been a problem in that such technology has not been provided. For example, the conventional technology disclosed in Patent Document 1 extracts areas of change in the observed object, but does not enable users to understand the circumstances under which an observed object, including areas without change, changed or did not change. Therefore, such conventional technology does not allow users to estimate the basis for the changes, and the above-mentioned problem cannot be solved.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to enable a user to be provided with information indicating whether or not there has been a change in the object of observation in a manner that allows the basis for that information to be estimated.

[0006] The radar image display control device disclosed herein includes a brightness difference calculation unit that compares radar images taken at two different times in a time series of radar images of a target area including an observation target on a pixel-by-pixel basis to generate a brightness difference image that shows the brightness difference at each pixel; a coherence calculation unit that compares the radar images taken at two different times in a time series of radar images of a target area including an observation target on a pixel-by-pixel basis to generate a correlation image that shows the coherence that represents the correlation between each pixel; an artifact extraction unit that generates an artifact image that shows artifacts present in the target area based on geographic information of the target area; a synthesis processing unit that assigns a color element corresponding to the brightness difference to each pixel of the brightness difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of an artifact to each pixel of the artifact image, so that they become different color elements, and generates a synthesized image by combining the brightness difference image, the correlation image, and the artifact image after the color elements have been assigned; and a display control unit that displays change information that shows the presence or absence of a change in the observation target based on the synthesized image in a form that shows the presence or absence of a brightness difference between the radar images taken at two different times, the level of coherence, and the presence of an artifact.

[0007] According to the present disclosure, the radar image display control device is configured as described above, and therefore can provide the user with information indicating whether or not there is a change in the observed object in a manner that allows the user to estimate the basis for that information.

[0008] 2A shows an example of a configuration of a radar image display control device according to embodiment 1. FIG. 2B is a diagram for explaining an example of a color-assigned luminance difference image, a color-assigned correlation image, or a color-assigned artifact image after a color element assignment unit has performed color element assignment processing in embodiment 1, where FIG. 2A shows an example of a color-assigned luminance difference image, FIG. 2B shows an example of a color-assigned artifact image, and FIG. 2C shows an example of a color-assigned correlation image. FIG. 2A is a diagram for explaining an example of a composite image generated by a composition unit performing image composition processing in embodiment 1. In embodiment 1, this is an example of a screen displayed on a display device by a display control unit based on the composite image shown in FIG. 3. In embodiment 1, when the display control unit has a function of performing grounds estimation processing, this is a diagram showing an example of content of grounds estimation condition information that the display control unit refers to in the grounds estimation processing. FIG. 2C is a flowchart for explaining the operation of the radar image display control device according to embodiment 1. 7A and 7B are diagrams illustrating a display screen in a case where an image showing a changed area of ​​an observation target is displayed based on radar images taken at two time points, before and after a disaster, in a conventional technology, where Fig. 7A shows an example of a radar image taken after a disaster has occurred, in which an image of a target area including the observation target has been captured, and Fig. 7B shows an example of an image displayed using conventional technology showing a changed area of ​​the observation target that has changed due to the occurrence of a disaster. Figs. 8A and 8B are diagrams illustrating an example of a hardware configuration of a radar image display control device according to embodiment 1.

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0010] Embodiment 1. Fig. 1 is a diagram showing an example of the configuration of a radar image display control device 1 according to embodiment 1. As shown in Fig. 1, the radar image display control device 1 is connected to a radar image storage device 3, a geographic information storage device 4, and a display device 5 via a network.

[0011] The radar device 2 observes the situation of an area including an observation target (hereinafter referred to as the "target area") and stores radar images showing the observed situation in a radar image storage device 3 in chronological order. In the first embodiment, the observation target is assumed to be land or a building. The radar device 2 is assumed to be, for example, a synthetic aperture radar (SAR), which is a known sensor that measures the reflection of microwave pulses emitted from an artificial satellite or the like on the Earth's surface. The radar image storage device 3 is connected to the radar device 2 and stores radar images of the target area captured by the radar device 2 in chronological order. Note that the radar images are provided with information indicating the date and time when the radar images were captured.

[0012] The geographic information storage device 4 stores geographic information about specific locations or regions on Earth, including geographic information about observation targets. Geographic information is any information related to geographic locations, such as information on a map that shows the location of a specific location, region, or building, etc., and its associated attributes (e.g., whether it is an artificial object or a natural object). The geographic information stored in the geographic information storage device 4 is obtained, for example, from a GIS (Geographic Information System) provided by the Geospatial Information Authority of Japan.

[0013] The radar image display control device 1 displays, on the display device 5, information indicating whether or not there has been a change in the radar images between the two periods (hereinafter referred to as "change information") based on the radar images at two different times among the time-series radar images of the observation target captured by the radar device 2 and geographic information, as information indicating a change that has occurred in the observation target, in a manner that enables estimation of the basis of the change, such as under what circumstances the observation target has changed, how it has changed, or whether it has not changed. In the first embodiment, the radar images from the two periods are referred to as the first radar image and the second radar image, respectively. The first radar image is a radar image captured earlier than the second radar image.

[0014] The display device 5 is provided in, for example, a personal computer (PC) or a mobile terminal such as a tablet terminal. The PC or mobile terminal is provided in a workroom or the like where the user works, or is held by the user. For example, the user operates an input device (not shown) to instruct the radar image display control device 1 to display the change information from the PC or mobile terminal, etc., and causes the display device 5 to display the change information.

[0015] In the following first embodiment, as an example, the radar images from the two periods are radar images taken before and after a disaster occurs in a target area including the observation target. That is, based on two radar images taken at two periods, namely, a first radar image taken of the target area before the disaster occurs and a second radar image taken of the target area after the disaster occurs, among the time-series radar images of the target area taken by the radar device 2, the radar image display control device 1 displays change information indicating whether or not there has been a change in the radar images between the two periods on the display device 5 as information indicating changes in the observation target before and after the disaster occurs in the target area, in a manner that allows estimation of the basis for the changes, such as the situation and how the observation target changed or did not change. A detailed configuration example of the radar image display control device 1 will be described later. Also, an example of a screen on which the radar image display control device 1 displays change information on the display device 5 will be described later.

[0016] 1, the radar image display control device 1 acquires radar images from the radar device 2 via the radar image storage device 3, but this is merely an example. For example, the radar image display control device 1 may be connected to the radar device 2 and acquire radar images directly from the radar device 2. For example, the radar image storage device 3 may be included in the radar image display control device 1. Furthermore, for example, the geographic information storage device 4 may be included in the radar image display control device 1. The radar image display control device 1, the radar device 2, the radar image storage device 3, the geographic information storage device 4, and the display device 5 constitute a radar image display control system.

[0017] An example configuration of a radar image display control device 1 according to embodiment 1 will now be described. The radar image display control device 1 according to embodiment 1 is provided, for example, in a workroom where a user works, or in a PC or a mobile terminal carried by the user. As shown in Fig. 1 , the radar image display control device 1 includes a radar image acquisition unit 11, a geographic information acquisition unit 12, a brightness difference calculation unit 13, a coherence calculation unit 14, an artifact extraction unit 15, a synthesis processing unit 16, and a display control unit 17. The synthesis processing unit 16 includes a color element assignment unit 161 and a synthesis unit 162.

[0018] The radar image acquisition unit 11 acquires, from the radar image storage device 3, radar images at two periods, which are a first radar image and a second radar image captured at different times from a time series of radar images of a target area including an observation target captured by the radar device 2. Here, the radar image acquisition unit 11 acquires, from the radar image storage device 3, radar images at two periods, which are a first radar image and a second radar image captured before and after a disaster occurs in a target area including an observation target.

[0019] For example, the user operates the input device to specify the first radar image and the second radar image. Specifically, the user operates the input device to call up an input screen on the display device 5 for inputting the date and time when the first radar image was captured (hereinafter referred to as the “first date and time”) and the date and time when the second radar image was captured (hereinafter referred to as the “second date and time”), and inputs the first date and time and the second date and time from the called up input screen. In the radar image storage device 3, the radar image acquisition unit 11 accepts information indicating the first date and time and the second date and time input by the user (hereinafter referred to as “date and time designation information”), and acquires radar images captured at the dates and times designated by the accepted date and time designation information from the radar image storage device 3 as radar images for two periods. The radar image acquisition unit 11 can identify the radar images for the two periods to be acquired by comparing the dates and times designated by the date and time designation information with the dates and times assigned to the radar images stored in the radar image storage device 3.

[0020] The radar image acquisition unit 11 outputs the acquired radar images at two times, in other words, the first radar image and the second radar image, to the brightness difference calculation unit 13 and the coherence calculation unit 14 .

[0021] The geographic information acquisition unit 12 acquires geographic information of the target area from the geographic information storage device 4. The geographic information acquisition unit 12 outputs the acquired geographic information to the artificial object extraction unit 15.

[0022] The brightness difference calculation unit 13 compares the radar images acquired by the radar image acquisition unit 11 at two times, i.e., the first radar image and the second radar image, on a pixel-by-pixel basis to generate an image showing the brightness difference at each pixel (hereinafter referred to as a "brightness difference image"). For example, the brightness difference calculation unit 13 calculates the brightness difference for each corresponding pixel of the first radar image and each corresponding pixel of the second radar image using the following equation (1). In the first embodiment, when a pixel (referred to as a first pixel) on the first radar image and a pixel (referred to as a second pixel) on the second radar image are pixels located at the same position on the radar image (first radar image or second radar image), it is said that "the first pixel and the second pixel correspond to each other." Note that the pixel value of each pixel of the radar image captured by the radar device 2 is a complex number. ΔS = ||S １ |-|S ２ || ... (1) ΔS: luminance difference S １ = pixel value of each pixel on the first radar image S ２ = pixel value of each pixel on the second radar image

[0023] After calculating the brightness difference between each corresponding pixel, the brightness difference calculation unit 13 generates a brightness difference image indicating the calculated brightness difference. The brightness difference image is, for example, an image in which a value indicating the calculated brightness difference between a pixel on the first radar image and a pixel on the second radar image (hereinafter referred to as a "brightness difference value") is substituted for each pixel on the radar image. The brightness difference calculation unit 13 sets the brightness difference value in accordance with, for example, the following brightness difference value setting conditions. The brightness difference value setting conditions are set in advance by a developer or the like, and information indicating the brightness difference value setting conditions (hereinafter referred to as "brightness difference value setting condition information") is stored in an internal buffer or the like of the brightness difference calculation unit 13. The brightness difference value setting conditions may be updated as needed by a user or the like. Note that, in the following brightness difference value setting conditions, "first brightness difference determination threshold value<second brightness difference determination threshold value" is satisfied. The developer or the like sets a first luminance difference determination threshold value and a second luminance difference determination threshold value, and stores them together with the luminance difference value setting condition information in an internal buffer or the like of the luminance difference calculation unit 13. The luminance difference calculation unit 13 references the luminance difference value setting condition information and sets a luminance difference value for each pixel on the luminance difference image in accordance with the luminance difference value setting conditions.

[0024] <Conditions for Setting the Brightness Difference Value> If the brightness difference is equal to or less than the first brightness difference determination threshold, the brightness difference value is set to 0. If the brightness difference is equal to or greater than the second brightness difference determination threshold, the brightness difference value is set to 1. If the brightness difference is greater than the first brightness difference determination threshold but less than the second brightness difference determination threshold, the brightness difference value is set to a value between 0 and 1 according to the brightness difference, with the value approaching 1 as the brightness difference increases.

[0025] After generating the brightness difference image, the brightness difference calculation unit 13 outputs the generated brightness difference image to the synthesis processing unit 16 .

[0026] The coherence calculation unit 14 compares the radar images acquired by the radar image acquisition unit 11 at two different times, i.e., the first radar image and the second radar image, on a pixel-by-pixel basis to generate an image showing coherence representing the correlation between each pixel (hereinafter referred to as a "correlation image"). For example, the coherence calculation unit 14 calculates the coherence for each corresponding pixel of the first radar image and each corresponding pixel of the second radar image using the following equation (2). Note that in the first embodiment, the correlation between each pixel represented by the coherence is assumed to be the similarity of the complex values ​​of the pixel values ​​of each pixel. Coherence is expressed as a numerical value between 0 and 1. The higher the coherence, i.e., the closer the coherence is to 1, the more similar the pixels are. C: Coherence S １ = pixel value of each pixel on the first radar image S ２ = pixel value of each pixel on the second radar image

[0027] The coherence calculation unit 14 calculates the coherence of each corresponding pixel and generates a correlation image indicating the calculated coherence. The correlation image is, for example, an image in which the pixel value of each pixel on the radar image is substituted with the calculated coherence between the pixel on the first radar image and the pixel on the second radar image.

[0028] After generating the correlation image, the coherence calculation unit 14 outputs the generated correlation image to the synthesis processing unit 16 .

[0029] In the first embodiment, the brightness difference calculation unit 13 and the coherence calculation unit 14 may each have the functions of the radar image acquisition unit 11. In this case, the radar image display control device 1 may be configured without the radar image acquisition unit 11.

[0030] The artifact extraction unit 15 generates an image (hereinafter referred to as an "artifact image") showing artifacts present in the target area based on the geographic information of the target area acquired by the geographic information acquisition unit 12. More specifically, the artifact extraction unit 15 extracts artifacts present in the target area based on the geographic information and generates an artifact image showing the extracted artifacts. The artifact image is an image in which, for each pixel on the radar image, a value indicating the presence of an artifact is assigned to the pixel value of pixels included in an area where an artifact is present (hereinafter referred to as an "artifact area pixel"), and a value indicating the presence of a natural object is assigned to the pixel value of pixels included in an area where an artifact is not present, in other words, an area where a natural object is present (hereinafter referred to as a "natural object area pixel"). The artifact extraction unit 15 generates the artifact image by setting the pixel value of the artifact area pixel to "1" and the pixel value of the natural object area pixel to "0". The artificial object image is an image in which the pixel value of each pixel on the radar image is assigned "1" if it is a pixel in an artificial object area, or "0" if it is a pixel in a natural object area.

[0031] After generating the artifact image, the artifact extraction unit 15 outputs the generated artifact image to the synthesis processing unit 16 .

[0032] In the first embodiment, the artificial object extraction unit 15 may have the function of the geographic information acquisition unit 12. In this case, the radar image display control device 1 may be configured without the geographic information acquisition unit 12.

[0033] The synthesis processing unit 16 performs a color element assignment process in which a color element corresponding to the luminance difference (hereinafter referred to as a "luminance difference color element") is assigned to each pixel of the luminance difference image output from the luminance difference calculation unit 13, a color element corresponding to the coherence (hereinafter referred to as a "correlated color element") is assigned to each pixel of the correlation image output from the coherence calculation unit 14, and a color element corresponding to the presence or absence of an artifact (hereinafter referred to as an "artifact color element") is assigned to each pixel of the artifact image output from the artifact extraction unit 15. In the color element assignment process, the synthesis processing unit 16 assigns the luminance difference color element, the correlation color element, and the artifact color element to be mutually different color elements. Then, the synthesis processing unit 16 performs an image synthesis process in which the luminance difference image to which the color elements have been assigned in the color element assignment process (hereinafter referred to as a "color-assigned luminance difference image"), the correlation image (hereinafter referred to as a "color-assigned correlation image"), and the artifact image (hereinafter referred to as a "color-assigned artifact image") are RGB-combined to generate a composite image. In the composition processing unit 16, a color element allocation unit 161 performs the color element allocation process. In the composition processing unit 16, a composition unit 162 performs the image composition process.

[0034] The color element allocation process performed by the color element allocation unit 161 will be described in detail with reference to an example. The color element allocation unit 161 allocates color elements to the luminance difference image, correlation image, and artifact image, respectively, in accordance with color allocation conditions. The color allocation conditions define which color elements are to be allocated in accordance with the luminance difference in the luminance difference image, which color elements are to be allocated in accordance with the coherence in the correlation image, and which color elements are to be allocated to the area containing the artifact in the artifact image. The color allocation conditions are set in advance by, for example, a developer, and information indicating the color allocation conditions (hereinafter referred to as "color allocation condition information") is stored in an internal buffer or the like of the color element allocation unit 161. Note that this is merely an example, and the color allocation conditions may be set by the user. For example, the user may operate an input device to call up an input screen for inputting the color allocation conditions on the display device 5, and input the color allocation conditions from the called input screen. In the radar image storage device 3, the color element allocation unit 161 accepts color allocation condition information indicating color allocation conditions input by the user, stores the accepted color allocation condition information in an internal buffer or the like, and performs color allocation processing in accordance with the color allocation condition information. The color allocation conditions may be updated by the user or the like as appropriate.

[0035] For example, suppose the color assignment conditions are set such that a blue color element is assigned in accordance with the luminance difference in the luminance difference image, a green color element is assigned in accordance with the coherence in the correlation image, and a red color element is assigned to an area where an artifact is present in the artifact image. In this case, the color element assignment unit 161 assigns a blue color element in accordance with the luminance difference to each pixel in the luminance difference image, a green color element in accordance with the coherence to each pixel in the correlation image, and a red color element in accordance with the presence or absence of an artifact to each pixel in the artifact image. The color element assignment unit 161 assigns the above color elements using, for example, an RGB color model in which the color of each pixel is represented by three components: red, green, and blue. Each component is specified in the range of 0 to 255, with the RGB value representing perfect red being (255,0,0), the RGB value representing perfect green being (0,255,0), and the RGB value representing perfect blue being (0,0,255).

[0036] For example, the color element assignment unit 161 assigns a blue color element to pixels in the brightness difference image whose assigned brightness difference value is closer to 1, in other words, whose pixels are determined to have a larger brightness difference between the first radar image and the second radar image, such that the blue becomes darker. That is, when a brightness difference value assigned to a pixel in the brightness difference image is 1, the pixel is assigned an RGB value of (0, 0, 255) representing a perfect blue. For example, the color element assignment unit 161 assigns a green color element to pixels in the correlation image whose assigned pixel value is closer to 1, in other words, whose pixel has a higher coherence between the first radar image and the second radar image, such that the pixel becomes darker green. That is, when a pixel value assigned to a pixel in the correlation image is 1, the pixel is assigned an RGB value of (0, 255, 0) representing a perfect green. For example, the color component assignment unit 161 assigns a completely red color component of (255, 0, 0) to pixels in the artificial object image that have a pixel value of 1 assigned to them, in other words, to pixels in the artificial object region. Note that the color component assignment unit 161 assigns a completely black color component of (0, 0, 0) to pixels in the artificial object image that have a pixel value of 0 assigned to them, in other words, pixels in the natural object region.

[0037] FIG. 2 is a diagram illustrating an example of a color-assigned luminance difference image, a color-assigned correlation image, or a color-assigned artifact image after the color element assignment unit 161 has performed a color element assignment process in Embodiment 1. FIG. 2A shows an example of a color-assigned luminance difference image (denoted by "Im1"), FIG. 2B shows an example of a color-assigned artifact image (denoted by "Im2"), and FIG. 2C shows an example of a color-assigned correlation image (denoted by "Im3"). Note that FIG. 2 illustrates a color-assigned luminance difference image, a color-assigned correlation image, or a color-assigned artifact image in a case where the color assignment conditions are set to assign a blue color element in accordance with the luminance difference in the luminance difference image, a green color element in accordance with the coherence in the correlation image, and a red color element to an area where an artifact is present in the artifact image. In addition, in FIG. 2, for convenience, differences in the colors blue, red, green, and black are expressed by different patterns on the drawing, and words indicating each color are illustrated on the areas of each color.

[0038] As shown in FIG. 2A , the region in the color-assigned luminance difference image to which a blue color element is assigned (the region indicated by "R1") is a region that includes pixels in the luminance difference image whose pixel values ​​are set to 1 or values ​​close to 1. For convenience, in FIG. 2A , each pixel in the color-assigned luminance difference image is assumed to be assigned either a completely blue color element or a completely black color element. In reality, each pixel in the color-assigned luminance difference image may be assigned an RGB value (RGB values ​​(0,0,0) to (0,0,255)) that represents a color element corresponding to the pixel value of each pixel in the luminance difference image, ranging from 0 to 1, such as completely blue, dark blue, light blue, light black, or completely black. The color-assigned luminance difference image is an image that represents the luminance difference between each pixel in the first radar image and each pixel in the second radar image using colors. A pixel in the color-assigned luminance difference image that is assigned a color element closer to completely blue indicates a larger luminance difference between the first radar image and the second radar image.

[0039] Note that, although the above-described conditions are set as the brightness difference value setting conditions here, this is merely an example. For example, the brightness difference value setting conditions may be set as follows: "When the brightness difference is less than the third brightness difference determination threshold, the brightness difference value is set to 0; when the brightness difference is equal to or greater than the third brightness difference determination threshold, the brightness difference value is set to 1." In this case, the brightness difference calculation unit 13 assigns a value of 1 or 0 to the pixel value of each pixel on the brightness difference image. As a result, the color element assignment unit 161 generates a color-assigned brightness difference image, as shown in FIG. 2A , in which the brightness difference between each pixel on the first radar image and each pixel on the second radar image is represented by color, using either completely blue or completely black.

[0040] As shown in FIG. 2C , the region in the color-assigned correlation image to which a green color component is assigned (the region indicated by "R3") is a region that includes pixels in the correlation image whose pixel values ​​are set to 1 or values ​​close to 1. For convenience, in FIG. 2C , each pixel in the color-assigned correlation image is assumed to be assigned either a completely green color component or a completely black color component. In reality, each pixel in the color-assigned correlation image may be assigned an RGB value (RGB values ​​(0,0,0) to (0,255,0)) that represents a color component corresponding to the pixel value of each pixel in the correlation image, ranging from 0 to 1, such as completely green, dark green, light green, light black, or completely black. The color-assigned correlation image is an image that represents the coherence between each pixel in the first radar image and each pixel in the second radar image using color. Pixels in the color-assigned correlation image that are assigned a color component closer to completely green have higher coherence between the first radar image and the second radar image.

[0041] Note that, although it is assumed here that the coherence calculation unit 14 assigns a value between 0 and 1 to the pixel value of each pixel on the correlation image depending on the coherence, this is merely an example. For example, the coherence calculation unit 14 may set the coherence to be assigned to the correlation image (hereinafter referred to as the "assigned coherence") in accordance with a coherence setting condition such as the following <Coherence Setting Condition (1)> or <Coherence Setting Condition (2)>. The coherence setting condition is set in advance by a developer or the like, and information indicating the coherence setting condition (hereinafter referred to as the "coherence setting condition information") is stored in a buffer or the like within the coherence calculation unit 14. The coherence setting condition may be updateable as needed by a user or the like. The coherence calculation unit 14 references the coherence setting condition information and sets the assigned coherence for each pixel on the correlation image in accordance with the coherence setting condition.

[0042] <Condition (1) for setting coherence> If the coherence is equal to or less than the first coherence determination threshold, the assigned coherence is set to 0. If the coherence is equal to or greater than the second coherence determination threshold, the assigned coherence is set to 1. If the coherence is greater than the first coherence determination threshold and less than the second coherence determination threshold, the calculated coherence is set to the assigned coherence.

[0043] <Condition for setting coherence (2)> If the coherence is less than the third coherence determination threshold, the assigned coherence is set to 0, and if the coherence is equal to or greater than the third coherence determination threshold, the assigned coherence is set to 1.

[0044] For example, when the assigned coherence for each pixel on the correlation image is set in accordance with the above <Condition for Coherence Setting (2)>, the coherence calculation unit 14 assigns a value of 1 or 0 to the pixel value of each pixel on the correlation image. As a result, the color element assignment unit 161 generates a color-assigned correlation image, as shown in Fig. 2C, in which the coherence of each pixel on the first radar image and each pixel on the second radar image is represented by color using either completely green or completely black.

[0045] As shown in FIG. 2B , the region on the color-assigned artifact image to which a red color component is assigned (the region indicated by "R2") is a region on the artifact image that includes pixels whose pixel value is set to 1. Each pixel on the color-assigned artifact image is assigned either a completely red color component or a completely black color component. The color-assigned artifact image is an image in which each pixel in an area on the radar image where an artifact exists is represented by color, and pixels on the color-assigned artifact image that are assigned a completely red color component are pixels included in an area where an artifact exists.

[0046] The color element assignment unit 161 performs the color assignment process described above, and outputs the color-assigned luminance difference image, color-assigned correlation image, and color-assigned artifact image generated by the color assignment process to the composition unit 162 .

[0047] The image synthesis process performed by the synthesis unit 162 will be described in detail using an example. FIG. 3 is a diagram illustrating an example of a synthesized image generated by the synthesis unit 162 performing the image synthesis process in the first embodiment. FIG. 3 shows a synthesized image (indicated by "SIm") obtained by the synthesis unit 162 performing RGB synthesis of the color-assigned luminance difference image shown in FIG. 2A , the color-assigned correlation image shown in FIG. 2C , and the color-assigned artifact image shown in FIG. 2B . As a result of the synthesis unit 162 performing RGB synthesis of the color-assigned luminance difference image shown in FIG. 2A , the color-assigned correlation image shown in FIG. 2C , and the color-assigned artifact image shown in FIG. 2B , a synthesized image is generated in which the area indicated by "S1" is blue, the area indicated by "S2" is yellow, the area indicated by "S3" is red, the area indicated by "S4" is magenta, and the area indicated by "S5" is black, as shown in FIG. 3 . In FIG. 3, for convenience, differences in the colors blue, yellow, red, magenta, and black are represented by different patterns on the drawing, and words indicating each color are illustrated above the areas of each color.

[0048] The area indicated by "S1" is an area made up of pixels represented by blue color elements (RGB values ​​(0,0,255)), and therefore has a difference in brightness between the radar images from the two periods, low coherence, and is an area where natural objects exist. The area indicated by "S2" is an area made up of pixels represented by yellow color elements (RGB values ​​(255,255,0)), and therefore has no difference in brightness between the radar images from the two periods, high coherence, and is an area where artificial objects exist. The area indicated by "S3" is an area made up of pixels represented by red color elements (RGB values ​​(255,0,0)), and therefore has no difference in brightness between the radar images from the two periods, low coherence, and is an area where artificial objects exist. The area indicated by "S4" is made up of pixels represented by magenta color elements (RGB values ​​(255,0,255)), and therefore has a difference in brightness between the radar images from the two periods, low coherence, and is an area where artificial objects exist. The area indicated by "S5" is made up of pixels represented by black color elements (RGB values ​​(0,0,0)), and therefore has no difference in brightness between the radar images from the two periods, low coherence, and is an area where natural objects exist.

[0049] 2A and 2C, color elements ranging from completely blue to completely black according to the luminance difference value and color elements ranging from completely red to completely black according to the coherence can be assigned, respectively. Therefore, in the composite image shown in FIG. 3, each pixel can be represented by the color of a color element according to the RGB value obtained by RGB composition.

[0050] The synthesis unit 162 outputs the synthesized image generated by the image synthesis process to the display control unit 17 .

[0051] The display control unit 17 displays, on the display device 5, change information indicating whether or not there is a change in the observed object, in a form that indicates whether or not there is a difference in brightness between the radar images at two times, the level of coherence, and the presence of artificial objects, based on the composite image output from the synthesis processing unit 16, more specifically, the synthesis unit 162 of the synthesis processing unit 16.

[0052] More specifically, the display control unit 17, for example, causes the display device 5 to display, as change information, information indicating which of the following first to eighth regions the region is, how the luminance difference and coherence of the radar images at two time points have changed for each of the first to eighth regions, and whether an artificial object is present in the region, based on the composite image. The display control unit 17 can determine the following first to eighth regions from the color elements of each pixel in the composite image. Region 1: A region where there is a luminance difference, high coherence, and an artificial object is present. Region 2: A region where there is a luminance difference, high coherence, and no artificial object is present. Region 3: A region where there is a luminance difference, low coherence, and an artificial object is present. Region 4: A region where there is a luminance difference, low coherence, and no artificial object is present. Region 5: A region where there is no luminance difference, high coherence, and an artificial object is present. Region 6: Region with no luminance difference, high coherence, and no artifacts. Region 7: Region with no luminance difference, low coherence, and artifacts. Region 8: Region with no luminance difference, low coherence, and artifacts.

[0053] 4 is a diagram showing an example of a screen that the display control unit 17 displays on the display device 5 in Embodiment 1. For example, as shown in FIG. 4 , the display control unit 17 causes the display device 5 to display an image (hereinafter referred to as a "region image") in which the target region is divided into any of the first to eighth regions, and a message indicating whether each region is a region with a luminance difference, high coherence, and an artifact, a region with a luminance difference, high coherence, and no artifact, a region with a luminance difference, low coherence, and an artifact, a region with a luminance difference, low coherence, and no artifact, a region with no luminance difference, high coherence, and an artifact, a region with no luminance difference, high coherence, and no artifact, a region with no luminance difference, high coherence, and no artifact, a region with no luminance difference, low coherence, and no artifact.

[0054] FIG. 4 shows an example of a screen displayed by the display control unit 17 on the display device 5 based on the composite image shown in FIG. 3 in the first embodiment. For example, based on the composite image shown in FIG. 3, the display control unit 17 can determine which region in the target region corresponds to which of the first to eighth regions, from the color elements of each pixel in the composite image. The composition processing unit 16 outputs, together with the composite image, information indicating which color element is assigned to each pixel in the composite image according to the luminance difference, which color element is assigned according to the coherence, and which color element is assigned to a region containing an artificial object (hereinafter referred to as "color assignment information"). The composition processing unit 16 may also output color assignment condition information to the display control unit 17 along with the composite image. Based on the color allocation information or color allocation condition information, the display control unit 17 can determine which color is assigned to which color element of each pixel on the composite image, and can determine which area in the target area corresponds to which of the first to eighth areas from the color elements of each pixel in the composite image.

[0055] For example, in the composite image shown in FIG. 3 , the display control unit 17 determines the region indicated by “S1” as a fourth region where there is a difference in brightness between the radar images at two time points, the coherence is low, and no artificial objects are present, in other words, a region where natural objects are present, because the region indicated by “S1” is a region made up of pixels represented by blue color elements. The display control unit 17 also determines the region indicated by “S2” as a fifth region where there is no difference in brightness between the radar images at two time points, the coherence is high, and an artificial object is present, because the region indicated by “S2” is a region made up of pixels represented by yellow color elements. The display control unit 17 also determines the region indicated by “S3” as a seventh region where there is no difference in brightness between the radar images at two time points, the coherence is low, and an artificial object is present, because the region indicated by “S3” is a region made up of pixels represented by red color elements. The display control unit 17 also determines that the area indicated by "S4" is a third area where there is a difference in brightness between the radar images taken at two different times, the coherence is low, and an artificial object exists, because the area is an area made up of pixels represented by magenta color elements.The display control unit 17 also determines that the area indicated by "S5" is an eighth area where there is no difference in brightness between the radar images taken at two different times, the coherence is low, and an artificial object exists, because the area is an area made up of pixels represented by black color elements.

[0056] The display control unit 17 then divides the target region into a fourth region, a fifth region, a seventh region, a third region, and an eighth region, and displays a region image on the display device 5, in which each region is displayed in a different color. Here, as shown in FIG. 4 , the display control unit 17 displays the fourth region, the fifth region, the seventh region, the third region, or the eighth region in blue, yellow, red, magenta, or black, respectively, which are colors indicated by the color elements of each pixel included in each region in the composite image. However, for convenience, in FIG. 4 , the differences in color (blue, yellow, red, magenta, or black) are represented by different patterns on the diagram, and words indicating each color are illustrated on the region of each color. On the screen displayed on the display device 5, the fourth region, the fifth region, the seventh region, the third region, or the eighth region are displayed in blue, yellow, red, magenta, or black, respectively, without displaying words indicating each color. This is merely an example, and the display control unit 17 may display the fourth, fifth, seventh, third, or eighth region in a color different from the color indicated by the color element of each pixel included in each region in the composite image. It is sufficient that the fourth, fifth, seventh, third, and eighth regions are displayed in colors different from each other.

[0057] Furthermore, as shown in FIG. 4 , the display control unit 17 causes the display device 5 to display, together with the region image, the following phrases: "luminance change and natural object area" describing the first region; "high coherence and artificial object area" describing the second region; "no luminance change, low coherence and artificial object area" describing the third region; "luminance change, low coherence and artificial object area" describing the fourth region; and "no luminance change and natural object area" describing the fifth region. The display control unit 17 may determine the phrases to be displayed corresponding to each region on the region image in accordance with, for example, the phrase setting conditions. The phrase setting conditions define which phrases should be set to describe each of the first to eighth regions. The phrase setting conditions are set in advance by a developer or the like, and information indicating the phrase setting conditions (hereinafter referred to as "phrase setting condition information") is stored in a buffer or the like within the display control unit 17. The wording setting conditions may be updated by the user or the like as needed.

[0058] As described above, in a composite image, each pixel may actually be represented by the color of a color element corresponding to the RGB value obtained by RGB composition. Therefore, it is not possible to directly use the color elements corresponding to the RGB values ​​of each pixel in the composite image to classify the image into five colors: completely blue (RGB value (0,0,255)), completely yellow (RGB value (255,255,0)), completely red (RGB value (255,0,0)), completely magenta (RGB value (255,0,255)), or completely black (RGB value (0,0,0)). In this case, the display control unit 17 may, for example, set thresholds for the RGB values ​​indicating the color elements and determine the RGB values ​​of the color elements that are considered to be completely blue, completely yellow, completely red, completely magenta, or completely black, thereby classifying the image into the first to eighth regions.

[0059] 4 is merely an example, and other screens may be displayed. For example, the display control unit 17 may cause the display device 5 to display a screen in which only area images showing the first to eighth areas in different colors are displayed as change information, without any description of each area. Alternatively, the display device 5 may display a screen in which the area images are images in which the areas are separated without color coding, and the area images and description of each area are displayed as change information. Furthermore, for example, the display control unit 17 may use a composite image as change information and cause the display device 5 to display a screen on which the composite image is displayed. Furthermore, for example, the display control unit 17 may use a composite image and description of the first, second, third, fourth, fifth, sixth, seventh, or eighth area on the composite image as change information, and cause the display device 5 to display a screen on which the change information is displayed.

[0060] The display control unit 17 may be configured to display on the display device 5 change information indicating whether or not there is a change in the observed object in a form that indicates whether or not there is a difference in brightness between the radar images at two different times, the level of coherence, and the presence of artificial objects.

[0061] The display device 5 displays the change information under the control of the display control unit 17. By looking at the screen displayed by the display device 5, the user can infer the basis for the change in the observation target from the change information displayed on the screen.

[0062] For example, if the display device 5 displays a screen such as that shown in Fig. 4, the user can infer that the area corresponding to the fourth area (the area shown in blue in Fig. 4) has a brightness change (i.e., a brightness difference), is a natural object area, and has low coherence, and therefore that this area is an area where a disaster occurred in an environment where there are no artificial objects, and where human damage due to collapses, etc. is expected to be small, but where changes have occurred in natural objects, and therefore is an area where natural objects have been damaged. Note that, in general, changes in natural objects on radar images can be easily seen from the brightness difference in radar images taken at two different times, and changes in artificial objects on radar images can be easily seen from the coherence in radar images taken at two different times.

[0063] Furthermore, for example, the user can infer that the area corresponding to the fifth area (the area shown in yellow in Figure 4) is an artificial area with high coherence and no change in brightness, and therefore that although a disaster occurred in a situation where artificial objects were present, there was no collapse or the like, and it is highly likely that no human casualties occurred, making it an unaffected artificial area, meaning that immediate relief is not considered necessary.

[0064] Furthermore, for example, the user can infer that the area corresponding to area 7 (the area shown in red in Figure 4) has no change in brightness, low coherence, and is an area containing man-made objects, and therefore this area is a man-made area where a disaster has occurred in an environment where man-made objects are present, and although collapses etc. have occurred, the collapses etc. are not major, and the area is a man-made area that has been partially affected, i.e., it is considered to have a lower priority for rescue compared to areas where major collapses etc. are expected to have occurred.

[0065] Furthermore, for example, the user can infer that the area corresponding to the third area (the area shown in magenta in Figure 4) has a change in brightness, low coherence, and is an area containing man-made objects, and therefore the area is a man-made area that is likely to be affected by a disaster where man-made objects are present, resulting in major collapses and other damage, with great potential for human casualties, and therefore is likely to have a high priority for rescue.

[0066] Furthermore, for example, the user can estimate that the area corresponding to area 8 (the area shown in black in Figure 4) is a natural object area with no change in brightness and low coherence, and therefore the area is an unaffected natural object area where a disaster occurred without any man-made objects, but no substantial damage occurred. Even if there is no change in the observed object, the coherence of each pixel in the radar images from two time periods may be calculated to be low. For example, the radar reflection characteristics may change due to vegetation growth, the swaying of leaves in the wind, or changes in ground humidity. Furthermore, the coherence may be calculated to be low due to noise or interference contained in the radar image. Therefore, the user can estimate that the low coherence is due to changes in the radar reflection characteristics, such as those described above, and that the area is unaffected, for example, because the area is an area with no man-made objects but natural objects, and there is no change in brightness.

[0067] For example, in the radar image display control device 1 according to the first embodiment, the display control unit 17 may perform a basis estimation process to estimate the basis for a change in the observed object in the determined first, second, third, fourth, fifth, sixth, seventh, or eighth region, and may include information indicating the estimation result of the basis estimation process in the change information and display the change information on the display device 5. In this case, in the basis estimation process, the display control unit 17 may estimate the basis for the change in the observed object based on, for example, a composite image in accordance with a basis estimation condition. The basis estimation condition is, for example, a condition defined by associating information indicating each of the first to eighth regions with information indicating the basis for the change in the observed object (hereinafter referred to as "basis information"). For example, a developer or the like may set the basis estimation condition in advance and store information indicating the basis estimation condition (hereinafter referred to as "basis estimation condition information") in an internal buffer or the like of the display control unit 17. For example, a user or the like may be able to update the basis estimation condition as needed.

[0068] FIG. 5 illustrates an example of the content of the basis estimation condition information referenced by the display control unit 17 in the basis estimation process when the display control unit 17 has the function of performing the basis estimation process in the first embodiment. Note that in FIG. 5 , the basis estimation conditions are configured to associate information indicating each of the first to eighth regions with the basis information, as well as information indicating the presence or absence of a luminance difference, information indicating the level of coherence, and information indicating the presence or absence of an artificial object. However, the association of the information indicating the presence or absence of a luminance difference, information indicating the level of coherence, and information indicating the presence or absence of an artificial object is not essential. For example, the display control unit 17 estimates the fourth region as a "disaster-affected natural object area." Then, the display control unit 17 displays, for example, on a screen such as that shown in FIG. 4 , the estimated result of the basis for the change along with a description of the fourth region. As a specific example, the display control unit 17 displays, for example, on a screen such as that shown in FIG. 4 , the following statement for the fourth region: "Since there is a luminance change and it is a natural object area, it is a disaster-affected natural object area."

[0069] The display control unit 17 has the function of performing basis estimation processing and causes the display device 5 to display basis information, so that the radar image display control device 1 can provide the user with information that will help them more easily estimate the basis for changes in the observed object.

[0070] The operation of the radar image display control device 1 according to the first embodiment will now be described. FIG. 6 is a flowchart for explaining the operation of the radar image display control device 1 according to the first embodiment. For example, when the radar image display control device 1 receives an instruction to start operation from a user, the radar image display control device 1 performs the operation shown in the flowchart of FIG. 6. The instruction to start operation from the user is given, for example, by inputting date and time designation information. For example, when the date and time designation information is input, a control unit (not shown) of the radar image display control device 1 receives the input and operates the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, and the display control unit 17.

[0071] The radar image acquisition unit 11 acquires, from the radar image storage device 3, a first radar image from a time series of radar images of a target area including an observation target captured by the radar device 2 (step ST1). The radar image acquisition unit 11 also acquires a second radar image from the time series of radar images of a target area including an observation target captured by the radar device 2 (step ST2). The radar image acquisition unit 11 outputs the acquired radar images from the two periods, in other words, the first radar image and the second radar image, to the brightness difference calculation unit 13 and the coherence calculation unit 14.

[0072] The brightness difference calculation unit 13 compares the radar images acquired by the radar image acquisition unit 11 at two times in steps ST1 and ST2, i.e., the first radar image and the second radar image, on a pixel-by-pixel basis, calculates the brightness difference between each pixel of the first radar image and each pixel of the second radar image corresponding to each other, and generates a brightness difference image indicating the calculated brightness difference (step ST3). After generating the brightness difference image, the brightness difference calculation unit 13 outputs the generated brightness difference image to the synthesis processing unit 16.

[0073] The coherence calculation unit 14 compares the radar images acquired by the radar image acquisition unit 11 at two times in steps ST1 and ST2, i.e., the first radar image and the second radar image, on a pixel-by-pixel basis, calculates coherence for each pixel of the first radar image and each pixel of the second radar image corresponding to each other, and generates a correlation image indicating the calculated coherence (step ST4). After generating the correlation image, the coherence calculation unit 14 outputs the generated correlation image to the synthesis processing unit 16.

[0074] The geographic information acquisition unit 12 acquires the geographic information of the target area from the geographic information storage device 4 (step ST5). The geographic information acquisition unit 12 outputs the acquired geographic information to the artificial object extraction unit 15.

[0075] The artifact extraction unit 15 extracts artifacts present in the target object based on the geographic information of the target area acquired by the geographic information acquisition unit 12 in step ST5, and generates artifact images showing the extracted artifacts (step ST6). After generating the artifact images, the artifact extraction unit 15 outputs the generated artifact images to the synthesis processing unit 16.

[0076] The synthesis processing unit 16 performs color element assignment processing in which, in step ST3, a luminance difference color element is assigned to each pixel of the luminance difference image output from the luminance difference calculation unit 13, in step ST4 a correlation color element is assigned to each pixel of the correlation image output from the coherence calculation unit 14, and in step ST6 an artifact color element is assigned to each pixel of the artifact image output from the artifact extraction unit 15, and then performs image synthesis processing in step ST7 to generate a synthesized image by RGB-combining the color-assigned luminance difference image, the color-assigned correlation image, and the color-assigned artifact image. The synthesis processing unit 16 outputs the synthesized image generated by the image synthesis processing to the display control unit 17.

[0077] The display control unit 17 displays change information indicating whether or not there is a change in the observation target on the display device 5 in a form that indicates whether or not there is a difference in brightness between the radar images at the two times, the level of coherence, and the presence of artificial objects, based on the composite image output from the composition processing unit 16 in step ST7 (step ST8). The display control unit 17 may perform a grounds estimation process in step ST8, and may include information indicating the estimation result of the grounds estimation process in the change information and display it on the display device 5.

[0078] In the operation of the radar image display control device 1 shown in the flowchart of FIG. 6, the processing is performed in the order of step ST1 and step ST2. However, this is merely an example. The processing may be performed in the order of step ST2 and step ST1, or the processing of step ST1 and the processing of step ST2 may be performed in parallel. In the operation of the radar image display control device 1 shown in the flowchart of FIG. 6, the processing is performed in the order of step ST3 and step ST4. However, this is merely an example. The processing may be performed in the order of step ST4 and step ST3, or the processing of step ST3 and the processing of step ST4 may be performed in parallel. In the operation of the radar image display control device 1 shown in the flowchart of FIG. 6, the processing of steps ST1 to ST4 and the processing of steps ST5 to ST6 are performed in parallel. However, this is merely an example. For example, the processing of steps ST1 to ST4 may be performed first, followed by the processing of steps ST5 to ST6, or the processing of steps ST5 to ST6 may be performed first, followed by the processing of steps ST1 to ST4. It is sufficient that the processes of steps ST1 to ST6 are completed before the process of step ST7 is performed.

[0079] In this way, the radar image display control device 1 generates a brightness difference image by comparing radar images from two periods (first radar image and second radar image) pixel by pixel. The radar image display control device 1 also generates a correlation image by comparing radar images from two periods pixel by pixel. The radar image display control device 1 also generates an artifact image based on geographic information of the target area. The radar image display control device 1 assigns a color element corresponding to the brightness difference to each pixel of the brightness difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of an artifact to each pixel of the artifact image, so that the color elements are different from each other, and generates a composite image by RGB-compositing the brightness difference image after the color elements have been assigned (color-assigned brightness difference image), the correlation image (color-assigned correlation image), and the artifact image (color-assigned artifact image). The radar image display control device 1 then displays change information indicating the presence or absence of a change in the observation target based on the composite image, in a form that shows the presence or absence of a brightness difference, the level of coherence, and the presence of an artifact in the radar images from the two periods. This allows the radar image display control device 1 to provide the user with information indicating whether or not there is a change in the observation target in a manner that allows the user to estimate the basis for that information.

[0080] 7A and 7B are diagrams illustrating a display screen when an image showing a changed area of ​​an observation target is displayed based on radar images taken before and after a disaster using the conventional technology described above. Fig. 7A shows an example of a radar image taken after a disaster, in which an object area including the observation target is captured. Fig. 7B shows an example of an image displayed using the conventional technology described above, showing a changed area of ​​the observation target that has changed due to the disaster. As shown in Fig. 7B, the conventional technology described above can display areas that have been affected and areas that have not been affected, but it does not allow users to see under what circumstances the observation target, including areas that have not changed, has changed or has not changed. In contrast, the radar image display control device 1, configured as described above, displays change information on the display device 5, categorizing, for example, whether a disaster-affected area is an area where there is a difference in brightness between pixels in radar images taken at two different times, the coherence of each pixel in the radar images taken at two different times is low, and natural objects are present; an area where there is no difference in brightness between pixels in radar images taken at two different times, the coherence of each pixel in the radar images taken at two different times is low, and artificial objects are present; or an area where there is a difference in brightness between pixels in radar images taken at two different times, the coherence of each pixel in the radar images taken at two different times is low, and artificial objects are present (see, for example, FIG. 4 ). This allows the user to estimate whether the disaster-affected area is considered to be an area of ​​damaged natural objects, an area of ​​partially damaged artificial objects, or an area of ​​collapsed artificial objects. In this way, the radar image display control device 1 can provide the user with information indicating whether or not there is a change in the observed object, in a manner that allows the user to estimate the basis for such an estimate.

[0081] In the first embodiment, the radar images from two periods are the first radar image and the second radar image taken before and after a disaster occurs in a target area including the observation target. However, this is merely an example. The first radar image and the second radar image are not limited to radar images taken before and after a disaster occurs in a target area including the observation target. They may be radar images taken at two periods at different times within a time series of radar images of a target area including the observation target captured by the radar device 2. For example, the user may specify the dates and times when radar images from any two periods taken at different times were captured. Alternatively, conditions for identifying radar images from two periods (hereinafter referred to as "image acquisition conditions") may be set, such as 9:00 a.m. on the current day and 9:00 a.m. one month prior. Information indicating the image acquisition conditions (hereinafter referred to as "image acquisition condition information") may be stored in an internal buffer or the like of the radar image acquisition unit 11. The radar image acquisition unit 11 may refer to the image acquisition condition information to identify radar images from the two periods and acquire the identified radar images from the radar image storage device 3. The image acquisition conditions are set by, for example, a user, and may be updated by the user as needed.

[0082] In the first embodiment, the compositing processing unit 16 generates a composite image by RGB compositing the brightness difference image, the correlation image, and the artifact image. However, this is merely an example, and the compositing processing unit 16 may generate a composite image using, for example, other color compositing methods. For example, the compositing processing unit 16 may generate a composite image by CMYK compositing. It is sufficient for the compositing processing unit 16 to generate a composite image by color-compositing the brightness difference image, the correlation image, and the artifact image.

[0083] In the first embodiment, the radar image display control device 1 is provided in, for example, a workroom where a user works, or in a PC or a mobile terminal held by the user, but this is merely an example. For example, some or all of the radar image acquisition unit 11, geographic information acquisition unit 12, brightness difference calculation unit 13, coherence calculation unit 14, artifact extraction unit 15, color element assignment unit 161, composition unit 162, display control unit 17, and a control unit (not shown) included in the radar image display control device 1 may be provided in a server (not shown).

[0084] An example of the hardware configuration of a radar image display control device 1 according to embodiment 1 will be described. Figures 8A and 8B are diagrams illustrating an example of the hardware configuration of the radar image display control device 1 according to embodiment 1. In embodiment 1, the functions of the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit (not shown) are realized by a processing circuit 1001. That is, the radar image display control device 1 includes the processing circuit 1001 for controlling the display device 5 to display change information based on two radar images captured at different times in a time series of radar images of an observation target captured by the radar device 2 and geographic information, as information indicating a change that has occurred in the observation target, in a manner that enables estimation of the basis of the change, such as the circumstances under which the observation target has changed, how the observation target has changed, or whether the observation target has not changed. The processing circuitry 1001 may be dedicated hardware as shown in FIG. 8A, or may be a processor 1004 that executes a program stored in memory 1005 as shown in FIG. 8B.

[0085] If the processing circuit 1001 is dedicated hardware, the processing circuit 1001 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0086] When the processing circuit is the processor 1004, the functions of the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit (not shown) are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 1005. The processor 1004 reads and executes the program stored in the memory 1005 to execute the functions of the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit (not shown). In other words, the radar image display control device 1 includes the memory 1005 for storing a program that, when executed by the processor 1004, results in the execution of steps ST1 to ST8 of FIG. 6 described above. In addition, it can also be said that the program stored in memory 1005 causes the computer to execute the processing procedures or methods of the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit not shown. Here, the memory 1005 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM, a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

[0087] Note that the functions of the radar image acquisition unit 11, the geographic information acquisition unit 12, the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit (not shown) may be partially implemented by dedicated hardware and partially implemented by software or firmware. For example, the functions of the radar image acquisition unit 11 and the geographic information acquisition unit 12 may be implemented by a processing circuit 1001 as dedicated hardware, while the functions of the brightness difference calculation unit 13, the coherence calculation unit 14, the artifact extraction unit 15, the synthesis processing unit 16, the display control unit 17, and a control unit (not shown) may be implemented by a processor 1004 reading and executing programs stored in a memory 1005. The radar image display control device 1 also includes an input interface device 1002 and an output interface device 1003 that communicate via wired or wireless communication with devices such as the radar image storage device 3, the geographic information storage device 4, or the display device 5.

[0088] As described above, according to the first embodiment, the radar image display control device 1 includes a brightness difference calculation unit 13 that compares radar images captured at two different times in a time series of radar images of a target area including an observation target, on a pixel-by-pixel basis, to generate a brightness difference image showing the brightness difference at each pixel; a coherence calculation unit 14 that compares the radar images captured at the two different times in a pixel-by-pixel basis to generate a correlation image showing the coherence that represents the correlation between each pixel; an artifact extraction unit 15 that generates an artifact image showing artifacts present in the target area based on geographic information of the target area; The radar image display control device 1 is configured to include a synthesis processing unit 16 that assigns a color element corresponding to the brightness difference to each pixel of the difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of an artifact to each pixel of the artifact image, so that the color elements are different from one another, and generates a synthesized image by synthesizing the brightness difference image, correlation image, and artifact image in color after the color elements have been assigned, and a display control unit 17 that displays change information indicating the presence or absence of a change in the observed object based on the synthesized image in a form that shows the presence or absence of a brightness difference between the radar images from two time periods, the level of coherence, and the presence of an artifact. Therefore, the radar image display control device 1 can provide the user with information indicating the presence or absence of a change in the observed object in a manner that allows the user to estimate the basis for that information.

[0089] Any of the components of the embodiments may be modified or omitted.

[0090] A radar image display control device according to the present disclosure can provide a user with information indicating whether or not there is a change in the observed object in a manner that allows the user to estimate the basis for that information.

[0091] 1 radar image display control device, 11 radar image acquisition unit, 12 geographic information acquisition unit, 13 brightness difference calculation unit, 14 coherence calculation unit, 15 artifact extraction unit, 16 synthesis processing unit, 161 color element assignment unit, 162 synthesis unit, 17 display control unit, 2 radar device, 3 radar image storage device, 4 geographic information storage device, 5 display device, 1001 processing circuit, 1002 input interface device, 1003 output interface device, 1004 processor, 1005 memory.

Claims

1. A brightness difference calculation unit that compares radar images taken at two different times in a time series of radar images of a target area including an observation target on a pixel-by-pixel basis to generate a brightness difference image showing the brightness difference at each pixel; a coherence calculation unit that compares the radar images taken at two different times in a pixel-by-pixel basis to generate a correlation image showing the coherence that represents the correlation between each pixel; an artifact extraction unit that generates an artifact image showing artifacts present in the target area based on geographic information of the target area; and a synthesis processing unit that assigns a color element corresponding to the brightness difference to each pixel of the brightness difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of an artifact to each pixel of the artifact image so that the color elements are different from one another, and generates a synthesized image by combining the brightness difference image, the correlation image, and the artifact image after the color elements have been assigned. and a display control unit that displays change information indicating whether or not there is a change in the observed object based on the composite image, in a form that shows the presence or absence of the brightness difference between the radar images at the two times, the level of the coherence, and the presence of the artificial object.

2. The radar image display control device according to claim 1, wherein the change information is the composite image.

3. The display control unit determines, from the color elements of each pixel in the composite image, the following regions on the composite image: a first region where the luminance difference is present, the coherence is high, and the artifact is present; a second region where the luminance difference is present, the coherence is high, and the artifact is absent; a third region where the luminance difference is present, the coherence is low, and the artifact is present; a fourth region where the luminance difference is present, the coherence is low, and the artifact is absent; a fifth region where the luminance difference is absent, the coherence is high, and the artifact is present; a sixth region where the luminance difference is absent, the coherence is high, and the artifact is absent; a seventh region where the luminance difference is absent, the coherence is low, and the artifact is present; and an eighth region where the luminance difference is absent, the coherence is low, and the artifact is absent.

2. The radar image display control device according to claim 1, wherein a region image showing the first region, the second region, the third region, the fourth region, the fifth region, the sixth region, the seventh region, or the eighth region on the image, and text explaining the first region, the second region, the third region, the fourth region, the fifth region, the sixth region, the seventh region, or the eighth region on the composite image are displayed as the change information.

4. A radar image display control device according to claim 3, characterized in that in the area image, the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area is color-coded.

5. The display control unit determines, from the color elements of each pixel in the composite image, the following regions on the composite image: a first region where the luminance difference is present, the coherence is high, and the artifact is present; a second region where the luminance difference is present, the coherence is high, and the artifact is absent; a third region where the luminance difference is present, the coherence is low, and the artifact is present; a fourth region where the luminance difference is present, the coherence is low, and the artifact is absent; a fifth region where the luminance difference is absent, the coherence is high, and the artifact is present; a sixth region where the luminance difference is absent, the coherence is high, and the artifact is absent; a seventh region where the luminance difference is absent, the coherence is low, and the artifact is present; and an eighth region where the luminance difference is absent, the coherence is low, and the artifact is absent.

2. The radar image display control device according to claim 1, wherein a region image in which the first region, the second region, the third region, the fourth region, the fifth region, the sixth region, the seventh region, or the eighth region is color-coded on the image is displayed as the change information.

6. The display control unit determines, from the color elements of each pixel in the composite image, the following regions on the composite image: a first region where the luminance difference is present, the coherence is high, and the artifact is present; a second region where the luminance difference is present, the coherence is high, and the artifact is absent; a third region where the luminance difference is present, the coherence is low, and the artifact is present; a fourth region where the luminance difference is present, the coherence is low, and the artifact is absent; a fifth region where the luminance difference is absent, the coherence is high, and the artifact is present; a sixth region where the luminance difference is absent, the coherence is high, and the artifact is absent; a seventh region where the luminance difference is absent, the coherence is low, and the artifact is present; and an eighth region where the luminance difference is absent, the coherence is low, and the artifact is absent.

2. The radar image display control device according to claim 1, wherein the composite image and a description of the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area on the composite image are displayed as the change information.

7. A radar image display control device according to any one of claims 1 to 6, characterized in that the radar images at the two time periods are radar images taken before and after a disaster occurs in the target area.

8. The radar images at the two times are the radar images taken before and after the target to be observed was hit by a disaster, and the display control unit, based on the color elements of each pixel in the composite image, determines on the composite image: a first region where there is a brightness difference, the coherence is high, and the artificial object is present; a second region where there is a brightness difference, the coherence is high, and the artificial object is not present; a third region where there is a brightness difference, the coherence is low, and the artificial object is present; a fourth region where there is a brightness difference, the coherence is low, and the artificial object is not present; a fifth region where there is no brightness difference, the coherence is high, and the artificial object is present; a sixth region where there is no brightness difference, the coherence is high, and the artificial object is not present; a seventh region where there is no brightness difference, the coherence is low, and the artificial object is present; and an eighth region where there is no brightness difference, the coherence is low, and the artificial object is not present. the seventh area is a man-made object area that is not collapsed but is partially damaged, and the eighth area is a natural object area that is not damaged; and displays, as the change information, a region image showing the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area, together with information showing the estimation result of the grounds estimation process.

9. A radar image display control device according to claim 8, characterized in that in the area image, the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area is color-coded.

10. The radar image display control device according to claim 8 or 9, characterized in that the display control unit displays the area image, information indicating the estimation result obtained by the basis estimation process, and text describing the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area on the composite image as the change information.

11. The radar images at the two times are the radar images taken before and after the target of observation was hit by a disaster, and the display control unit, based on the color elements of each pixel in the composite image, identifies the following regions on the composite image: a first region where there is a brightness difference, the coherence is high, and the artificial object is present; a second region where there is a brightness difference, the coherence is high, and the artificial object is not present; a third region where there is a brightness difference, the coherence is low, and the artificial object is present; a fourth region where there is a brightness difference, the coherence is low, and the artificial object is not present; a fifth region where there is no brightness difference, the coherence is high, and the artificial object is present; a sixth region where there is no brightness difference, the coherence is high, and the artificial object is not present; and a seventh region where there is no brightness difference, the coherence is low, and the artificial object is present. an eighth region where there is no brightness difference, where the coherence is low, and where there are no man-made objects; performing a grounds estimation process to infer that the first region is a man-made object area that has not collapsed but may be damaged, the second region is a natural object area that has been partially damaged, the third region is a man-made object area that has collapsed, the fourth region is a natural object area that has been damaged, the fifth region is a man-made object area that has not been damaged, the sixth region is a natural object area that has not been damaged, the seventh region is a man-made object area that has not collapsed but is partially damaged, and the eighth region is a natural object area that has not been damaged; and displaying the composite image and information indicating the estimation results of the grounds estimation process as the change information.

12. The radar image display control device according to claim 11, characterized in that the display control unit displays the synthetic image, information indicating the estimation result obtained by the basis estimation process, and text describing the first area, the second area, the third area, the fourth area, the fifth area, the sixth area, the seventh area, or the eighth area on the synthetic image as the change information.

13. A radar image display control device according to any one of claims 1 to 12, characterized in that the synthesis processing unit receives color allocation condition information specifying the color elements to be assigned to each pixel of the brightness difference image, each pixel of the correlation image, and each pixel of the artificial object image, and assigns the color elements based on the received color allocation condition information.

14. A brightness difference calculation unit compares radar images taken at different times in a time series of radar images of a target area including an observation target on a pixel-by-pixel basis, the radar images being taken at two different times, to generate a brightness difference image showing the brightness difference at each pixel; a coherence calculation unit compares the radar images taken at two different times in a pixel-by-pixel basis, to generate a correlation image showing the coherence that represents the correlation between each pixel; an artifact extraction unit generates an artifact image showing artifacts present in the target area based on geographic information of the target area; and a synthesis processing unit assigns a color element corresponding to the brightness difference to each pixel of the brightness difference image, a color element corresponding to the coherence to each pixel of the correlation image, and a color element corresponding to the presence or absence of the artifact to each pixel of the artifact image, so that the color elements are different from one another, and generates a synthesized image by combining the brightness difference image, the correlation image, and the artifact image after the color elements have been assigned. and a step in which a display control unit displays, based on the composite image, change information indicating whether or not there is a change in the observed object in a form that shows whether or not there is a difference in brightness between the radar images at the two times, the level of the coherence, and the presence of the artificial object.