Information providing device, information providing system, information providing method, and computer program

Abstract

An information providing device (14) according to the present disclosure provides composite data comprising of a plurality of items of observation data for each frequency observed by a synthetic aperture radar (SAR), the information providing device (14) comprising an acquiring unit (141), a position identifying unit (143), and an output unit (144). The plurality of items of observation data are data obtained as a result of the intensities of frequency components of a transmission radio wave changing when the transmission radio wave is reflected by a reflecting member (11). The acquiring unit (141) acquires the plurality of items of observation data relating to an observation area in which the reflecting member (11) is disposed. The position identifying unit (143) identifies position information of the reflecting member (11) on the basis of the plurality of items of observation data. The output unit (144) outputs the composite data including the identified position information.　Employing the present disclosure makes it easy for objects present on the ground surface to be identified.

Description

Information provision device, information provision system, information provision method, and computer program

[0001] This disclosure relates to an information provision device, an information provision system, an information provision method, and a computer program. This application claims priority to Japanese Application No. 2023-102478 filed on June 22, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Technology is being developed to detect objects on the Earth's surface using synthetic aperture radar (SAR) mounted on artificial satellites. Because artificial satellites can observe any area at any time, they can be used for regular observations, not just for disasters (Non-Patent Document 1).

[0003] Patent Document 1 discloses a vehicle speed calculation device that calculates the speed of a vehicle on a road from observation data obtained by SAR.

[0004] JP 2010-230373 A

[0005] Evolution and deepening of marine monitoring technology using satellite-based synthetic aperture radar [online], [Retrieved April 4, 2023], Internet <https: / / www.mesw.co.jp / business / report / pdf / mss_22_02.pdf>

[0006] An information providing device according to one aspect of the present disclosure is an information providing device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, wherein the multiple observation data are data in which the intensity of the frequency components of the transmitted radio waves is changed when the transmitted radio waves are reflected by a reflective member, and the information providing device includes: an acquisition unit that acquires the multiple observation data related to an observation area in which the reflective member is located; a position identification unit that identifies position information of the reflective member based on the multiple observation data; and an output unit that outputs the composite data including the identified position information.

[0007] The present disclosure can be realized not only as an information providing device having the above-described characteristic configuration, an information providing system, a control method in which characteristic processing in the information providing device is performed as steps, and a program for causing the information providing device to perform the characteristic processing, but also as a semiconductor integrated circuit in which part or all of the information providing device is realized.

[0008] FIG. 1 is a schematic diagram showing the configuration of an entire system in embodiment 1. FIG. 2 is a schematic diagram showing an example of the overview of a Van Atta array antenna. FIG. 3 is a schematic diagram showing the arrangement and connection relationship of each antenna element. FIG. 4 is a schematic diagram showing an example of the configuration of an ID-attached Van Atta array antenna that does not reflect electromagnetic waves of a predetermined frequency. FIG. 5 is a block diagram showing an example of the configuration of a communication device. FIG. 6 is a block diagram showing an example of the configuration of an information providing device. FIG. 7 is a schematic diagram showing an example of a Van Atta array antenna provided with two stubs. FIG. 8 is a diagram showing a response when FMCW waves are incident on a Van Atta array antenna. FIG. 9 is a schematic diagram for explaining the operation of a synthetic aperture radar. FIG. 10 is a diagram showing an example of an SAR image. FIG. 11A is a diagram showing an example of an image of primary SAR data. FIG. 11B is a diagram showing an example of an image of primary SAR data. FIG. 11C is a diagram showing an example of an image of primary SAR data. FIG. 12A is a diagram showing an example of an image of secondary SAR data. FIG. 12B is a diagram showing an example of an image of secondary SAR data. FIG. 12C is a diagram showing an example of secondary SAR data in which reflective members that do not reflect electromagnetic waves of frequency f1 are extracted. FIG. 12D is a diagram showing an example of secondary SAR data in which reflective members that do not reflect electromagnetic waves of frequency f2 are extracted. FIG. 12E is a diagram showing an example of secondary SAR data generated by adding two pieces of secondary SAR data. FIG. 13 is an example of a text representation of identification information and position information of a reflective member. FIG. 14 is a block diagram showing functional blocks of an information providing device according to the first embodiment. FIG. 15 is a diagram showing an example of a relationship between frequency and identification information. FIG. 16 is a diagram showing examples of acquired position information, identification information, and time information. FIG. 17 is a sequence diagram showing the operation of the entire system according to the first embodiment. FIG. 18 is a schematic diagram showing the configuration of the entire system according to the second embodiment. FIG. 19 is a schematic diagram showing an example of a display on a display device of a user device. FIG. 20 is a functional block diagram showing an example of a function of the information providing device according to the second embodiment. Fig. 21 is a sequence diagram showing the operation of the entire system in embodiment 2. Fig. 22 is a functional block diagram showing an example of the functions of the information providing device when correcting the position.

[0009] [Problem to be Solved by the Present Disclosure] Images obtained by SAR are black and white images that visualize the intensity of electromagnetic waves reflected from the Earth's surface, making it difficult to identify objects present on the Earth's surface.

[0010] Effect of the Present Disclosure According to the present disclosure, it is possible to easily identify objects existing on the earth's surface.

[0011] <Outline of Embodiments of the Present Disclosure> Below, an outline of embodiments of the present disclosure will be listed and described.

[0012] (1) An information providing device according to this embodiment provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, the multiple observation data being data in which the intensities of frequency components of transmitted radio waves are changed when the transmitted radio waves are reflected by a reflective member, and the information providing device includes: an acquisition unit that acquires the multiple observation data related to an observation area in which the reflective member is disposed; a position identification unit that identifies position information of the reflective member based on the multiple observation data; and an output unit that outputs the composite data including the identified position information. This makes it possible to easily identify objects present on the ground surface.

[0013] (2) In the above (1), the position information may be information that identifies a position where an intensity of a frequency component corresponding to identification information that identifies the reflecting member has changed as the position of the reflecting member corresponding to the identification information. This makes it possible to identify the reflecting member and then specify the position of the reflecting member.

[0014] (3) In the above (1) or (2), the information providing device may further include a storage unit that stores identification information of the reflective member, and a frequency identification unit that identifies the frequency at which intensity has been changed from the plurality of observation data, wherein the acquisition unit acquires the plurality of observation data relating to an observation area in which a plurality of the reflective members having different frequency components whose intensity is changed are arranged, and the output unit associates the identification information of the identified reflective member with the position information included in the composite data. This makes it possible to identify the reflective member and then determine its position.

[0015] (4) In any one of (1) to (3) above, the observation data may be image data including pixels corresponding to the observation area, with pixel values ​​representing reflection intensity, the position identification unit may further include a pixel identification unit that identifies the pixels corresponding to the reflective member based on the pixel values, and the output unit may use information regarding the position of the observation area corresponding to the identified pixels as the position information. This makes it possible to obtain position information indicating the position of the reflective member from the observation data.

[0016] (5) In the above (3), the output unit may associate the location information included in the composite data with time information indicating a time when the observation data was generated, thereby making it possible to know the time at which the location information is information.

[0017] (6) In the above (5), a database may be further provided in which the composite data including the position information, the identification information, and the time information of the reflecting member is stored, thereby making it possible to accumulate the position information, the identification information, and the time information of the reflecting member.

[0018] (7) In the above (6), a search unit may be further provided that searches the database based on search conditions related to at least one of the position information, the identification information, and the time information, thereby making it possible to search for the position information, identification information, and time information of the reflective member stored in the database.

[0019] (8) In any one of the above (1) to (7), the reflecting member may be provided on a specific monitoring target that exists on the ground surface, thereby making it possible to easily identify the location and type of the monitoring target.

[0020] (9) In any one of (1) to (8) above, a generating unit may be further provided that generates display information in which an icon representing the reflective member is superimposed on a predetermined position on a digital map. This allows the map and the icon of the reflective member to be superimposed and the position of the reflective member to be easily grasped.

[0021] (10) In any one of (1) to (9) above, the reflective member may include a reference member installed at a location in the observation area whose absolute coordinates are known, and the information providing device may further include a setting unit that sets the absolute coordinates to position information of the reference member. This makes it possible to align the position indicated by the position information corresponding to the reflective member with a correct position.

[0022] (11) An information provision system according to this embodiment includes at least one reflective member disposed in an observation area and the information provision device according to any one of (1) to (10) above, thereby enabling easy identification of objects present on the ground surface.

[0023] (12) An information providing method according to the present embodiment is an information providing method executed by an information generating device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, the multiple observation data being data in which the intensities of frequency components of transmitted radio waves are changed when the transmitted radio waves are reflected by a reflective member, the method including the steps of: acquiring the multiple observation data related to an observation area in which the reflective member is disposed; identifying position information of the reflective member based on the multiple observation data; and outputting the composite data including the identified position information. This makes it possible to easily identify objects present on the ground surface.

[0024] (13) In the above (12), the reflecting member may be a reflecting member installed at a position where a specific event occurs on the ground surface, thereby making it possible to easily identify the type and position of an event that has occurred on the ground surface.

[0025] (14) A computer program according to this embodiment causes a computer to function as an information generating device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, the multiple observation data being data in which the intensities of frequency components of transmitted radio waves are changed when the transmitted radio waves are reflected by a reflective member, and causes the computer to function as an acquisition unit that acquires the multiple observation data related to an observation area in which a reflective member is disposed, a position identification unit that identifies position information of the reflective member based on the multiple observation data, and an output unit that outputs the composite data including the identified position information, thereby making it possible to easily identify objects present on the ground surface.

[0026] 1. First Embodiment Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0027] 1 is a schematic diagram showing the configuration of the overall system according to embodiment 1. The overall system according to this embodiment includes a reflecting member 11, a SAR satellite 12, a communication device 13, an information providing device 14, and a communication line 15.

[0028] [1-1-1. Reflective Member] The reflective member in the present disclosure includes a transmitting / receiving antenna that retroreflects irradiated waves (electromagnetic waves) and a limiting section that limits the frequency of the transmitted radio waves to be retroreflected. The retroreflected electromagnetic waves are primarily reflected in the direction from which they arrived, but some of the electromagnetic waves are also reflected in directions deviated from the direction from which they arrived. A reflective member that reflects electromagnetic waves in the direction from which they arrived is also called a retroreflector. An example of a retroreflector is a corner cube reflector, which is configured by combining three orthogonal reflecting plates. Microwaves have wavelengths ranging from several centimeters to several tens of centimeters, so their size is large, measuring several tens of centimeters or more.

[0029] <Van Atta Array Antenna> Figure 2 is a schematic diagram showing an example of the general appearance of a Van Atta array antenna. Figure 3 is a schematic diagram showing the arrangement and connection relationship of each antenna element. For microwaves, in addition to corner cube reflectors, Van Atta array antennas are known as retroreflecting antennas that reflect electromagnetic waves in the direction of arrival. As shown in Figure 2, for microwaves, for example, a configuration can be made in which rectangular conductors 21 are arranged in an array on a dielectric substrate 22. Each conductor 21 is a planar antenna. The length of one side of the conductor may be half the wavelength of the incident electromagnetic wave. The wavelength λ of the electromagnetic wave in a dielectric with a relative dielectric constant ε is ｄ is the wavelength of an electromagnetic wave in free space, λ ０ Sometimes λ ｄ = λ ０ / ε 1 / 2 It is expressed as follows. For example, when the frequency of the electromagnetic wave is 9.6 GHz on a polyimide substrate with a relative dielectric constant of 3.4, the length of one side of the planar antenna is 8.5 mm. Therefore, the planar antenna including a rectangular conductor on a dielectric can be configured as a square flat plate with a side length of about 10 cm. For this reason, the Van Atta array antenna is configured to be small and lightweight. As shown in Figure 3, each antenna element of the Van Atta array antenna is a pair of antenna elements arranged symmetrically with respect to the center of the array, and is connected by a transmission line. For example, the transmission line is a microstrip line provided on a dielectric substrate.

[0030] <Van Atta Array Antenna with ID> Figure 4 is a conceptual diagram showing an example of the configuration of a Van Atta array antenna with ID (Identifier) ​​that does not reflect electromagnetic waves of a predetermined frequency. This antenna has a notch filter installed in the middle of a transmission line connecting a pair of antenna elements arranged symmetrically with respect to the center of the array. The notch filter is a filter that prevents signals of a predetermined frequency from propagating to the next stage. In the transmission line, the notch filter can be configured using a stub. In other words, the notch filter corresponds to a limiting section that imposes a limit on the frequency of the transmitted radio waves to be retroreflected.

[0031] [1-1-2. Synthetic Aperture Radar] Synthetic aperture radar (SAR) is a type of radar that is mounted on a flying object such as an artificial satellite (hereinafter sometimes referred to as a SAR satellite) and moves around, functioning as a virtually large aperture (radar diameter). Radar irradiates an object with electromagnetic waves (hereinafter referred to as microwaves) that typically have a wavelength of 30 cm to 3 cm, and observes the object by analyzing the reflected electromagnetic waves. Therefore, synthetic aperture radar includes a transmitting antenna that irradiates the object with electromagnetic waves, a transmitting device that outputs predetermined electromagnetic waves to the transmitting antenna, a receiving antenna that receives the electromagnetic waves reflected from the irradiated electromagnetic waves, a receiving device that converts the received electromagnetic waves into signals that a control unit can process, and a control unit that generates SAR data (described later) based on the signals converted by the receiving device.

[0032] 5 is a block diagram showing an example of the configuration of a communication device 13. The communication device 13 includes a control unit 51, a memory 52, a communication interface 53, and a transceiver 54. The communication device 13 may perform some or all of the post-processing that was previously performed by the SAR satellite 12.

[0033] <Transmitter / Receiver> The transmitter / receiver 54 is communicatively connected to the antenna 56 and to the communication bus 55. The transmitter / receiver 54 receives signals from the antenna 56, which receives electromagnetic waves carrying SAR data transmitted by the SAR satellite 12. The transmitter / receiver 54 extracts the SAR data from the received signals and converts them into data readable by the control unit 51. The converted data is transmitted to the control unit 51 via the communication bus 55. The communication bus 55 is a bus for mutual data communication between the transmitter / receiver 54, the control unit 51, the communication interface 53, and the memory 52.

[0034] <Control Unit> The control unit 51 includes a circuit configuration such as a processor. Specifically, the control unit 51 includes one or more central processing units (CPUs). The processor included in the control unit 51 may be a graphics processing unit (GPU). In this case, the control unit 51 reads out computer programs stored in the memory 52 and performs various calculations and controls.

[0035] The control unit 51 may include a processor in which a predetermined program is written in advance. For example, the control unit 51 may be an integrated circuit such as a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). In this case, the control unit 51 executes various calculations and controls based on the program written in advance.

[0036] <Memory> The memory 52 includes a volatile memory and a nonvolatile memory, and stores various types of data. The volatile memory includes, for example, a random access memory (RAM). The nonvolatile memory includes, for example, a flash memory, a hard disk drive (HDD), a solid state drive (SSD), or a read-only memory (ROM).

[0037] The memory 52 stores, for example, computer programs and various parameters in a non-volatile memory, and may store computer programs downloaded from an external device (not shown) via a network (not shown) and a communication device (not shown).

[0038] <Communication Interface> The communication interface (hereinafter referred to as communication I / F) 53 is communicatively connected to the communication bus 55. The communication I / F 53 is also communicatively connected to the communication line 15. The communication I / F 53 receives signals flowing through the communication line 15 via respective ports (not shown) and converts the signals into signals readable by the control unit 51. The communication bus 55 is a bus for mutual data communication between the control unit 51, the memory 52, and the communication I / F 53. The communication line 15 is connected to the information providing device 14, which will be described later. The communication I / F 53 transmits SAR data to the information providing device 14 via the communication line 15.

[0039] 6 is a block diagram showing an example of the configuration of the information providing device 14. The information providing device 14 includes a control unit 61, a memory 62, a communication I / F 63, and a communication bus 64. The control unit 61, the memory 62, the communication I / F 63, and the communication bus 64 have the same configurations as the control unit 51, the memory 52, the communication I / F 53, and the communication bus 55 of the communication device 13 described above, respectively, and therefore detailed description thereof will be omitted.

[0040] [1-2. Function of the Overall System] The function of the overall system according to this embodiment is realized by the cooperation of the reflecting member 11, the SAR satellite 12, the communication device 13, and the information providing device 14. [1-2-1. Reflecting Wave Member] The reflecting member in the present disclosure changes the intensity of a predetermined frequency component of the electromagnetic waves from the synthetic aperture radar and reflects the electromagnetic waves in the direction of arrival. An example of a reflecting member in the present disclosure is a Van Atta array antenna with ID.

[0041] <Van Atta Array Antenna> As shown in Figure 3, the Van Atta array antenna 31 has pairs of antenna elements arranged symmetrically about the center of the array, connected by transmission lines. The Van Atta array antenna reflects electromagnetic waves from a synthetic aperture radar in the direction of arrival of the electromagnetic waves. Electromagnetic waves (illumination waves) from a satellite incident on one of the antennas 32 propagate through the transmission line, are delayed by a predetermined phase from the incident wave, and are emitted from the other antenna connected to the transmission line (reflected wave). The spacing between each antenna and the length of the transmission line are configured so that the wavefront created by the reflected wave coincides with the direction of arrival of the illumination wave.

[0042] <ID-Equipped Van Atta Array Antenna> The ID-Equipped Van Atta array antenna includes a transmitting / receiving antenna that retroreflects electromagnetic waves (irradiated waves) from the synthetic aperture radar and a limiting unit that limits the frequency of the retroreflected transmitted radio waves. An ID-Equipped Van Atta array antenna, which is a plurality of reflective members with different restricted frequencies, is placed in the observation area. As shown in FIG. 4 , a stub is provided midway along a transmission line, such as a microstrip line. The stub changes the intensity of a predetermined frequency component. In the microstrip line 41, the stub 42 is a convex transmission line provided midway along the microstrip line. The length L of the stub 42 is L = λd / 4 + n*λd / 2 (n = 0, 1, ...), where λd is the wavelength of the electromagnetic waves propagating through the microstrip line 41. The electromagnetic waves branching from the microstrip line 41 and entering the stub 42 are reflected at the end of the stub 42 and return to the branched microstrip line 41. When n = 0, the electromagnetic wave propagating through the stub 42 is delayed by a quarter wavelength on the way there and a quarter wavelength on the way back, and is therefore delayed by a half wavelength when it returns to the microstrip line 41. Therefore, the phases of the electromagnetic wave propagating through the microstrip line 41 and the electromagnetic wave that has traveled back and forth through the stub 42 are opposite and cancel each other out. Therefore, the electromagnetic wave propagating through the microstrip line 41 cannot travel beyond the position of the stub 42. Therefore, the stub 42 can prevent electromagnetic waves of a specified frequency from propagating to the next stage, and functions as a notch filter. In other words, the stub 42 changes the intensity of the frequency component of the reflected wave as the reflection characteristic of the antenna.

[0043] A Van Atta array antenna with a stub on a microstrip line does not reflect electromagnetic waves with a wavelength corresponding to the length of the stub back in the direction from which the electromagnetic waves arrived. Because of the stub on the microstrip line, electromagnetic waves with a wavelength corresponding to the length of the stub cannot propagate through the microstrip line. Therefore, even though a pair of antenna elements arranged symmetrically about the center of the array are physically connected by a transmission line, electromagnetic waves incident on the first antenna do not propagate to the second antenna and are not transmitted from the second antenna. Therefore, the Van Atta array antenna does not function as a retroreflector antenna, and does not reflect electromagnetic waves with a wavelength corresponding to the length of the stub 42 back in the direction from which the electromagnetic waves arrived.

[0044] FIG. 7 is a conceptual diagram showing an example of a Van Atta array antenna provided with two stubs. While the above description has been given of a case in which one stub 42 is provided on a microstrip line 41, two or more stubs may be provided. In this case, the lengths of the stubs 42 may be different. In FIG. 7, the length of stub 71a is L1, and the length of stub 71b is L2. Each stub can block the propagation of electromagnetic waves with a wavelength corresponding to its length. Stub 71a blocks the propagation of electromagnetic waves with frequency f1 corresponding to length L1. Stub 71b blocks the propagation of electromagnetic waves with frequency f2 corresponding to length L2. Therefore, the Van Atta array antenna 31 provided with stubs 71a and 71b does not reflect electromagnetic waves with frequencies f1 and f2.

[0045] FIG. 8 is an explanatory diagram showing the response of a Van Atta array antenna when an FMCW (Frequency Modulated Continuous Wave) wave is incident on it. The solid line shows the change in frequency of the electromagnetic wave (radiated wave) fs transmitted by the SAR satellite. The dashed line shows the change in frequency of the reflected wave fd reflected by the Van Atta array antenna. Disconnected portions of the dashed line indicate that the electromagnetic wave is not reflected. The time delay of the dashed line relative to the solid line along the time axis indicates the time it takes for the electromagnetic wave to propagate from the SAR satellite to the Van Atta array antenna. The FMCW wave is an electromagnetic wave whose frequency has been changed by a predetermined number of hertz over a predetermined period of time. As an example, the microstrip line 41 of the Van Atta array antenna 31 is provided with two stubs 71a and 71b. The stub 71a has a length L1 corresponding to the electromagnetic wave of frequency f1. The stub 71b has a length L2 corresponding to the electromagnetic wave of frequency f2. The SAR satellite transmits an FMCW wave fs, whose frequency changes from f0 to fn between times t0 and tn, to the Earth's surface. The Van Atta array antenna 31 reflects the radiation wave fs that reaches the Earth's surface as a reflected wave fd. The Van Atta array antenna 31 has stubs 71a and 71b, so it does not reflect electromagnetic waves with frequencies f1 and f2. The frequency of the radiation wave fs changes from f0 to fn, so the intensity of the reflected wave fd reflected by the Van Atta array antenna 31 decreases at times t1 and t2, when it becomes frequency f1 and frequency f2, respectively. The SAR satellite 12 that transmitted the FMCW wave receives the reflected wave fd with reduced intensity at times t1 and t2.

[0046] There are four cases in which stubs 71a and 71b are provided on the microstrip line 41: a first case in which no stub is provided, a second case in which one stub 71a is provided, a third case in which one stub 71b is provided, and a fourth case in which both stubs 71a and 71b are provided. If the first to fourth cases are associated with the first to fourth Van Atta array antennas, respectively, the first to fourth Van Atta array antennas can be identified based on the timing at which the intensity of the reflected wave fd decreases. If the intensity of the reflected wave fd does not decrease, it is identified as the first Van Atta array antenna. If the intensity of the reflected wave fd decreases at timing t1, it is identified as the second Van Atta array antenna. If the intensity of the reflected wave fd decreases at timing t2, it is identified as the third Van Atta array antenna. If the intensity of the reflected wave fd decreases at the timings t1 and t2, it is identified as the fourth Van Atta array antenna.

[0047] Needless to say, in addition to identifying Van Atta array antennas by focusing on the timing at which the strength of the reflected wave fd decreases, Van Atta array antennas can also be identified by determining the decrease in strength with respect to frequency components across the frequency band of the reflected wave as the reflection characteristics of the antenna and comparing these reflection characteristics with the reflection characteristics of each Van Atta array antenna. Comparing across the frequency band makes it easier to improve identification accuracy, and averaging multiple observation results from the same location can reduce the influence of noise at specific times.

[0048] When there are two stubs of different lengths, four Van Atta array antennas are identified. By adding more stubs of different lengths, even more Van Atta array antennas can be identified. When there are four stubs of different lengths, there are 16 possible cases, so 16 Van Atta array antennas can be identified. When there are eight stubs of different lengths, there are 256 possible cases, so 256 Van Atta array antennas can be identified.

[0049] Although the above description has been given of an example of limiting the frequency by using a stub notch filter to reduce the intensity of electromagnetic waves at a predetermined frequency, this can also be implemented by using an active element to increase the intensity of electromagnetic waves at a predetermined frequency. In this case, the reflective member can still be identified based on the increased frequency.

[0050] [1-2-2. Synthetic Aperture Radar] Figure 9 is a conceptual diagram to explain the operation of synthetic aperture radar. Microwaves are also used in SAR. Because microwaves have a longer wavelength than visible light, synthetic aperture radar can make observations without being affected by clouds or other factors. The resolution of lenses and antennas in observation equipment that use electromagnetic waves is inversely proportional to the wavelength, so radar that uses microwaves has a much lower resolution than an optical lens of the same diameter.

[0051] However, the concept of synthetic aperture radar is to arrange a number of virtual antennas p1 to pn on the flight path of an aircraft, as shown in Figure 9. Synthetic aperture radar repeatedly irradiates electromagnetic waves onto an object while it is moving along its flight path, and by combining the electromagnetic waves reflected from the object, it forms a virtual antenna with a large aperture, thereby improving resolution. A SAR satellite 12 equipped with synthetic aperture radar flies in a predetermined orbit around the Earth.

[0052] Figure 10 is a diagram showing an example of a SAR image. The SAR satellite 12 synthesizes data obtained at positions p1 to pn while flying to obtain a SAR image such as that shown in Figure 10. Furthermore, pulse compression processing is performed by utilizing the Doppler effect of the moving SAR satellite 12, improving the resolution in the direction of satellite movement. Furthermore, by converting the microwaves from the SAR satellite into FMCW waves, which change the frequency by a predetermined number of hertz over a predetermined period of time, a pseudo-Doppler effect is generated, thereby performing pulse compression and improving the resolution.

[0053] The SAR satellite 12 first emits electromagnetic waves toward the Earth's surface, receives reflected waves from the emitted electromagnetic waves, and generates directly obtained data (referred to as zeroth-order SAR data) based on the received reflected waves. At this time, the SAR satellite 12 assigns to the generated zeroth-order SAR data time information indicating the time of generation and location information indicating the location of the generated zeroth-order SAR data on the Earth's surface. The assigned time information and location information are maintained in each SAR data even when primary SAR data and secondary SAR data are generated. Next, the SAR satellite 12 combines multiple zeroth-order SAR data to generate a SAR image (referred to as primary SAR data). Furthermore, the SAR satellite 12 performs post-processing, described below, on the primary SAR data to generate secondary SAR data. The SAR satellite 12 then transmits at least one of the zero-order SAR data, primary SAR data, and secondary SAR data onto a predetermined electromagnetic wave to a ground-based communication device 13. The zero-order SAR data, primary SAR data, and secondary SAR data are hereinafter collectively referred to as SAR data. As shown in Figure 10, a SAR image is a black-and-white image that visualizes the intensity of waves reflected from the Earth's surface, and it is more difficult to identify objects than in full-color photographs taken by optical satellites.

[0054] <Post-Processing> The SAR satellite 12 performs post-processing on the acquired SAR data as needed. Post-processing is performed on the acquired zero-order SAR data and first-order SAR data. Electromagnetic waves reflected by an ID-marked Van Atta array antenna have the intensity of electromagnetic waves at a predetermined frequency changed. The zero-order SAR data and first-order SAR data generated from reflected waves, including those reflected from a reflecting member equipped with an ID-marked Van Atta array antenna, are characterized by the frequency at which the Van Atta array antenna changed its intensity at the location where the reflecting member is present. Post-processing identifies the location characterized by the frequency as the location where a reflecting member equipped with a Van Atta array antenna is present. Because the frequency is associated with identification information that identifies the reflecting member, post-processing identifies the reflecting member based on the frequency.

[0055] Figures 11A to 11C are example images of first-order SAR data for the same region. Figure 11A is an image 111a of first-order SAR data synthesized from zero-order SAR data of frequency f1 in Figure 8. Figure 11B is an image 111b of first-order SAR data synthesized from zero-order SAR data of frequency f2 in Figure 8. Figure 11C is an image 111c of first-order SAR data synthesized from zero-order SAR data of frequency f3 in Figure 8. Frequency information indicating the frequency of the electromagnetic waves (reflected waves) from which the zero-order SAR data and first-order SAR data were generated is assigned to the zero-order SAR data and first-order SAR data.

[0056] An example will be described in which reflecting members 112 and 113 including ID-attached Van Atta array antennas are installed in the areas of images 111a, 111b, and 111c of the primary SAR data. The reflecting members 112 and 113 are configured to reflect electromagnetic waves of frequency f3 but not of frequencies f1 and f2, as shown in FIG. 8 . Because the reflecting members 112 and 113 are configured not to reflect electromagnetic waves of frequencies f1 and f2, the primary SAR data images 111a and 111b have small pixel values ​​at the positions where the reflecting members 112 and 113 are installed, and appear black in FIGS. 11A and 11B . On the other hand, because the reflecting members 112 and 113 are configured to reflect electromagnetic waves of frequency f3, the primary SAR data image 111c has large pixel values ​​at the positions where the reflecting members 112 and 113 are installed, and appear white in FIG. 11C . Hereinafter, when a pixel value indicates "black", it may be simply referred to as "black", and when a pixel value indicates "white", it may be simply referred to as "white".

[0057] A predetermined calculation is performed on the images 111a, 111b, and 111c of the primary SAR data, and positions where the pixel signal intensity changes, for example, are identified as positions where the reflecting members 112 and 113 are present. When the images 111a, 111b, and 111c of the primary SAR data are viewed superimposed, the pixel values ​​are the same in the images 111a, 111b, and 111c of the primary SAR data in areas other than the positions where the reflecting members 112 and 113 are installed, and all appear black or all appear white. On the other hand, the pixel values ​​of the positions where the reflecting members 112 and 113 are installed are different in the images 111a, 111b, and 111c, and they appear black in the images 111a and 111b of the primary SAR data and white in the image 111c of the primary SAR data. Therefore, by overlapping the images of the primary SAR data 111A and 111B and identifying the positions of pixels where the pixel values ​​differ between the images 111a, 111b, and 111c, it is possible to identify that the reflecting members 112 and 113 are installed at the identified positions.

[0058] Fig. 12A is a diagram showing an example of an image of secondary SAR data displaying the identification result. In this example, the signal intensity of pixels at positions corresponding to the identified reflectors 112 and 113 is enhanced. Fig. 12B is a diagram showing an example of an image of secondary SAR data displaying the identification result. In this example, only the pixels of the identified reflectors 112 and 113 are displayed.

[0059] Furthermore, the primary SAR data images 111a and 111b are characterized by frequencies f1 and f2 at which the reflective members 112 and 113 change their intensity. In other words, the pixel values ​​of the images 111a and 111b appear small and black. This indicates that the primary SAR data frequencies from which the secondary SAR data image 121b was generated are f1 and f2. If the frequencies f1 and f2 are associated with identification information, such as ID3, that identifies the reflective members 112 and 113, then information indicating ID3 is associated with the secondary SAR data image 121b as the identification information for the secondary SAR data image 121b.

[0060] The above description has been given for the case where the reflecting members 112 and 113 do not reflect electromagnetic waves of frequencies f1 and f2. This is not limiting, and for example, the reflecting member 112 may reflect electromagnetic waves of frequency f2 but not electromagnetic waves of frequency f1, and the reflecting member 113 may reflect electromagnetic waves of frequency f1 but not electromagnetic waves of frequency f2. In this case, the ID-equipped Van Atta array antenna of the reflecting member 112 is configured with stubs so as not to reflect electromagnetic waves of frequency f1. The ID-equipped Van Atta array antenna of the reflecting member 113 is configured with stubs so as not to reflect electromagnetic waves of frequency f2.

[0061] 12C is an example of secondary SAR data in which a reflecting member 112 that reflects electromagnetic waves of frequency f2 but not electromagnetic waves of frequency f1 is extracted. FIG. 12D is an example of secondary SAR data in which a reflecting member 113 that reflects electromagnetic waves of frequency f1 but not electromagnetic waves of frequency f2 is extracted. Similarly to the above, image 121c of the secondary SAR data shown in FIG. 12C is obtained by overlaying images 111a, 111b, and 111c of the primary SAR data, and positions where pixel values ​​correspond to "black," "white," and "white" are identified as positions where reflecting member 112 exists. Similarly, image 121d of the secondary SAR data shown in FIG. 12D is obtained by overlaying images 111a, 111b, and 111c of the primary SAR data, and positions where pixel values ​​correspond to "white," "black," and "white" are identified as positions where reflecting member 113 exists. The image 121c of the secondary SAR data is associated with information indicating, for example, ID1 as identification information, and the image 121d of the secondary SAR data is associated with information indicating, for example, ID2 as identification information.

[0062] 12E is a diagram showing an example in which one secondary SAR data image 121e is generated by adding together secondary SAR data images 121c and 121d. In the above example, two secondary SAR data items are generated by generating secondary SAR data image 121c corresponding to frequency f1 and secondary SAR data image 121d corresponding to frequency f2. To further reduce the amount of data, one secondary SAR data item is generated instead of generating secondary SAR data for each frequency. In this case, the identification information is associated with the positional information of the reflecting member, rather than with the secondary SAR data. For example, information indicating ID1 is associated as identification information with the positional information of the reflecting member 112, and information indicating ID2 is associated as identification information with the positional information of the reflecting member 113.

[0063] FIG. 13 shows an example in which the identification information and location information of a reflective member are expressed as text data. In the example shown in FIG. 12E, image data is used, but text data may also be used to further reduce the amount of data. In this case, as shown in FIG. 13, identification information and location information are associated with each of the reflective members 112 and 113. In this example, information indicating ID3 is associated with the reflective member 112 as identification information and longitude = x1 east, latitude = y1 as location information, and information indicating ID3 is associated with the reflective member 113 as identification information and longitude = x2 east, latitude = y2 as location information.

[0064] Since the position of the SAR satellite on its satellite orbit can be determined by a predetermined method, for example, by measuring the positions of multiple stars, the position of the satellite on the Earth's surface of the secondary SAR data image 121b can be determined. For example, position information indicating the latitude and longitude of the position of the lower left corner of the secondary SAR data image 121b is assigned to the secondary SAR data image 121b. Since the relative positions of the reflecting members 112 and 113 in the secondary SAR data image 121b are determined, the latitude and longitude of the reflecting members 112 and 113 can also be determined based on the position information of the secondary SAR data image 121b.

[0065] In the above, the post-processing is performed by the SAR satellite 12, but this is not limiting, and some or all of the post-processing may be performed by the communication device 13 described below. Which processing is performed by the SAR satellite 12 and which subsequent processing is performed by the communication device 13 may be determined taking into consideration, for example, the processing capacity of the SAR satellite 12 and the communication speed between the SAR satellite 12 and the communication device 13.

[0066] [1-2-3. Communication Device] The communication device 13 receives electromagnetic waves carrying the SAR data transmitted by the SAR satellite 12 and extracts the SAR data from the received electromagnetic waves. The communication device 13 may perform some or all of the post-processing performed by the SAR satellite 12 on the extracted SAR data. The communication device 13 transmits the extracted SAR data to the information providing device 14. Alternatively, the communication device 13 stores the extracted SAR data in memory 52. ​​A server (not shown) provided external to the communication device may store some or all of the data stored in memory 52. ​​In this case, the communication device 13 stores the data in the server via the communication line 15.

[0067] The communication device 13 may function as a data server that manages the stored SAR data. When functioning as a data server, the communication device 13 receives designation information that designates data from the information providing device 14 described below, searches for a data server based on the designation information, and transmits the designated data to the information providing device 14. Although the case where the communication device 13 functions as a data server has been described, the present invention is not limited to this. A separate server may be provided and the server may perform the data server function, or the information providing device 14 may perform the data server function.

[0068] 14 is a block diagram showing functional blocks of the information providing device 14 in embodiment 1. The information providing device 14 includes, as functional blocks, an acquisition unit 141, a frequency identification unit 142, a position identification unit 143, and an output unit 144. The information providing device 14 provides synthetic data of multiple pieces of observation data for each frequency observed by the synthetic aperture radar.

[0069] The acquisition unit 141 acquires the plurality of observation data relating to an observation area in which a reflecting member is arranged. The frequency identification unit 142 identifies the restricted frequency based on the reflected wave. The position identification unit 143 identifies position information of the reflecting member based on the plurality of observation data. The output unit 144 outputs the combined data including the identified position information.

[0070] The information providing device 14 processes observation data generated from reflected waves of electromagnetic waves emitted by a synthetic aperture radar mounted on an aircraft and provides the obtained information. Specifically, an SAR satellite 12, which is an example of an aircraft, is equipped with a synthetic aperture radar and emits electromagnetic waves (microwaves) toward the Earth's surface. The electromagnetic waves emitted to the Earth's surface are reflected by the Earth's surface and a reflecting member 11 installed on the surface. The reflected electromagnetic waves (reflected waves) are received by the synthetic aperture radar. The synthetic aperture radar generates observation data (SAR data) based on the received reflected waves and transmits the generated SAR data to the communication device 13. The communication device 13 receives the transmitted SAR data and transmits the received SAR data to the information providing device 14. The information providing device 14 performs predetermined processing on the received SAR data and then outputs the obtained data to, for example, a user device that displays the data.

[0071] <Acquisition Unit> The acquisition unit 141 acquires the plurality of pieces of observation data relating to the observation area in which the reflective members are arranged. Specifically, the observation data is SAR data. The SAR data is, for example, the secondary SAR data shown in FIGS. 12A to 12E. As shown in FIGS. 12A to 12E, pixels at the positions where the reflective members 11 are located are emphasized, and the SAR data includes information for identifying the positions of the reflective members 11. The SAR data may also be, for example, the primary SAR data shown in FIGS. 11A to 11C.

[0072] As shown in Fig. 1, the acquisition unit 141 acquires SAR data from a SAR satellite 12 (synthetic aperture radar) via a communication device 13. The information providing device 14 acquires the SAR data by transmitting designation information specifying the SAR data to the communication device. The designation information may specify a location and a type of data, for example, "east longitude = x1, north latitude = y1, secondary SAR data." The designation information may also be identification information for identifying a reflective member or time information indicating the time the SAR data was generated.

[0073] The communication device 13 receives the designation information and searches for SAR data stored in the memory 52 based on the received designation information. The communication device 13 transmits SAR data that matches the designation information to the information providing device 14. The information providing device 14 acquires the SAR data by receiving the SAR data transmitted by the communication device 13. The information providing device 14 stores the acquired SAR data in the memory 62.

[0074] The frequency identification unit 142 identifies the limited frequency based on the reflected wave. Specifically, the zero-order SAR data and the first-order SAR data are provided with frequency information indicating the frequency of the electromagnetic wave (reflected wave) from which the data was generated, and the frequency identification unit 142 identifies the frequency based on the frequency information.

[0075] The frequency restricted by the restricting portion of the reflecting member is associated with identification information for identifying the reflecting member. The identification information of the reflecting member is stored in a storage unit, such as the memory 62. A plurality of reflecting members with different restricted frequencies are arranged in the observation area. FIG. 15 is a diagram showing an example of the association between frequencies and identification information. Correspondence information indicating the association between frequencies and identification information is pre-stored in the memory 62 of the information providing device 14. FIG. 15 illustrates three examples of identification information. If the reflecting member (Van Atta array antenna) 11 is configured not to reflect electromagnetic waves of frequency f1, the reflecting member is associated with identification information ID1. In this case, ID1 indicates that a fire has occurred. If the reflecting member 11 is configured not to reflect electromagnetic waves of frequency f2, ID2 is associated with the reflecting member 11, and ID2 indicates that a building has collapsed. If the reflecting member 11 is configured not to reflect electromagnetic waves of frequencies f1 and f2, ID3 is associated with the reflecting member 11, and ID3 indicates that a seriously injured person is present.

[0076] <Position Identification Unit> The position identification unit 143 identifies position information of the reflective member based on the plurality of observation data. Furthermore, the pixel identification unit 143a included in the position identification unit 143 identifies the pixel corresponding to the reflective member based on the pixel value. Here, the observation data is image data including pixels corresponding to the observation area, and the pixel values ​​represent reflection intensity.

[0077] Specifically, the SAR data, which is the observation data, includes images 111a, 111b, and 111c of primary SAR data corresponding to frequencies f1, f2, and f3, as shown in Figures 11A to 11C. Each image includes a plurality of pixels corresponding to a position within the observed Earth's surface area. Each pixel has a pixel value, e.g., a luminance value, indicating the intensity of the reflected wave. For example, in Figures 11A to 11C, focus is placed on reflecting members 112 and 113. At frequency f1 (Figure 11A), the pixel values ​​at the positions of reflecting members 112 and 113 are small (shown as "black"); at frequency f2 (Figure 11B), the pixel values ​​at the positions of reflecting members 112 and 113 are small (shown as "black"); and at frequency f3 (Figure 11C), the pixel values ​​at the positions of reflecting members 112 and 113 are large (shown as "white"). 11A to 11C, the pixel values ​​of pixels at positions other than the reflective members 112 and 113 are values ​​corresponding to "black," "black," "black" or "white," "white," "white." These values ​​are different from the pixels at positions corresponding to the reflective members 112 and 113, which have pixel values ​​corresponding to "black," "black," and "white." Based on this difference, the pixel positions corresponding to the reflective members 112 and 113 are identified.

[0078] In another specific example, the SAR data, which is the observation data, may be secondary SAR data such as those shown in Figures 12A to 12E. In this case, the pixel values ​​of the pixels at the positions of the reflecting members 112 and 113 are "white" or "black," which are different from the pixel values ​​of the pixels at positions other than the reflecting members 112 and 113, and the pixel positions corresponding to the reflecting members 112 and 113 are identified based on this difference.

[0079] <Output Unit> The output unit 144 outputs the composite data including the identified position information. The output unit 144 may associate the position information of the composite data with identification information of the identified reflective member. The identification information of the reflective member is stored in a storage unit. Specifically, the storage unit is the memory 62. The output unit 144 may use information regarding the position of the observation area corresponding to the identified pixel as the position information.

[0080] The output unit 144 may further associate time information indicating the time when the observation data was generated with the position information included in the combined data. Since the primary SAR data and secondary SAR data, which are observation data, are assigned time information indicating the time when the data was generated, the output unit 144 outputs the time information in association with position information indicating the position identified based on the primary SAR data and secondary SAR data. This associates the position information with the time information, making it possible to know when and where the reflective members 112 and 113 were located.

[0081] 16 is a diagram showing an example of the acquired position information, identification information, and time information. The information providing device 14 may further include a database in which the composite data including the position information, identification information, and time information of the reflective member is stored. The output unit 144 may output the position information, identification information, and time information to the database. The database is, for example, the memory 62 of the information providing device 14. Data such as that shown in FIG. 16 is stored in the memory 62, which is a database.

[0082] [1-3. Operation of the Overall System] Figure 17 is a sequence diagram showing the operation of the overall system. The overall system operates in cooperation with the SAR satellite 12, communication device 13, and information providing device 14. The operation of the overall system will be explained below. The overall system starts with the SAR satellite.

[0083] [1-3-1. SAR Satellite] <Step S01> First, the SAR satellite 12 (synthetic aperture radar) irradiates electromagnetic waves onto the Earth's surface while moving on a satellite orbit. The irradiated electromagnetic waves are FMCW waves, the frequency of which changes by a predetermined number of hertz over a predetermined period of time. After irradiating the electromagnetic waves, the SAR satellite 12 proceeds to step S02.

[0084] <Step S02> Next, the SAR satellite 12 receives electromagnetic waves (reflected waves) reflected by the Earth's surface and the reflecting members 11 installed on the Earth's surface. After receiving the reflected waves, the SAR satellite 12 proceeds to step S03.

[0085] <Step S03> Next, the SAR satellite 12 generates zero-order SAR data obtained directly based on the received reflected waves. At this time, the SAR satellite 12 assigns to the generated zero-order SAR data time information indicating the time the zero-order SAR data was generated, position information indicating the position on the Earth's surface of the generated zero-order SAR data, and frequency information indicating the frequency of the electromagnetic waves (reflected waves) from which the zero-order SAR data was generated. After generating the zero-order SAR data, the SAR satellite 12 proceeds to step S04.

[0086] <Step S04> Next, the SAR satellite 12 combines the multiple zero-order SAR data to generate primary SAR data for each frequency as shown in Figures 11A to 11C. The generated primary SAR data is assigned time information indicating the time the primary SAR data was generated, position information indicating the position of the generated primary SAR data on the Earth's surface, and frequency information indicating the frequency of the electromagnetic waves (reflected waves) from which the primary SAR data was generated. After generating the primary SAR data, the SAR satellite 12 proceeds to step S05.

[0087] <Step S05> Next, the SAR satellite 12 generates secondary SAR data based on the primary SAR data. For example, in images 111a, 111b, and 111c of the primary SAR data, positions where the intensity of pixel values ​​of pixels changes are identified as positions where reflectors 112 and 113 are present. The SAR satellite 12 enhances the intensity of the pixel values ​​of pixels at positions corresponding to the identified reflectors 112 and 113, generating secondary SAR data image 121a as shown in FIG. 12A and secondary SAR data image 121b as shown in FIG. 12B. After generating the secondary SAR data, the SAR satellite 12 proceeds to step S06.

[0088] <Step S06> Next, the SAR satellite 12 transmits at least one of the generated zero-order SAR data, primary SAR data, and secondary SAR data on electromagnetic waves to the communication device 13. After the SAR satellite transmits the SAR data, the process proceeds to step S07.

[0089] [1-3-2. Communication Device] <Step S07> Next, communication device 13 receives the electromagnetic waves carrying the SAR data transmitted by SAR satellite 12. Communication device 13 extracts the SAR data from the received electromagnetic waves and stores the extracted SAR data in memory 52. ​​If a server (not shown) external to the communication device stores some or all of the data stored in memory 52, communication device 13 stores the SAR data in the server via communication line 15. After storing the SAR data, communication device 13 proceeds to step S08.

[0090] <Step S08> Next, the communication device 13 transmits the stored SAR data to the information providing device 14. For example, the communication device 13 receives a specified condition specifying data from the information providing device 14, performs a search based on the specified information, and transmits the results to the information providing device 14. After the communication device 13 transmits the SAR data, the process proceeds to step S09.

[0091] [1-3-3. Information Providing Device] <Step S09> Next, the acquisition unit 141 of the information providing device 14 acquires the plurality of pieces of observation data related to the observation area in which the reflective member is arranged. Specifically, the observation data is SAR data. The SAR data is, for example, the secondary SAR data shown in FIGS. 12A to 12E. As shown in FIGS. 12A to 12E, pixels at the positions where the reflective member 11 is located are emphasized, and the SAR data includes information for identifying the position of the reflective member 11. The SAR data may also be, for example, the primary SAR data shown in FIGS. 11A to 11C.

[0092] The information providing device 14 acquires the SAR data by transmitting designation information specifying the SAR data to the communication device. The designation information may specify the location and type of data, for example, "east longitude = x1, north latitude = y1, secondary SAR data." The designation information may also be identification information that identifies the reflective member or time information that indicates the time the SAR data was generated. The information providing device 14 stores the acquired SAR data in the memory 62. After storing the SAR data, the information providing device 14 proceeds to step S10.

[0093] <Step S10> Next, the frequency identification unit 142 of the information providing device 14 identifies the limited frequency based on the reflected wave. Specifically, the zero-order SAR data and the first-order SAR data are provided with frequency information indicating the frequency of the electromagnetic wave (reflected wave) from which the data was generated, and the frequency identification unit 142 identifies the frequency based on the frequency information. After identifying the frequency, the information providing device 14 proceeds to step S11.

[0094] <Step S11> Next, the position identifying unit 143 of the information providing device 14 identifies position information of the reflective member based on the plurality of observation data. Furthermore, the pixel identifying unit 143a included in the position identifying unit 143 identifies the pixel corresponding to the reflective member based on the pixel value. Here, the observation data is image data including pixels corresponding to the observation area, and the pixel value represents reflection intensity.

[0095] Specifically, the SAR data, which is the observation data, is shown, for example, in FIGS. 11A to 11C . In FIGS. 11A to 11C , attention is focused on the reflective members 112 and 113. At frequency f1 ( FIG. 11A ), the pixel values ​​at the positions of the reflective members 112 and 113 are values ​​corresponding to “black.” At frequency f2 ( FIG. 11B ), the pixel values ​​at the positions of the reflective members 112 and 113 are values ​​corresponding to “black.” At frequency f3 ( FIG. 11C ), the pixel values ​​at the positions of the reflective members 112 and 113 are values ​​corresponding to “black,” “black,” “black,” or “white,” “white,” “white.” In FIGS. 11A to 11C , the pixel values ​​are different from the pixels at the positions corresponding to the reflective members 112 and 113, which are values ​​corresponding to “black,” “black,” and “white.” Based on this difference, pixel positions corresponding to the reflecting members 112 and 113 are identified.

[0096] In another specific example, the SAR data, which is the observation data, may be secondary SAR data such as those shown in Figures 12A to 12E. In this case, the pixel values ​​of the pixels at the positions of the reflecting members 112 and 113 are "white" or "black," which are different from the pixel values ​​of pixels at positions other than the reflecting members 112 and 113, and the pixel positions corresponding to the reflecting members 112 and 113 are identified based on this difference. After identifying the pixel positions, the information providing device 14 proceeds to step S12.

[0097] <Step S12> The output unit 144 of the information providing device 14 outputs the composite data including the specified position information. The output unit 144 may associate the position information of the composite data with identification information of the specified reflective member. The identification information of the reflective member is stored in a storage unit. Specifically, the storage unit is the memory 62. The output unit 144 may use information regarding the position of the observation area corresponding to the specified pixel as the position information.

[0098] The output unit 144 may output the position information, identification information, and time information to a database. In this case, the information providing device 14 further includes a database in which the composite data including the position information, identification information, and time information of the reflective member is stored. The database is, for example, the memory 62 of the information providing device 14. After outputting the data, the information providing device 14 ends the operation of providing information based on the observation data.

[0099] [1-4. Summary] As described above, the information providing device 14 outputs identification information and time information, as well as location information indicating the location of the reflective member acquired based on the SAR data. This makes it possible to easily identify objects on the Earth's surface. When using a SAR satellite provided by a third party, the information providing system may be configured as a system including at least one reflective member 11 placed in the observation area and the information providing device 14. In this case as well, the information providing system can easily identify objects on the Earth's surface.

[0100] The observation data acquired by the acquisition unit may not be the SAR data itself, but may be processed SAR data. The information providing device 14 outputs the position information indicating the position of the reflective member acquired based on the processed data, as well as the identification information and time information, which can of course be used to identify objects on the ground.

[0101] [2. Second Embodiment] A second embodiment will be described. Note that a description of the same configuration as in the first embodiment will be omitted, and only the different parts will be described, with the same reference numerals used for the same configuration. The second embodiment differs from the first embodiment in that it further includes a user device that displays on the display device based on at least one of location information, identification information, and time information.

[0102] [2-1. Overall System Configuration] Figure 18 is a schematic diagram showing the configuration of the overall system in embodiment 2. As shown in Figure 18, the system includes a reflecting member 11, a SAR satellite 12, a communication device 13, an information providing device 14, and a user device 181. The reflecting member 11, the SAR satellite 12, and the communication device 13 have the same configurations and functions as those in embodiment 1. The information providing device 14 further includes a search unit and a generation unit. Therefore, the configuration, functions, and operations of the user device 181, as well as the functions and operations of the added search unit, will be described.

[0103] [2-2-1. Configuration of User Device] The user device 181 is, for example, a personal computer with a display device. Therefore, the configuration of the user device 181 includes, for example, a control unit (not shown), a memory (not shown), a communication interface (not shown), an input device (not shown), and a display device (not shown). The input device is, for example, a keyboard and a mouse. The display device is, for example, a liquid crystal display. The communication interface is connected to the communication line 15.

[0104] [2-2-2. Functions of the User Device] The control unit of the user device 181 can transmit and receive data and commands to and from an external server via the communication interface and the communication line 15. The external server is, for example, the information providing device 14 functioning as a data server. In this case, the control unit of the user device 181 transmits a predetermined command to the information providing device 14 to acquire location information, time information, and identification information stored in the information providing device 14. The predetermined command is, for example, a search condition related to at least one of the location information, time information, and identification information. The search condition is, for example, the identification information "ID1" and the time information "T4." This request is for location information corresponding to the identification information "ID1" and the time information "T4." The search condition is input from an input device. The user inputs the search condition for acquiring the required data from the input device.

[0105] The search conditions transmitted by the user device 181 are received by the information providing device 14. A search is performed based on the received search conditions by a search unit 201 (described later) of the information providing device 14. Then, the search results obtained by the search are transmitted to the user device 181 via the communication line 15.

[0106] The user device 181 receives the search results transmitted from the information providing device 14 via the communication line 15. The user device 181 displays the search results received from the information providing device 14 on a display device. Map information for displaying a map on the display device is stored, for example, in a memory. The map information is obtained, for example, from an external server via the communication line 15. Alternatively, the user device may display display information generated by a generation unit 202 of the information providing device 14, which will be described later.

[0107] FIG. 19 is a schematic diagram of an example displayed on the display device of the user device 181. The shaded areas represent buildings. The white areas represent roads. The triangles represent reflective member symbols indicating the locations where reflective members are installed. Each reflective member is configured not to reflect electromagnetic waves of a predetermined frequency, and the predetermined frequency is associated with identification information that identifies the reflective member. The numbers inside the triangles represent identification information. 1 represents ID1, 2 represents ID2, and 3 represents ID3 in this example. The user device 181 acquires location information corresponding to each reflective member from the information providing device 14 and displays the reflective member symbol superimposed on the map at the position corresponding to the acquired location information. The user device 181 also acquires identification information corresponding to each reflective member from the information providing device 14 and displays a number corresponding to the acquired identification information on the reflective member symbol.

[0108] 20 is a functional block diagram showing an example of the functions of the information providing device in embodiment 2. The information providing device 14 in embodiment 2 further includes a search unit 201 and a generation unit 202 in addition to an acquisition unit 141, a frequency identification unit 142, a position identification unit 143, and an output unit 144. The functions of the acquisition unit 141, the frequency identification unit 142, the position identification unit 143, and the output unit 144 are the same as those in embodiment 1, and therefore description thereof will be omitted.

[0109] <Search Unit> The search unit 201 searches the database based on search conditions related to at least one of the position information, the time information, and the identification information. The database is provided in the information providing device 14, and specifically, is the memory 62. The database stores the composite data including the position information, the identification information, and the time information of the reflective member. The search conditions are transmitted from the user device. Then, the search results obtained by the search are transmitted to the user device 181 via the communication line 15. Alternatively, the search results are passed to a generation unit, which will be described later.

[0110] <Generation Unit> The generation unit 202 generates display information in which an icon representing the reflective member is superimposed at a predetermined position on the digital map. When the search unit 201 passes search results to the generation unit 202, the generation unit 202 generates display information in which an icon representing the reflective member is superimposed at a predetermined position on the digital map based on the passed search results. The display information is display information to be displayed on a browser, for example.

[0111] 21 is a sequence diagram showing the operation of the overall system when including the user device 181. Since steps up to step S12 are the same as those in the first embodiment, a description of steps up to step S12 will be omitted.

[0112] <Step S13> First, the user device 181 transmits search conditions to the information providing device 14 in order to search for location information, time information, and identification information stored in the information providing device 14. The search conditions are search conditions related to at least one of location information, time information, and identification information. The search conditions are input from an input device. The user inputs search conditions for acquiring the required data from the input device. After the user device 181 transmits the search conditions to the information providing device 14, the process proceeds to step S14.

[0113] <Step S14> The search unit 201 of the information providing device 14 receives the search conditions sent by the user device 181. The search unit 201 searches the database based on the received search conditions. The search conditions are search conditions related to at least one of location information, time information, and identification information.

[0114] If the search results obtained by the search are to be transmitted to the user device 181 via the communication line 15, the information providing device 14 proceeds to step S15. Alternatively, if the search results are to be passed to the generation unit, the information providing device 14 proceeds to step S16.

[0115] <Step S15> In step S15, the information providing device 14 transmits the search results to the user device 181. After the information providing device 14 transmits the search results to the user device 181, the process proceeds to step S18.

[0116] <Step S16> In step S16, the generation unit 202 of the information providing device 14 generates display information for superimposing a map of the area and a reflective member symbol placed in a portion of the map corresponding to the position of the reflective member indicated by the location information. The area is an area on the ground surface where reflective members are placed. When the search unit 201 passes the search results to the generation unit 202, the generation unit 202 generates display information in which an icon representing the reflective member is superimposed in a predetermined position on the digital map based on the passed search results. After the generation unit 202 generates the display information, the process proceeds to step S17.

[0117] <Step S17> In step S17, the information providing device 14 transmits the generated display information to the user device 181. After the information providing device 14 transmits the display information to the user device 181, the process proceeds to step S18.

[0118] <Step S18> In step S18, the user device 181 outputs the received search results or display information. The output destination is, for example, an LCD display. The user device 181 displays the received search results or display information on the LCD display in a predetermined format.

[0119] [2-5. Summary] As described above, the search results or display information output by the information providing device 14 is output to the user device. When the user sees the output search results, they can easily identify objects on the ground. Identification can be made even easier by displaying a display indicating a reflective member at the position indicated by the location information superimposed on the map.

[0120] 3. Application Examples Next, application examples of the information providing device according to the present disclosure will be described.

[0121] 19 shows an example of a display on a user device when the present disclosure is applied to a disaster information transmission system. In this application example, a reflective member is installed at a position on the ground where a specific event occurs.

[0122] In FIG. 19 , a triangle and a map are superimposed. The triangle is an icon indicating the location of a reflective element. The location where the triangle is displayed is based on the obtained location information. In FIG. 19 , numbers are also displayed within the triangle, and the numbers correspond to identification information. "1" corresponds to identification information "ID1," "2" corresponds to identification information "ID2," and "3" corresponds to identification information "ID3." For example, identification information ID1, ID2, and ID3 indicate the events shown in FIG. 15 . In this case, reflective element symbol 191 indicates that a fire has occurred at the location. reflective element symbol 192 indicates that a building has collapsed at the location. reflective element symbol 193 indicates that a person is seriously injured at the location. When a disaster such as an earthquake occurs, fires, building collapses, and many seriously injured people occur simultaneously. According to an application example of the present disclosure, the location and type of these disasters can be identified at once. This allows fire departments, local governments, and other organizations responding to such disasters to appropriately dispatch disaster response resources to the location. Furthermore, power outages may occur at the same time. Even in such cases, the reflective member according to the present disclosure functions without a power source, so that the type and location of the disaster can be known even during a power outage.

[0123] Needless to say, changes in the situation after a disaster can be grasped by implementing the monitoring system described below. Also, when a new monitoring target appears, a procedure is taken to install a reflective member at the location where the monitoring target appears.

[0124] [3-2. Surveillance System] The present disclosure can be applied to a surveillance system that monitors a target. In this application example, a reflective member is installed on a specific target that exists on the ground surface.

[0125] That is, the reflective member according to the present disclosure is provided on a monitored object, such as a vehicle, a hiker, infrastructure such as a road, or a construction sign.

[0126] <In the case of vehicles> When the target of monitoring is a vehicle, a reflective member according to the present disclosure is installed, for example, on the ceiling of the vehicle. The frequency at which the reflective member changes its intensity is associated with the type of vehicle. Examples of vehicle types include trucks and police cars. The reflective member according to the present disclosure can be configured in a sheet shape with sides of approximately 10 cm. The reflective member functions without a power supply, eliminating the need for power wiring. Therefore, the reflective member can be easily installed on the ceiling of a vehicle. If a truck becomes stranded during snowfall, the truck equipped with the reflective member is superimposed on a map to display the position and identification information of the reflective member, making it easy to determine which truck is stranded and where. Furthermore, by selecting identification information indicating a police car, the position of the police car can be displayed superimposed on a map, allowing police cars to be quickly deployed to the location of the incident. If the reflective member is installed on a truck entering or leaving a port parking lot, the availability of the parking lot can be easily determined.

[0127] <In the case of a hiker> If the target of surveillance is a hiker, the reflective material is attached to the hiker's backpack, for example. SAR data can be used to monitor the target over a wide area, through obstacles such as trees, day or night, and in any weather. This makes it easy to find lost hikers over a wide area. Furthermore, even if the target is hidden by trees and cannot be seen from the air, the search is possible regardless of day or night or weather.

[0128] <In the case of infrastructure> When the monitored object is infrastructure such as a road, the reflective member is attached to the surface of the road, for example. When the road is covered with ice, the reflective member does not reflect electromagnetic waves, so the reflective member monitoring the monitored object disappears, and it is detected that the road is covered with ice. Furthermore, the reflective member according to the present disclosure is functional without requiring a power source. Therefore, it can be used as a monitoring sensor without a battery, reducing maintenance costs. Furthermore, the monitored object can be monitored for a long period of time, until the life of the reflective member expires.

[0129] <Construction Signs> When the object of monitoring is a construction sign, reflective elements corresponding to the construction status are installed at the location where the construction is taking place. By installing reflective elements corresponding to different identification information for when construction is underway and when construction has ended, it is possible to know when the construction has started and ended.

[0130] [3-3. Position Correction] By placing a reflective member at a reference point, it is possible to correct the position indicated by the position information. For example, it becomes possible to align an image of SAR data with a map of the earth's surface corresponding to the SAR data. Specifically, a setting unit 221 is added as a functional block to the information providing device 14. FIG. 22 is a functional block diagram showing an example of the functions of an information providing device to which a setting unit has been added. The setting unit 221 sets absolute coordinates in the position information of the reference member. Here, the reference member is a reflective member installed in the observation area, and is installed at a location whose absolute coordinates are known.

[0131] That is, the predetermined position on the Earth's surface is, for example, a mobile phone base station. This is because the location of the mobile phone base station is accurately known in order to identify the location of the mobile phone. Then, a reference point reflector serving as a reference point is placed at the predetermined position. In such a case, the latitude and longitude indicated by the obtained position information corresponding to the reference point reflector will have an error from the actual latitude and longitude of the predetermined position on the Earth's surface. However, since the actual latitude and longitude of the predetermined position on the Earth's surface is clear, the difference from the latitude and longitude indicated by the obtained position information corresponding to the reference point reflector can be used as a correction value for correcting the position information. Then, by correcting the position of the SAR data image based on the correction value, it is possible to align it with the Earth's surface map corresponding to the SAR data.

[0132] [4. Supplementary Note] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope of the claims.

[0133] REFERENCE SIGNS LIST 11 Reflecting member 12 SAR satellite 13 Communication device 14 Information providing device 15 Communication line 21 Conductor 22 Dielectric substrate 31 Van Atta array antenna 32 Antenna 41 Microstrip line 42 Stub 51 Control unit 52 Memory 53 Communication interface 54 Transceiver device 55 Communication bus 56 Antenna 61 Control unit 62 Memory 63 Communication interface 64 Communication bus 71a, 71b Stub 112, 113 Reflecting member 111a, 111b, 111c Primary SAR data image 121a, 121b, 121c, 121d, 121e Secondary SAR data image 141 Acquisition unit 142 Frequency identification unit 143 Position identification unit 143a Pixel identification unit 144 Output unit 181 User device 191, 192, 193 Reflection member symbol 201 Search unit 202 Generation unit 221 Setting unit f1, f2, f3 Frequency fs Irradiation wave fd Reflection wave ID1, ID2, ID3 Identification information ε Relative dielectric constant λ ｄ , λ ０ wavelength

Claims

1. An information providing device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, The aforementioned multiple observation data represent data in which the intensity of the frequency component of the transmitted radio wave is changed when the transmitted radio wave is reflected by the reflective material. An acquisition unit that acquires the plurality of observation data relating to the observation area where the reflective member is arranged, A position identification unit that identifies the position information of the reflective member based on the plurality of observation data, The system comprises an output unit that outputs the composite data including the identified location information, Information provision device.

2. The information providing device according to claim 1, wherein the position information is information that identifies the position of the reflective member corresponding to the identification information, where the intensity of the frequency component corresponding to the identification information for identifying the reflective member has been changed.

3. The aforementioned information providing device is A storage unit for storing identification information of the reflective member, The system further includes a frequency identification unit that identifies the frequency whose intensity has been changed from the aforementioned plurality of observation data, The acquisition unit is, Multiple observation data are acquired for an observation area in which multiple reflective members with different frequency components that change the intensity are arranged. The output unit is, The information providing device according to claim 1, wherein the identification information of the identified reflective member is associated with the position information included in the composite data.

4. The aforementioned observation data is The image data includes pixels corresponding to the aforementioned observation area, and the pixel values ​​represent the reflection intensity. The aforementioned position identification unit is The pixel identification unit further includes a pixel identification unit that identifies the pixel corresponding to the reflective member based on the aforementioned pixel value, The information providing device according to any one of claims 1 to 3, wherein the output unit uses as the position information information information relating to the position of the observation area corresponding to the identified pixel.

5. The output unit is, The information providing device according to claim 3, which associates the position information included in the composite data with time information indicating the time when the observation data was generated.

6. The information providing device according to claim 5, further comprising a database in which the composite data, including the position information, identification information, and time information of the reflective member, is stored.

7. The information providing device according to claim 6, further comprising a search unit that searches the database based on search conditions relating to at least one of the location information, the identification information, and the time information.

8. The information providing device according to any one of claims 1 to 3, wherein the reflective member is provided on a specific object being monitored located on the ground surface.

9. The information providing device according to any one of claims 1 to 3, further comprising a generation unit that generates display information in which an icon representing the reflective member is superimposed on a predetermined position on a digital map.

10. The reflective member is This includes a reference member installed at a location with known absolute coordinates within the observation area, The information providing device according to any one of claims 1 to 3, further comprising a setting unit for setting the absolute coordinates to position information of the reference member.

11. At least one reflective element placed in the observation area, An information provision system comprising an information provision device according to any one of claims 1 to 3.

12. An information provision method performed by an information generation device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, The aforementioned multiple observation data represent data in which the intensity of the frequency component of the transmitted radio wave is changed when the transmitted radio wave is reflected by the reflective material. The steps include: acquiring the plurality of observation data relating to the observation area where the reflective member is arranged; The steps include: determining the position information of the reflective member based on the plurality of observation data; An information provision method comprising the step of outputting the composite data including the identified location information.

13. The information provision method according to claim 12, wherein the reflective member is a reflective member installed at the location where a specific event occurs on the ground surface.

14. A computer program that causes a computer to function as an information generation device that provides composite data of multiple observation data for each frequency observed by a synthetic aperture radar, The aforementioned multiple observation data represent data in which the intensity of the frequency component of the transmitted radio wave is changed when the transmitted radio wave is reflected by the reflective material. The aforementioned computer, An acquisition unit that acquires the plurality of observation data relating to the observation area where the reflective member is arranged. A positioning unit that identifies the position information of the reflective member based on the aforementioned plurality of observation data, and It functions as an output unit that outputs the composite data including the identified location information. Computer program.