Radar reflection system and measurement method

Abstract

To provide a radar reflection system that enables a synthetic aperture radar reflector to be installed so as not to create a barrier to others even in a place where people and cars come and go, and a measurement method using the same.SOLUTION: A radar reflection system includes: an underground hole with a hole axis being appropriately vertical (including being vertical) and a reflector for reflecting a synthetic aperture radar. The reflector is installed in the underground hole. The present invention thus pays attention to making use of an underground hole, that is, installing the reflector at a position lower than the ground surface, and is based on a novel idea.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to technology related to measurements using synthetic aperture radar, and more specifically to a radar reflection system in which a reflector is installed in an underground hole, and a measurement method using this system. [Background technology]

[0002] Japan is known as a country prone to earthquakes, and in recent years has experienced major earthquakes such as the 2024 Noto Peninsula Earthquake, the Tohoku Pacific Coast Earthquake, and the Southern Hyogo Prefecture Earthquake, each of which has caused extensive damage. Furthermore, due to global warming, there has been an increase in large-scale wind and flood damage, including unprecedented torrential rains and typhoons.

[0003] When widespread building damage occurs due to earthquakes, typhoons, or other disasters, aerial surveys are conducted to grasp the full extent of the damage. For example, aircraft may fly overhead and take photographs (so-called aerial photography), and the images may be used to confirm the extent of the damage. Techniques for surveying large areas include aerial photography and synthetic aperture radar (SAR). For example, differential interferometric synthetic aperture radar (SAR) analysis, which compares SAR measurement results from two different periods, can reveal displacements on the order of a few centimeters over a wide area. The Advanced Land Observing Satellite-2 (ALOS-2) was launched in May 2014, and the development and launch of privately-run micro-SAR satellites is also underway, further promoting the use of SAR.

[0004] Measurements made using synthetic aperture radar (hereafter simply referred to as "synthetic aperture radar measurements") involve microwaves emitted from a satellite being reflected off the ground, and the position and displacement of a feature being determined from the signal strength and phase of the reflected waves. Synthetic aperture radar measurements sometimes use reflectors that strongly reflect synthetic aperture radar (i.e., microwaves). The waves reflected by a reflector are much stronger than the surrounding area, making them distinguishable from waves reflected by other features, so reflectors (sometimes called corner reflectors) are installed at reference points with known coordinates, for example.

[0005] Typically, once a reflector is installed, it is not moved for a long period of time, and the tilt of the reflector (e.g., a metal plate) included in the reflector is not changed. Therefore, when installing a reflector, considerable care is required, such as selecting a location that does not create a barrier for others and arranging the reflector so that it is always tilted appropriately. Therefore, various technologies related to reflectors for synthetic aperture radar have been proposed. For example, Patent Document 1 proposes a "reference point reflector" that is fixed to the ground and is intended to reflect satellite radio waves from various directions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-220905 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, reflectors are usually not moved for long periods of time, so they are naturally installed in places that do not create a barrier to others. On the other hand, depending on the object to be measured, it may be desirable to install reflectors in places that are used by many people, such as roads or parks. However, conventional reflectors, including the reference point reflector of Patent Document 1, are placed on the ground, so they cannot be installed on roads or the like.

[0008] The object of the present invention is to solve the conventional problems, that is, to provide a radar reflection system in which a reflector for synthetic aperture radar can be installed so as not to become a barrier to others, even in places where people and vehicles are passing by, and a measurement method using the same. [Means for solving the problem]

[0009] The present invention focuses on utilizing an underground hole, i.e., installing a reflector at a position lower than the ground surface, and is an invention based on an idea that has not been seen before.

[0010] The radar reflection system of the present invention comprises a borehole whose axis is substantially vertical (including vertical), and a reflector that reflects synthetic aperture radar. The reflector is installed inside the borehole.

[0011] The radar reflection system of the present invention may further include a base plate on which the reflector is placed. This base plate can rotate around a substantially vertical axis (including vertical) with the reflector placed thereon.

[0012] The radar reflection system of the present invention can further include a bottom plate, a support, and a locking body. The bottom plate is attached to the lower end of the support, and the locking body is attached to the upper end of the support. In this case, when the locking body is locked to the edge of the opening of the underground hole, the bottom plate (i.e., the reflector) is suspended within the underground hole via the support.

[0013] The radar reflection system of the present invention can further include a bottom plate, a support, and a cover. The bottom plate is attached to the lower end of the support, and the cover is attached to the upper end of the support. The cover is made of a material that is transparent to the microwaves of the synthetic aperture radar. In this case, when the cover is placed at the opening of the underground hole, the bottom plate (i.e., the reflector) is suspended within the underground hole via the support.

[0014] The radar reflection system of the present invention may further include an independent reflector that reflects the synthetic aperture radar. This independent reflector is installed on the inner surface of the underground hole. The independent reflector itself may also serve as the reflector of the radar reflection system of the present invention.

[0015] The measurement method of the present invention is a method for performing synthetic aperture radar measurement using the radar reflection system of the present invention, and includes a reflector installation step in which a reflector is installed in an underground borehole.

[0016] The measurement method of the present invention may further include a parameter calculation step, in which the size of the reflective surface of the reflector is calculated based on the angle of incidence of the synthetic aperture radar at the borehole and the shape and dimensions of the borehole. In this case, the reflector installation step involves installing in the borehole a reflector with a reflective surface of the size calculated in the parameter calculation step. [Effects of the Invention]

[0017] The radar reflection system and measurement method of the present invention have the following advantages. (1) Because the reflector is installed in an underground hole, it will not become a barrier to others, even if it is installed in a place where many people use it, such as on a road or in a park. (2) Reflectors can be installed on roads, etc., which expands the scope of synthetic aperture radar measurement compared to conventional technology. (3) It is possible to easily construct a radar reflection system by simply installing a reflector in the underground hole. In particular, it is easier to construct a radar reflection system when using an existing underground hole such as a manhole. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a side view schematically showing a radar reflection system 100 according to the present invention. [Figure 2] FIG. 2 is a front view schematically showing a reflector formed by a bottom reflecting surface, a left reflecting surface, and a right reflecting surface, all of which are triangular. [Figure 3] FIG. 2 is a front view schematically showing a reflector formed by a bottom reflective surface, a left reflective surface, and a right reflective surface, all of which are rectangular. [Figure 4] FIG. 10 is a side view schematically showing a bottom plate that rotates around a substantially vertical axis. [Figure 5] (a) is a side view showing a schematic diagram of a reflector placed on a bottom plate suspended in an underground borehole by a support and a locking body, and (b) is a plan view of the support and the locking body viewed from above. [Figure 6] (a) is a side view showing a schematic diagram of a reflector placed on a bottom plate suspended in an underground borehole by a support and a cover, and (b) is a plan view of the support and the cover seen from above. [Figure 7] (a) is a side view showing a schematic diagram of an underground hole with an independent reflector installed on its inner surface, and (b) is a plan view of the independent reflector installed on the inner surface of the underground hole, viewed from above. [Figure 8] 1 is a flowchart showing the flow of main steps of a measurement method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An example of an embodiment of the radar reflection system and measurement method of the present invention will be described with reference to the drawings.

[0020] 1. Measurement System First, the radar reflection system of the present invention will be described. The measurement method of the present invention is a method for performing synthetic aperture radar measurement using the radar reflection system of the present invention. Therefore, the radar reflection system of the present invention will be described first, and then the measurement method of the present invention will be described.

[0021] 1 is a side view (however, the inside of the ground is a cross-sectional view cut along a vertical plane) that shows a schematic diagram of a radar reflection system 100 of the present invention. As shown in this figure, the radar reflection system 100 of the present invention is configured to include a reflector 110 and an underground hole 120, and can also be configured to include a bottom plate 130, a cover 140, a tilting jig 150, as well as support materials, locking bodies, and independent reflectors, which will be described later.

[0022] A conventional reflector 110 can be used, and a so-called corner reflector consisting of a three-sided reflector can also be used. For example, the reflector 110 shown in Fig. 2 is made up of three triangular reflectors joined together. For convenience, the reflector placed on the bottom surface will be referred to as the "bottom reflecting surface 111," and the reflectors placed on both sides of the bottom reflecting surface 111 will be referred to as the "left reflecting surface 112" and the "right reflecting surface 113," respectively. Of course, the bottom reflecting surface 111, the left reflecting surface 112, and the right reflecting surface 113 are made of a material that strongly reflects synthetic aperture radar (i.e., microwaves), such as a metal such as iron or copper.

[0023] 3, the reflector 110 can be formed by a bottom reflecting surface 111, a left reflecting surface 112, and a right reflecting surface 113, all of which are rectangular. Alternatively, the reflector 110 can be formed by a reflecting plate of another shape, or by one or more reflecting plates.

[0024] The reflector 110 is installed in an underground hole 120 as shown in Figure 1. At this time, the reflector 110 can be placed directly on the bottom surface (hole bottom) of the underground hole 120, or as shown in this figure, the reflector 110 can be placed on a bottom plate 130 placed on the bottom surface of the underground hole 120. When tilting the reflector 110, it is recommended to use a tilting jig 150 to place the reflector 110.

[0025] The underground hole 120 has a central axis (hereinafter referred to as the "hole axis") that is approximately vertical (including vertical), and can be constructed by excavation for the purpose of the present invention, or an existing underground hole such as a manhole can be used as the underground hole 120. Of course, the cross-sectional shape of the underground hole 120 can be circular, or can be any shape such as an oval, square, or polygon.

[0026] Because the top of the ground hole 120 is open, the synthetic aperture radar from the satellite is reliably irradiated onto the reflector 110, and the waves reflected by the reflector 110 are also reliably sent into the sky. On the other hand, having an open top of the ground hole 120 is undesirable from a safety standpoint, as it could lead to someone falling in. For this reason, it is advisable to install a lid 140 at the top of the ground hole 120 to close the opening. However, this lid 140 is made of a material that is easily penetrated by synthetic aperture radar, such as resin (plastic), FRP (Fiber Reinforced Plastics), paper, or wood.

[0027] There may be cases where it is desired to change the orientation (particularly the direction) of the reflector 110 after it has been installed in the underground hole 120. In such cases, it is preferable to use a structure in which the bottom plate 130 rotates around a substantially vertical (including vertical) axis (hereinafter referred to as the "rotation axis") as shown in FIG. 4. FIG. 4 is a side view (however, the ground is a cross-sectional view cut along a vertical plane) that schematically shows the bottom plate 130 rotating around the rotation axis. By rotating the bottom plate 130 with the reflector 110 placed on it, the reflector can be adjusted to the desired orientation. Note that various conventional techniques, such as a turntable, can be used to rotate the bottom plate 130.

[0028] As explained above, an existing manhole or the like can be used as the ground hole 120. However, if the existing hole (such as a manhole) is deep, it is possible that the synthetic aperture radar will not reach the hole if the reflector 110 is installed at the bottom of the hole. In this case, as shown in FIG. 5, the reflector 110 can be placed on a bottom plate 130 suspended within the ground hole 120. FIG. 5(a) is a side view (however, the ground is a cross-section cut along a vertical plane) showing the state in which the reflector 110 is placed on the bottom plate 130 suspended within the ground hole 120 by a support material 160 and a locking body 170, and FIG. 5(b) is a plan view of the support material 160 and the locking body 170 as viewed from above. Note that in FIG. 5(b), the hole wall of the ground hole 120 is indicated by a dashed line.

[0029] As shown in Fig. 5, the support member 160 has the bottom plate 130 attached to its lower end and the locking body 170 attached to its upper end. In other words, the bottom plate 130 and the locking body 170 are connected via the support member 160. Note that, as shown in this figure, when rod-shaped support members 160 are used, the bottom plate 130 and the locking body 170 are connected by multiple support members 160 (eight in Fig. 5(b)), and when cylindrical (annular) support members 160 are used, the bottom plate 130 and the locking body 170 are connected by one support member 160.

[0030] As shown in Figure 5(b), the locking body 170 can be made ring-shaped with an outer diameter slightly larger than the inner diameter of the ground hole 120. As a result, when the locking body 170 is locked onto the edge of the opening, as shown in Figure 5(a), the bottom plate 130 is suspended within the ground hole 120 by the support material 160. When the reflector 110 is placed on the bottom plate 130 in this state, the reflector 110 can be placed at a relatively shallow position within the ground hole 120, which means that it can reliably receive synthetic aperture radar from a satellite.

[0031] When the locking body 170 is placed on the ground, it will protrude from the ground surface by the amount of its thickness. If this state is inconvenient, it is recommended to excavate the edge of the opening so that it is partially cut away, that is, to install the locking body 170 so that its upper surface is flush with the ground surface. Furthermore, the locking body 170 is not limited to a continuous ring-shaped locking body 170 as shown in Figure 5(b), and an independent locking body 170 can also be used for each rod-shaped support member 160.

[0032] When installing a cover 140 on top of the ground hole 120, the cover 140 can be used instead of the locking body 170, as shown in Figure 6. Figure 6(a) is a side view (however, the ground is a cross-sectional view cut along a vertical plane) showing the reflector 110 placed on the bottom plate 130 suspended within the ground hole 120 by the support material 160 and the cover 140, and Figure 6(b) is a plan view of the support material 160 and the cover 140 viewed from above. Note that in Figure 6(b), the hole wall of the ground hole 120 is indicated by a dashed line. Furthermore, even in cases where the cover 140 is used instead of the locking body 170, the cover 140 is still made of a material that is easily penetrable by synthetic aperture radar, such as resin (plastic) or FRP.

[0033] A reflector (hereinafter referred to as an "independent reflector 180") different from the reflector provided in the reflector 110 can also be installed on the inner circumferential surface (i.e., the hole wall) of the ground hole 120, as shown in Figure 7. Figure 7(a) is a side view showing the ground hole 120 with the independent reflector 180 installed on its inner circumferential surface (however, the inside of the ground is a cross-sectional view cut along a vertical plane), and Figure 7(b) is a plan view of the independent reflector 180 installed on the inner circumferential surface of the ground hole 120, viewed from above.

[0034] The independent reflector 180, like the bottom reflecting surface 111, is made of a material that strongly reflects synthetic aperture radar, such as a metal such as iron or copper. The independent reflector 180 is formed in a plate shape, but is bent to fit the cross-sectional shape of the underground hole 120 and then installed on the inner surface thereof, as shown in FIG. 7(b). The independent reflector 180 shown in FIG. 7(b) is installed so as to cover the entire inner surface of the underground hole 120, but it can also be installed so as to cover only a portion of the inner surface of the underground hole 120 (for example, with the right side missing). Also, it is possible to install only the independent reflector 180 without installing the reflector 110; in other words, it is possible to use the independent reflector 180 as the reflector 110 instead of the reflector 110 shown in FIG.

[0035] 2. Measurement method Next, the measurement method of the present invention will be described with reference to Figure 8. The measurement method of the present invention is a method of performing synthetic aperture radar measurement using the radar reflection system 100 described up to this point. Therefore, we will avoid explanations that overlap with the contents explained in the radar reflection system 100, and will mainly explain the contents unique to the measurement method of the present invention. In other words, the contents not described here are the same as those explained in "1. Radar reflection system."

[0036] Figure 8 is a flow diagram showing the flow of the main steps of the measurement method of the present invention. When performing synthetic aperture radar measurement using the radar reflection system 100 of the present invention, it is advisable to first calculate the specifications of the reflector 110 as shown in this figure (Step 201 in Figure 8). Specifically, the underground hole 120 in which the reflector 110 will be installed is planned, and specifications such as the dimensions, shape, and placement orientation of the reflector (e.g., bottom reflecting surface 111, left reflecting surface 112, and right reflecting surface 113) are calculated based on the incident angle (azimuth and elevation) of the synthetic aperture radar (i.e., microwaves) at the underground hole 120, the shape and dimensions (e.g., inner diameter) of the underground hole 120, and the installation depth of the reflector 110.

[0037] Once the specifications of the reflector 110 are obtained, the reflector 110 is manufactured based on the specifications (Step 202 in FIG. 8). The manufactured reflector 110 is then installed in the planned underground hole 120 (Step 203 in FIG. 8), and synthetic aperture radar measurement is performed using the reflector 110 (Step 204 in FIG. 8). [Industrial Applicability]

[0038] The radar reflection system and measurement method of the present invention can be used in various places, such as on roads. The present invention allows synthetic aperture radar measurements to be performed anywhere, and in particular, it can quickly grasp damage to buildings caused by disasters over a wide area. Considering this, the present invention can be said to be an invention that can be used industrially and is also expected to contribute to society. [Explanation of symbols]

[0039] 100 Radar reflection system of the present invention 110 Reflector (of a radar reflection system) 111 (of reflector) bottom reflective surface 112 (of the reflector) left reflective surface 113 (of reflector) right reflective surface 120 Borehole (for radar reflecting systems) 130 (Radar Reflection System) Base Plate 140 (Radar Reflection System) Cover 150 (Radar Reflection System) Tilt Jig 160 (Radar Reflection System) Support 170 (Radar Reflection System) Stopper 180 Independent reflector (for radar reflecting systems)

Claims

1. a borehole whose axis is vertical or approximately vertical; a reflector that is installed in the underground hole and reflects the synthetic aperture radar; A radar reflecting system characterized by:

2. Further provided is a bottom plate on which the reflector is placed, The bottom plate rotates around a vertical or substantially vertical axis with the reflector placed thereon.

2. The radar reflector system of claim 1.

3. a bottom plate on which the reflector is placed; a support attached to the bottom plate; a locking body attached to an upper end of the support material, When the engaging body is engaged with the edge of the opening of the underground hole, the bottom plate is suspended via the support material.

2. The radar reflector system of claim 1.

4. a bottom plate on which the reflector is placed; a support attached to the bottom plate; a cover that is transparent to the synthetic aperture radar, The lid is attached to the upper end of the support member, When the cover body is installed on the opening of the underground hole, the bottom plate is suspended via the support material.

2. The radar reflector system of claim 1.

5. Further provided is an independent reflector that reflects the synthetic aperture radar, The independent reflector is installed on the inner surface of the underground hole.

2. The radar reflector system of claim 1.

6. The reflector is a plate-like member installed on the inner surface of the underground hole.

2. The radar reflector system of claim 1.

7. a reflector installation step of installing a reflector that reflects the synthetic aperture radar in an underground hole whose hole axis is vertical or approximately vertical, The reflector is utilized to perform measurement by the synthetic aperture radar. A measuring method characterized by:

8. a parameter calculation step of calculating a size of a reflecting surface of the reflector based on an incident angle of the synthetic aperture radar at the underground hole and a shape and a dimension of the underground hole, In the reflector installation step, the reflector having the reflective surface of the size calculated in the specification calculation step is installed.

8. The measuring method according to claim 7.

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