JP7107764B2 - Reference point reflector - Google Patents

Description

The present invention relates to a reference point reflector that can be installed at any position and does not require adjustment of the installation angle.

In recent years, artificial satellite-mounted synthetic aperture radar (SAR) is expected to be used in the construction field. It is a technology that captures the unevenness of the ground surface by capturing scattered waves). With satellite SAR, the same region is observed at two or more different observation opportunities, and by analyzing the difference between them, it is possible to perform an analysis (differential interferometric analysis) to grasp time-series changes on the earth's surface.

In the differential interferometric analysis using the observation data of this satellite SAR, it is necessary to align multiple sets of observation data according to the latitude and longitude of the observation target (earth surface). Reflectors, such as corner reflectors, are used and these reflectors are placed at appropriate locations in the observation area.

The corner reflector is made by assembling metal plates such as aluminum plates that reflect radio waves into a box-shaped trihedral shape. It reflects toward the SAR and is displayed as a point with strong reflection intensity on the intensity image of the satellite SAR.

Kamal Sarabandi, Tsen-Chieh Chiu: Optimum Corner Reflectors for Calibration of Imaging Radars, IEEE Transactions on Antennas and Propagation, Vol.44, No.10, Oct.1996

By the way, the corner reflectors currently used for reference point generation such as differential interference analysis in satellite SAR correspond to the use wavelength band of satellite SAR used for surface observation, the satellite orbit, the incident angle of the irradiated radio waves, etc. Therefore, it was necessary to adjust the size and installation angle.

Here, if the installation angle of the corner reflector deviates by more than a few degrees in both azimuth and elevation, the corner reflector will not be able to properly reflect radio waves toward the satellite, and as a result, the reflection point may not be displayed in the observation data. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reference point reflector that can be installed at any position and that does not require adjustment of the installation angle.

In order to solve the above-described problems and achieve the object, a reference point reflector according to the present invention is arranged so that the center axis is in the vertical direction, a cylinder formed of metal, and the above-mentioned at the bottom of the cylinder. and a bottom plate that is arranged perpendicular to the central axis and made of metal.

In the above invention, the reference point reflector according to the present invention includes a GNSS reception antenna, and an antenna pole having the GNSS reception antenna arranged at the upper end and arranged at the central axis. characterized by

Further, the reference point reflector according to the present invention is characterized in that, in the above invention, the lower end of the cylinder and the bottom plate are arranged apart from each other.

Further, in the reference point reflector according to the present invention, in the above invention, the cylinder is formed with a plurality of holes for ventilation.

According to the present invention, it can be installed at any position, and adjustment of the installation angle becomes unnecessary.

FIG. 1 is a front view showing the configuration of a reference point reflector that is an embodiment of the present invention. FIG. 2 is a cross-sectional view of the reference point reflector shown in FIG. 1 taken along the line AA. FIG. 3 is an explanatory diagram showing a state of reflection of radio waves by the reference point reflector shown in FIG. FIG. 4 is a diagram comparing images of reference points obtained by a conventional corner reflector and a reference reflector according to the present embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a front view showing the configuration of a reference point reflector 1 according to an embodiment of the present invention. 2 is a cross-sectional view of the reference point reflector 1 shown in FIG. 1, taken along the line AA. The reference point reflector 1 reflects radio waves from the satellite SAR and retroreflects them as backscattered waves.

As shown in FIGS. 1 and 2, the reference point reflector 1 has a cylinder 10 and a bottom plate 20 . The cylinder 10 is arranged so that the central axis C is vertical, and is made of metal such as aluminum. The cylinder 10 is formed by winding a metal net 4 around the outer periphery of a plurality of support poles 3 arranged in an annular shape on a concrete block 2 and attaching it to the surface of the net 4 . The cylinder 10 is formed with a plurality of holes 11 for ventilation. Dimples may be formed on the outer peripheral surface of the cylinder 10 instead of the holes 11 . Wind resistance is suppressed by these holes 11 or dimples, and the strength of the reference point reflector 1 can be maintained.

The bottom plate 20 is a metal plate such as aluminum placed on the concrete block 2 below the cylinder 10 , and is formed with holes 11 like the cylinder 10 . The bottom plate 20 is made easier to manufacture by using the same perforated metal plate as the cylinder 10 . The bottom plate 20 is rectangular and has a size that includes at least the cross-sectional circle of the cylinder 10 .

An antenna pole 30 is arranged on the concrete block 2 on the central axis C of the cylinder 10 . A GNSS receiving antenna 31 is arranged on the upper end of the antenna pole 30 . Therefore, the reference point reflector 1 can simultaneously measure the position of this reference point reflector. In particular, since the GNSS reception antenna 31 is arranged at the center of the reference point reflector 1, highly accurate positioning can be performed while the reference point reflector 1 remains installed.

A gap d is formed between the cylinder 10 and the bottom plate 20 . The gap d is provided to ensure workability because there is a possibility that the inside of the cylinder 10 may be entered for maintenance work of the GNSS receiving antenna 31 or the like. Further, when the reference point reflector 1 is installed in a snowy area, the gap d has a snow removal function and facilitates the snow removal work. Even if the gap d is provided, there is no problem even if the cylinder 10 does not exist because this part contributes little to the reflection of radio waves.

It is assumed that the reference point reflector 1 has a size of about 2 m cubic, and the radio waves from the satellite SAR are in the L band.

As shown in FIG. 3, radio waves emitted from the satellite SAR (S1, S2) are reflected twice by the reference point reflector 1 and retroreflected toward the satellite SAR (S1, S2). Reflection by the reference point reflector 1 is not perfect retroreflection, but the backscattered wave is strongly reflected. In particular, the reference point reflector 1 has a symmetrical shape with respect to the central axis C. As shown in FIG. There is no horizontal dependence. In addition, the dependence of the angle of elevation or the angle of incidence on the reference point reflector 1 is small. The GNSS receiving antenna 31 can easily receive radio waves from a plurality of positioning satellites S10 and S11.

Radio waves passing through the central axis C are retroreflected, but the antenna pole 30 becomes an obstacle. However, since the diameter of the antenna pole is about several centimeters, which is smaller than the wavelength of the L band (20 to 60 cm), the reflection occurs due to diffraction.

In the present embodiment, the radio waves from the satellite SAR can be reflected in all directions regardless of the wavelength band used by the satellite SAR, the satellite orbit, and the incident angle of the irradiation radio waves. As a result, when performing differential interference analysis or the like using satellite SAR, since the reference point does not disappear, efficient and highly accurate differential interference analysis can be performed.

FIG. 4A shows an example of an SAR image when a conventional corner reflector is placed at a reference point, and FIG. is an SAR image of In FIG. 4A, the image P1 at the position where the reference point is arranged disappears due to the deviation of the incident angle of the radio wave, but in FIG. can be visually recognized as a shining point.

Although the embodiments to which the inventions made by the present inventors are applied have been described above, the present invention is not limited by the descriptions and drawings forming part of the disclosure of the present invention according to the embodiments and modifications. That is, other embodiments, modifications, operation techniques, etc. made by those skilled in the art based on the present embodiment and modifications are all included in the scope of the present invention.

1 Reference point reflector 2 Concrete block 3 Support pole 4 Net 10 Cylinder 11 Hole 20 Bottom plate 30 Antenna pole 31 Receiving antenna C Central axis d Gap P1, P2 Image S1, S2 Satellite SAR
S10, S11 positioning satellite

Claims (5)

a cylinder formed of metal around the outer periphery of a plurality of support poles arranged in an annular shape and arranged so that the central axis is in the vertical direction;
a bottom plate that is arranged perpendicular to the central axis at the bottom of the cylinder and is made of metal;
A reference point reflector, comprising: A cylinder made of metal arranged so that the central axis is in the vertical direction;
a bottom plate that is arranged perpendicular to the central axis at the bottom of the cylinder and is made of metal;
a GNSS receiving antenna;
The GNSS receiving antenna is arranged at the upper end, and an antenna pole arranged on the central axis;
A reference point reflector, comprising: a GNSS receiving antenna;
The GNSS receiving antenna is arranged at the upper end, and an antenna pole arranged on the central axis;
2. The reference point reflector according to claim 1, comprising: 4. The reference point reflector according to claim 1 , wherein the lower end of the cylinder and the bottom plate are spaced apart. The reference point reflector according to any one of claims 1 to 4 , wherein the cylinder is formed with a plurality of holes for ventilation.

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