JP7231394B2 - Sea level display device and sea level measurement system - Google Patents

Description

The present disclosure relates to technology for measuring sea surface waves.

A technique for measuring waves on the sea surface is disclosed in Patent Document 1 and the like. In Patent Document 1, waves on the sea surface are measured by arranging a plurality of buoys on the sea surface and photographing them with a camera.

JP 2018-096827 A

In Patent Literature 1, it is necessary to maintain and manage a plurality of buoys, which is troublesome, and it is necessary to detect the motions of the plurality of buoys as images, which is difficult to detect.

Therefore, in order to solve the above problems, an object of the present disclosure is to reduce maintenance and management and facilitate image detection when measuring waves on the sea surface.

In order to solve the above problems, we decided to measure sea surface waves by measuring sea surface clutter in radar images. Specifically, the length of the arrow, the direction of the arrow, the numerical value, the gradation, or the like is used to symbolize the waves on the sea surface in the radar image.

Specifically, the present disclosure is a sea surface display device characterized by symbolically displaying at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface in a radar image.

According to this configuration, when measuring the waves on the sea surface, it is sufficient only to perform maintenance and management of the radar system, and it is only necessary to perform image detection of sea surface clutter. Then, in the sea area represented by the radar image, the waves on the sea surface can be symbolically displayed quantitatively.

The present disclosure also uses line segments to symbolize wave crests on the sea surface, line segment spacing to symbolize sea surface wavelengths, and the direction perpendicular to the line segments to symbolize wave direction on the sea surface. This sea surface display device is characterized by symbol display.

According to this configuration, in the sea area represented by the radar image, it is possible to quantitatively symbolize the wavelength and wave direction of the sea surface using the line segment that symbolizes the wave crest of the sea surface.

In addition, in symbolizing the wave crest of the sea surface using a line segment, the present disclosure updates the line segment each time the radar image is updated, and uses the speed of movement of the line segment to symbolize the wave speed of the sea surface. It is a sea surface display device characterized by the following.

According to this configuration, in the sea area represented by the radar image, the wave velocity on the sea surface can be quantitatively symbolized using the line segment that symbolizes the crest of the wave on the sea surface.

Further, the present disclosure is a sea surface display device characterized by displaying a radar image superimposed on at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface.

According to this configuration, it is possible to visually display the waves on the sea surface by using the portions with high reflection intensity that reflect the wave crests on the sea surface in the sea area represented by the radar image.

Further, the present disclosure is a sea surface display device characterized by displaying at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface by user selection.

According to this configuration, it is possible to simplify the symbol display of the waves on the sea surface.

Further, the present disclosure is a sea surface display device characterized by displaying whether it is safe to launch or land on the sea surface using a radar image.

According to this configuration, it is possible to display the safety of the sea area represented by the radar image.

In addition, the present disclosure measures at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface in radar images based on the sea surface display device described above and wave number space analysis or real space analysis in radar images. A sea level measurement system characterized by comprising a sea level measurement device for

According to this configuration, when measuring the waves on the sea surface, it is sufficient only to perform maintenance and management of the radar system, and it is only necessary to perform image detection of sea surface clutter. Then, in the sea area represented by the radar image, the waves on the sea surface can be symbolically displayed quantitatively.

Thus, the present disclosure can reduce maintenance and facilitate image detection when measuring waves on the sea surface.

1 is a diagram showing a configuration of a sea level measurement system of the present disclosure; FIG. FIG. 3 illustrates a method of displaying sea surface parameters of the present disclosure; FIG. 3 is a diagram illustrating a method of displaying sea surface wavelength and wave direction of the present disclosure; FIG. 3 is a diagram showing a method of displaying sea surface wavelength, wave direction, and wave speed according to the present disclosure; FIG. 2 illustrates a sea surface parameter and two-dimensional radar image superposition method of the present disclosure; FIG. 2 is a diagram illustrating sea surface parameters and a method of superimposing three-dimensional radar images of the present disclosure; FIG. 2 illustrates a user-selectable display method for sea surface parameters of the present disclosure; FIG. 3 illustrates a safety indication method based on sea level parameters of the present disclosure; FIG. 2 illustrates a method of measuring sea surface wavelength and wave direction of the present disclosure; FIG. 2 illustrates a method of measuring sea surface wave speed according to the present disclosure; FIG. 2 is a diagram illustrating a method of measuring sea surface wave heights of the present disclosure;

Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementing the present disclosure, and the present disclosure is not limited to the following embodiments.

FIG. 1 shows the configuration of the sea level measurement system of the present disclosure. The sea level measurement system S is composed of a radar transmitter 1 , a radar receiver 2 , a sea level measuring device 3 and a sea level display device 4 . The sea level measurement device 3 is composed of an image dividing section 31 and a sea level measurement section 32 .

A radar transmission unit 1 emits a radar beam toward the sea. The radar receiver 2 receives radar beams reflected from the sea. The sea surface measurement device 3 measures sea surface waves by measuring sea surface clutter in radar images. The sea level display device 4 visualizes and displays the radar image data acquired, processed and created by the sea level measurement device 3 .

The image dividing unit 31 divides the radar image to generate each divided image. The sea surface measurement unit 32 measures at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface in each divided image based on wave number space analysis or real space analysis in each divided image. Note that the image dividing unit 31 does not have to divide the radar image. In addition, the sea surface measurement unit 32 may measure at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface in an undivided radar image.

The method of displaying sea level parameters of the present disclosure is illustrated in FIG. The sea surface display device 4 symbolizes at least one of the wavelength, wave direction, wave speed and wave height of the sea surface in each divided image.

In the left column of FIG. 2, the radar image is divided into 8 divisions in the x direction and 8 divisions in the y direction, for a total of 8×8=64 divisions. In the right column of FIG. 2, a legend is displayed how the wavelength, wave direction, wave speed and wave height at the sea surface are symbolized. The wavelength of the sea surface is represented by the length of the arrow in FIG. 2, the direction of the wave on the sea surface is represented by the direction of the arrow in FIG. 2, the wave velocity on the sea surface is represented by the numerical values in FIG. is represented by the gradation in FIG. Note that the size of the sea surface parameter may be represented by the thickness of the arrow, the size of the circle, or the like.

In this way, when measuring waves on the sea surface, it is only necessary to perform maintenance and management of the sea surface measurement system S, and it is only necessary to perform image detection of sea surface clutter. Then, in the sea area represented by the radar image, the waves on the sea surface can be symbolically displayed quantitatively.

FIG. 3 shows a method of displaying sea surface wavelength and wave direction according to the present disclosure. The sea surface display device 4 symbolizes the crest of the sea surface using line segments, symbolizes the wave length of the sea surface using the interval between the line segments, and symbolizes the wave direction of the sea surface using the direction perpendicular to the line segments. Symbolize.

In the left column of FIG. 3, in the radar image, sea surface clutter with high reflection intensity is observed as wave crests on the sea surface and symbolized using line segments. In the middle column of FIG. 3, the wavelength of the sea surface is represented by the interval of the line segments, and the wave direction of the sea surface is represented by the direction perpendicular to the line segments. In the right column of FIG. 3, a legend is displayed how the wavelength and wave direction of the sea surface are symbolized.

In this way, in the sea area represented by the radar image, the wavelength and wave direction of the sea surface can be quantitatively symbolized using the line segment symbolizing the crest of the sea surface. The wavelength and wave direction of the sea surface can then be visually symbolized better than when line segments are not used.

FIG. 4 shows a method of displaying sea surface wavelength, wave direction, and wave speed according to the present disclosure. The sea surface display device 4 symbolizes the crest of the sea surface using line segments, updates the line segments each time the radar image is updated, and uses the speed of movement of the line segments to symbolically display the wave velocity of the sea surface. .

In the upper left column and the lower left column of FIG. 4 , sea surface clutter with high reflection intensity is observed as wave crests on the sea surface in the radar images before and after updating, respectively, and symbolized using line segments. In the middle upper and middle lower columns of FIG. 4, before and after updating the radar image, the wavelength of the sea surface is represented by the interval of the line segment, and the wave direction of the sea surface is in the direction perpendicular to the line segment. and the wave velocity on the sea surface is represented by the velocity of the line segment movement. In the right column of FIG. 4, a legend is displayed for how the wavelength, wave direction and wave speed at the sea surface are symbolized.

In this way, in the sea area represented by the radar image, the wave velocity on the sea surface can be quantitatively symbolized using the line segment symbolizing the crest of the wave on the sea surface. Then, the sea surface wave speed can be symbolically displayed more visually than when line segments are not used.

FIG. 5 shows the method of superimposing sea surface parameters and two-dimensional radar images of the present disclosure. FIG. 6 shows the method of superimposing sea surface parameters and three-dimensional radar images of the present disclosure. The sea surface display device 4 superimposes a radar image on at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface.

In the left column of FIG. 5, the radar image is a two-dimensional radar image consisting of the x-axis and the y-axis, divided into 8 in the x direction, 8 in the y direction, and 8×8=64 in total. . In the right column of FIG. 5, a legend is displayed as to how the wavelength, wave direction, wave speed and wave height at the sea surface are symbolized. The wavelength of the sea surface is represented by the length of the arrow in FIG. 5, the wave direction on the sea surface is represented by the direction of the arrow in FIG. 5, the wave velocity on the sea surface is represented by the numerical values in FIG. is represented by the gradation of FIG. 5, and the two-dimensional radar image is displayed superimposed on the parameters of the sea surface.

In the left column of FIG. 6, the radar image is a three-dimensional radar image consisting of the x-axis, the y-axis, and the reflection intensity axis (corresponding to the wave height axis), divided into eight in the x direction and eight in the y direction, It is divided into 8×8=64 as a whole. In the right column of FIG. 6, a legend is displayed for how the wavelength, wave direction and wave height at sea surface are symbolized. The wavelength of the sea surface is represented by the length of the arrow in FIG. 6, the direction of the wave on the sea surface is represented by the direction of the arrow in FIG. A three-dimensional radar image is superimposed on the parameters.

In this way, in the sea area represented by the radar image, it is possible to visually display the waves on the sea surface by using the portions with high reflection intensity that reflect the wave crests on the sea surface.

Note that each time the radar image is updated, not only the line segment in FIG. 4 but also the parameters of the sea surface may be updated, and the superimposed radar image may be updated. In addition, it may be switched whether to superimpose the radar image or not, and it may be switched which of the two-dimensional radar image and the three-dimensional radar image is to be superimposed.

A user-selectable display method for sea level parameters of the present disclosure is illustrated in FIG. The sea surface display device 4 displays at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface according to the user's selection.

In FIG. 7, the radar image is divided into 8 in the x direction, 8 in the y direction, and 8×8=64 as a whole. In the upper left column of FIG. 7, the user has selected the display of sea surface wavelengths, which are represented by the length of the arrow and how they are symbolized, with a legend. In the upper right column of FIG. 7, the user has selected to display wave direction on the sea surface, where the wave direction on the sea surface is represented by the direction of the arrow and how it is symbolized is displayed with a legend. . In the lower left column of FIG. 7, the user has selected to display the wave speed on the sea surface, where the wave speed on the sea surface is represented numerically and a legend is displayed as to how it is symbolized. In the lower right column of FIG. 7, the user has selected the display of the wave height of the sea surface, and the wave height of the sea surface is represented by gradation, and a legend is displayed as to how it is symbolically displayed.

In this way, the symbol display of waves on the sea surface can be simplified.

A safety indication method based on sea level parameters of the present disclosure is illustrated in FIG. The sea surface display device 4 displays whether it is safe to launch or land on the sea surface in the radar image.

In FIG. 8, the radar image is divided into 4 parts in the x direction, 4 parts in the y direction, and 4×4=16 parts as a whole. In the upper left column of FIG. 8, the wavelength of the sea surface is represented by gradation. Something is shown. In the upper right column of FIG. 8, the direction of the waves on the sea surface is represented by the direction of the arrow, the direction of the bow of the ship or the nose of the aircraft is represented as the upward direction in FIG. Based on the fact that launching or landing on the water is more dangerous if the direction hits the port side or starboard side of the aircraft or the left side or starboard side of the aircraft, the part where the direction of the arrow is the left-right direction in Figure 8 is dangerous. It is displayed that it is a sea area. In the lower left column of FIG. 8, the wave speed on the sea surface is represented by gradation, and based on the fact that the faster the wave speed on the sea surface, the more dangerous it is to launch or land on the water. Something is shown. In the lower right column of FIG. 8, the wave height of the sea surface is represented by gradation, and based on the fact that the higher the wave height of the sea surface, the more dangerous it is to launch or land on the water. is displayed.

In this way, it is possible to display the safety of the sea area represented by the radar image.

First, a method for measuring the wavelength, wave direction, wave speed, and wave height of the sea surface in each divided image by the sea surface measurement unit 32 based on the "wavenumber space analysis" in each divided image will be described.

FIG. 9 shows the method of measuring sea surface wavelength and wave direction of the present disclosure. The sea surface measurement unit 32 measures at least one of the wavelength and wave direction of the sea surface in each divided image based on the peak position in the wavenumber space of each Fourier spectrum.

Specifically, the B-scope image is coordinate-transformed into an XY coordinate image, STC processing is performed, and only a square image is cut out from the circular image to be used as a radar image for sea level measurement. Next, each spectrum of the previous scan and the current scan is generated for each divided image of the previous scan and the current scan. Next, each spectrum of the previous scan and the current scan are multiplied to generate each cross spectrum CS between the previous scan and the current scan. Next, each cross spectrum CS between the previous scan and the current scan is converted from wave number coordinates with k _x and k _y as wavelengths with λ _x =1/k _x and λ _y =1/k _y as coordinate axes. Coordinate transformation to coordinates.

Here, in each cross spectrum between the previous scan and the current scan, the peak positions are (λ _xp , λ _yp ). Therefore, the wavelength λ and the wave direction θ are calculated by Equations 1 and 2.

Thus, wave number space analysis makes it possible to easily measure at least one of the wavelength and wave direction of the sea surface compared to real space analysis. Then, at least one of the wavelength and wave direction of the sea surface can be individually measured in each sea area represented by each divided image. In measuring at least one of the wavelength and wave direction of the sea surface, each cross spectrum after multiplication may be used, but each spectrum before multiplication may be used. Further, in calculating each cross spectrum after multiplication or each spectrum before multiplication, a plurality of cross spectra after multiplication or each spectrum before multiplication from the past to the present may be averaged.

FIG. 10 shows the method of measuring the wave velocity on the sea surface of the present disclosure. The sea surface measurement unit 32 measures the wave velocity of the sea surface in each split image based on the difference between the peak phase of each Fourier spectrum at the earlier time and the peak phase of each Fourier spectrum at the later time. do.

Specifically, the B-scope image is coordinate-transformed into an XY coordinate image, STC processing is performed, and only a square image is cut out from the circular image to be used as a radar image for sea level measurement. Next, each spectrum of the previous scan and the current scan is generated for each divided image of the previous scan and the current scan. Next, each spectrum of the previous scan and the current scan is multiplied to generate each cross spectrum CS between the previous scan and the current scan.

Here, in each cross spectrum between the previous scan and the current scan, the peak positions are (k _xp , _kyp ). Therefore, the peak phase CS _θ (k _xp , _kyp ) of each cross spectrum is calculated by Equation 3, and the wave velocity v is calculated by Equation 4. However, τ is the time interval between the previous scan and the current scan (for example, the rotation period of the antenna).

Thus, the wave velocity on the sea surface can be easily measured by the wave number space analysis compared to the real space analysis. Then, the wave velocity on the sea surface can be individually measured in each sea area represented by each divided image. It should be noted that when the Nyquist condition 2πv/λ<π/τ is not satisfied, the wave velocity on the sea surface cannot be measured correctly. Further, in calculating each cross spectrum after multiplication or each spectrum before multiplication, a plurality of cross spectra after multiplication or each spectrum before multiplication from the past to the present may be averaged.

FIG. 11 shows the method of measuring the wave height of the sea surface of the present disclosure. (1) Based on the difference between the phase at each wavenumber of each Fourier spectrum at the earlier time and the phase at each wavenumber of each Fourier spectrum at the later time, each Calculate the measured wave velocity corresponding to each wavenumber of the Fourier spectrum, and (2) Calculate the theoretical wave velocity corresponding to each wavenumber of each Fourier spectrum based on the dispersion relationship of gravitational waves and the wavelength corresponding to each wavenumber of each Fourier spectrum. and (3) classifying the amplitude at each wavenumber of each Fourier spectrum into a signal component and a noise component based on the degree of agreement between the measured wave velocity and the theoretical wave velocity corresponding to each wavenumber of each Fourier spectrum, ( 4) Measure the sea surface wave height at each segmented image based on the empirical formula for significant wave height and the signal-to-noise ratio over all wavenumbers of each Fourier spectrum.

Specifically, the B-scope image is coordinate-transformed into an XY coordinate image, STC processing is performed, and only a square image is cut out from the circular image to be used as a radar image for sea level measurement. Next, each spectrum of the previous scan and the current scan is generated for each divided image of the previous scan and the current scan. Next, each spectrum of the previous scan and the current scan is multiplied to generate each cross spectrum CS between the previous scan and the current scan.

Then, the phase CS _θ (k _x , _ky ) at each wave number of each cross spectrum is calculated by Equation 5, and the amplitude CS _p (k _x , _ky ) at each wave number of each cross spectrum is calculated by Equation 6. Then, the measured wave velocity v _m (k _x , _ky ) corresponding to each wave number of each cross spectrum is calculated by Equation 7, and the theoretical wave velocity v _t (k _x , _ky ) corresponding to each wave number of each cross spectrum is calculated as It is calculated by Equation 8. Here, g is the gravitational acceleration (=9.8 m/s ² ), and in the dispersion relationship of the gravitational waves, it is considered that the water depth is sufficiently deeper than the wave height offshore.

Then, when the measured wave velocity v _m (k _x , _ky ) and the theoretical wave velocity v _t (k _x , _ky ) match to some extent, the amplitude CS _p (k _x , _ky ) is replaced by the signal component S (k _x , k _y ). On the other hand, when the measured wave velocity v _m (k _x , _ky ) and the theoretical wave velocity v _t (k _x , _ky ) do not match to some extent, the amplitude CS _p (k _x , _ky ) is replaced by the noise component N(k _x , k _y ). Further, the signal-to-noise ratio SNR over all wavenumbers of each cross spectrum is calculated by Equation 9, and the wave height H is calculated by Equation 10. Here, a and b are values based on actual measurement results of significant wave height.

In this way, the wave height of the sea surface can be easily measured by the wave number space analysis compared to the real space analysis. Then, the wave height of the sea surface can be individually measured in each sea area represented by each divided image. In measuring the wave height of the sea surface, each cross spectrum after multiplication may be used, but each spectrum before multiplication may be used. Further, in calculating each cross spectrum after multiplication or each spectrum before multiplication, a plurality of cross spectra after multiplication or each spectrum before multiplication from the past to the present may be averaged.

Next, a method for measuring the wavelength, wave direction, wave speed, and wave height of the sea surface in each split image by the sea surface measurement unit 32 based on the "real space analysis" in each split image will be described.

The sea surface measurement unit 32 (1) observes sea surface clutter with high radar reflection intensity as wave crests on the sea surface, (2) measures the wavelength of the sea surface based on the interval between the wave crests on the sea surface, and (3) wave crests on the sea surface. (4) measure the wave height on the sea surface based on the contrast of the radar reflection intensity of the sea surface clutter.

The sea level display device and the sea level measurement system of the present disclosure can, for example, identify sea areas where sea surface waves are severe, and can identify sea areas inaccessible to ships or aircraft.

S: Sea level measurement system 1: Radar transmission unit 2: Radar reception unit 3: Sea level measurement device 4: Sea level display device 31: Image division unit 32: Sea level measurement unit

Claims (6)

Symbolize at least one of wave direction, wave velocity, and wave height on the sea surface in the radar image , symbolize the wave crest on the sea surface using line segments, and symbolize the wave length on the sea surface using the line segment spacing. and a direction perpendicular to the line segment to symbolize the direction of waves on the sea surface . In symbolizing the wave crest on the sea surface using line segments, the line segments are updated each time the radar image is updated, and the speed of movement of the line segments is used to symbolize the wave velocity on the sea surface. The sea surface display device according to claim 1 . 3. The sea surface display device according to claim 1, wherein a radar image is superimposed on at least one of the wavelength, wave direction, wave speed and wave height of the sea surface. 4. The sea surface display device according to any one of claims 1 to 3 , wherein at least one of the wavelength, wave direction, wave speed and wave height of the sea surface is displayed according to a user's selection. 5. The sea surface display device according to any one of claims 1 to 4 , which displays whether it is safe to launch or land on the sea surface in a radar image. a sea surface display device according to any one of claims 1 to 5 ;
a sea surface measuring device that measures at least one of the wavelength, wave direction, wave speed, and wave height of the sea surface in radar images based on wave number space analysis or real space analysis in radar images;
A sea level measurement system comprising:

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