JP2000310678A - Wave observation system with radar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wave observing radar capable of observing waves at a high accuracy and high efficiency by using a short-wavelength marine surveillance radar. SOLUTION: The wave observation system combines signal intensities showing wave peaks to raise the signal intensities of the wave peaks by an integration processor 4, based on output signals from a marine surveillance radar 1, specifies the wave position, integrates the spectra of observed waveforms with respect to the component frequencies of the spectra to obtain C.C.S. by a signal spectrum calculator 7 and measures the height of the waves, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for observing waves, and more particularly to a method for observing waves using a marine surveillance radar installed on land or the like and used in the field of marine traffic.

[0002]

2. Description of the Related Art Wave observation methods include a method of measuring wave height using ultrasonic waves, a method of installing a pressure sensor and the like in the sea, a method of mooring a pressure sensor and the like to a sea surface using a buoy and a ship, or 2. Description of the Related Art There is known a method of installing a structure under the sea and installing a sensor on the structure. There is also a method of performing remote sensing from a land or a satellite using a measuring device. When using a satellite,
In general, a method of observing a significant wave height at an irradiation point by using a microwave pulse radiated toward the sea surface from a radar altimeter mounted on a mobile satellite. However, this method is suitable for the purpose of observing the wave height in a wide area of the sea in a short time by using a mobile satellite, and is not suitable for the purpose of constantly observing a specific sea area.

For the purpose of constantly observing a specific sea area, a remote sensing system using land facilities is desirable. One of the reasons is that in a method other than remote sensing, the sea area to be observed is limited to a narrow sea area around the sensor installation location. Therefore, a remote sensing method is indispensable for observing a wide range of specific sea areas at all times and with high accuracy.

[0004] Based on such a background, an HF radar for wave observation using the HF band has been developed. In this technique, a reflected wave from a wave having a half wavelength of a radar wave is observed by using Bragg scattering of an irradiated radio wave based on the principle of a diffraction grating when a wave peak is regarded as a grating. That is, an irradiation wave having a certain wavelength L is reflected most strongly to a wave having a wavelength of L / 2, and the reflected wave has a Doppler frequency component corresponding to the propagation speed of the wave. . Waves corresponding to the wavelength of the radiated radio waves are observed using this property, and significant wave heights, dominant wave frequencies, sea surface currents, etc. are being observed based on wave spectra selected from reflected waves. I have.

[0005]

However, the wavelength of a wave which should be originally observed is a long wave ranging from several tens of meters to several hundreds of meters. In particular, waves have higher energy as wavelengths are longer, and in that sense, it is important to observe waves with longer wavelengths. However, the wavelength of the HF band radio wave is only about 100 meters even in the lowest frequency of 3 MHz band. In this case, the observable wave wavelength is about 50 meters, which is half the wavelength of the radio wave. Stay in. At such a low frequency, the beam width in transmission and reception is wide,
Mixing of signals outside the observation area is also an unavoidable problem.

In order to solve the above problems, the present invention is to provide a method capable of observing a long wavelength wave with high accuracy even by a radar using a short wavelength wave such as a marine surveillance radar. is there.

[0007]

In order to solve the above-mentioned problems, according to the present invention, the reception intensity of a reflected wave of a radar is analyzed, and the wave height of waves is calculated from the maximum value and the minimum value of the reception intensity. It includes a procedure, a procedure for calculating the position of the wave peak from the history of the fluctuation of the reception intensity, and a procedure for further calculating the wave form from the calculated position of the wave peak.

[0008]

Embodiments of the present invention will be described below. FIG. 1 schematically shows the wavelength of a wave selected from the position of a wave peak. In the drawing, the wavelength of a wave is represented by L. This wavelength is assumed to be several tens meters to several hundred meters. 2L, nL
Denotes an integer multiple of the wavelength L. Here, n is any positive integer. Wave peaks appear as parallel lines at regular intervals as shown in the figure. not to mention,
The constant interval is the wavelength L. FIG. 2 conceptually shows how radar waves are reflected by sea surface waves.

FIG. 3 conceptually shows a longitudinal section of the wave shown in FIGS. A wave bottom occurs just in the middle of each wave peak, that is, at a position L / 2 away from the wave peak. FIG. 3 also schematically shows a radar wave applied to the wavefront. In FIG. 3, a radar wave is applied to the wavefront from the upper right of the figure. Therefore, the portion of the wavefront indicated by the solid line in the drawing, that is, the surface inclined from upper left to lower right in the drawing reflects the radar wave and causes the reflected wave to reach the radar. The radar wave does not reach the portion shown by the broken line in the figure, that is, the surface inclined from the upper right to the lower left in the figure, or even if the radar wave arrives and is reflected by the wavefront, the reflected wave is The reflected wave does not reach the radar.

At this time, based on the principle of radar,
The reflection intensity of the radar radio wave is the highest at the wave peak, and the reflection intensity is low at the wave bottom. In other parts of the wavefront,
The reflection intensity is intermediate between the wavefronts. For this reason,
The level of the reflection intensity generates a waveform that directly reflects the wave wavelength. FIG. 4 schematically shows the relationship between the reflection intensity and the wavelength. In the figure, R indicates the distance from the radar to a specific wave peak. As shown in the figure, the position where the reflection intensity of the reflected wave of the radar is maximum indicates the wave peak, and the position where the reflection intensity is minimum indicates the wave bottom. The difference between the maximum value and the minimum value of the reflection intensity of the reflected wave indicates the difference between the wave front of the wave peak and the wave bottom, that is, the wave height.

From this, it can be seen that the distribution of the reflection intensity of the reflected wave indicates the height and position of the wavefront. However, although the expression of the position of the wavefront is used here, the saw-like figure of FIG. 4 showing the intensity distribution of the reflected wave does not exactly indicate the wavelength of the actual wave as it is. This is because radar waves do not always reflect perpendicular to the waves. However, also in this case, it is possible to calculate the actual wavelength of the wave by calculation from the position of the wavefront obtained by the reflected wave, for example, the position of the wave peak.

The calculation method will be described with reference to FIG. In the figure, wave peak positions ak and am are determined by radar waves in the direction of azimuth line A from radar O, and wave peak positions bk and bm are determined by radar waves in the direction of azimuth line B.
It is assumed that the wave peak positions ck and cm are obtained as observation data by radar waves in the direction of the azimuth line C. straight line K from the peak positions of ak, bk and ck
Is a straight line M from the peak positions of am, bm and cm.
Must exist, respectively. At this time, the distance between the straight line K and the straight line M corresponds to the wavelength L described above.

If the radar O is considered as the origin of the coordinates, for example, the wave peaks ak, bk, ck and the wave peaks am, b
m and cm are specific points on the coordinate plane. At this time, it is well known that an equation on the coordinate of the straight line K is obtained from the coordinates of the wave peaks ak, bk, and ck, and an equation on the coordinate of the straight line M is obtained from the coordinates of the wave peaks am, bm, and cm. It is easily possible by using the regression analysis technique described above. If the equations of the straight line K and the straight line M can be obtained in this manner, the distance between these two straight lines can be easily obtained by a known method.
The distance between the two straight lines determined in this way, that is, the wavelength L
Is equivalent to

However, the height of the wave peak is not always constant. In an actual wave, an irregular fluctuation occurs in the height of the wave peak, and as a result, there is a case where it is difficult to recognize the wave peak as it is with the intensity of the reflected wave as it is. This is because a threshold value is provided for the signal strength when the reflected wave is processed as an input signal. That is, as is well known in the art, marine surveillance radars are designed to ignore signals of minute reflected waves. This avoids the problem of a display such as a ship existing where nothing actually exists due to multiple reflections of radar waves, etc. This is for the purpose of strictly distinguishing the display of the mark and realizing a highly reliable display. Therefore, it is actually difficult to make the threshold extremely low in order to use the radar for marine surveillance.

Therefore, in the present invention, as shown in FIG. 6, a signal having a value obtained by adding the signal intensities at each wave peak as a new intensity is synthesized, and the signal is processed based on the synthesized signal. At this time, the new signal strength obtained by the addition can make the above-mentioned threshold value higher even when compared with the signal strength at the wave peak before the addition. This advantageously satisfies the condition of distinguishing the false display from the display of the actual target.

At this time, in order to detect the position of each wave peak, for example, by differentiating the signal intensity with time,
The position where the signal intensity is maximized may be regarded as a peak, and in the addition process, for example, the signal intensity of a peak adjacent to the peak is added to the signal intensity of the peak for which a new intensity is to be obtained. You may make it. By doing so, it is possible to obtain a signal in which the signals of the respective peaks have substantially the same signal strength as each other and the signal strengths of the respective signals are sufficiently strong.

The principle is as described above. However, actually, the signal obtained as described above is a pseudo wave waveform to the last, and the spectrum differs for each observation. This is a phenomenon that occurs because waves are estimated from the position of the peak of the reflected wave and the signal intensity. In order to eliminate the effect of this phenomenon and obtain a stable spectrum, for example, it is conceivable to perform observations many times and perform statistical processing on the obtained data.

However, by using the method described below, it is possible to estimate a wave spectrum without repeating observation many times.

That is, the focus is not on the wave spectrum itself but on the energy of the entire wave. Waves are generated by obtaining energy from the wind at sea,
As a generation process, when a wind of a certain wind speed blows on the sea surface, first a wave of a relatively short wavelength is generated, and when the wave grows over time and reaches a predetermined amplitude according to the wind speed, a relatively short wave is generated. The growth of short wavelength waves stops. Thereafter, the energy provided by the wind is supplied to longer wavelength waves, which begin to grow. Therefore, the energy of the wave is given as a result of integrating the spectrum of the short-wave wave into the spectrum of the long-wave wave.

The configuration of a system for performing this processing is as follows:
As shown in FIG. In FIG. 7, reference numeral 1 denotes a conventionally known marine surveillance radar, and reference numeral 2 denotes a conventionally known wave height meter. Since the marine surveillance radar 1 and the wave height meter 2 are all well known, the description of the configuration shown in the drawing will be omitted.

Reference numeral 3 denotes a waveform storage unit. Here, the data that has been detected by the marine surveillance radar 1 until the detection is temporarily stored. The waveform storage unit 3 can be configured by, for example, a general memory element or the like according to the form of the output signal of the marine surveillance radar. Reference numeral 4 denotes an integration processing unit. The integration processing unit 4 may be constituted by a general integration circuit, or may realize the same function by software processing. Reference numeral 5 denotes a waveform back interpolation processing unit. As described above, since the irradiation wave of the marine surveillance radar does not always reflect on the back of the wave peak and reaches the radar, the waveform back interpolation processing unit 5 performs a process of interpolating the waveform of this portion. Reference numeral 6 denotes a sampling circuit. Based on the waveform obtained by the waveform back-side interpolation processing unit 5, this part performs a process of performing a Fourier transform to extract a component of a specific wavelength.

Reference numeral 7 denotes a signal spectrum calculator. A wave spectrum is calculated from the wave components decomposed and extracted for each wavelength in the sampling circuit 6, and is further described in C.I. C.
S. Is a part for calculating. 8 is the calculated C.I. C.
S. Is a part for determining whether or not is a sea area including the wave height meter 2. This determination can be made easily by comparing the irradiation range of the marine surveillance radar 1 with the position of the wave height meter 2. As a result of the determination, the calculated C.I. C. S. Is a sea area including the wave height meter 2, a correlation calculation is performed in the signal spectrum calculation unit 9 described below. Otherwise, it is determined at 10 whether or not there is a correlation with the wave height meter. 9 described later indicates C.I. of the signal spectrum. C. S. And C. of the wave spectrum. C. S. And a signal spectrum calculation unit for calculating a correlation with the signal spectrum. The process of obtaining the correlation is performed based on the output of the wave spectrum calculation unit 14 and the output of the wind direction measurement unit 15 described later. Reference numeral 10 denotes a portion for determining whether or not there is correlation data with the wave height meter 2. If the correlation data exists, the wave height calculating unit 11 calculates the wave height. Otherwise, the waveform storage unit 3 collects new data again.

Reference numeral 12 denotes an antenna, which plays a role in transmitting wave height data 13 from the wave height meter 2 on the sea to the wave spectrum calculating unit 14. Reference numeral 14 denotes a wave spectrum calculation unit which uses the wave height data 13 sent from the wave height meter 2 to calculate the wave spectrum and the C.I. C. S. Is calculated.

FIG. 8 shows the wave observation performed using this configuration using simulation results of a wave model. First, FIG. 8A shows a wave model simulated from the Neumann spectrum as a wave completely grown at a wind speed of 36 knots. Here, data with a significant wave height of 10.4 meters, an average wave height of 6.5 meters, and wave energy of 13.6 kV2 are shown. FIG.
FIG. 8B shows a graph of a wave spectrum calculated using the Fourier transform from the swell model of FIG. This is consistent with the Neumann spectrum described above.

FIG. 8C shows a radar reception processing wave for the wave model of FIG. 8A, that is, a spectrum of a simulated wave which is a radar observation result obtained by simulation. This graph corresponds to the output of the marine surveillance radar 1 shown in FIG. Looking at the graph of FIG. 8C, it cannot be said that the trend is consistent with the graph of FIG. 8B showing the spectrum of the wave itself. In particular, the spectral component at a low frequency, that is, at a long wavelength. For the spectral components of
The spectral components are disturbed, and the difference from the graph of FIG. As described above, this disturbance can be adjusted by a number of observations and statistical processing.
Now consider the integration of the wave spectrum.

FIG. 8D is an integration curve obtained by integrating the wave spectrum of FIG. 8B, which is the wave (model) itself, with the component frequency of the spectrum. This integral curve is
This integral curve is called “Cumulative Spectora”, and in this application, this integral curve is referred to as C.I. C.
S. Abbreviated. As described above, the energy of a wave is given as a result of integrating the spectrum of a short-wave wave into the spectrum of a long-wave wave. C. S. Indicates the energy of the waves. Similarly, FIG. 8 (e) shows a pseudo wave spectrum simulating radar observation, FIG. C.
S. It is. This graph corresponds to the output of the signal spectrum calculator 7 shown in FIG. This C. C.
S. , It can be seen that they are well matched. Generally, this C.I. C. S. The curve shows a higher value as the wind speed increases. So the wind speed was 24 knots, 28 knots,
When a value at 0.079 Hz in the case of 32 knots and 36 knots is obtained by a simulation, a slight difference is caused due to a difference in the waveform of the wave model at each wind speed.

Wind speed (knot) Energy parameter (m 2) C. S. (KV2) 24 1.78 12.01 28 3.87 19.85 32 7.54 27.43 36 13.57 41.57

From the above relationship, the C.I. C. S. The following equation is obtained as an equation for calculating the energy parameter from the value.

LogE (m2) = 1.638 · log
C. C. S. (KV2)-1.519

As an example of waves of incomplete growth, 0.
FIG. 9 shows an example of a wave that does not include a component of 1 Hz or less.
9 are the same as those in FIG. 9 except that the wave model is incompletely grown and has a significant wave height of 4.7 meters, an average wave height of 3.0 meters, and a wave energy of 2.8 kV2. FIG. 9 (a) is a simulation of a simulated wave spectrum, FIG. 9 (b) is a wave spectrum calculated from the swell model of FIG. 9 (a) using Fourier transform, and FIG. FIG. 9 (a) shows a radar reception processing wave for the wave model shown in FIG. 9 (a), that is, a spectrum of a simulated wave which is a radar observation result. FIG. 9 (d) shows a wave (model) itself.
C. which integrated the wave spectrum of (b). C. S. , FIG. 9
(E) is a C.D. wave obtained by integrating the pseudo wave spectrum diagram (c) simulating radar observation. C. S. It is.

In the case of such imperfectly growing waves,
Since the long wavelength wave component has not grown, C.I. C. S. Does not show an increase in the integrated value below about 0.1 Hz, and its energy level is given by about 20 kV2. This makes it possible to obtain the energy parameter E (m2) and calculate the significant wave height, average wave height, wind speed, and the like.

[0032]

As described above, according to the present invention, a conventional short-wavelength marine surveillance radar can be used.
Waves of long wavelengths that are important for observation can be observed with high accuracy. In addition, high-precision observation is possible without burdening a large number of observations and statistical processing. Therefore, it is expected to improve the navigational safety of ships.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing wavelengths of waves.

FIG. 2 is a schematic diagram showing aspects of reflection of waves and radar waves.

FIG. 3 is a schematic view showing a vertical section of a wave.

FIG. 4 is a schematic diagram illustrating a relationship between a wavelength of a wave and a reflection intensity of a radar reflected wave.

FIG. 5 is a schematic diagram showing the concept of calculating the wavelength of a wave.

FIG. 6 is a schematic diagram illustrating the concept of combining signal strengths.

FIG. 7 is an explanatory diagram showing an example of a system configuration for realizing the present invention.

FIG. 8 shows C.I. C. S. 6 is a graph showing a simulation result of FIG.

FIG. 9 shows C.I. of radar observation of imperfect waves. C. S. 6 is a graph showing a simulation result of FIG.

[Explanation of symbols]

 1: Marine monitoring radar 2: Wave height meter

Continued on the front page F term (reference) 5J070 AB01 AC01 AC04 AC20 AE07 AE14 AF01 AH02 AH04 AH14 AH19 AH25 AH33 AH35 AH50 AJ06 AJ10 AJ13 AK22 AK40 BD10

Claims (2)

[Claims] In a wave observation system for irradiating a radar wave to a sea surface and receiving a reflected wave of the radar wave to observe the sea surface, each of the sea surfaces at a specific distance corresponding to the wavelength of the wave on the sea surface. Find the sum of the signal strength of the reflected waves from the position,
A wave observation method, wherein a position of a wave peak or a wave trough is obtained from each of the positions obtained from the reflected waves and a distance between the positions. 2. The wave observation method according to claim 1, wherein a wave energy spectrum is obtained by integrating a wave spectrum obtained from the reflected wave with a component frequency of the spectrum. Observation method.