JP2007248293A - Ocean radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ocean radar device capable of inferring the distribution of two-dimensional ocean current velocity vectors, based on the information of a radar image acquired from one-site radar site. <P>SOLUTION: A ripple pattern is extracted from an echo intensity distribution in each mesh area calculated from an observation period and an actually-probable maximum ocean current velocity from the radar image, and the current velocity in the area is calculated from the moving amount. The ocean current velocity can be calculated with uniform accuracy in the same domain as a coverage of the radar by only the information from one radar site. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ocean radar apparatus for observing the ocean velocity distribution.

  An ocean radar apparatus is an apparatus that observes a sea current, a wave height, and the like by irradiating radio waves to the sea surface, receiving signals scattered on the sea surface, and performing frequency analysis. As such an ocean radar apparatus, the wave information after a predetermined time is predicted by obtaining the three-dimensional Fourier spectrum of the current wave from the reflection intensity (shadow information) of the radar image and correcting the phase of the wave spectrum. The method is known. The wave information in this case is for calculating the height of the individual wave prediction wavefront. (See Patent Document 1)

Also, the sea surface is irradiated with a radar beam by the FMCW (Frequency Modulated Continuous Wave) method or the FWICW (Frequency Modulated Interrupted Continuous Wave) method. Some estimate the ocean current velocity. Then, in order to obtain the two-dimensional information of the ocean current velocity, a plurality of radar sites with different antenna directions are operated, the flow velocity distribution in the line-of-sight direction is calculated, and the line-of-sight flow velocity of the plurality of radar sites is vector-synthesized Was measured (see Patent Document 2).
JP 2004-338580 A JP 2000-314773 A

However, the marine radar device disclosed in Patent Document 1 is intended for ship radar and assumes a state in which the top of the wave cannot be clearly observed because the radar installation position is low. The purpose is to calculate the wave height. From the wave number estimated from the result of spectrum analysis of PPI (Plan Position Indicator) image, the flow velocity in the line of sight may be estimated, but it is difficult to calculate the two-dimensional flow velocity vector. is there.
Further, the ocean radar apparatus disclosed in Patent Document 2 is intended for ocean velocity distribution in a wide coverage area, and there is a problem that the ocean current velocity near the coast cannot be accurately calculated. On the other hand, in recent years, there has been an increasing interest in the distribution of ocean current velocity near the coast, such as the investigation of countermeasures against flooding of nuclear power plants and coastal roads. In addition, the above method deteriorates the observation accuracy in an observation area where the crossing angle in the line-of-sight direction from each radar site is more than 90 degrees. For this reason, there are problems that only a part of the observation coverage of each radar site can be used for the analysis of the flow velocity vector, and it is difficult to select a plurality of radar site installation positions suitable for the observation target coverage.

  In order to solve the above problems, the present invention provides an ocean radar apparatus capable of estimating a two-dimensional ocean current velocity vector distribution based on radar image information obtained from a radar site at one site. It is for the purpose.

  A marine radar apparatus according to the present invention includes a signal processing unit that processes a reflected wave obtained by radiating radio waves on the sea surface as a video signal, a display processing unit that generates a high resolution radar image from the video signal from the signal processing unit, A flow velocity calculation unit that calculates a flow velocity distribution based on the high resolution radar image generated by the display processing unit, and a display unit that superimposes and displays the flow velocity distribution calculated by the flow velocity calculation unit on the high resolution radar image. It is characterized by that.

  The marine radar apparatus according to the present invention calculates a two-dimensional velocity vector in each mesh from the ripple pattern extracted from the radar image, so that the ocean current velocity can be obtained with uniform accuracy within the radar coverage by using only one radar site information. Make the distribution calculable.

  Furthermore, the calculation accuracy can be improved by supplementarily using the flow velocity in the antenna line-of-sight direction calculated from the Doppler velocity.

Embodiment 1
Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a marine radar apparatus according to Embodiment 1 of the present invention. In FIG. 1, an antenna unit 1 radiates, for example, short-wave radio waves (3 to 30 MHz) to the ocean surface and receives reflected waves scattered on the ocean surface, and is provided on the ground or a ship near the ocean surface to be observed. The transmission / reception unit 2 transmits a transmission signal of a radio wave radiated from the antenna unit 1, and detects and amplifies a reception signal of a reflected wave from the ocean surface received by the antenna unit 1. The signal processing unit 3 converts the received signal from the transmission / reception unit 2 into a video signal that can be viewed on a display unit such as a monitor. The antenna unit 1, the transmission / reception unit 2, and the signal processing unit 3 used here are configured by a conventionally used technique and are not particularly new. The display processing unit 4 passes the video signal from the signal processing unit 3 through a noise filter or the like, and generates a high-resolution radar image (PPI = Plan Position Indicator image) with respect to distance and azimuth. The flow velocity calculation unit 5 calculates the flow velocity distribution on the ocean surface based on the high resolution radar image from the signal processing unit 4. The display unit 6 is a monitor that superimposes and displays the flow velocity distribution calculated by the flow velocity calculation unit 5 and the high-resolution laser image generated by the display processing unit 4.

  As an operation of the marine radar apparatus shown in FIG. 1, first, a radio wave of a transmission signal transmitted from the transmitting / receiving unit 2 is radiated from the antenna unit 1 toward the ocean surface. An echo of a reflected wave that is a scattered wave from the ocean surface is received via the antenna unit 1 and input to the transmission / reception unit 2. The signal processing unit 3 processes the received signal from the transmission / reception unit 2 and converts it into a video signal so that it can be displayed on the display unit 6 of the monitor. Based on the video signal information obtained by the signal processing unit 3, the display processing unit 4 generates a high-resolution radar image for the observation coverage so that the ripple (ocean surface wave) data can be easily extracted. Based on the high-resolution laser image from the display processing unit 4, the flow velocity calculation unit 5 digitizes the grayscale data of the laser image and extracts ripple data, as will be described in the detailed configuration diagram of FIG. A two-dimensional ocean velocity distribution in each mesh is calculated from the ripple data. The display unit 6 superimposes and displays the flow velocity distribution calculated by the flow velocity calculation unit 5 and the high-resolution radar image generated by the display processing unit 4 to obtain the ocean flow velocity distribution.

  FIG. 2 is a detailed configuration diagram of the flow velocity calculation unit 5 shown in FIG. 1. A ripple extraction unit 51 that extracts ripple data from the radar image from the display processing unit 4, the ripple data previously extracted by the ripple extraction unit 51 and this time The extracted ripple data is combined to calculate the movement vector Δd. The movement amount calculation means 52 calculates the velocity vector from the movement vector Δd calculated by the movement amount calculation means 52 and the observation time interval Δt (observation period). The flow velocity vector calculation means 53 to be calculated and the ripple data storage device 54 that temporarily stores the ripple data extracted by the ripple extraction means 51 are configured. The observation time interval Δt is a pulse repetition period in the case of the pulse radar method and a sweep time interval in the case of the FMICW method.

  The operation in FIG. 2 will be described based on the flowchart shown in FIG. First, in step ST1, the high-resolution radar image (PPI image) received from the display processing unit 4 is binarized by the ripple extraction means 51, and ripple data that is a characteristic image of the ripple is extracted. FIG. 4 shows the concept of the ripple data extraction. The horizontal axis represents the azimuth angle Az indicating the azimuth, and the vertical axis represents the range Rng indicating the distance. The ripple data is extracted using the Rng-Az coordinates. Do. In FIG. 4, the mesh portions of the squares indicate binarized detection bins, and ripple data is extracted using the distance from adjacent bins and the amplitude intensity as evaluation values. The broken line in FIG. 4 represents ripple data that has been rejected as a result of the evaluation, and represents the ripple data in which the solid line is adopted. Each processing unit of the ripple data extraction is set to a range larger than the width of the maximum flow velocity speed in the XY coordinates × the observation time interval, and is converted from the Rng-Az coordinates to the XY coordinates after the processing.

  In this way, the ripple data is extracted using the Rng-Az coordinates that are the radar coordinates, so that the data detected by the radar can be used without waste. However, when calculating the movement amount from the ripple data, it is easier to calculate by using coordinate conversion from the Rng-Az coordinate to the XY coordinate and using the XY coordinate, and there are fewer errors.

  The ripple data extracted in step ST1 is stored in the ripple data storage device 54. Next, in step ST2, the movement amount calculation means 52 stores in the ripple data storage device 54 for each image meshed in a quadrangle of one side having a maximum flow velocity Vmax × observation time interval Δt as shown in FIG. The previously observed ripple data (image before one sample = image from the current sample Δt before) and the ripple data observed this time (current sample image) are compared and synthesized, and the ripple data per mesh per observation The movement vector Δd (movement amount and movement direction) is calculated. In FIG. 5, the composite image moves downward from the previous sample to the current sample, and the amount of movement is Δd.

  Next, in step ST3, the flow velocity vector calculation means 53 calculates the movement vector Δd ÷ observation time interval Δt = flow velocity vector from the movement vector Δd and the observation time interval Δt, and converts the movement amount into a speed. Then, the flow velocity vector is calculated for each mesh. This flow velocity vector represents the movement amount per unit time of the movement vector Δd obtained in Step 2, and represents a two-dimensional flow velocity. In step ST4, the flow velocity vector data for each mesh calculated by the flow velocity vector calculation means 53 is obtained by collecting the flow velocity vectors in all the meshes to obtain the ocean current velocity distribution, which is processed by the display processing unit 4 in the display unit 6. The superimposed high resolution radar image is displayed. In this way, by collecting the flow velocity vectors calculated in units of meshes, the distribution of ocean current velocity vectors in the observation range can be obtained.

  As described above, for each mesh area calculated from the observation period and maximum flow velocity from the radar image, ripple data is extracted from the intensity distribution of the reflected wave, and the flow velocity for the area is calculated from the movement amount of the ripple data. As a result, the ocean current velocity can be calculated with uniform accuracy within the radar coverage in the same area as the radar coverage with only one radar site information.

In the above description, the ripple data of the laser coordinates are converted into XY coordinates, and a square mesh with one side as shown in FIG. 5 having a maximum flow velocity Vmax × observation time interval Δt is used. Although the movement vector Δd is calculated, it is also possible to calculate the movement vector Δd directly from the laser coordinate data without performing coordinate conversion.
When the movement vector Δd is calculated using the laser coordinate data as it is, the mesh of the maximum flow velocity Vmax × the observation time interval Δt is not a quadrangle, but a fan-shaped mesh obtained by cutting the coordinates of the circular radar screen at a predetermined angle. It becomes. In this case, the calculation error of the movement vector Δd becomes slightly larger as the distance increases.

Embodiment 2
In the first embodiment shown in FIG. 1, the ocean current velocity distribution is calculated based only on the radar image, but in the second embodiment, the signal processing unit 3 can calculate the Doppler velocity, and the Bragg scattering mechanism is used. By applying the calculated flow velocity in the direction of the line of sight to the flow velocity calculation section 5, the calculation accuracy of the ocean current velocity is improved.

In general, the marine radar also detects the velocity of an object existing on the ocean in the observation area. The object is, for example, a ship, an offshore buoy, a land (island), or the like. If the spectrum of the velocity of such ocean objects is sufficiently far from the ocean current velocity spectrum, it can be easily recognized that the object has a different velocity, but the object and ocean current velocity spectrum overlap or are close to each other. In such a case, it becomes difficult to identify the two. The second embodiment of the present invention can measure the ocean current velocity with high accuracy even in such a case.
As shown in FIG. 6, when the clutter C is largely detected in the radar image due to a floating object such as a ship, the ripple data in the previous observation and the ripple in the current observation necessary for calculating the flow velocity vector. There is a possibility of incorrect data comparison. In that case, based on the ocean current velocity in the direction of the antenna line of sight, calculation of the ocean current velocity is performed by detecting the ripple data for comparison only in the ripple movement prediction gates Ga to Gb centered on the ripple destination. Accuracy can be increased.

  The marine radar apparatus of the present invention is particularly suitable for measuring the distribution of ocean current velocity near the coast, but is not limited to this, and it is also possible to measure the ocean current velocity distribution in a wide coverage area. Since the radar reception intensity increases with the wave height, the present invention can be easily extended to a tsunami warning device.

It is a block diagram of the marine radar apparatus according to Embodiment 1 of the present invention. It is a detailed block diagram of the flow velocity calculation part of the marine radar apparatus according to the first embodiment of the present invention. It is a figure which shows the flowchart of operation | movement of the marine radar apparatus which concerns on Embodiment 1 of this invention. It is a figure showing the concept of the ripple extraction means of the marine radar apparatus which concerns on Embodiment 1 of this invention. It is a figure showing the concept of the movement amount calculation means of the marine radar apparatus which concerns on Embodiment 1 of this invention. It is a figure showing the concept of the movement amount calculation means of the marine radar apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

1: antenna part, 2: transmission / reception part,
3: signal processing unit, 4: display processing unit,
5: Flow velocity calculation unit, 6: Display unit,
51: ripple extraction means, 52: movement amount calculation means,
53: Flow velocity vector calculation means, 54: Ripples data storage device

Claims (4)

  A signal processing unit that processes a reflected wave obtained by radiating radio waves on the sea surface as a video signal, a display processing unit that generates a high-resolution radar image from the video signal from the signal processing unit, and a high-frequency generated by the display processing unit A marine radar comprising: a flow velocity calculation unit that calculates a flow velocity distribution based on a resolution radar image; and a display unit that superimposes and displays the flow velocity distribution calculated by the flow velocity calculation unit on the high resolution radar image. apparatus.   The flow velocity calculation unit extracts ripple data from the intensity distribution of the reflected wave for each mesh area calculated from the observation period and the maximum ocean current velocity, and calculates the flow velocity for the area from the movement amount of the ripple data. The marine radar apparatus according to claim 1.   The flow velocity calculation unit includes a ripple extraction unit that binarizes a radar image and extracts ripple data, a movement amount calculation unit that compares the ripple data observed last time with the ripple data observed this time, and calculates a movement vector; The marine radar apparatus according to claim 1, further comprising a velocity vector calculating unit that calculates a velocity vector from the movement vector and the observation time interval.   The signal processing unit has means to perform Doppler measurement in the line-of-sight direction. Based on the Doppler velocity obtained by this signal processing unit, the current velocity in the line-of-sight calculated by the Bragg scattering mechanism is used to calculate the flow velocity distribution. The marine radar device according to any one of claims 1 to 3, wherein the accuracy is improved.

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