Radar device, radar detection method, and radar program

Abstract

To provide a user with a highly reliable radar image regardless of rolling of a ship.SOLUTION: A radar device includes: an antenna for transmitting and receiving electromagnetic waves; a reception signal processing section for generating and holding sweep data on the basis of a reception signal; a correlation coefficient setting section for setting a correlation coefficient showing weighting between current sweep data, and past sweep data generated on the basis of a reception signal obtained at one or multiple pieces of timing before optional timing; a scan correlation processing section for performing scan correlation processing for composing current sweep data and past sweep data on the basis of a correlation coefficient and generating image data; a posture information acquisition section for acquiring posture information of an antenna while relating it to an azimuth; and an elevation angle calculation section for calculating an elevation angle of an antenna in an azimuth on the basis of posture information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a radar device that generates an image by transmitting and receiving electromagnetic waves.

Background Art

[0002] In order to make the maritime navigation of ships safer and better, a radar device accurately detects the azimuth and position of a target that may collide with other ships or the like, and further tracks it. In particular, a marine radar device transmits radio waves while rotating an antenna, converts received data in a polar coordinate system obtained by reflection from a target into a rectangular coordinate system, stores it in an image memory, and then displays it on a display by a raster scanning method. Here, the received data includes not only components reflected by the target of interest but also unnecessary components (hereinafter referred to as "(sea surface) clutter") due to sea surface reflection or the like.

[0003] A series of data corresponding to a specific azimuth on the polar coordinates is data for one sweep, and data corresponding to one rotation of the radar is data for one scan. Therefore, a scan image is created by combining a plurality of sweep data. Generally, in a magnetron radar or a phased array radar, one sweep data is created by one transmission and reception, but in a continuous wave radar such as FM-CW, arbitrarily cut data becomes one sweep data.

[0004] Conventionally, scan correlation processing for creating a radar image by adjusting the image level from a plurality of scan images based on statistical processing of echoes acquired not only currently but also in the past is known. By performing scan correlation processing, it is possible to suppress echoes of sea surface reflection that vary greatly for each scan image.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, since a ship is on the water surface such as the sea, it may shake greatly depending on the wind and wave conditions. Then, the antenna mounted on the ship also moves up and down in the radiation angle (elevation angle) of the electromagnetic wave due to the shaking, making it difficult to stably receive the reflected wave from a target such as another ship that should be originally acquired.

[0007] An object of the present invention is to provide a radar device that provides a highly reliable radar image to a user even when such a ship shakes.

Means for Solving the Problems

[0008] The problems to be solved by the present invention are as described above. Next, the means for solving this problem and its effects will be described.

[0009] The radar device of the present invention is a radar device installed on a moving body moving on the water surface, and includes an antenna that transmits electromagnetic waves while changing the azimuth at a predetermined cycle, receives reflected waves, and sends out received signals, a received signal processing unit that generates and holds sweep data based on the received signals, a correlation coefficient setting unit that sets a correlation coefficient indicating the weighting between the current sweep data generated based on the received signals acquired at an arbitrary timing in a specific azimuth and the past sweep data generated based on the received signals obtained at one or more timings before the timing in the specific azimuth, a scan correlation processing unit that performs scan correlation processing for synthesizing the current sweep data and the past sweep data based on the correlation coefficient to generate image data, an attitude information acquisition unit that acquires the attitude information of the antenna in association with the azimuth, and an elevation angle calculation unit that calculates the elevation angle of the antenna in the azimuth based on the attitude information.

[0010] In the radar device of the present invention, in the scan correlation process, for the current sweep data, scan correlation processing is performed between the current sweep data calculated by the scan correlation process and the immediately preceding sweep data in the same azimuth to generate image data. Here, in the scan correlation process, the current sweep data may be multiplied by a first correlation coefficient, the immediately preceding sweep data may be multiplied by a second correlation coefficient, and the two may be added together.

[0011] In the radar device of the present invention, the antenna is installed on a ship, rotates in a horizontal plane at a predetermined period during non-shaking, and the elevation angle is defined with reference to the horizontal plane.

[0012] The first correlation coefficient is set to be smaller as the elevation angle increases. The second correlation coefficient may be set to be larger as the elevation angle increases.

[0013] The first correlation coefficient may be set to a predetermined standard value in advance when the elevation angle is below a predetermined threshold value, and set to be smaller than the standard value when the elevation angle is larger than the threshold value.

[0014] When values based on the elevation angle in the same azimuth are continuously larger than the reference value for a plurality of scans, the correlation coefficient setting unit may stop setting the correlation coefficient based on the elevation angle in that azimuth.

[0015] The radar device of the present invention may include a display for displaying image data. The radar device of the present invention may also be configured such that the attitude information acquisition unit acquires attitude information from a GNSS receiver mounted on the moving body.

[0016] The radar detection method of the present invention is a method for monitoring the vicinity of a moving object moving on the water surface, which transmits electromagnetic waves while changing the azimuth at a predetermined period from an antenna, receives the reflected waves, sends out a received signal, generates and holds sweep data based on the received signal, obtains the attitude information of the antenna in association with the azimuth, calculates the elevation angle of the antenna in the azimuth based on the attitude information, determines a correlation coefficient indicating the weighting of both between the current sweep data generated based on the received signal obtained at an arbitrary timing in a specific azimuth and the past sweep data generated based on the received signal obtained at one or a plurality of timings before the timing in the specific azimuth based on the elevation angle, and performs a scan correlation process of synthesizing the current sweep data and the past sweep data based on the correlation coefficient to generate image data.

[0017] The computer program of the present invention is a computer program including computer-executable instructions, which, when executed by a computer, causes the computer to transmit electromagnetic waves while changing the azimuth at a predetermined period from an antenna, receive the reflected waves, send out a received signal, generate and hold sweep data based on the received signal, obtain the attitude information of the antenna in association with the azimuth, calculate the elevation angle of the antenna in the azimuth based on the attitude information, determine a correlation coefficient indicating the weighting of both between the current sweep data generated based on the received signal obtained at an arbitrary timing in a specific azimuth and the past sweep data generated based on the received signal obtained at one or a plurality of timings before the timing in the specific azimuth based on the elevation angle, and perform a scan correlation process of synthesizing the current sweep data and the past sweep data based on the correlation coefficient to generate and output image data.

Advantages of the Invention

[0018] As a result, even if a ship or the like equipped with a radar device sways, a highly reliable radar image can be obtained.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0020] Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main configuration of a radar device 100 for a ship according to this embodiment.

[0021] The radar antenna 1 rotates in a horizontal plane at a predetermined rotation period and transmits electromagnetic waves to the outside at a predetermined transmission / reception period, and receives the electromagnetic waves reflected by a target. The receiving unit 2 detects and amplifies the received signal, and the AD conversion unit 3 converts this analog-form received signal into a digital signal (received data) composed of a plurality of bits.

[0022] The sweep memory 4 stores the received data for one sweep that has been digitally converted in real time, and holds the data for this one sweep until the received data obtained by the next transmission is rewritten again. The scan correlation processing unit 5 performs correlation processing between the data for the most recent one sweep (current sweep data) obtained from the same azimuth and one or a plurality of sweep data (past sweep data) obtained previously, and the result is output to the image memory 6 and displayed on the display unit 7.

[0023] The radar device 100 of the present invention further includes a radiation azimuth information acquisition unit 8 that acquires information on the azimuth of the antenna 1, that is, the azimuth at the time when the electromagnetic wave is transmitted, and an attitude information acquisition unit 9 that acquires information on the attitude of a ship or the like equipped with the radar device, and an elevation angle calculation unit 10 that calculates the elevation angle of the antenna 1, that is, the elevation angle at which the main lobe of the electromagnetic wave is radiated, for each azimuth from the azimuth information and the attitude information.

[0024] When the elevation angle is calculated for each azimuth of the antenna 1, the elevation angle is output to the scan correlation processing condition setting unit 11 at any time. The scan correlation processing condition correlation setting unit 11 sets the value of the correlation coefficient in the scan correlation processing based on the value of the elevation angle.

[0025] In the radar device of the present invention, the elevation angle of the antenna is calculated according to the sway state at that time for each azimuth at which the antenna 1 transmits electromagnetic waves, and the correlation coefficient of the scan correlation processing is appropriately changed. Specific setting of the correlation coefficient based on the value of the elevation angle will be described later.

[0026] FIG. 2 is a diagram showing an example of a scan correlation processing unit of a radar device according to an embodiment of the present invention.

[0027] Here, a drawing address generation unit (not shown) uses the center of the sweep as the start address, and from the center to the periphery, based on a predetermined direction (for example, the bow direction), from the angle θ of the antenna and the read position r of the sweep memory, creates an address for designating a pixel of the image memory arranged in the corresponding orthogonal coordinate system. Specifically, this drawing address generation unit is configured by hardware that realizes the following equations.

[0028] [Equation 1] X = Xs + r·sinθ [Equation 2] Y = Ys + r·cosθ

[0029] Here, X, Y: Address for designating a pixel of the image memory, Xs, Ys: Center address of the sweep, r: Distance from the center, θ: Angle of the sweep (antenna).

[0030] During one rotation of the sweep (radar antenna 1), for each pixel of the orthogonal coordinate system set by the drawing address generation unit on the correlation processing image memory 306, the time point when this sweep first accesses or the last access time point is detected. Since it is necessary to limit the update of each pixel of the scan correlation processing image memory to only once per rotation of the sweep, the FIRST signal or the LAST signal is used as this timing.

[0031] Perform scan correlation processing using the image data by the sweep obtained based on the most recently received signal and the image data of one rotation before the sweep stored in the correlation processing image memory 306, and store it in the image memory 306 again.

[0032] Here, for example, in the scan correlation process, the received data input from the sweep memory 4 shown in FIG. 1 is denoted as N(t), and the correlation process image data at the pixel position corresponding to the received data obtained up to the previous time and input from the correlation process image memory 306 is denoted as W(t - 1). Then, the correlation process image data W(n) is calculated using the following equation.

[0033] [Equation 3] W(t) = α·N(t) + β·W(t - 1)

[0034] Here, α and β are arbitrary numbers, and by changing the values of α and β, the content of the scan correlation process can be changed.

[0035] The correlation process image memory 306 has a capacity to store the received data (correlation process image data) for one rotation of the sweep (radar antenna 1). For the scan correlation process, the correlation process image data before one rotation is fed back to the scan correlation processing unit. Also, when the display 7 is raster scanned by a display control unit (not shown), the correlation process image memory 306 outputs the correlation process image data in synchronization with this raster scan.

[0036] The flow of the received signal processing and the scan correlation process described above is shown in the flowchart of FIG. 3.

[0037] Next, the setting of the correlation coefficient in the radar device of the present invention will be described.

[0038] Returning to FIG. 1, the elevation angle of the antenna 1 calculated by the elevation angle calculation unit 10 is input to the scan correlation process condition determination unit 11. As an embodiment of the radar device of the present invention, as shown in FIG. 4, a threshold value is set for the elevation angle. Here, the threshold value is set to plus or minus 10 degrees with respect to the horizontal plane. When the calculated elevation angle is within this range, that is, at timings (1), (4), and (6) from the left in FIG. 4, the correlation coefficient α is set to the standard value in all cases.

[0039] On the other hand, when the ship sways and swings significantly upward as shown in timing (2) such that the elevation angle exceeds the plus 10 degrees of the threshold value, or conversely, when it swings downward as shown in timing (3) and falls below minus 10 degrees, the correlation coefficient is set to the first set value. Each timing indicates the case when the antenna rotates at a predetermined period and is in the same azimuth.

[0040] When the elevation angle exceeds the threshold value range, it is highly likely that the received signal is not properly received. Since it is better to relatively reduce the weighting of the current sweep data, the correlation coefficient α is also set relatively smaller compared to the standard value.

[0041] Next, an example of setting the value of the correlation coefficient α according to the threshold value and the elevation angle is shown.

[0042] FIG. 5 is a diagram showing the relationship between the sway of the ship on which the radar device according to an embodiment of the present invention is mounted, the elevation angle, and the set correlation coefficient. The horizontal axis represents the elevation angle θ, and the vertical axis represents the correlation coefficient α. In this example, when the elevation angle is 10 degrees or less (similarly when the elevation angle is downward), the correlation coefficient α is set to 0.25, and when the elevation angle is greater than 10 degrees, the correlation coefficient α is set to 0.05 which is smaller than the above.

[0043] FIG. 6 is a diagram showing another example of the relationship between the elevation angle and the set correlation coefficient in the radar device according to an embodiment of the present invention. Here, the relationship between the elevation angle θ and the correlation coefficient α indicated by each of the four types of lines, 602, 604, 606a, and 606b, of the graph will be described.

[0044] In the setting shown by graph 602, assuming that the elevation angle fluctuates up to a maximum of 20 degrees, when the elevation angle is zero, the correlation coefficient α is set to 0.25, and it linearly decreases from 0.25 to 0.05 until the elevation angle reaches 20 degrees. In the setting shown by graph 604, the range from 0 degrees to 20 degrees is divided into four regions, and as shown in the figure, the correlation coefficient α is set stepwise such that it becomes smaller as the elevation angle increases. For graphs 606a and 606b, as the elevation angle θ increases, the correlation coefficient α is gradually set to be smaller, with the former being convex downward and the latter being convex upward. Which setting to select can also be chosen according to the sea state and the type of target to be detected.

[0045] Figure 7 is a diagram showing another example of the relationship between the elevation angle and the set correlation coefficient in the radar apparatus according to an embodiment of the present invention. Similar to what has been shown so far, the correlation coefficient α set depending on whether the elevation angle θ is within a threshold range is different. Note that the elevation angle θ may set the correlation coefficient α with an absolute value based on the horizontal plane. However, as shown by the arrow, when there is a large change in the elevation angle α between certain scans (when the difference in elevation angle between scans is large and is shown by the arrow between scans), the correlation coefficient may be set relatively small.

[0046] With the radar apparatus of the present invention described so far, even when a ship equipped with the radar apparatus is shaken under the influence of wind and waves, clutter can be appropriately removed and targets can be accurately detected.

[0047] However, when the shaking continues to occur, the scan correlation process itself will continue to be suppressed during this period. Therefore, the radar apparatus of the present invention stores the scan correlation processing conditions determined by the elevation angle for each scan in the same direction, and when the state where the scan correlation processing deviates from the standard conditions continues for a predetermined number of times, the conditions of the scan correlation processing can be reset to other conditions. For example, as another condition, it can be reset to the standard conditions.

[0048] Figure 8 is a diagram showing a part related to the setting of the correlation coefficient in the radar apparatus according to another embodiment of the present invention.

[0049] The scan correlation processing unit 41, the image memory 42, and the elevation angle calculation unit 43 have the same functions as those of an embodiment of the radar device of the present invention described above. The scan correlation processing condition determination unit 44 also determines a correlation coefficient when performing scan correlation processing according to a predetermined rule based on the elevation angle calculated by the elevation angle calculation unit 43, and outputs this to the scan correlation processing unit 41.

[0050] A scan correlation processing count unit 45 is connected to the scan correlation processing determination unit 44, and here, the conditions determined by the scan correlation processing determination unit 44 for each scan are input and stored.

[0051] Count the state where the value based on the elevation angle deviates from the reference due to shaking, and when this count number exceeds a predetermined number of times, for example, continuously exceeds 10 times, stop determining the correlation coefficient based on the elevation angle once and return it to the standard value. Alternatively, when the ratio of the correlation coefficient determined outside the standard value among a predetermined number of scan times exceeds a predetermined ratio, for example, exceeds 50%, it may be adjusted so that appropriate scan correlation processing is performed according to the same state, such as returning to the standard value or setting another intermediate value.

[0052] The value based on the elevation angle may be the elevation angle itself, the correlation coefficient, or a separately calculated value. The reference is determined according to the nature of the value based on the elevation angle. For example, if the value based on the elevation angle is the elevation angle, the reference can be set to 20 degrees or the like.

[0053] FIG. 9 is a diagram comparing the result of scan correlation processing of the radar device according to another embodiment of the present invention with the configuration without scan correlation processing and the result when performed by conventional scan correlation processing.

[0054] FIG. 9 is a diagram comparing the detection status according to the presence or absence of scan correlation processing and the difference in processing methods when there are other ships and clutter around the own ship. Column A shows the state of change in the sway of the own ship. Column B shows the detection results in each state of sway when scan correlation processing is not performed. Column C shows the conventional scan correlation processing, that is, when the correlation coefficient is fixed. Column D shows the scan correlation processing in the radar apparatus of the present invention, where the correlation coefficient is changed according to the change in elevation angle. Column E shows the case where the correlation coefficient is further changed according to the number of times the correlation coefficient deviates from the standard value.

[0055] When scan correlation processing is not performed in Column B, the detection results vary significantly according to the elevation angle due to the sway of the ship. When the own ship in state 1 is in a substantially horizontal state, the clutter remains as it is without being removed, and the target is also captured as it is.

[0056] When performing the conventional scan correlation processing in Column C, when there is no sway (state 1), the clutter is removed and the target is detected as it is. In state 2 where the sway of the own ship continues, the clutter is suppressed, but the target is also suppressed. In state 3 where the sway continues, the clutter is suppressed and the target is further suppressed.

[0057] On the other hand, in the scan correlation processing of the radar apparatus of the present invention shown in Column D, when there is no sway, the same results of clutter suppression and target detection as the conventional scan correlation processing can be obtained. In the states where sway continues (states 2 and 3), the correlation coefficient is changed according to the change in elevation angle due to the sway, and when the elevation angle is large, the correlation coefficient is made small, so that while obtaining a clutter suppression effect, the target is not suppressed.

[0058] In the configuration where the correlation coefficient is reset to the standard value under predetermined conditions in the scan correlation processing of the radar apparatus of the present invention shown in Column E, the same effect as the conventional scan correlation processing can be obtained in state 1 where there is no sway. In states 2 and 3 where sway occurs, the same effect as the configuration where the correlation coefficient shown in Column D is not reset is obtained.

[0059] FIG. 10 is a diagram for comparing the result of the scan correlation process of the radar device according to another embodiment of the present invention with the configuration without the scan correlation process and the result when performed by the conventional scan correlation process, and shows the result in a state different from FIG. 9.

[0060] In FIG. 10, it represents the case where the sway continues further as shown in states 6 to 12 and the radar cannot be continuously and properly transmitted in a specific direction. In this case, an area (blank) where the transmitted wave of the radar does not reach the target and a reception signal cannot be obtained properly occurs. Specifically, when the period of the rotating radar is almost the same as the period of the wave colliding with the ship, when the radar antenna faces a specific direction, the ship tilts greatly, and a long blank occurs in a specific azimuth range. If the blank is short, it is reasonable to display the target based on the past information before the blank. However, if the blank continues for a long time, since the target is likely to have moved, it is not reasonable to display the target based on the past information before the blank. That is, when the blank continues for a long time, the video in a state where the past correlation coefficient before the blank is high has low reliability.

[0061] In the configuration shown in column D, since the correlation coefficient remains low from states 6 to 10, the information of the past target continues to remain in states 11 to 12. However, the display of the target in a state where the transmission signal has not been transmitted at an appropriate elevation angle for a long time is likely to be incorrect. Here, when the reliability of the past information in a predetermined area is low, in order to prevent the user from misrecognition, a method of increasing the correlation coefficient of the current sweep data with high reliability in the area can be considered.

[0062] In the configuration shown in column E, since the state where the correlation coefficient remains small in a predetermined direction continues from states 6 to 9, for example, the correlation coefficient of the sweep is reset in state 10 and returned to the standard value. Then, the display of the target that is likely to have moved becomes faint or invisible (states 11 to 12).

[0063] Here, the correlation coefficient was reset in state 10. However, the conditions for resetting the correlation coefficient can be set to various conditions, such as when the correlation coefficient is less than or equal to a specified reference value for a set number of seconds, or when the elevation angle is greater than or equal to a specified reference angle for a predetermined number of scans or more. Although it was configured to reset to the standard value, it may be changed to a predetermined correlation coefficient under predetermined conditions, or the correlation coefficient of the most recent sweep data may be determined according to the correlation coefficient of past information.

[0064] As a specific example of E, consider the case of creating a radar image to be displayed next using two images: the radar image displayed on the screen and the scan image generated only from the most recent scan. When the correlation coefficient of past sweep data is 0.9 at time point of state 6 and the correlation coefficient of current sweep data is 0.1, after a lapse of time, in state 10, it is conceivable that the correlation coefficient of past sweep data is set to 0.5 and the correlation coefficient of current sweep data is set to 0.5. By doing so, the weight of the received signal in the sweep where the radar is not appropriately displayed increases, and the target image in the radar image disappears earlier compared to D.

[0065] Although one embodiment of the radar device of the present invention has been described, the radar antenna 1 included in the radar device 100 of this embodiment can transmit a pulsed transmission wave such as a microwave generated by a magnetron, and receives the reflected wave of the transmission wave as a received signal.

[0066] The transmission wave transmitted by the radar device 100 is not limited to a pulsed wave and may be a continuous wave. Also, the transmission wave may be generated by a semiconductor element or the like instead of a magnetron. That is, the present invention can also be applied to an individualized radar or an FM-CW radar.

[0067] In addition, the radar antenna 1 repeats the transmission and reception of transmission waves while rotating in the horizontal plane at a predetermined rotation period. Note that instead of the radar device 100 of the present embodiment, a radar device having a configuration in which the radar antenna 1 is not rotated may be used. For example, a radar device having an antenna element in the entire circumferential direction or a radar device that detects only a specific direction such as the front does not require the radar antenna to be rotated. Further, the radar antenna 1 may perform the transmission and reception of radio waves with one antenna, or may have separate antennas for transmission and reception.

[0068] Note that the time taken from transmitting the transmission wave until the echo returns is proportional to the distance from the radar antenna 1 to the target. Therefore, by setting the time from transmitting the transmission wave until receiving the received signal as the radial distance r and the antenna angle at the time of transmitting the transmission wave as the deflection angle θ, the position of the target can be acquired in a polar coordinate system centered on the radar antenna 1. By plotting the position of the target acquired in this polar coordinate system on a plane, a radar image can be obtained.

[0069] The display unit 7 is a display such as a liquid crystal display and is a raster scan type display device capable of graphic display. The radar image created as described above is displayed on the display unit 8.

[0070] FIG. 11 shows a general configuration of a marine radar device. The ship 910 transmits electromagnetic waves in a predetermined cycle to the surroundings from the antenna 904 of the radar device attached to the upper part of the hull in order to detect targets that become obstacles to the navigation of the own ship such as other ships, receives the reflected waves reflected by the target, converts them into received signals by the receiving unit 906, further performs scan correlation processing by the processing circuit 908, removes clutter unnecessary for target detection, and displays it on the display 922.

[0071] The conventional structure of a radar device that performs such scan correlation processing will be briefly described with reference to FIG. 12. FIG. 12 is a block diagram showing the main part of a conventional radar device with scan correlation processing. The radar antenna 91 rotates in a horizontal plane at a predetermined rotation period and transmits pulsed radio waves to the outside at a predetermined transmission / reception period, and also receives the radio waves reflected by a target. The receiving unit 92 detects and amplifies the received signal and outputs it to the AD conversion unit 93. The AD conversion unit 93 converts this analog-form received signal into a digital signal (received data) consisting of multiple bits. The sweep memory 94 stores the received data for one sweep that has been digitally converted in real time, and holds this data for one sweep until the received data obtained by the next transmission is rewritten again.

[0072] The scan correlation processing unit 95 performs correlation processing between the data for the most recent one sweep obtained from the same azimuth and one or a plurality of sweep data obtained previously, and the result is output to the image memory 96 and displayed on the display unit.

Explanation of Signs

[0073] 1, 91, 904 Radar antenna 2, 906 Receiving unit 3 A / D conversion unit 4, 94 Sweep memory 5, 41, 95 Scan correlation processing unit 6, 42, 96, 306 Image memory 7, 97, 922 Display unit 8 Azimuth information acquisition unit 9 Attitude information acquisition unit 10, 43 Elevation angle calculation unit 11, 44 Correlation coefficient setting unit 45 Scan correlation processing count unit 100, 902 Radar device 908 Processing circuit 110, 910 Own ship (ship equipped with radar device) 112, 912 Electromagnetic wave 914 Wave 916 Target (other ship) 920 Communication (communication means, whether wired or wireless)

Claims

1. A radar device installed on a moving body that moves on the water surface, an antenna that transmits electromagnetic waves while changing the azimuth at a predetermined period, receives the reflected waves, and sends out a received signal; a received signal processing unit that generates and holds sweep data based on the received signal; a correlation coefficient setting unit that sets a correlation coefficient indicating the weighting of both between the current sweep data generated based on the received signal obtained at an arbitrary timing in a specific azimuth and the past sweep data generated based on the received signals obtained at one or more timings before that timing in the specific azimuth; a scan correlation processing unit that performs scan correlation processing for synthesizing the current sweep data and the past sweep data based on the correlation coefficient to generate image data; an attitude information acquisition unit that acquires the attitude information of the antenna in association with the azimuth; an elevation angle calculation unit that calculates the elevation angle of the antenna in the azimuth based on the attitude information; The correlation coefficient setting unit sets the correlation coefficient based on the elevation angle. Radar device.

2. The radar device according to Claim 1, wherein the past sweep data is the sweep data immediately before in the same azimuth in the scan before the current sweep data. Radar device.

3. The radar device according to Claim 2, wherein the scan correlation processing multiplies the current sweep data by a first correlation coefficient, multiplies 1 by a second correlation coefficient for the immediately preceding sweep data, and synthesizes both. Radar device.

4. The radar device according to Claim 3, wherein the antenna is installed on a ship and rotates in a horizontal plane at a predetermined period when not swaying, and the elevation angle is defined based on the horizontal plane. Radar device.

5. The radar device according to Claim 4, wherein the first correlation coefficient is set smaller as the elevation angle increases. Radar device.

6. The radar device according to Claim 5, wherein the second correlation coefficient is set larger as the elevation angle increases. Radar device.

7. The radar device according to Claim 4, wherein the first correlation coefficient is set to a predetermined standard value when the elevation angle is less than or equal to a predetermined threshold value, and is set smaller than the standard value when the elevation angle is greater than the threshold value. Radar device.

8. The radar device according to Claim 7, The correlation coefficient setting unit sets the correlation coefficient based on the elevation angle in a plurality of scans for the same azimuth. Radar device.

9. The radar device according to claim 8, When a value based on the elevation angle in the same azimuth is continuously greater than a reference value for a plurality of scans, the correlation coefficient setting unit stops setting the correlation coefficient based on the elevation angle in that azimuth. Radar device.

10. The radar device according to claim 9, When the correlation coefficient setting unit stops setting the correlation coefficient based on the elevation angle, it sets the correlation coefficient to a predetermined value. Radar device.

11. The radar device according to any one of claims 1 to 10, further comprising: A display for displaying the image data. Radar device.

12. The radar device according to claim 11, further comprising: The attitude information acquisition unit acquires the attitude information from a GNSS receiver mounted on the moving body. Radar device.

13. A detection method for a radar installed on a moving body moving on the water surface, Transmitting electromagnetic waves while changing the azimuth at a predetermined period from an antenna, receiving the reflected wave and sending out a received signal, Generating and holding sweep data based on the received signal, acquiring the attitude information of the antenna in association with the azimuth, and calculating the elevation angle of the antenna in the azimuth based on the attitude information. Between the current sweep data generated based on the received signal acquired at an arbitrary timing in a specific azimuth and the past sweep data generated based on the received signal obtained at one or more timings before that timing in the specific azimuth, a correlation coefficient indicating the weighting of both is determined based on the elevation angle. Performing a scan correlation process of synthesizing the current sweep data and the past sweep data based on the correlation coefficient to generate image data. Radar detection method.

14. The radar detection method according to claim 13, The past sweep data is the sweep data immediately before the same azimuth in the scan before the current sweep data. Radar detection method.

15. A computer program including computer-executable instructions, which when executed by a computer, Transmits electromagnetic waves while changing the azimuth at a predetermined period from an antenna, receives the reflected wave and causes a received signal to be sent out. Generate and hold sweep data based on the received signals obtained from the same orientation, obtain the attitude information of the antenna in association with the orientation, and calculate the elevation angle of the antenna in the orientation based on the attitude information. Between the current sweep data generated based on the received signals obtained at an arbitrary timing in a specific orientation and the past sweep data generated based on the received signals obtained at one or more timings before the timing in the specific orientation, determine a correlation coefficient indicating the weighting of both based on the elevation angle. Perform scan correlation processing to synthesize the current sweep data and the past sweep data based on the correlation coefficient, generate image data, and output it. Radar detection program.

Images