Radar signal processing device, radar signal processing program, radar image display device, and autonomous navigation device

Abstract

This disclosure aims to determine whether, when autonomous navigation of a vessel or other vessel is performed using radar images or sonar images, waves or clutter such as rain and snow are appropriately contained, regardless of the frequency band, antenna length, or mounting position. [Solution] This disclosure acquires radar images before clutter suppression from multiple radar transceivers A-1, A-2 having the same or different frequency bands or antenna lengths. Then, among the radar images after clutter extraction, if there are more clutter displayed in one radar image after clutter extraction compared to another radar image after clutter extraction, the clutter suppression parameters are feedback controlled so that the displayed clutter is further displayed in that radar image after clutter extraction.

Description

Technical Field

[0001] The present disclosure relates to a technology for autonomous navigation using radar images.

Background Art

[0002] There has conventionally been a technology for autonomous navigation of ships and the like using radar images or sonar images. By performing autonomous navigation of ships and the like, the safety of ships and the like can be improved, and the shortage of crew and the like can be eliminated. On the other hand, by involving the navigation judgment of crew and the like, obstacles of ships and the like can be avoided in areas where ships and the like are congested in a strait or the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in performing autonomous navigation of ships and the like, after controlling the suppression parameters of clutter such as waves or rain and snow, by using a radar image including clutter such as waves or rain and snow, the influence of weather or sea state can be avoided, and efficient autonomous navigation can be performed.

[0005] Here, in Patent Document 1, for the sensor signal of one system of radar device, after controlling the suppression parameters of clutter such as waves or rain and snow, a radar image including clutter such as waves or rain and snow is displayed. However, one system of radar device has advantages or disadvantages in terms of resolution, maximum distance or visible area depending on the frequency band, antenna length or mounting position. Therefore, it has not been possible to clearly determine whether a radar image of one system appropriately includes clutter such as waves or rain and snow in performing autonomous navigation of ships and the like.

[0006] Therefore, in order to solve the aforementioned problems, this disclosure aims to determine whether, when autonomous navigation of a vessel or the like is performed using radar images or sonar images, waves or clutter such as rain and snow are appropriately contained, regardless of the frequency band, antenna length, or mounting position. [Means for solving the problem]

[0007] To solve the aforementioned problem, in preparation for autonomous navigation of ships and the like, radar images after clutter extraction are output for multiple radar devices (mounting positions inevitably differ) that have the same or different frequency bands or antenna lengths.

[0008] Here, multiple radar devices compensate for each other's shortcomings in terms of resolution, maximum range, or visible area, depending on the frequency band, antenna length, or mounting position. Therefore, when there is more clutter displayed in one radar image compared to the other, the clutter suppression parameters are feedback-controlled so that the clutter is displayed more in the radar image of the other.

[0009] Specifically, the present disclosure is a radar signal processing device characterized by comprising: a radar image acquisition unit that acquires radar images before clutter suppression from a plurality of radar transceivers having the same or different frequency bands or antenna lengths; a clutter suppression unit that suppresses both or one of the wave clutter and rain / snow clutter from each of the radar images before clutter suppression and outputs each radar image after clutter suppression; a clutter extraction unit that subtracts each radar image after clutter suppression from each of the radar images before clutter suppression to extract both or one of the wave clutter and rain / snow clutter and outputs each radar image after clutter extraction; and a radar image comparison unit that, when there are more displayed clutter in one of the radar images after clutter extraction compared to another, feedback controls the suppression parameters of both or one of the wave clutter and rain / snow clutter so that the displayed clutter is further displayed in the radar image after clutter extraction.

[0010] With this configuration, when autonomous navigation of a vessel or other vehicle is performed using radar or sonar images, it is possible to determine whether clutter such as waves or rain / snow is adequately contained, regardless of the frequency band, antenna length, or mounting position. If it is determined that the clutter is adequately contained, the clutter can be further displayed.

[0011] Furthermore, this disclosure relates to a radar signal processing device characterized in that the radar image comparison unit provides feedback control to suppression parameters of both or one of the wave clutter and the rain / snow clutter so that, in a radar image after clutter extraction, the suppression of both or one of the wave clutter and the rain / snow clutter is strengthened, thereby further displaying the clutter that is displayed.

[0012] With this configuration, when autonomous navigation of a ship or other vessel is performed using radar or sonar images, if the clutter suppression unit further suppresses the clutter, the clutter extraction unit can display the clutter if it determines that the clutter can be appropriately contained.

[0013] Furthermore, this disclosure relates to a radar signal processing device characterized in that the clutter suppression unit outputs each of the clutter-suppressed radar images based on both or one of the wave information and rain / snow information acquired from an external source.

[0014] With this configuration, when autonomous navigation of a vessel or other vehicle is performed using radar or sonar images, the control method for clutter suppression parameters can be adjusted based on wave information and rain / snow information (highly reliable information not obtained from radar) acquired from external sources.

[0015] Furthermore, this disclosure relates to a radar signal processing device characterized in that the clutter suppression unit feedback-controls the suppression parameters of both or one of the wave clutter and the rain / snow clutter based on the degree of agreement between each of the radar images after clutter extraction (current or past radar images) and information of both or one of the wave information and the rain / snow information (the current or the past information).

[0016] With this configuration, when autonomous navigation of a ship or other vessel is performed using radar images or sonar images, the control method for controlling clutter suppression parameters can be feedback-controlled based on current wave information and rain / snow information (highly reliable information predicted externally) or past wave information and rain / snow information (even more reliable information actually observed).

[0017] In addition, in the present disclosure, the clutter extraction unit separates and extracts the wave clutter from the rain and snow clutter based on the suppression parameter of the wave clutter for each radar image after the clutter extraction, or separates and extracts the rain and snow clutter from the wave clutter based on the suppression parameter of the rain and snow clutter for each radar image after the clutter extraction. The radar signal processing apparatus is characterized by this.

[0018] According to this configuration, when performing autonomous navigation of a ship or the like using a radar image or a sonar image, the wave clutter and the rain and snow clutter can be separated and extracted.

[0019] In addition, the present disclosure is a radar signal processing program for causing a computer to execute each processing step executed by each processing unit included in the radar signal processing apparatus described above.

[0020] According to this configuration, a program having the effects described above can be provided.

[0021] In addition, the present disclosure is a radar image display device that at least displays a certain radar image after clutter extraction output by the radar signal processing apparatus described above.

[0022] According to this configuration, an image display device having the effects described above can be provided.

[0023] In addition, the present disclosure is an autonomous navigation device that performs autonomous navigation using at least a certain radar image after clutter extraction output by the radar signal processing apparatus described above.

[0024] According to this configuration, an autonomous navigation device having the effects described above can be provided.

[0025] Note that the inventions of the above disclosures can be combined as much as possible.

Effects of the Invention

[0026] Thus, when performing autonomous navigation of a ship or the like using radar images or sonar images, the present disclosure can determine whether clutter such as waves or rain and snow is appropriately included regardless of the frequency band, antenna length, or mounting position.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram showing the configuration of the radar system of the present disclosure. [Figure 2] It is a diagram showing the procedure of the clutter extraction process of the present disclosure. [Figure 3] It is a diagram showing a specific example of the clutter extraction process of the present disclosure. [Figure 4] It is a diagram showing a specific example of the clutter extraction process of the present disclosure. [Figure 5] It is a diagram showing a specific example of the clutter extraction process of the present disclosure. [Figure 6] It is a diagram showing the procedure of the radar image comparison process of the present disclosure. [Figure 7] It is a diagram showing a specific example of the radar image comparison process of the present disclosure. [Figure 8] It is a diagram showing a specific example of the radar image comparison process of the present disclosure. [Figure 9] It is a diagram showing a specific example of the autonomous navigation process of the present disclosure.

Mode for Carrying Out the Invention

[0028] Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of the implementation of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0029] (Configuration of the radar system of the present disclosure) The configuration of the radar system of this disclosure is shown in Figure 1. The radar system R comprises radar transceivers A-1 and A-2, weather information acquisition device M, radar signal processing device S, radar image display device D, and autonomous navigation device N. The radar signal processing device S comprises clutter suppression units 1-1 and 1-2, clutter extraction units 2-1 and 2-2, and radar image comparison unit 3, and can be implemented by installing the radar signal processing program shown in Figures 2 and 6 onto a computer.

[0030] As shown in Figures 6-8, in preparation for autonomous navigation of ships and other vessels, multiple radar transceivers (mounting locations will inevitably differ) with the same or different frequency bands or antenna lengths output radar images after clutter extraction from each device.

[0031] Here, multiple radar transceivers compensate for each other's shortcomings in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting position. Therefore, when there is more clutter displayed in one radar image compared to the other, the clutter suppression parameters are feedback-controlled so that the clutter is displayed more in the radar image of the other.

[0032] (Procedure for clutter extraction as described in this disclosure) The procedure for the clutter extraction process of this disclosure is shown in Figure 2. Specific examples of the clutter extraction process of this disclosure are shown in Figures 3 to 5. Radar transceivers A-1 and A-2 transmit an irradiation radar signal and receive a reflected radar signal. Weather information acquisition device M acquires information from an external source, either or both of the following: wave information (including wind direction and speed information, etc.) and rain / snow information.

[0033] The radar signal processing device S acquires pre-clutter suppression radar images from multiple radar transceivers A-1 and A-2 (which are necessarily mounted in different locations) that have the same or different frequency bands or antenna lengths (step S1). Here, the multiple radar transceivers A-1 and A-2 compensate for each other's shortcomings with the advantages of the other in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting location.

[0034] The clutter suppression units 1-1 and 1-2 suppress both or one of the wave clutter and rain / snow clutter in the radar images obtained from each of the multiple radar transceivers A-1 and A-2 before clutter suppression, based on information from both or one of the wave information and rain / snow information acquired from an external source, and output the radar images after clutter suppression (step S2).

[0035] In other words, the clutter suppression units 1-1 and 1-2 control the suppression parameters for wave clutter and rain / snow clutter in the wave distribution and rain / snow distribution included in the wave information and rain / snow information, respectively, for the radar image before clutter suppression. Here, the wave distribution included in the wave information is strong around ships, strong upwind of ships, and weak downwind of ships. On the other hand, the rain / snow distribution included in the rain / snow information extends over a wide area, including the area around ships, not just around ships.

[0036] In the left column of Figure 3, in each radar image before clutter suppression, the target signal is obscured by wave clutter and rain / snow clutter. In the middle column of Figure 3, in each radar image during clutter suppression, wave information (including wind direction and speed information, etc.) includes wave distribution, and rain / snow information includes rain / snow distribution. In the right column of Figure 3, in each radar image after clutter suppression, the target signal is not obscured by wave clutter and rain / snow clutter.

[0037] Clutter extraction units 2-1 and 2-2 subtract the radar image after clutter suppression from the radar image before clutter suppression to extract both or one of the wave clutter and rain / snow clutter, and output the radar image after clutter extraction (step S3).

[0038] Here, wave and rain / snow information is not based on actual observations, but rather on predictions for the short term from the present, and covers a wide area not limited to the vicinity of ships, etc. On the other hand, the radar images after clutter extraction are not based on predictions for the short term from the present, but rather on actual observations, and are pinpoint information limited to the vicinity of ships, etc.

[0039] In the left column of Figure 4, in each radar image before clutter suppression, the target signal is obscured by wave clutter and rain / snow clutter. In the middle column of Figure 4, in each radar image after clutter suppression, the target signal is not obscured by wave clutter and rain / snow clutter. In the right column of Figure 4, in each radar image after clutter extraction, wave clutter and rain / snow clutter are extracted.

[0040] Clutter extraction units 2-1 and 2-2 separate and extract wave clutter from rain and snow clutter based on the suppression parameters for wave clutter in the radar images after clutter extraction. Alternatively, clutter extraction units 2-1 and 2-2 separate and extract rain and snow clutter from wave clutter based on the suppression parameters for rain and snow clutter in the radar images after clutter extraction (step S4).

[0041] In other words, the clutter extraction units 2-1 and 2-2 set clutter suppression parameters for the waves (or rain / snow) clutter on the radar images after clutter extraction for each wave and rain / snow, and output the radar images after clutter suppression for each wave (or rain / snow). Then, the clutter extraction units 2-1 and 2-2 subtract the radar images after clutter suppression for each wave (or rain / snow) clutter from the radar images after clutter extraction for each wave and rain / snow, and output the radar images after clutter separation extraction for each rain / snow (or wave).

[0042] In the left column of Figure 5, wave clutter and rain / snow clutter are extracted from the radar images after clutter extraction for each wave and rain / snow. Here, a suppression parameter for wave (or rain / snow) clutter is set, and the radar images after suppression of wave (or rain / snow) clutter are subtracted. In the right column of Figure 5, wave (or rain / snow) clutter is extracted from the radar images after clutter separation extraction for each wave (or rain / snow).

[0043] Clutter suppression units 1-1 and 1-2 provide feedback control to suppress both or one of the wave clutter and rain / snow clutter based on the degree of agreement between the radar image after clutter extraction (current or past radar image) and the wave information and / or rain / snow information (current or past information). (Steps S5-S7)

[0044] In other words, the clutter suppression units 1-1 and 1-2 determine the degree of agreement between the radar images after clutter extraction and the wave information and rain / snow information (step S5). Then, if the degree of agreement is low (step S6, NO), the clutter suppression units 1-1 and 1-2 perform feedback control of the suppression parameters for wave clutter and rain / snow clutter (step S7, right column of Figure 5) and return to step S4. On the other hand, if the degree of agreement is high (step S6, YES), the clutter suppression units 1-1 and 1-2 finish the feedback control of the suppression parameters for wave clutter and rain / snow clutter (right column of Figure 5) and proceed to step S8.

[0045] Here, the clutter suppression units 1-1 and 1-2 can precisely feedback control the suppression parameters of the current wave clutter and rain / snow clutter when determining the degree of agreement between the radar images after extraction of each clutter in the current state and the wave information and rain / snow information (highly reliable information predicted externally).

[0046] Furthermore, when the clutter suppression units 1-1 and 1-2 determine the degree of agreement between the radar images after extracting each clutter from the "past" and the wave information and rain / snow information from the "past" (even more reliable information that was actually observed), they can provide even more precise feedback control of the suppression parameters for the "present" wave clutter and rain / snow clutter.

[0047] Clutter extraction units 2-1 and 2-2 output their respective radar images after clutter extraction (after coordinate transformation, coordinate rotation, and range adjustment, etc., but before radar image comparison and before recontrol of suppression parameters) to the radar image comparison unit 3 (step S8).

[0048] In this way, when autonomous navigation of ships, etc., is performed using radar images or sonar images, the control method for clutter suppression parameters can be adjusted based on wave information and rain / snow information acquired from external sources (highly reliable information not obtained by radar). Wave clutter and rain / snow clutter can then be separated and extracted. Furthermore, the control method for clutter suppression parameters can be feedback-controlled based on current wave information and rain / snow information (highly reliable information predicted externally) or past wave information and rain / snow information (even more reliable information actually observed).

[0049] As a variation, the clutter extraction units 2-1 and 2-2 may output their respective radar images after clutter extraction using CFAR processing or STC processing, etc., without relying on either or both of the wave information and rain / snow information acquired from an external source.

[0050] (Procedure for radar image comparison processing as disclosed herein) The procedure for the radar image comparison processing of this disclosure is shown in Figure 6. Specific examples of the radar image comparison processing of this disclosure are shown in Figures 7 and 8. The radar signal processing device S acquires pre-clutter suppression radar images from a plurality of radar transceivers A-1 and A-2 (mounting positions are necessarily different) that have the same or different frequency bands or antenna lengths (step S1). Here, the plurality of radar transceivers A-1 and A-2 compensate for each other's shortcomings with the advantages of the other in terms of resolution, maximum distance, or visible area, depending on the frequency band, antenna length, or mounting position. The advantages and disadvantages of resolution, maximum distance, or visible area are described below.

[0051] Firstly, the higher the frequency band (e.g., X-band), the higher the distance and azimuthal resolution, but the shorter the maximum distance corresponding to the amount of water vapor. On the other hand, the lower the frequency band (e.g., S-band), the longer the maximum distance corresponding to the amount of water vapor, but the lower the distance and azimuthal resolution.

[0052] Next, the longer the antenna length, the higher the azimuth resolution, but the lower the antenna rotation rate. Furthermore, the lower the antenna rotation rate, the lower the frequency of radar image updates, but the higher the number of hits (number of radar irradiations) per target. On the other hand, the shorter the antenna length, the lower the azimuth resolution, but the higher the antenna rotation rate. Furthermore, the higher the antenna rotation rate, the higher the frequency of radar image updates, but the lower the number of hits (number of radar irradiations) per target.

[0053] Next, if the mounting position is not obstructed by a mast or similar structure, clutter may be displayed in all directions. On the other hand, if the mounting position is obstructed by a mast or similar structure, clutter will not be displayed in the direction of the obstruction. However, even in the direction of the obstruction, diffraction may occur at long distances, resulting in diffuse reflection or multipath reflection, but clutter may still be displayed.

[0054] The radar image comparison unit 3 determines whether there are more clutters displayed in one radar image after clutter extraction compared to other radar images after clutter extraction, based on the radar images after clutter extraction input from multiple clutter extraction units 2-1 and 2-2 (step S11).

[0055] Then, when there are more clutters to display (step S12, YES), the radar image comparison unit 3 provides feedback control to suppress both or one of the wave clutter and rain / snow clutter so that the clutter that is displayed is further displayed in the radar image after a certain clutter has been extracted (step S13), and proceeds to step S14.

[0056] Here, the radar image comparison unit 3 provides feedback control to the suppression parameters of both or one of the wave clutter and rain / snow clutter so that the displayed clutter is further displayed in the radar image after a certain clutter has been extracted, by strengthening the suppression of both or one of the wave clutter and rain / snow clutter (step S13). For example, the suppression parameters of both or one of the wave clutter and rain / snow clutter can be provided via feedback control based on information from both or one of the wave information and rain / snow information.

[0057] On the other hand, when there are fewer clutters to display (step S12, NO), the radar image comparison unit 3 finishes feedback control of the suppression parameters for both or one of the wave clutter and rain / snow clutter in both the radar image after one clutter extraction and the radar image after the other clutter extraction, and proceeds to step S14.

[0058] In the left column of Figure 7, fewer clutter particles are displayed in the radar image after S-band or X-band clutter extraction. In the middle column of Figure 7, more clutter particles are displayed in the radar image after X-band or S-band clutter extraction. In the middle column of Figure 7, compared to the left column of Figure 7, more clutter particles are displayed (higher clutter intensity and wider clutter distribution) due to advantages in resolution or maximum distance.

[0059] In the right-hand column of Figure 7, in the radar image after controlling the X-band or S-band suppression parameters, the clutter suppression parameters are increased, strengthening clutter suppression, resulting in more clutter being displayed (higher clutter intensity and wider clutter distribution). In other words, one of the advantages, either resolution or maximum distance, is further enhanced.

[0060] In the left column of Figure 8, the radar image after clutter extraction from a radar with obstructions shows no clutter in the direction of the obstruction. In the middle column of Figure 8, the radar image after clutter extraction from an unobstructed radar shows more clutter. In the middle column of Figure 8, compared to the left column of Figure 8, more clutter is shown (higher clutter intensity and wider clutter distribution) due to the advantage of the visible range.

[0061] In the right column of Figure 8, in the radar image after controlling the suppression parameters of an unobstructed radar, the clutter suppression parameters are increased, and the clutter suppression is strengthened, resulting in more clutter being displayed (higher clutter intensity and wider clutter distribution). In other words, one of the advantages is further enhanced in the visible region.

[0062] The radar image comparison unit 3 displays each of the radar images after clutter extraction (after coordinate transformation, coordinate rotation, and range adjustment, etc., and after radar image comparison and recontrol of suppression parameters) on the radar image display device D (step S14). Here, only the radar images after clutter extraction, in which the advantages of the radar are further enhanced, may be displayed.

[0063] In this way, when autonomous navigation of ships, etc., is performed using radar images or sonar images, it is possible to determine whether clutter such as waves or rain and snow is adequately contained, regardless of the frequency band, antenna length, or mounting position. When it is determined that the clutter is adequately contained, the clutter can be further displayed. Furthermore, if the clutter is further suppressed by any of the clutter suppression units, and it is determined that the clutter can be adequately contained by any of the clutter extraction units, the clutter can be further displayed.

[0064] (Specific examples of autonomous navigation processing in this disclosure) A specific example of the autonomous navigation process of this disclosure is shown in Figure 9. The radar image display device D displays each of the radar images after clutter extraction output by the radar signal processing device S separately (step S14). Here, only the radar images after clutter extraction, in which the advantages of the radar are further enhanced, may be displayed. The autonomous navigation device N performs autonomous navigation using each of the radar images after clutter extraction output by the radar signal processing device S. Here, autonomous navigation may be performed using only the radar images after clutter extraction, in which the advantages of the radar are further enhanced.

[0065] In the left column of Figure 9, wave clutter is extracted in the radar image after each wave clutter separation and extraction (land signals are also displayed, and wave information may be superimposed). In the right column of Figure 9, rain and snow clutter is extracted in the radar image after each rain and snow clutter separation and extraction (land signals are also displayed, and rain and snow information may be superimposed).

[0066] The autonomous navigation system N then confirms the destination of the vessel and uses radar images to autonomously navigate in a direction where wave clutter and rain / snow clutter are not displayed. In other words, the autonomous navigation system N confirms the destination of the vessel and uses radar images to autonomously navigate in a way that avoids adverse weather conditions such as waves and rain / snow. [Industrial applicability]

[0067] The radar signal processing device and radar signal processing program of this disclosure can determine whether to appropriately include waves or clutter such as rain and snow, regardless of the frequency band, antenna length, or mounting position, when performing autonomous navigation of a ship or the like using radar images or sonar images.

[0068] The radar image display device of this disclosure can display radar images or sonar images necessary for autonomous navigation of a vessel or the like using radar images or sonar images. The autonomous navigation device of this disclosure can perform autonomous navigation of a vessel or the like using the radar images or sonar images thus output. [Explanation of symbols]

[0069] R: Radar system A-1, A-2: Radar transceiver M: Weather information acquisition device S: Radar signal processing device D: Radar image display device N:Autonomous navigation device 1-1, 1-2: Clutter suppression section 2-1, 2-2: Clutter extraction section 3: Radar Image Comparison Section

Claims

1. A radar image acquisition unit that acquires radar images from multiple radar transceivers having the same or different frequency bands or antenna lengths, before clutter suppression, A clutter suppression unit suppresses both or one of the wave clutter and rain / snow clutter in each of the radar images before clutter suppression, and outputs each radar image after clutter suppression. A clutter extraction unit subtracts the radar image after clutter suppression from each of the radar images before clutter suppression to extract both or one of the wave clutter and the rain / snow clutter, and outputs the radar image after clutter extraction for each; A radar image comparison unit provides feedback control of the suppression parameters of both or one of the wave clutter and rain / snow clutter so that, when a radar image after clutter extraction contains more clutter than other radar images after clutter extraction, the clutter is further displayed in the radar image after clutter extraction. A radar signal processing device characterized by comprising:

2. The radar image comparison unit provides feedback control to the suppression parameters of both or one of the wave clutter and the rain / snow clutter so that, in a radar image after clutter extraction, the suppression of both or one of the wave clutter and the rain / snow clutter is strengthened, thereby further displaying the clutter that is being shown. The radar signal processing device according to claim 1, characterized in that

3. The clutter suppression unit outputs the respective radar images after clutter suppression based on either or both of the wave information and / or rain / snow information acquired from an external source. The radar signal processing device according to claim 1, characterized in that

4. The clutter suppression unit provides feedback control to suppress both or one of the wave clutter and the rain / snow clutter based on the degree of agreement between each of the radar images after clutter extraction (current or past radar images) and the wave information and / or the rain / snow information (the current or past information). The radar signal processing device according to claim 3, characterized in that

5. The clutter extraction unit separates and extracts the wave clutter from the rain and snow clutter based on the suppression parameters of the wave clutter in each radar image after clutter extraction, or separates and extracts the rain and snow clutter from the wave clutter based on the suppression parameters of the rain and snow clutter in each radar image after clutter extraction. The radar signal processing device according to claim 1, characterized in that

6. A radar signal processing program for causing a computer to perform each processing step performed by each processing unit of the radar signal processing device according to any one of claims 1 to 5.

7. A radar image display device that displays at least one of the radar images after clutter extraction, output by a radar signal processing device according to any one of claims 1 to 5.

8. An autonomous navigation device that performs autonomous navigation using at least a radar image after clutter extraction, output by a radar signal processing device according to any one of claims 1 to 5.

Images