A method for ship-to-shore separation based on secondary scanning

Abstract

The present application relates to a kind of based on twice scanning coast-ship separation method.By adding single pulse angle measurement in radar search, the angle resolution is improved, the tangential distribution of target caused by angle measurement error is obtained by two scans in opposite directions, and the coast-ship separation threshold of each target is adaptively obtained using the geometric distribution, which can avoid real-time calculation of the position relationship between missile and island coastline, and reduce the coast-ship separation threshold under the background of complex coastline.The method improves the angle resolution by adding single pulse angle measurement in radar search, obtains the tangential distribution of target caused by angle measurement error by two scans in opposite directions, and adaptively obtains the coast-ship separation threshold of each target using the geometric distribution, which can avoid real-time calculation of the position relationship between radar and island coastline, and reduce the coast-ship separation threshold under the background of complex coastline.

Description

Technical Field

[0001] This invention relates to the field of near-shore target detection, and specifically to a shore-to-ship separation method based on secondary scanning. Background Technology

[0002] For radars detecting naval targets, when the target ship appears in near-shore or island / reef waters, they often face the challenge of having a coastline within the search area. The island / reef itself, as well as shore-based structures and large undulating terrain such as cliffs, can all generate strong reflections, increasing the risk of radar target detection and false acquisition. Therefore, effectively separating shore-based naval targets is a prerequisite for radar to correctly acquire targets in an island / shore context.

[0003] Traditional target area island and shore echo suppression mainly relies on geographic information to plan radar search maps, i.e., controlling the range search range at different angles to exclude islands and shores from the search area. Due to the poor angular resolution of radar beams, while the range resolution is relatively high due to bandwidth, this method achieves the highest resolution when the radar detects the target at a perpendicular angle to the island / shoreline, and the lowest resolution when it is parallel to the island / shoreline. It requires real-time calculation of the positional relationship between the island / shoreline and the attack direction, and incorporating different shore-to-ship separation thresholds for different island / shore shapes and locations to plan the search area. Furthermore, for complex coastlines, the presence of multiple parallel relationships can lead to a large non-separation threshold, such as... Figure 1 As shown. Summary of the Invention

[0004] Technical problems to be solved

[0005] To address the challenge of separating shore-to-ship targets under varying island coastline morphologies, and considering that existing methods require real-time calculation of the positional relationship between the island coastline and the detection direction, and that complex coastlines often exhibit large non-separation thresholds due to multiple parallel relationships, this invention provides a shore-to-ship separation method based on a two-scan approach. By incorporating single-pulse angle measurement during radar search to improve angular resolution, and performing two scans in opposite directions to acquire the target tangential distribution caused by angle measurement errors, this geometric distribution is used to adaptively determine the shore-to-ship separation threshold for each target. This method avoids the need for real-time calculation of the missile's positional relationship with the island coastline and reduces the shore-to-ship separation threshold in complex coastline scenarios.

[0006] Technical solution

[0007] A shore-to-ship separation method based on secondary scanning, characterized by the following steps:

[0008] Step 1: After the radar sets the search parameters, start the first search, i.e., leftward scan. During the scan, perform single-pulse angle measurement on all detected targets and calculate the target angle by combining the scan frame angle. Based on the radar's target distance, convert the target from the polar coordinate system to the geographic coordinate system.

[0009] Step 2: After the left scan is completed, start the second scan, i.e., the right scan. During the scan, perform single-pulse angle measurement on all detected targets and calculate the target angle by combining the scan frame angle. Based on the radar target distance, convert the target from the polar coordinate system to the geographic coordinate system.

[0010] Step 3: Compare the targets in the two scans one by one. The targets that meet the relevant position conditions are the detection results of the same target in the two searches, referred to as target 1 and target 2. After extraction, the geometric mean position of the same target in the two scans is obtained, referred to as target 3.

[0011] Step 4: Match targets 1, 2, and 3 with prior geographic information. If one or more targets among targets 1, 2, and 3 are identified as island / shore targets, the target is identified as an island / shore target; otherwise, it is identified as a ship, thus completing the separation of shore and ship.

[0012] The specific conditions for correlation in step 3 are as follows: if the detection distance between the two scans is less than twice the distance resolution unit and the angle between the two scans is less than 1 / 10 of the beamwidth, then the correlation is considered successful.

[0013] Beneficial effects

[0014] This invention provides a shore-to-ship separation method based on a two-scan approach, addressing the shortcomings of existing methods. These methods require real-time calculation of the positional relationship between the island's coastline and the detection direction, and the inability to apply different shore-to-ship separation thresholds based on varying island and coastline shapes for search area planning. Furthermore, complex coastlines often exhibit large non-separation thresholds due to multiple parallel relationships. This new method improves angular resolution by incorporating single-pulse angle measurement during radar search. It acquires the target tangential distribution caused by angle measurement errors through two scans in opposite directions, and adaptively determines the shore-to-ship separation threshold for each target using this geometric distribution. This approach avoids real-time calculation of the radar's positional relationship with the island's coastline and reduces the shore-to-ship separation threshold in complex coastline scenarios. Attached Figure Description

[0015] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0016] Figure 1 Schematic diagram of the shortcomings of traditional shore-to-ship separation (left image: parallel island-to-shore search - right image: vertical island-to-shore search);

[0017] Figure 2 A process for shore-to-ship separation based on secondary scanning;

[0018] Figure 3 Geometric position distribution of the real target in secondary scanning;

[0019] Figure 4 Adaptive shore-to-ship separation under different perspectives;

[0020] Figure 5 Measured data on shore-to-ship separation under different positional relationships;

[0021] Figure 6 Implementation examples. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] A shore-to-ship separation method based on secondary scanning is as follows: Figure 2 As shown, the details are as follows:

[0024] First, after the radar sets the search parameters, the first search (leftward scan) is initiated. During the scan, monopulse angle measurement is performed on all detected targets, and the target angle is calculated by combining the scan frame angle. Based on the radar's target range, the target is converted from polar coordinates to geographic coordinates. After the left scan is completed, the second search (rightward scan) is initiated. During the scan, monopulse angle measurement is performed on all detected targets, and the target angle is calculated by combining the scan frame angle. Based on the radar's target range, the target is converted from polar coordinates to geographic coordinates. Targets from both scans are compared one by one. Targets that meet the correlation conditions (detection distance less than twice the range resolution cell in both scans, and scan angle less than 1 / 10 of the beamwidth in both scans are considered to have successfully correlated) are the detection results of the same target in both scans, referred to as Target 1 and Target 2. After extraction, the geometric mean position of the same target in both scans is calculated, referred to as Target 3. The targets 1, 2, and 3 are matched with prior geographic information. If one or more of the targets 1, 2, and 3 are identified as island / shore targets, the target is identified as an island / shore target; otherwise, it is identified as a ship, thus completing the separation of shore and ship.

[0025] The specific mechanism is as follows: Because the two scans are performed in opposite directions, the errors caused by the delay in angle sensing and transmission within the scanning frame, as well as the time consumed by coherent accumulation during single-pulse angle measurement, accumulate in two opposite directions, resulting in a certain regular geometric distribution of the three target positions. That is, the target is biased to the right in the left scan circle, biased to the left in the right scan circle, and the geometrically averaged target is closest to the true position. For example... Figure 3 The image shows the results of 24 detections of real ship targets in a certain sea area, with the actual positions output by RTK positioning equipment. The upper left circle represents the target position in the left scan circle, the lower right circle represents the target position in the right scan circle, the pentagram represents the geometric mean position, and the square represents the true target value output by RTK. It can be seen that the target positions in the two circles are distributed around the target's actual position, with the average position being closest to the actual position. The tangential position deviation is dynamically positively correlated with the detection error for each scan, while the radial error is guaranteed by the radar's range resolution and does not change with the scanning direction. The dashed line in the figure connects the two circles of positions in each set of search data. This clearly corroborates the above conclusions; the connecting line passes through the actual target's location, meaning the range dimension error is very small, and the main error is located in the tangential direction perpendicular to the detection direction. Therefore, when the island / shore background is perpendicular to the detection direction, the resolution is optimal; when it is parallel to the detection direction, the resolution is worst due to angular resolution limitations. The identification strategy needs to handle these situations differently to maximize the separation of shore and ship targets without introducing ground targets. Based on the above distribution patterns, different circles of targets can be used to adaptively make decisions based on different detection directions. Figure 4As shown, when the detection direction is perpendicular to the island / shore direction, the minimum shore-ship separation threshold distance R is essentially the radar resolution (generally within 10 meters), which is less than the accuracy of a typical map grid. This means that, except when a ship and a ground target are within the same grid and cannot be identified, shore-ship separation is possible in all other cases, reducing the threshold to the grid size. This direction is most advantageous for target detection and has the strongest ability to separate shore and ship targets. When attacking in a parallel direction, the shore-ship separation threshold is the distance R between the target in the left circle and the actual target. This distance R is caused by angular error. Using the three-point criterion, it is equivalent to achieving a dynamic threshold for each search. This distance R is the actual error distance in each search. When the distance between the target and the shore is less than the distance R caused by the angular measurement error, the target is judged as a ground target. Taking a typical radar as an example, its beamwidth is α, and the angular measurement error is generally 1 / 10 to 1 / 20 of the beamwidth. When detecting in a parallel direction, when the target is L away from the radar, the island-shore separation distance threshold is R = (0.1 to 0.2) × α × L, which dynamically changes with the actual angular measurement error in each search. During tilt direction detection, the tilt angle between the island / shore and the detection direction is θ, and the shore-ship separation threshold is R×cos(θ), which adaptively changes with the angle θ and the angular measurement error of each target. For ground targets under the above three angle conditions, and under the special convex-shaped island / shore line, at least one point will necessarily be located within the ground, making misjudgment impossible. Therefore, such special island / shore targets protruding into the sea surface can be eliminated. In summary, the shore-ship separation method based on two-scanning approaches utilizes the geometric distribution patterns caused by two reverse scans to dynamically and adaptively set a shore-ship separation threshold for each target based on the angular measurement error under different distance-angle relationships.

[0026] Using this invention, multiple detection experiments were conducted on sea surface targets at different positions in a nearshore sea area. The detection results are as follows: Figure 5 As shown, a total of 84 search and capture tests were conducted in this scenario, and the sea surface target was correctly captured in all 84 tests. The test results show that the method of this invention can adaptively obtain the shore-to-ship separation threshold for each target, avoid real-time calculation of the relationship between the radar and the island coastline, and reduce the shore-to-ship separation threshold in the context of complex coastline morphology.

[0027] To enable those skilled in the art to better understand the present invention, the invention will be described in detail below with reference to specific embodiments. For example... Figure 6 As shown, the specific implementation steps are as follows:

[0028] 1. Power on the radar and set the search parameters;

[0029] 2. Perform the first search, scanning to the left, and perform single-pulse angle measurement on the target during the scan;

[0030] 3. Obtain target 1 from the first search (left scan circle) and convert it into the geographic coordinate system;

[0031] 4. Perform a second search, scanning to the right, and perform single-pulse angle measurement on the target during the scan;

[0032] 5. Obtain target 2 from the second search (right sweep circle) and convert it into the geographic coordinate system;

[0033] 6. Match the second target with the first target, and link the search results of the same target in different rounds;

[0034] 7. Calculate the geometric mean of target 1 and 2 for target 3;

[0035] 8. The above three targets are matched with the prior map information to determine whether they are island or shore targets. If one or more of the targets 1, 2, and 3 are identified as island or shore targets, the target is identified as an island or shore target; otherwise, it is identified as a ship.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A shore-to-ship separation method based on secondary scanning, characterized in that... The steps are as follows: Step 1: After the radar sets the search parameters, start the first search, i.e., leftward scan. During the scan, perform single-pulse angle measurement on all detected targets and calculate the target angle by combining the scan frame angle. Based on the radar's target distance measurement, transform the target from the polar coordinate system to the geographic coordinate system. Step 2: After the leftward scan is completed, start the second scan, i.e. the rightward scan. During the scan, perform single-pulse angle measurement on all detected targets and calculate the target angle by combining the scan frame angle. Based on the radar target distance, convert the target from the polar coordinate system to the geographic coordinate system. Step 3: Compare the targets obtained from the two scans one by one. Targets that meet the correlation position conditions are the detection results of the same target in the two searches, referred to as target 1 and target 2. After extraction, the geometric mean position of the same target in the two scans is obtained, referred to as target 3. The correlation position conditions are as follows: the detection distance between the two scans is less than twice the range resolution unit, and the scanning angle between the two scans is less than 1 / 10 of the beamwidth. If the correlation is successful, it is considered to be successful. Step 4: Match targets 1, 2, and 3 with prior geographic information. If one or more targets among targets 1, 2, and 3 are identified as island / shore targets, the target is identified as an island / shore target; otherwise, it is identified as a ship, thus completing the separation of shore and ship.

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