Low altitude and ultra-low altitude target recognition and elevation correction method

Abstract

The present application relates to a kind of low altitude ultra-low altitude target identification and elevation correction method, belong to radar data processing field.The present application is to overcome the problem that the precision of pitch angle is poor due to multipath effect when medium-range air-based early warning radar detects low altitude, ultra-low altitude target, using radar ranging result and topographic data and other information, the method for target elevation correction is carried out.The present application first uses high-precision geographic information to identify low altitude, ultra-low altitude target, then estimates the flight height of target from ground, uses target distance, target flight height (estimated value) from ground to correct radar pitch angle information, this method has practical significance for radar deployed on aircraft, airship and high mountain, detects medium, long distance negative elevation low altitude, ultra-low altitude flying target.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of radar data processing, and particularly relates to a low-altitude and ultra-low-altitude target identification and elevation angle correction method. BACKGROUND

[0002] In the field of radar detection, it is necessary to measure the elevation angle of a low-altitude and ultra-low-altitude air target. Common side angle methods mainly include amplitude comparison angle measurement, phase comparison angle measurement, stacked multi-beam measurement, and super-resolution measurement. Generally, a medium-range or long-range detection radar has a low frequency band and a wide elevation beam width, and these angle measurement methods cannot overcome and solve the adverse effects of multipath on radar elevation angle measurement. In a serious case, the track may be lost due to a large elevation deviation during track prediction.

[0003] When a radar deployed on an airplane, a floating airship, or a high mountain detects a low-altitude and ultra-low-altitude target, the target is often at a negative elevation angle. The error of the elevation angle measured by a traditional method is converted to the height dimension, and the error is 300 to 1000 meters. The error interval is greater than the height of the target flight, and even a false image of the target flight below the ground surface is caused.

[0004] The present application proposes a target elevation angle correction method for the failure of the above-mentioned traditional angle measurement methods. The method first identifies and judges a low-altitude and ultra-low-altitude target. If the target is judged to be an ultra-low-altitude target and the target distance and radar height meet certain conditions, the method can be used. The average flight height of the target is calculated using the results of track filtering and terrain correction as the flight height of the target at the current position. The target elevation angle is calculated by the cosine theorem and used as the corrected elevation angle result. This method can effectively improve the elevation angle measurement accuracy of low-altitude and ultra-low-altitude targets. SUMMARY

[0005] (I) Technical problem to be solved

[0006] The technical problem to be solved by the present application is how to provide a low-altitude and ultra-low-altitude target identification and elevation angle correction method to solve the problem of how to improve the elevation angle measurement accuracy of a radar for low-altitude and ultra-low-altitude targets when the traditional elevation angle measurement method fails in the case of an overhead angle.

[0007] (II) Technical solution

[0008] To solve the above technical problem, the present application proposes a low-altitude and ultra-low-altitude target identification and elevation angle correction method, which comprises the following steps:

[0009] S1, obtaining basic measurement information

[0010] The position, elevation, and distance measurement data of a primary plot are obtained by using a radar detection method, and the real-time position information of the primary plot is obtained by using radar position information to perform coordinate system conversion on the primary plot;

[0011] S2, track correlation

[0012] First, track correlation is performed, if the track correlation is successful, S3 is entered, if the track correlation is not successful, point plot correction is performed first, then point plot correlation is performed, and an initial target track is established according to a track establishment criterion; if the track correlation is successful, the next process is entered;

[0013] S3, failure judgment and applicability judgment

[0014] After the number of target track points is greater than a preset number, failure judgment is performed on the target height measurement result point by point, if the proportion of the target height measurement result to the terrain elevation is greater than a first threshold value, it is judged that the target is in a low-altitude or ultra-low-altitude flight state, and the traditional height measurement method faces the risk of failure; and applicability judgment is performed, under the condition that the target distance is greater than 0.5 times the radar visibility distance, the target height is calculated by using the method of the present application;

[0015] S4, target pitch angle correction

[0016] If the failure judgment is established, and under the condition that the target distance is greater than 0.5 times the radar visibility distance, the target average flight height calculated by using the track filtering result is used as the estimated target current position flight height, the terrain height plus the estimated target flight height is the target elevation H1, the length of the earth radius plus the target elevation is the length of one side R0+H1, the measured distance from the radar to the target is the length of the other side r, and the length from the earth center to the radar position is the length of the third side R0+H, and the angle calculated according to the law of cosines is used as the corrected target pitch measurement angle θ; if the failure judgment or the applicability judgment is not established, the point plot is corrected to the ground, and the angle calculated according to the law of cosines is used as the corrected target pitch measurement angle θ;

[0017] S5, track updating

[0018] The corrected target track is used for track filtering and track updating, and the target track includes: target distance, azimuth, and corrected target pitch measurement angle θ.

[0019] (Three) beneficial effects

[0020] The present application provides a low altitude and ultra-low altitude target recognition and elevation correction method, and provides a pitch angle correction method for a low altitude and ultra-low altitude target, which can be used for height measurement of an air target in a negative elevation angle situation by an air radar or a high mountain radar. The method proposes two points, one is that the proportion of the target height measurement result being lower than the terrain elevation is greater than 30% (threshold example, which can be adjusted according to the situation), and the target is in a low altitude and ultra-low altitude flight state; the other is that the average height from the ground of the track is used as the estimated value of the target height from the ground, and the pitch angle of the current track point is calculated as the pitch angle measurement value by using the cosine theorem. This method has practical value for early warning aircraft, manned / unmanned aircraft radar, balloon radar, high mountain radar and the like. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a low altitude and ultra-low altitude target pitch angle correction principle diagram of the present application;

[0022] Figure 2 It is a low altitude and ultra-low altitude target pitch angle correction flow chart. DETAILED DESCRIPTION

[0023] In order to make the purpose, content and advantages of the present application clearer, the specific embodiments of the present application are further described in detail below in combination with the drawings and examples.

[0024] The present application relates to a low altitude and ultra-low altitude target recognition and elevation correction method, and belongs to the field of radar detection. In order to overcome the problem of poor pitch angle accuracy caused by multipath effect when a medium and long range air-based early warning radar detects a low altitude and ultra-low altitude target, the present application uses radar ranging results and terrain data and other information to correct the target elevation. Because the early warning radar has a ground view, for a low altitude and ultra-low altitude penetration target, target detection is carried out in a strong clutter background, the main beam hits the ground, multipath effect is serious, and the pitch angle accuracy of the radar is poor. The wider the pitch beam of the radar, the poorer the pitch angle accuracy. The insufficient pitch angle accuracy leads to mismatch between the tracking prediction and the actual elevation of the target, and in a serious case, the target will be out of control and lost. In the process of handover between the early warning detection radar and the fire unit, poor pitch angle accuracy also increases the capture time of the target by the fire control radar (optoelectronic device), affects the handover time and success rate, and produces adverse factors for the interception of the air defense weapon system. For the present application, first, high-precision geographic information is used to identify a low altitude and ultra-low altitude target, then the least square method is used to estimate the target height from the ground, and the target distance and the target height from the ground (estimated value) are used to correct the radar pitch angle information. This method has practical significance for radars deployed on aircraft, aerostats and high mountains to detect low altitude and ultra-low altitude targets in a negative elevation angle situation.

[0025] The basic process of the present application is as follows Figure 2As shown, it includes five basic steps, namely obtaining basic measurement information, track correlation, failure judgment, target pitch angle correction, and track updating.

[0026] S1, obtaining basic measurement information

[0027] The azimuth, elevation, and distance measurement data of the primary track are obtained by using the conventional detection method of the radar, the coordinate system conversion of the primary track is performed by using the radar position information, and the real-time position (longitude, latitude, and height) information of the track is obtained; wherein, for the static platform, the radar position information is obtained by pre-subscription, and for the dynamic platform, the radar position information is obtained by using the real-time data obtained by the radar.

[0028] S2, track correlation

[0029] Firstly, the track correlation is performed, if the track correlation is successful, S3 is entered; if the track correlation is not successful, the track is corrected first, then the track correlation is performed, and the initial target track is established according to the track establishment criterion; if the track correlation is successful, the next process is entered;

[0030] S3, failure judgment and applicability judgment

[0031] After the number of target track points is greater than a preset number (the preset number is 10 points), the failure judgment of the target height measurement result is performed point by point, if the proportion of the target height measurement result to the terrain height is greater than a first threshold value (the first threshold value is 30%, and the threshold value is an example, which can be adjusted according to the situation), it is judged that the target is in a low-altitude or ultra-low-altitude flight state, and the traditional height measurement method faces the risk of failure, and the applicability judgment is performed, and under the condition that the target distance is greater than 0.5 times the radar visibility distance (if the radar power is infinite, the maximum detection distance of the target relative to the ground is zero height), the target height is calculated by using the method of the present application.

[0032] S4, target pitch angle correction

[0033] If the failure judgment is established, and under the condition that the target distance is greater than 0.5 times the radar visibility distance, the average flight height of the target calculated by using the track filtering result is used as the estimated flight height of the target at the current position, the terrain height plus the estimated flight height of the target is the target height H1, the length of the earth radius plus the target height is the length of one side R0+H1, the measured distance from the radar to the target is the length of the other side r, and the length from the earth center to the radar position is the length of the third side R0+H, and the angle calculated according to the cosine theorem is used as the corrected target pitch angle θ, as shown in the accompanying drawings; if the failure judgment or the applicability judgment is not established, the track is corrected to the ground, and the angle calculated according to the cosine theorem is used as the corrected target pitch angle θ. Figure 1

[0034] S5, track updating​

[0035] The modified target track (target distance, azimuth, target elevation angle) is used for track filtering and track updating. The target track represented by longitude, latitude and height can also be used for track filtering and track updating.

[0036] Embodiment 1

[0037] The basic flow of the present application is shown in the following figure, which includes five basic steps, namely obtaining basic measurement information, track correlation, failure judgment, target elevation angle correction, and track updating.

[0038] S1. Obtain basic measurement information

[0039] S11, the azimuth, elevation angle and distance measurement data of the primary track are obtained by using the conventional detection method of the radar,

[0040] S12, the radar position information (dynamic platform) is obtained by using the pre-bound (static platform) or real-time obtained data of the radar, and the coordinate system conversion is performed on the primary track to obtain the real-time position (longitude, latitude and height) information of the track;

[0041] S2. Track correlation

[0042] S21, first, track correlation is performed, if the track correlation is successful, the process of "3. Failure judgment and applicability judgment" is entered;

[0043] S22, if the track correlation is not successful, first, the track is corrected, that is, the target elevation of the primary track report of the signal processor is compared with the high-precision terrain data elevation, if the target elevation result is lower than the terrain elevation, the track elevation is forcibly corrected to the terrain elevation, if the target elevation result is higher than the terrain elevation, no processing is performed. Then, track correlation is performed, and according to the track establishment criterion, track initiation is performed to establish an initial target track;

[0044] S3. Failure judgment and applicability judgment

[0045] S31, after the number of target track points is greater than 10 points (threshold example, which can be adjusted according to the situation), it is judged point by point if the proportion of the target elevation result lower than the terrain elevation is greater than 30% (threshold example, which can be adjusted according to the situation), if so, it is judged that the target is in a low-altitude or ultra-low-altitude flight state, the traditional height measurement method faces the risk of failure, and S32 is executed; if not, the track is corrected to the ground by using the digital map;

[0046] S32, it is judged whether the target distance is greater than 0.5 times the radar visibility distance, if so, it is suggested to use the method of the present application to calculate the target height, and step S4 is executed; if not, the track is corrected to the ground by using the digital map;

[0047] S4. Target elevation angle correction

[0048] If the failure judgment and the method applicability judgment are established, then:

[0049] S41, using the target average flight height above ground calculated by the track filtering result as the flight height above ground of the target current position,

[0050] S42, the terrain height plus the estimated target flight height above ground is the target elevation, the total length of the earth radius + the target elevation is recorded as one side R0+H1, the measured target distance r is the other side, the length of the earth center to the radar position is the third side R0+H, and the angle θ calculated according to the cosine theorem is used as the corrected radar elevation measurement angle;

[0051] If the failure judgment and the method applicability judgment are not established, then the track is corrected to the ground using the digital map, the terrain height is used as the target elevation, the length of the earth radius + the ground elevation is recorded as one side, the measured target distance is the other side, the length of the earth center to the radar position is the third side, and the angle calculated according to the cosine theorem is used as the corrected target elevation measurement angle;

[0052] S5, track updating

[0053] S51, coordinate system conversion is performed again, the corrected target track coordinates are calculated using the corrected target elevation measurement angle, and the longitude, latitude and height are obtained;

[0054] S52, track filtering and track updating are performed in the geodetic coordinate system using the corrected target track coordinates.

[0055] The present application proposes a method for correcting the elevation measurement angle of a low-altitude or ultra-low-altitude target, which can be used for height measurement of an airborne target in a negative elevation angle situation by an airborne radar or a high-mountain radar. The method proposes two points, one is that the proportion of the target height measurement result being lower than the terrain elevation is > 30% (threshold example, which can be adjusted according to the situation), which determines that the target is in a low-altitude or ultra-low-altitude flight state; the other is that the average height above ground of the track is used as the target height above ground estimation value, and the elevation angle of the current track calculated according to the cosine theorem is used as the elevation angle measurement value. This method has practical value for early warning aircraft, manned / unmanned aircraft radar, balloon-borne radar, high-mountain radar, etc.

[0056] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A low altitude and ultra-low altitude target identification and elevation correction method, characterized in that, The method comprises the following steps: S1, obtaining basic measurement information The azimuth, elevation and distance measurement data of the primary plot are obtained by using a radar detection method, and the coordinate system conversion is performed on the primary plot by using radar position information to obtain real-time position information of the plot; S2, track correlation First, track correlation is performed, if the track correlation is successful, S3 is entered; if the track correlation is not successful, plot correction is performed first, then plot correlation is performed, and a new track is established according to the track establishment criterion; If the track correlation is successful, the next process is entered; S3, failure judgment and applicability judgment After the number of target track points is greater than a preset number, failure judgment is performed on the target height measurement result point by point, if the proportion of the target height measurement result is lower than the terrain elevation is greater than a first threshold value, it is judged that the target is in a low-altitude or ultra-low-altitude flight state; and adaptability judgment is performed, under the condition that the target distance is greater than 0.5 times the radar visibility distance, the target height is calculated by S4; S4, target pitch angle correction If the failure judgment is established, and under the condition that the target distance is greater than 0.5 times the radar visibility distance, the average flight height of the target calculated by the track filtering result is used as the estimated flight height of the target at the current position, the terrain height plus the estimated flight height of the target is the target height H1, the length of the earth radius plus the length of the target height is the length of one side R0+H1, the measured distance from the radar to the target is the length of the other side r, and the length from the earth center to the radar position is the length of the third side R0+H, and the angle calculated according to the cosine theorem is used as the corrected target pitch angle θ; If the failure judgment or the applicability judgment is not established, the plot is corrected to the ground, and the angle calculated according to the cosine theorem is used as the corrected target pitch angle θ; S5, track update The corrected target plot is used for track filtering and track updating, and the target plot includes target distance, azimuth and corrected target pitch angle θ.

2. The low altitude and ultra-low altitude target identification and elevation correction method according to claim 1, characterized in that, In the step S1, for a static platform, the radar position information is obtained by pre-subscription, and for a dynamic platform, the radar position information is obtained by using real-time navigation data of the radar.

3. The low altitude and ultra-low altitude target identification and elevation correction method according to claim 1, characterized in that, In the step S3, the preset number is 10 points.

4. The low altitude and ultra-low altitude target identification and elevation correction method according to claim 1, characterized in that, In the step S3, the first threshold value is 30%.

5. The low altitude and ultra-low altitude target identification and elevation correction method according to any one of claims 1-4, characterized in that, The step S1 specifically comprises: S11, obtaining the azimuth, elevation and distance measurement data of the primary plot by using a radar detection method, S12, obtaining the radar position information by using the pre-subscription or real-time data of the radar, and performing coordinate system conversion on the primary plot to obtain real-time position information of the plot, the real-time position information of the plot including longitude, latitude and height information.

6. The low altitude and ultra-low altitude target identification and elevation correction method according to claim 5, characterized in that, The step S2 specifically comprises: S21, first, track correlation, if the track correlation is successful, S3 process is entered; S22, if the track correlation is unsuccessful, first, the point track is corrected, that is, the target height of the point track report of the signal processor is compared with the height of the high-precision terrain data, if the target height measurement result is lower than the terrain height, the point track height is forcibly corrected to the terrain height, if the target height measurement result is higher than the terrain height, no processing is performed, then the point track correlation is performed, and the track is started according to the track establishment criterion, and the initial target track is established.

7. The low altitude and ultra-low altitude target identification and elevation correction method according to claim 6, characterized in that, The step S3 specifically comprises: S31, after the number of target track points is greater than a preset number, it is judged whether the proportion of the target height measurement result being lower than the terrain height is greater than a first threshold value, if yes, it is judged that the target is in a low-altitude or ultra-low-altitude flight state, and step S32 is executed, if not, the point track is corrected to the ground by using the digital map; S32, it is judged whether the target distance is greater than 0.5 times the radar visibility distance, if yes, the target height is calculated by using S4, and step S4 is executed, if not, the point track is corrected to the ground by using the digital map.

8. The low altitude, ultra-low altitude target identification and elevation correction method as claimed in claim 7, characterized in that, The step S4 specifically comprises: If the failure judgment and the method applicability judgment are correct, then: S41, the target average flight height calculated by using the track filtering result is used as the flight height of the current position of the target, S42, the terrain height plus the estimated target flight height is used as the target height, the total length of the earth radius plus the target height is used as a side R0+H1, the measured target distance r is used as another side, the length of the earth center to the radar position is used as a third side R0+H, and the angle θ calculated according to the cosine theorem is used as the corrected radar elevation angle; If the failure judgment and the method applicability judgment are not correct, then: The point track is corrected to the ground by using the digital map, the terrain height is set as the target height, the length of the earth radius plus the ground height is used as a side, the measured target distance is used as another side, the length of the earth center to the radar position is used as a third side, and the angle calculated according to the cosine theorem is used as the corrected target elevation angle.

9. The low altitude, ultra-low altitude target identification and elevation correction method of claim 8, wherein, The step S5 specifically comprises: S51, the coordinate system conversion is performed again, the corrected target point track coordinates are calculated by using the corrected target elevation angle, and the longitude, latitude and height are obtained; S52, the track filtering and track updating are performed in the geodetic coordinate system by using the corrected target point track coordinates.

10. The low altitude and ultra-low altitude target identification and elevation correction method of claim 1, wherein, The method is used for the radar deployed on an airplane, a floating device and a high mountain, and is used for detecting a target flying at a low altitude or an ultra-low altitude at a middle or long distance and a negative elevation angle.

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