A technology for display leakage repair of airport scene surveillance radar image

Abstract

The present invention relates to an airport scene surveillance radar image display leak repair technology, comprising the following steps: step 1, solving the polar coordinates of each pixel point in the image display; step 2, establishing a lookup table of the radar image display area; step 3, updating the ASMR data of the latest frame to the pixel point position corresponding to the display according to the lookup table. Aiming at the problem of a large number of leaks in direct ASMR image display, the present invention proposes an ASMR image display leak repair technology based on reverse lookup mapping relationship, which completely eliminates the "moiré" phenomenon of ASMR image display, effectively improves the image display quality, and ensures the performance of target detection and tracking.

Description

Technical Field

[0001] The invention relates to the field of image processing, and in particular to an airport scene surveillance radar image display leak repair technology. Background Art

[0002] Airport Surface Movement Radar (ASMR) is a device approved by the International Telecommunication Union for monitoring moving targets such as aircraft and motor vehicles on the airport surface. Air traffic controllers can accurately grasp the position, speed, and direction of movement of moving objects on the airport surface by monitoring the ASMR image display results, thereby completing target detection and tracking, and alarming possible conflicts or collisions.

[0003] Obviously, image display is the key technology of human-computer interaction in ASMR system. With the rapid development of computer technology, the use of software methods to process and display radar image information has become an effective and low-cost technical means. Computer display terminals, that is, monitors, display images in a rectangular coordinate system, while ASMR echo data are stored in a polar coordinate system. Therefore, the first task of radar image display is to transform the radar data from polar coordinate system to rectangular coordinate system.

[0004] However, when radar data is directly transformed from polar coordinates to rectangular coordinates and then displayed as an image, information redundancy will occur in the area near the center of the circle, and missing points will appear in the area far from the center of the circle. This is because all pixels in the display are evenly arranged and stored as integers, while radar data is floating point type and changes with the change of radar scanning angle and effective distance. For a given scanning angle area, the smaller the effective distance, the denser the data, and the longer the effective distance, the sparser the data. Therefore, when the radar image data after coordinate transformation is rounded, some pixels near the center of the circle in the display correspond to multiple radar data, while some areas far from the center of the circle always have missing points. This phenomenon is often called "moiré".

[0005] Information redundancy has little effect on image processing, but the missing point phenomenon will affect subsequent image processing, especially when the target of interest happens to appear in the missing point area, target detection will fail, target tracking will lose points, and observation blind spots will be generated. This is very unfavorable for the ASMR system to achieve full monitoring and anti-collision warning functions for moving targets in the airport.

[0006] To solve this problem, scholars have done a lot of research and have achieved certain results. The most commonly used method is to further refine the radar scanning angle interval and minimize the area where the leakage occurs. Although this method is simple in principle and can improve the image display quality to a certain extent, it cannot completely eliminate the "moiré" and greatly increases the calculation cost. Summary of the invention

[0007] In order to solve the existing technical problems, the present invention provides an airport scene surveillance radar image display leak repair technology.

[0008] The specific contents of the present invention are as follows: A technology for displaying leaks in airport scene surveillance radar images comprises the following steps:

[0009] Step 1, solving the polar coordinates of each pixel in the image display;

[0010] Step 2: Establish a lookup table for the radar image display area;

[0011] Step 3: Update the latest frame of ASMR data to the corresponding pixel position of the display according to the lookup table.

[0012] Further, in step 1, the polar coordinates of any pixel point (x′, y′) of the image display are solved using the following formula:

[0013]

[0014] Among them, the image display uses the upper left corner as the coordinate origin (0,0), (x0, y0) is the center position of the radar scanning image, ρ′ and θ′ are the azimuth code and effective range of the radar data point corresponding to the pixel point (x′, y′), respectively.

[0015] Furthermore, in step 1, after solving the polar coordinates corresponding to all pixel points in the radar scanning area in the image display, the data point closest to (ρ′, θ′) is selected in the radar data, and the quantization result of the data value of this point is used as the grayscale value of the image display pixel.

[0016] Furthermore, in step 2, the grayscale value in the radar image display area is expressed as

[0017] V xy (i,j)=uint8[V ρθ (n,m)],

[0018] i,j=0,1,…,2N

[0019] m=0,1,…,M

[0020] n=0,1,…,N

[0021] Among them, V xy (i, j), ρ′(i, j) and θ′(i, j) represent the grayscale value, polar radius and polar angle of the pixel at the i-th row and j-th column in the display, respectively. ρθ (n,m), ρ(n,m) and θ(n,m) represent the sampling point value, range and azimuth of the nth row and mth column in the radar data structure, and uint8[·] represents the 8-bit unsigned integer operation on the data;

[0022] M and N are both positive integers, M represents the number of scale values ​​of the horizontal axis azimuth code in the radar data point storage structure, and N represents the number of scale values ​​of the vertical axis sampling points in the radar data point storage structure.

[0023] Furthermore, the radar data points in the radar data point storage structure are arranged according to the antenna beam scanning direction. The horizontal axis is the azimuth code, with a total of M scale values, and the vertical axis is the sampling points arranged from near to far according to the effective distance, with a total of N scale values. The interval of each scale value is (c / f s ) meters, where c is the speed of light, f s is the sampling rate; in the radar highlight display result, the horizontal and vertical axes are evenly divided into 2N+1 pixel points, and the interval between each pixel point is the same as the interval between the sampling points on the vertical axis in the left figure.

[0024] Furthermore, the points in the lookup table are classified according to the order of the azimuth code to form M point sets, and the azimuth codes in the point sets are all the same but the effective distances are different.

[0025] Furthermore, the points within each azimuth code point set are arranged in order of effective distance from far to near.

[0026] Furthermore, in step three, each updated ASMR frame data finds the corresponding point set according to its azimuth code, and then quantizes the frame data value and assigns it to the corresponding display pixel point according to the order of the effective distance of each pixel point in the point set, completing the whole process of refreshing and displaying the ASMR image.

[0027] Aiming at the problem of a large number of leakage points in direct ASMR image display, the present invention proposes an ASMR image display leakage repair technology based on reverse search mapping relationship, which completely eliminates the "moiré" phenomenon of ASMR image display, effectively improves the image display quality, and ensures the performance of target detection and tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specific implementation of the present invention will be further explained below in conjunction with the accompanying drawings.

[0029] Figure 1 It is a schematic diagram of the transformation relationship between the display coordinate system and the radar coordinate system;

[0030] Figure 2It is a schematic diagram of the corresponding relationship between radar data points and image display;

[0031] Figure 3 It is the grayscale image of the data structure of the ASMR system at a certain moment in the polar coordinate system;

[0032] Figure 4 The display result of direct coordinate transformation of ASMR data;

[0033] Figure 5 This is the local magnification result of the "moiré" area;

[0034] Figure 6 The display result after using the airport surface surveillance radar image display leak repair technology of the present invention;

[0035] Figure 7 The figure shows the local enlarged result of the method of the present invention. DETAILED DESCRIPTION

[0036] The present invention first starts from the transformation relationship from the polar coordinate system to the rectangular coordinate system, then reversely transforms the positions of all pixel points in the image display area of ​​the display into polar coordinate form, and finally pairs the polar coordinate point with the radar data point to find the radar data point closest to it, and uses its quantized value as the grayscale value of the image display, so as to avoid the missing point phenomenon caused by the radar data point directly converted from the polar coordinate system to the rectangular coordinate system.

[0037] In order to improve the image display efficiency, the present invention also uses a table lookup method instead of coordinate conversion calculation to reduce the extra calculation caused by coordinate conversion. First, a lookup table corresponding to the image display area and the radar data point is established according to the above-mentioned inverse mapping relationship and the pairing result; then, the lookup table is divided into point sets according to the order of appearance of the ASMR scanning angle; finally, each point set is sorted from near to far according to the effective distance to meet the requirement of displaying and updating the radar data according to the scanning angle and from near to far.

[0038] Step 1: Solve the polar coordinates of each pixel in the image display

[0039] Attached Figure 1 A schematic diagram of directly converting the radar data points in the polar coordinate system to the rectangular coordinate system of the display for image display is given. The upper left corner of the display is the coordinate origin (0,0), and the center of the radar scanning image is located at (x0,y0). For any radar data point (ρ,θ), the position on the display can be expressed as

[0040]

[0041] Where ρ is the radar range, θ is the radar scanning angle, and the figure shows that the ASMR antenna is sweeping clockwise, and θ is the angle between the center of the antenna beam and the positive x-axis.

[0042] From formula (1), it is not difficult to find the polar coordinates corresponding to any pixel point (x′, y′) in the display:

[0043]

[0044] Obviously, according to formula (2), the polar coordinates corresponding to all pixels in the radar scanning area of ​​the display can be obtained, and then the data point closest to (ρ′, θ′) is selected in the radar data, and the quantization result of the data value of this point is used as the grayscale value of the image display pixel. This method of reversely traversing all pixels in the image display area to find the nearest radar data point is called the reverse search method in the present invention. This method can effectively prevent the occurrence of "dead addresses" and avoid the phenomenon of missing points caused by directly mapping radar data points to the display.

[0045] Step 2: Create a lookup table for the radar image display area

[0046] Considering that the positional relationship between the image display area and the radar data points is fixed and can be calculated in advance, the present invention adopts a table lookup method to replace the coordinate conversion calculation process to solve the problem of excessive system calculation caused by coordinate conversion operations, thereby improving the image display quality without increasing the system processing burden.

[0047] From the coordinate transformation relationship, we can know that on the display, in the area close to the center of the radar circle, there will be a situation where one pixel corresponds to multiple radar data points. In this case, in order not to lose important target information and ensure the image display effect, the method of selecting the larger of multiple points is generally used for processing; on the contrary, in the area far from the center of the radar circle, there will be a situation where multiple pixels correspond to one radar data point. Figure 2 As shown in the figure, the left side is the storage structure of radar data points, indicating that the radar data points are arranged according to the antenna beam scanning direction, the horizontal axis is the azimuth code, a total of M scale values, that is, the interval of each scale value is (360 / M) degrees, and the vertical axis is the sampling points arranged from near to far according to the effective distance, a total of N scale values, and the interval of each scale value is (c / f s ) meters, c is the speed of light, f s is the sampling rate. For the ASMR system, in order to improve the azimuth resolution, M>N is generally taken; the right side is a schematic diagram of the radar image display result, the horizontal axis and the vertical axis are evenly divided into 2N+1 pixel points, and the interval between each pixel point is the same as the interval between the sampling points on the vertical axis of the left figure.

[0048] By the attached Figure 2 From the corresponding relationship, we can know that the gray value in the radar image display area is expressed as

[0049]

[0050] In formula (3), V xy (i, j), ρ′(i, j) and θ′(i, j) represent the grayscale value, polar radius and polar angle of the pixel at the i-th row and j-th column in the display, respectively. ρθ (n,m), ρ(n,m) and θ(n,m) represent the sampling point value, range and azimuth of the nth row and mth column in the radar data structure, and uint8[·] represents the 8-bit unsigned integer operation on the data.

[0051] Step 3: Update the latest frame of ASMR data to the corresponding pixel position of the display according to the lookup table

[0052] Considering that the ASMR data is updated column by column in the order of the azimuth code, each column represents a frame, and each frame corresponds to the number of sampling points in a pulse, that is, the frame length is N. In order to avoid the need to traverse the entire lookup table every time the frame data is updated, the present invention first classifies the points in the lookup table according to the order of the azimuth code to form M point sets, the azimuth codes in the point sets are the same, and the effective distances are different.

[0053] Furthermore, considering that each frame data of ASMR is arranged in order from near to far according to the action distance, in order to ensure the consistency of image data update, the present invention also arranges each azimuth code point set in order from near to far according to the action distance.

[0054] After the above operations, each updated ASMR frame data can quickly find the corresponding point set according to its azimuth code, and then quantize the frame data value and assign it to the corresponding display pixel point according to the order of the effective distance of each pixel point in the point set, completing the whole process of high-quality refresh display of the ASMR image.

[0055] In this embodiment, the ASMR system data structure used is as follows: (1) Number of azimuth codes (M): 8192 (2) Number of range sampling points (N): 2048.

[0056] Attached Figure 3 The data structure grayscale diagram of the ASMR system at a certain moment in the polar coordinate system is given. The horizontal axis in the figure is the azimuth, the vertical axis is the distance, and the first 40 sampling points and the last 40 sampling points are the detection blind areas. Figure 3 The data in the formula (1) is directly converted into a rectangular coordinate system. The result is shown in the attached figure. Figure 4 As shown. Figure 4 It is not difficult to see that directly converting the radar data in the polar coordinate system to the rectangular coordinate system will result in obvious "moiré" phenomenon in the area far away from the center of the circle. Figure 5Yes Figure 4 The result of local magnification of the "moiré" area in the figure.

[0057] Attached Figure 6 This is the image display result after using the "ASMR image display leak repair technology based on reverse search mapping relationship" of the present invention. Figure 7 Yes Figure 6 Corresponding to the attachment Figure 5 The local magnification result of the area. Figure 7 and attached Figure 5 It can be seen from the results that after adopting the present invention, the "moiré" phenomenon is completely eliminated, and the quality of radar image display is effectively improved.

[0058] Eliminating the "moiré" phenomenon that appears in radar image display is of great significance for target detection and tracking of the ASMR system. The present invention breaks the traditional method of directly mapping radar data from the polar coordinate system to the rectangular coordinate system for image display. Through the coordinate transformation relationship, the azimuth code and effective range of all pixel points corresponding to the radar data point in the radar image display area are reversely obtained, and the closest point is found from the radar data point according to these azimuth codes and effective ranges, and its numerical value is quantified as the grayscale value of the pixel point for display, which completely solves the problem of missing points in ASMR image display and effectively improves the quality of radar image display. Furthermore, the present invention also proposes a fast table lookup method for the update rule of ASMR frame data, that is, updating in the order of azimuth codes and arranging from near to far according to effective ranges, which improves the image display quality while reducing the amount of calculation for updating ASMR image display data.

[0059] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for filling leakage in the display of airport scene surveillance radar images, characterized in that: The steps include: Step 1, solving the polar coordinates of each pixel in the image display; Step 2: Establish a lookup table for the radar image display area; Step 3, update the latest frame of ASMR data to the corresponding pixel position of the display according to the lookup table; In step 1, the polar coordinates of any pixel (x′, y′) on the image display are solved using the following formula: ， Among them, the image display uses the upper left corner as the coordinate origin (0,0), (x0, y0) is the center position of the radar scanning image, ρ′ and θ′ are the azimuth code and effective range of the radar data point corresponding to the pixel point (x′, y′) respectively; After solving the polar coordinates corresponding to all pixels in the radar scanning area in the image display, select the data point closest to (ρ′,θ′) in the radar data, and use the quantization result of the data value of this point as the grayscale value of the pixel in the image display; In step 2, the grayscale value in the radar image display area is expressed as ， Among them, V xy (i, j), ρ′(i, j) and θ′(i, j) represent the grayscale value, polar radius and polar angle of the pixel at the i-th row and j-th column in the display, respectively. ρθ (n,m), ρ(n,m) and θ(n,m) represent the sampling point value, range and azimuth of the nth row and mth column in the radar data structure, and uint8[·] represents the 8-bit unsigned integer operation on the data; M and N are both positive integers, M represents the number of scale values ​​of the horizontal axis azimuth code in the radar data point storage structure, and N represents the number of scale values ​​of the vertical axis sampling points in the radar data point storage structure; The radar data points in the radar data point storage structure are arranged according to the antenna beam scanning direction. The horizontal axis is the azimuth code, with a total of M scale values, and the vertical axis is the sampling points arranged from near to far according to the effective distance, with a total of N scale values. The interval of each scale value is (c / f s ) meters, where c is the speed of light, f s is the sampling rate; the horizontal and vertical axes in the radar highlight display result are evenly divided into 2N+1 pixel points, and the interval between each pixel point is the same as the interval between the sampling points on the vertical axis of the left figure; In step three, each updated ASMR frame data finds the corresponding point set according to its azimuth code, and then quantizes the frame data value and assigns it to the corresponding display pixel point according to the order of the effective distance of each pixel point in the point set, completing the entire process of refreshing and displaying the ASMR image.

2. The method for filling leakage in the display of airport surface surveillance radar image according to claim 1, characterized in that: The points in the lookup table are classified according to the order of the azimuth code to form M point sets. The azimuth codes in the point sets are the same but the effective distances are different.

3. The method for filling leakage in the display of airport surface surveillance radar image according to claim 1, characterized in that: The points within each azimuth code point set are arranged in order of effective distance from far to near.

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