A method for calculating and displaying radar blind spots based on terrain analysis

Abstract

The present invention discloses a method for calculating and displaying radar blind spots based on terrain analysis, which relates to the field of military equipment capability analysis and mapping display of command automation systems. Based on line-of-sight analysis, the method first calculates the obstruction points and tangent segments between the radar and the terrain in the scanning direction through binary search, then uses the equation of the tangent segment in the scanning direction and the equation of the geodetic ellipsoid at different altitudes to directly calculate the intersection point, and obtains the maximum detection range of the radar at the same altitude by connecting the intersection points of the tangent segments of all scanning directions on the ellipsoid at the same altitude. The obstruction lines and contour lines at different altitudes are drawn and displayed using different colors and line widths. The present invention has the characteristics of a simple, efficient and reliable calculation method, adaptability to various geographic computing platforms, concise and intuitive expression on a two-dimensional map, adaptability to parallel computing platforms, and the ability to adjust the calculation accuracy as needed and adaptability to various radar parameter types.

Description

Technical Field

[0001] The present invention relates to a radar blind area calculation and display method based on terrain analysis in the field of military equipment capability analysis and plotting display in a command automation system, and is particularly suitable for terrain-based detection capability analysis of typical air defense radar equipment in a command automation system and display of analysis results. Background Art

[0002] Long-range air defense warning radars and short-range field air defense radars are the main threats facing Army Aviation equipment. To avoid these threats or provide timely warnings, their detection capability analysis is an indispensable and important capability in the Army Aviation command automation system. Due to factors such as the curvature of the earth and terrain shielding, radar detection has terrain shielding blind spots. Rapid analysis and comprehensive and intuitive expression of terrain shielding blind spots have become a key technology. In the existing technology, the calculation method of radar terrain shielding blind spots mainly calculates the shielding of the line connecting the target point and the radar deployment location with all terrain surfaces on which the line lies, and obtains the minimum detection height of the target point, which is used as the blind spot clearance height of the target point. However, the above calculation method has cumbersome steps, the analysis is time-consuming, and the efficiency is low. In addition, the detection blind spots cannot be intuitively expressed and displayed on a two-dimensional map, which lacks support for combat command auxiliary analysis and result presentation capabilities. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to avoid the shortcomings of the above-mentioned background technology and provide a radar blind spot calculation and display method based on terrain analysis. The method is based on line of sight analysis. First, the obstruction points and tangent segments between the radar and the terrain in the scanning direction are calculated through binary search. Then, the intersection points are directly calculated using the tangent segment equations of the scanning direction and the geoid ellipsoid equations at different altitudes. By connecting the intersection points of the tangent segments of all scanning directions at the same altitude ellipsoid surface, the maximum detection range of the radar at that altitude is obtained. The obstruction lines and contour lines at different altitudes are drawn and displayed using different colors and line widths.

[0004] The present invention has the characteristics of simple, efficient and reliable calculation method, adaptability to various geographic computing platforms, concise and intuitive expression on two-dimensional maps, adaptability to parallel computing platforms, and calculation accuracy that can be adjusted as needed and adaptability to various radar parameter types.

[0005] The object of the invention is achieved like this:

[0006] A method for calculating and displaying radar blind spots based on terrain analysis specifically comprises the following steps:

[0007] Step 1: Based on the visibility calculation, use the binary search method to calculate the tangent of the terrain by the ray starting from the radar coordinate O and with the scanning azimuth α. Record the tangent point Q(α), and at the same time calculate the maximum operating distance point of the radar on this ray and record it as F(α).

[0008] Step 2: Determine whether the length of the line segment OF(α) is greater than the length of the line segment OQ(α). If it is greater, calculate the intersections of the line segments Q(α)F(α) with the geodetic ellipsoid surfaces at heights of 100 m, 200 m, 400 m, 800 m, 1600 m, 2400 m, and 3600 m respectively. If there are intersections, record them as H(α, 100), H(α, 200), H(α, 400), H(α, 800), H(α, 1600), H(α, 2400), and H(α, 3600) respectively.

[0009] Step 3: Repeat Steps 1 to 2 within the radar scanning azimuth range of αmin to αmax with a step of △α.

[0010] Step 4: Determine whether the tangent points of each calculated azimuth α and the adjacent azimuth α + △α satisfy OQ(α) < OF(α) and OQ(α + △α) < OF(α + △α). If they are satisfied, connect Q(α) and Q(α + △α) with a thick black line segment; otherwise, do not connect.

[0011] Step 5: Connect the maximum operating distance points F(α) and F(α + △α) of each calculated azimuth α and the adjacent azimuth α + △α with a thick red line segment.

[0012] Step 6: Set different colors for heights of 100 m, 200 m, 400 m, 800 m, 1600 m, 2400 m, and 3600 m. Determine whether there are intersections H(α, h) and H(α + △α, h) of the same height for each calculated azimuth α and the adjacent azimuth α + △α. If so, connect them with a thin line of the corresponding color for this height; otherwise, if only H(α, h) exists, connect H(α, h) to the tangent point Q(α + △α).

[0013] Further, the specific process of Step 2 is as follows:

[0014] Step 201: Convert the geodetic coordinates of points Q(α) and F(α) to geocentric coordinate system (xq, yq, zq), (xf, yf, zf), calculate the straight-line distance between (xq, yq, zq) and (xf, yf, zf). If it is less than 1 m, return no intersection; otherwise, continue the subsequent calculation.

[0015] Step 202: Set the height of the contour line to h. If the height of Q(α) is greater than h, return no intersection. Otherwise, set the major axis of the geodetic ellipsoid to a0 and the minor axis to b0, and calculate the new ellipsoid parameters a2 = (a0 + h)^2 and b2 = (b0 + h)^2.

[0016] Step 203, substitute the parametric equation of the point on the line segment formed by Q(α) and F(α) into the new ellipsoid parameters, calculate whether an intersection is formed, return if there is no intersection, return if there is one intersection, and return the intersection if there are two intersections, return the intersection closest to the maximum distance point F(α).

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] 1. The present invention is based on line-of-sight calculation and uses a binary search method to calculate the tangent between the scanning azimuth and the terrain. Therefore, it can be adapted to various geographic computing platforms, and the depth of the binary search can be set according to the pitch accuracy requirements.

[0019] 2. The present invention directly calculates the intersection point based on the detection range of the radar using the tangent equation and the geoid ellipsoid equation at different heights, so the calculation accuracy is high and it can adapt to radars of different heights and detection ranges according to different process parameters.

[0020] 3. The present invention adopts appropriate height parameters and uses different colors and line types to plot and display the obstruction lines, contour lines, and maximum detection range lines, thereby greatly supporting the comprehensiveness and intuitiveness of the results of drawing radar detection capabilities on two-dimensional maps.

[0021] 4. The calculation results of the present invention are easy to store and can be conveniently used in subsequent applications such as route planning and threat analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the present invention using a radar blind zone calculation and display method based on terrain analysis to achieve the drawing of radar detection capabilities. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples.

[0024] Reference Figure 1The present invention is based on line-of-sight calculation and binary search. It calculates the tangent point between the radar and the terrain in all directions. On the scan line, a line segment is formed with the tangent point as the starting point and the maximum detection range point as the end point. The intersection of the line segment and the geoid ellipsoid at different heights is calculated. The tangent points in all directions are connected by a black widened line as the blocking line, and the maximum detection range points in all directions are connected by a red widened line as the maximum detection range line. Different colors are used to connect the contour lines of the same height in all directions to form detection range lines of different heights, thereby realizing the final display of radar detection blind area results. The present invention uses different height intervals to calculate the detection range lines, so that the calculation results are evenly distributed, allowing users to quickly form a concise and intuitive understanding of the radar detection blind area.

[0025] A method for calculating and displaying radar blind areas based on terrain analysis, characterized by comprising the following steps:

[0026] ① Based on the line-of-sight calculation, use the binary search method to calculate the tangent line between the ray with the radar coordinate O as the starting point and α as the scanning direction and the terrain, record the tangent point Q(α), and at the same time calculate the point of maximum radar range on the ray and record it as F(α);

[0027] In the embodiment, the minimum pitch angle alpha_min and the maximum pitch angle alpha_max are set, O is taken as the origin, the azimuth is α, the pitch angle alpha_c = (alpha_min + alpha_max) / 2, the maximum detection distance rmax is used to calculate the maximum effective distance point Fa, and determine whether the line segment OFa is visible. If it is visible, alpha_max = alpha_c is set, otherwise alpha_min = alpha_c, and the pitch angle alpha_c = (alpha_min + alpha_max) / 2 and Fa are recalculated. The calculation is continued 20 times, and the occlusion point Q (α) and the maximum total effective distance point F (α) are calculated according to alpha_min.

[0028] ② Determine whether the length of line segment OF(α) is greater than the length of line segment OQ(α). If so, calculate the intersection points of line segment Q(α)F(α) with the geoid ellipsoid at altitudes of 100 meters, 200 meters, 400 meters, 800 meters, 1600 meters, 2400 meters, and 3600 meters, respectively. If intersection points exist, record them as H(α, 100), H(α, 200), H(α, 400), H(α, 800), H(α, 1600), H(α, 2400), and H(α, 3600), respectively.

[0029] ③ Using △α as a step, repeat steps ① and ② within the radar scanning azimuth range of αmin to αmax;

[0030] In the embodiment, αmin and αmax are the minimum and maximum scanning azimuths of the radar, which are generally set radar performance parameters. For an omnidirectional radar, αmin = 0 and αmax = 359.9. Starting from α = αmin, the azimuth is incremented by △α each time, i.e., α = α + △α. If α < αmax, the calculation continues; otherwise, the calculation stops.

[0031] ④ Draw occlusion lines: Determine whether the tangent points of each calculated azimuth α and the adjacent azimuth α + △α satisfy OQ(α) < OF(α) and OQ(α + △α) < OF(α + △α). If satisfied, connect Q(α) and Q(α + △α) with a thick black line segment; otherwise, do not connect.

[0032] In the embodiment, the geocentric coordinates of the radar position O are (xo, yo, zo), the occlusion point of azimuth α is Q(α) with geocentric coordinates (xq, yq, zq), the maximum range point is F(α) with geocentric coordinates (xf, yf, zf), the occlusion point of the adjacent azimuth α + △α is Q(α + △α) with geocentric coordinates (xq1, yq1, zq1), the maximum range point is F(α + △α) with geocentric coordinates (xf1, yf1, zf1), and the geocentric coordinate system is (xf1, yf1, zf1). If (xq - xo)^2 + (yq - yo)^2 + (zq - zo)^2 < (xf - xo)^2 + (yf - yo)^2 + (zf - zo)^2, then OQ(α) < OF(α). Similarly, if (xq1 - xo)^2 + (yq1 - yo)^2 + (zq1 - zo)^2 < (xf1 - xo)^2 + (yf1 - yo)^2 + (zf1 - zo)^2, then OQ(α + △α) < OF(α + △α).

[0033] ⑤ Draw maximum range lines: Connect the maximum range points F(α) and F(α + △α) of each calculated azimuth α and the adjacent azimuth α + △α with thick red line segments.

[0034] ⑥ Draw contour lines: Set different colors for heights of 100 m, 200 m, 400 m, 800 m, 1600 m, 2400 m, and 3600 m. Determine whether there are intersection points H(α, h) and H(α + △α, h) of the same height for each calculated azimuth α and the adjacent azimuth α + △α. If so, connect them with thin lines of the corresponding color for that height; otherwise, if only H(α, h) exists, connect H(α, h) to the tangent point Q(α + △α).

[0035] In the embodiment, the line width is set to 2 and the color is red at a height of 100 meters, the line width is set to 1 and the color is light red at a height of 200 meters, the line width is set to 2 and the color is green at a height of 400 meters, the line width is set to 1 and the color is light green at a height of 800 meters, the line width is set to 2 and the color is blue at a height of 1600 meters, the line width is set to 1 and the color is light blue at a height of 2400 meters, and the line width is set to 2 and the color is cyan at a height of 3600 meters.

[0036] Wherein, step ② specifically includes the following steps:

[0037] (201) Convert the geodetic coordinates of points Q(α) and F(α) into the geocentric coordinate system (xq, yq, zq) and (xf, yf, zf), and calculate the straight-line distance between (xq, yq, zq) and (xf, yf, zf). If it is less than 1 meter, return no intersection, otherwise continue with the subsequent calculation;

[0038] The embodiment calculates the distance Lqf = ((xf-xq)^2+(yf-yq)^2+(zf-zq)^2)^0.5. If Lqf<1, it means that the maximum return of the radar has no intersection, otherwise continue with subsequent calculations.

[0039] (202) Let the height of the contour be h. If the height of Q(α) is greater than h, return no intersection. Otherwise, let the major axis of the geodetic ellipsoid be a0 and the minor axis be b0. Calculate the new ellipsoid parameters a2 = (a0 + h)^2, b2 = (b0 + h)^2;

[0040] In the embodiment, the contour height is h, and the geodetic coordinates (Bq, Lq, Hq) of Q(α) are calculated. If Hq>h, it means that the height of the obstruction point is greater than the contour height. At this time, the intersection cannot be formed, so no intersection is returned. Otherwise, the intersection is calculated according to the new ellipsoid parameters, and the WGS84 coordinate system ellipsoid parameters are used. The major axis a0=6378137.0, the minor axis b0=6356752.3142, and the lengths of the major axis and minor axis are increased by h as the new major axis and minor axis.

[0041] (203) Substitute the parametric equation of the point on the line segment formed by Q(α) and F(α) into the new ellipsoid parameters and calculate whether an intersection is formed. If there is no intersection, return it. If there is one intersection, return the intersection. If there are two intersections, return the intersection closest to the maximum distance point F(α).

[0042] The embodiment calculates the vector (△x, △y, △z) = (xf, yf, zf) - (xq, yq, zq), calculates the parameters a = (△x*△x+△y*△y) / a2+△z*△z / b2, b = 2*(xq*△x+yq*△y) / a2+2*zq*△z / b2, c = (xq*xq+yq*yq) / a2+zq*zq / b2-1.0, flag = b*b-4*a*c, if flag < 0, then return no intersection, otherwise calculate the parameters it1 = (-b+flag^0.5) / (2*a), it2 = (-b-flag^0.5) / (2*a), if it1>it2, then swap the values ​​of the two. Determine whether it1 is in the range of 0 to 1.0. If it is, calculate the intersection point I1 = Q(α) + (F(α) - Q(α)) * it1. Similarly, calculate the intersection point I2. If the intersection point I2 exists, return the intersection point I2; otherwise, return the intersection point I1 and end.

[0043] Complete the radar blind spot calculation and display method based on terrain analysis.

Claims

1. A method for calculating and displaying radar blind spots based on terrain analysis, characterized in that: Specifically, it includes the following steps: Step 1: Set the minimum pitch angle alpha_min and the maximum pitch angle alpha_max. Taking O as the origin, with the azimuth as α, the pitch angle alpha_c = (alpha_min + alpha_max) / 2. Calculate the maximum action distance point Fa based on the maximum detection distance rmax. Determine whether the line segment OFa is visible. If it is visible, set alpha_max = alpha_c; otherwise, set alpha_min = alpha_c, recalculate the pitch angle alpha_c = (alpha_min + alpha_max) / 2 and Fa, and continue the calculation 20 times. Calculate the occlusion point Q(α) and the maximum total action distance point F(α) according to alpha_min; Step 2: Determine whether the length of the line segment OF(α) is greater than the length of the line segment OQ(α). If it is greater, calculate the intersection points of the line segments Q(α)F(α) with the geodetic ellipsoid surface at heights of 100 m, 200 m, 400 m, 800 m, 1600 m, 2400 m, and 3600 m respectively. If there are intersection points, record them as H(α, 100), H(α, 200), H(α, 400), H(α, 800), H(α, 1600), H(α, 2400), and H(α, 3600) respectively; Step 3: Repeat Steps 1 to 2 within the radar scanning azimuth range of α to αmax with △α as the step value, where △α is the step value; Step 4: Determine whether the tangent points between each calculated azimuth α and the adjacent azimuth α + △α satisfy OQ(α) < OF(α) and OQ(α + △α) < OF(α + △α). If they are satisfied, connect Q(α) and Q(α + △α) with a thick black line segment; otherwise, do not connect; Step 5: Connect the maximum action distance points F(α) and F(α + △α) of each calculated azimuth α and the adjacent azimuth α + △α with a thick red line segment; Step 6: Set different colors for heights of 100 m, 200 m, 400 m, 800 m, 1600 m, 2400 m, and 3600 m. Determine whether there are intersection points H(α, h) and H(α + △α, h) of the same height at each calculated azimuth α and the adjacent azimuth α + △α. If so, connect them with a thin line of the corresponding color at that height; otherwise, if only H(α, h) exists, connect H(α, h) to the tangent point Q(α + △α); 2. The method for calculating and displaying radar blind spots based on terrain analysis according to claim 1, characterized in that: The specific process of Step 2 is as follows: Step 201: Convert the geodetic coordinates of points Q(α) and F(α) to the geocentric coordinate system (xq, yq, zq), (xf, yf, zf), calculate the straight-line distance between (xq, yq, zq) and (xf, yf, zf). If it is less than 1 m, return no intersection point; otherwise, continue the subsequent calculation; Step 202: Set the height of the contour line as h. If the height of Q(α) is greater than h, return no intersection point; otherwise, set the long axis of the geodetic ellipsoid parameter as a0 and the short axis as b0, and calculate the new ellipsoid parameters a2 = (a0 + h)^2 and b2 = (b0 + h)^2; Step 203, substitute the parametric equation of the point on the line segment formed by Q(α) and F(α) into the new ellipsoid parameters, calculate whether an intersection is formed, return if there is no intersection, return if there is one intersection, and return the intersection if there are two intersections, return the intersection closest to the maximum distance point F(α).

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