Weather radar clearance condition calculation method based on geographic surveying and mapping technology

Abstract

The invention relates to the technical field of weather radar systems, in particular to a weather radar clearance condition calculation method based on a geographic surveying and mapping technology, and the method comprises the steps: converting geodetic coordinates into site coordinates; calculating the distance from the target to the station center, the azimuth angle and the pitch angle based on the conversion result; drawing a shielding distribution polar coordinate graph according to the distance from the target to the station center, the azimuth angle and the pitch angle; converting the station coordinate system into a geodetic coordinate system; iteratively calculating latitude and elevation to obtain geodetic coordinates containing clearance conditions; and converting the projection of the geodetic coordinate containing the clearance condition from WGS84 to UTM to obtain a coverage area plane of the radar. According to the method, a WGS84 ellipsoid model is adopted for coordinate transformation, and compared with traditional sphere hypothesis, the method is closer to the actual shape of the earth, so that calculation errors caused by model hypothesis are reduced, and the problem that an existing calculation method is large in error is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of weather radar systems, and in particular to a method for calculating weather radar clearance conditions based on geographic surveying and mapping technology. Background Art

[0002] Weather radar system detection is one of the important means to obtain meteorological target information, and plays an important role in meteorological monitoring, warning and forecasting services. Objectively and accurately judging whether the selected site is scientific and reasonable will directly affect the quality of radar detection data and the investment benefits of radar system equipment. Therefore, in the radar construction planning stage, the first problem to be solved is to calculate the clearance conditions of the proposed radar site and evaluate the improvement effect of the new radar on the detection coverage of the existing radar.

[0003] Currently, there are two main methods for obtaining occlusion elevation angle data: the field measurement method and the geographic information data method.

[0004] Field measurement method: At the radar site, use instruments such as theodolites, rangefinders, and total stations to measure the lowest elevation angle that does not block the line of sight every 1° starting from the north, and measure 360 ​​data in total to draw a blockage distribution map. The advantage is that the data is actually measured without the influence of position errors. The disadvantage is that the change in the blockage angle caused by the change in the height of the radar feed after the tower is built cannot be calculated. Second, the data accuracy of the on-site survey is affected by many factors such as instruments and equipment, weather conditions, and the operation of technicians.

[0005] Geographic information data method: Use high-precision geographic information data to obtain all terrain latitude, longitude and elevation information around the proposed radar site that is equal to or higher than the site altitude, and then calculate the shielding angle through relevant algorithms. The advantage is that there is no need for field investigation, and the use of geographic information data can be used to draw a map, and the impact of the increase in the height of the radar station building can be arbitrarily calculated. The disadvantage is that there are uncertain factors, such as the resolution and accuracy of the geographic information data source and the shielding angle algorithm used, which will make the shielding elevation angle unrealistic or deviate.

[0006] Especially when converting radar observation coordinates and geocentric coordinates, in order to simplify the calculation process, the earth is usually assumed to be a sphere, and radar site selection, quantitative precipitation measurement, and radar network jigsaw puzzle are carried out based on this assumption. However, such an assumption will bring certain errors. Summary of the invention

[0007] The purpose of the present invention is to provide a method for calculating weather radar clearance conditions based on geographic surveying and mapping technology, aiming to solve the problem of large errors in existing calculation methods.

[0008] To achieve the above object, the present invention provides a method for calculating weather radar clearance conditions based on geographic surveying and mapping technology, comprising the following steps:

[0009] Convert geodetic coordinates to site coordinates;

[0010] Based on the conversion results, the distance, azimuth and elevation angle from the target to the station center are calculated;

[0011] The distance, azimuth and elevation angle from the target to the station center are used to draw a polar coordinate diagram of the occlusion distribution;

[0012] Convert the site coordinate system to the geodetic coordinate system;

[0013] Iteratively calculate the latitude and altitude to obtain the geodetic coordinates including the clearance condition;

[0014] The geodetic coordinates including the clearance conditions are transformed from WGS84 to UTM projection to obtain the radar coverage plane.

[0015] Among them, in "Converting geodetic coordinates to site coordinates", the following steps are included:

[0016] Through mathematical transformation and iterative calculation, the geodetic coordinates of the points on the ellipsoid are converted into geocentric coordinates;

[0017] According to the association rules of rotation matrix and coordinate axis projection, the geocentric coordinates are converted into station coordinates with the radar feed as the station center.

[0018] Among them, in "drawing the polar coordinate diagram of the shielding distribution of the distance, azimuth and elevation angle from the target to the center of the station", the following steps are included:

[0019] Traverse the geographic information data, calculate the distance, azimuth and elevation angle of each grid point relative to the radar feed, and form polar coordinate data;

[0020] Group by azimuth angle, and select the data with the largest pitch angle in each group as valid data;

[0021] Organize the valid data and draw the polar coordinate diagram of occlusion distribution.

[0022] The following steps are included in "Converting the site coordinate system to the geodetic coordinate system":

[0023] Convert the site coordinate system to the auxiliary coordinate system;

[0024] Convert the auxiliary coordinate system to the geodetic coordinate system.

[0025] Among them, in "iteratively calculating latitude and elevation to obtain geodetic coordinates including clearance conditions", the following steps are included:

[0026] Convert valid data into rectangular coordinates;

[0027] Convert rectangular coordinates to geodetic coordinates including clearance conditions.

[0028] The present invention discloses a method for calculating the clearance conditions of a weather radar based on geographic surveying and mapping technology, comprising the following steps: converting geodetic coordinates to site coordinates; calculating the distance, azimuth and elevation angle from the target to the center of the site based on the conversion result; drawing a polar coordinate diagram of the shielding distribution based on the distance, azimuth and elevation angle from the target to the center of the site; converting the site coordinate system to the geodetic coordinate system; iteratively calculating the latitude and elevation to obtain the geodetic coordinates containing the clearance conditions; converting the geodetic coordinates containing the clearance conditions from WGS84 to UTM projection to obtain the radar coverage plane. The present invention adopts the "WGS84" ellipsoid model for coordinate conversion, which is closer to the actual shape of the earth than the traditional spherical assumption, thereby reducing the calculation error caused by the model assumption, thereby solving the problem of large errors in the existing calculation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the site coordinate system.

[0031] Figure 2 It is a schematic diagram of the geodetic coordinate system.

[0032] Figure 3 It is a schematic diagram of the geocentric coordinate system.

[0033] Figure 4 It is a schematic diagram of the plane rectangular coordinate system established on the meridian where point P is located.

[0034] Figure 5 It is a schematic diagram of a schematic diagram of the actual point P position.

[0035] Figure 6 It is a schematic diagram of the rotation of a plane rectangular coordinate system.

[0036] Figure 7 It is a schematic diagram of the mutual projection of the rotating coordinate axes.

[0037] Figure 8 It is a schematic diagram of the plane rectangular coordinate system established on the meridian where the actual point P is located.

[0038] Fig. 9 The present invention provides a flow chart of a method for calculating weather radar clearance conditions based on geographic surveying and mapping technology.

[0039] Fig.10 It is a flow chart for converting geodetic coordinates to site coordinates.

[0040] Fig.11 It is a flow chart for drawing the polar coordinate diagram of the occlusion distribution based on the distance, azimuth and elevation angle from the target to the station center.

[0041] Fig.12 This is a flowchart for converting the site coordinate system to the geodetic coordinate system.

[0042] Fig.13 It is a flowchart for iteratively calculating latitude and elevation to obtain geodetic coordinates including clearance conditions. DETAILED DESCRIPTION

[0043] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0044] See also Figures 1 to 13 The present invention provides a method for calculating weather radar clearance conditions based on geographic surveying and mapping technology, comprising the following steps:

[0045] S1 converts the geodetic coordinates to the site coordinates;

[0046] S11 converts the geodetic coordinates of points on the ellipsoid into geocentric coordinates through mathematical transformation and iterative calculation;

[0047] Specifically, the meridian circle where point P is located is used to establish a plane direct coordinate system with the center of the earth as the coordinate origin ( Figure 4 ), draw the normal line Pn of the original ellipsoid through point P, and the angle between it and the x-axis of the meridian rectangular coordinate system is B; draw the tangent line of the meridian through point P, and the angle between it and the x-axis is (90+B) degrees. Comparing with the geocentric coordinate system, we can get:

[0048]

[0049] According to the equation of the ellipse, point P on the ellipse satisfies:

[0050]

[0051] Derivative both sides with respect to x at the same time, according to the implicit function derivation rule, we have:

[0052]

[0053] According to analytic geometry, the derivative of an ellipse at a certain point is the slope of the tangent line at that point, so:

[0054]

[0055] Combining equations (3) and (4), we can get:

[0056] y=x(1-e 2 )tanB (5)

[0057] Where e is the first eccentricity of the ellipse:

[0058]

[0059] Let the Pn distance be N, then x = NcosB, and substituting into (5) we can get:

[0060] y=N(1-e 2 )sinB (6)

[0061] Substituting equation (6) into equation (1), we can obtain the coordinates of point P on the ellipsoid:

[0062]

[0063] Substituting (5) into the elliptic equation (2), we can simplify it to get:

[0064]

[0065] And x=NcosB, combining equation (8) we can get:

[0066]

[0067] By combining equations (7) and (9), we can obtain the coordinates of a point on the ellipsoid. However, this point does not yet contain height information. The actual point P(B, L, H) is the point at a height H along the normal vector of the point on the ellipsoid:

[0068] The plumb projection of the actual point P on the ellipsoid is point P 0 , click P 0 The unit normal vector at is n, such as Figure 5 As shown, we have:

[0069] P=P 0 +H·n (10)

[0070] The ellipsoidal surface is at P 0 The normal vector at is:

[0071]

[0072] Let n be parallel to the normal vector of a unit sphere. According to equation (11), the unit normal vector n can be obtained as:

[0073]

[0074] Combining equations (7), (10) and (12), we can obtain the geocentric coordinates of point P (X, Y, Z):

[0075]

[0076] By using the above method and selecting the basic constants of the WGS-84 coordinate reference ellipsoid (Table 1), the point P (B, L, H) in the geodetic coordinate system can be converted into the point P (X, Y, Z) in the geocentric coordinate system.

[0077] Table 1 Basic parameters of WGS-84 reference ellipsoid

[0078] Serial number parameter definition 1 Semi-major axis a=6378137.0m 2 Flattening f＝1 / 298.257223563 3 Earth's gravitational constant <![CDATA[μ=3.986005×10 14 m 3 / s 2 ]]> 4 Earth's rotation speed <![CDATA[ω e =7.2921151467×10 -5 rad / s]]>

[0079] S12 converts the geocentric coordinates into station coordinates with the radar feed as the station center according to the association rules of the rotation matrix and the coordinate axis projection.

[0080] Specifically, in the plane rectangular coordinate system, the black coordinate system is rotated counterclockwise by an angle θ (counterclockwise rotation is positive) to become the red coordinate system, (x, y) is the original coordinate, and (x', y') is the new coordinate after rotation ( Figure 6 ). Then the geometric relationship between point P in these two coordinate systems is as follows:

[0081]

[0082] The linear equation can be written in matrix form as:

[0083]

[0084] Axis rotation matrix Then there is

[0085] In a rectangular coordinate system, when the coordinate axis rotates under the action of a rotation matrix, the geometric meaning of each column (vector) of the rotation matrix is ​​the projection of each original coordinate axis (x or y) on the new coordinate axis (x' and y'). Figure 7 ).Right now,

[0086] The projection of the x-axis on the x'-axis is cosθ·x, and the projection of the x-axis on the y'-axis is -sinθ·x

[0087] The projection of the y-axis on the x'-axis is sinθ·y, and the projection of the y-axis on the y'-axis is cosθ·y

[0088] According to the association rule between the rotation matrix and the coordinate axis projection, the rotation form from the (x' / y') coordinate axis to the (x / y) coordinate axis can be obtained. That is,

[0089]

[0090] The coordinate axis rotation is extended from the two-dimensional plane rectangular coordinate system to the three-dimensional space rectangular coordinate system. Define the space rectangular coordinate system oxyz to satisfy the right-hand rule. There exists a vector a with coordinates [xyz] T , rotate the coordinate axis oxyz counterclockwise around the z axis by an angle of θ, define the thumb of the right hand pointing to the positive direction of the z axis, and the direction in which the four fingers are bent is the positive direction, and obtain the new coordinate system ox'y'z'. The coordinates of vector a in the new coordinate system ox'y'z' are [x' y' z'] T .

[0091] The coordinate axis rotates around the z-axis, and the coordinate of vector a on the z-axis remains unchanged. The coordinates on the x-axis and y-axis are the same as the rotation in the two-dimensional plane, so the coordinate of vector a in the new coordinate system ox'y'z' is:

[0092]

[0093] Rotation matrix R around the z axis Z for:

[0094]

[0095] Similarly, define the right thumb pointing to the positive direction of the x-axis, and the four fingers bent pointing to the positive direction, then the rotation matrix R of the coordinate axis rotating around the x-axis x for:

[0096]

[0097] Observation site coordinate system ( Figure 1 ) and the geocentric coordinate system ( Figure 3 ). When the longitude and latitude of the station are both 0 degrees, the station coordinate system coincides with the geocentric coordinate system, the East (x) axis is the Y direction, the North (y) axis is the Z direction, and the Up (x) axis is the X direction. The East (x) axis has nothing to do with latitude B, and its rotation changes with the change of longitude L; the North (y) axis has nothing to do with longitude L, and its rotation changes with the change of latitude B.

[0098] When converting from the geocentric coordinate system to the site coordinate system, you need to first translate the origin of the geocentric coordinate system to the origin of the site coordinate system. Then rotate around the X-axis of the geocentric coordinate system (π / 2-B), and then rotate around the Z-axis of the geocentric coordinate system (π / 2+L). According to equations (14) and (15), the rotation matrix R from the geocentric coordinate system to the site coordinate system is:

[0099]

[0100] Let the coordinates of the origin P of the site coordinate system in the geocentric coordinate system be (XP, YP, ZP). In summary, we have:

[0101]

[0102] Using formula (16), the point P(X, Y, Z) in the geocentric coordinate system can be converted into the point P(x, y, z) in the site coordinate system.

[0103] S2 calculates the distance, azimuth and elevation angle from the target to the station center based on the conversion results;

[0104] Specifically, using S11 and S12, the geodetic coordinates of the target are converted into coordinates under the station coordinates with the radar feed as the station center, and then the distance R from the target to the station center, the azimuth angle A and the pitch angle E are solved.

[0105] according to Figure 1 In the geometric relationship, the rectangular coordinates of the target in the site coordinate system are (x, y, z), and the polar coordinates of the target in the site coordinate system (R, A, E) are:

[0106]

[0107] The polar coordinates of the target in the site coordinate system are (R, A, E), and the rectangular coordinates of the target in the site coordinate system (x, y, z) are:

[0108] x=R·cosE·sinA

[0109] y=R·cosE·cosA

[0110] z=R·sinE (18)

[0111] The distance, azimuth and elevation angle of S3 target to the station center are used to draw a polar coordinate diagram of the occlusion distribution;

[0112] S31 traverses the geographic information data, calculates the distance, azimuth and elevation angle of each grid point relative to the radar feed, and forms polar coordinate data;

[0113] Specifically, within the maximum detection range of the radar, the geographic information data is traversed to obtain the latitude, longitude and elevation data of each grid point one by one. If the elevation value of the currently traversed grid point is not lower than the radar feed source height, the first to third steps are repeated to calculate the distance, azimuth and elevation of the current grid point relative to the radar feed source, and form a (R, A, E) data.

[0114] S32 groups data by azimuth angle, and selects the data with the largest pitch angle in each group as valid data;

[0115] Specifically, all the data calculated by S31 are grouped at intervals of 1° from 0° to 359° in azimuth. In the same group of azimuths, the data with the largest pitch angle is selected as the valid data of this group. If there is a lack of grouping in a certain azimuth, it means that there is no obstacle in this azimuth. The maximum detection radius of the radar is used as the distance value, the azimuth is used as the azimuth value, and 0° is used as the pitch angle value to form the (R, A, E) valid data of this group. After the fifth step is completed, a total of 360 (R, A, E) valid data are obtained, and there is only one in each azimuth.

[0116] S33 organizes valid data and draws a polar coordinate diagram of occlusion distribution.

[0117] Specifically, the 360 ​​(R, A, E) valid data obtained in S32 are reorganized, and in each data, if the pitch angle value is less than 0, the pitch angle is assigned to 0, and if it is greater than 5, it is assigned to 5. The organized data is used to draw a polar coordinate diagram of the occlusion distribution, where the polar diameter is the value of the pitch angle and the polar angle is the value of the azimuth angle.

[0118] S4 converts the site coordinate system to the geodetic coordinate system;

[0119] S41 converts the site coordinate system to the auxiliary coordinate system;

[0120] Specifically, the site coordinate system is converted to the auxiliary coordinate system, which is the inverse operation of S1. It is necessary to first rotate -(π / 2+L) around the Up(z) axis of the site coordinate system, then rotate -(π / 2-B) around the East(x) axis, and finally translate the origin of the site coordinate system to the origin of the geocentric coordinate system. The rotation matrix R from the site coordinate system to the geocentric coordinate system is:

[0121]

[0122] Let the coordinates of the origin P of the site coordinate system in the geocentric coordinate system be (XP, YP, ZP). In summary, we have:

[0123]

[0124] Using formula (19), the point P(x, y, z) in the site coordinate system can be converted into the point P(X, Y, Z) in the geocentric coordinate system.

[0125] S42 transforms the auxiliary coordinate system into the geodetic coordinate system.

[0126] Specifically, take the center of the earth as the origin of the coordinate system, establish a plane rectangular coordinate system with the meridian where the actual point P (B, L, H) is located, and add auxiliary lines. The coordinates of point P in the geocentric coordinate system are (X, Y, Z), the projection on the ellipsoid surface is P0, and the height is H, such as Figure 8 shown.

[0127] Because P 0 P 2 =P 0 Q·sinB,P 0 n=N=P 0 Q+Qn, compared with formula (6), we can get

[0128] Qn=Ne 2 (20)

[0129] According to plane analytic geometry, combined with equation (20), we have:

[0130]

[0131] so

[0132]

[0133] According to formula (13),

[0134]

[0135] According to equation (22) and equation (23), we can get:

[0136]

[0137] Using formula (24), the point P(X, Y, Z) in the geocentric coordinate system can be converted to the point P(B, L, H) in the geodetic coordinate system.

[0138] S5 iteratively calculates the latitude and elevation to obtain the geodetic coordinates including the clearance condition;

[0139] S51 converts the valid data into rectangular coordinates;

[0140] Specifically, when using formula (24) to solve, the longitude L can be directly calculated, but when calculating the latitude B, since the formula contains the quantity to be calculated B, an iterative solution is required.

[0141] <1> Let e 2 =0, calculate the initial value B 0

[0142]

[0143] <2> B 0 Substitute into (9) and (24) respectively and iteratively calculate N 1 and B 1

[0144]

[0145] <3> Set an acceptable latitude error to ε = 1 × 10-13 If |B 1 -B 0 |≥ε, then update B with B1 0 , bring it back <2> Calculate N 2 and B 2 , iterate until the algorithm converges, that is, |B 1 -B 0 |<ε. At this time, the calculated N n and B n , which is the exact B and N we are looking for.

[0146] <4> Will <3> Substitute the B and N required in (24) to obtain H.

[0147] According to the above method, the precise geodetic coordinates (B, L, H) of point P can be obtained.

[0148] S52 converts the rectangular coordinates into geodetic coordinates including clearance conditions.

[0149] Specifically, by repeatedly executing S41, S42 and S51 based on the result of S51, the (R, A, E) site polar coordinates including the clearance condition can be converted into (B, L, H) geodetic coordinates including the clearance condition.

[0150] S6 transforms the geodetic coordinates including the clearance conditions from WGS84 to UTM projection to obtain the radar coverage plane.

[0151] Specifically, the result of S6 is transformed from WGS84 to UTM projection to obtain the radar coverage plane. When projecting, the corresponding number of WGS84 in the geographic coordinate system is 4326. According to the longitude range of Chengdu, the UTM zone number is selected as 48N, that is, the name of the projection coordinate system is WGS_1984_UTM_Zone_48N, and the EPSG number is determined as 32648 in the projection coordinate system according to the name.

[0152] like Figure 1 As shown in the figure, when the weather radar at point P observes the azimuth and elevation of the meteorological target, it is done in the station coordinate system at point P. The station coordinate system takes the center of the radar station receiving antenna as the origin O of the coordinate system, the z-axis coincides with the normal of the earth ellipsoid, with upward as positive (up), the y-axis coincides with the short semi-axis of the earth ellipsoid (north), and the x-axis coincides with the long semi-axis of the earth ellipsoid (east), forming a right-handed rectangular coordinate system. The polar coordinates of a point in space are expressed in the station coordinate system as follows: the center of the station is the coordinate pole O, the horizontal plane (xoy plane) is the reference plane, the east axis (x axis) is the polar axis, R is the distance from the point to the center of the station, A is the azimuth angle, and E is the elevation angle.

[0153] However, in daily life, global coordinate systems such as WGS84 or CGCS2000 are usually used to express global geographic coordinate information, and locations are marked with latitude, longitude and altitude.

[0154] The "WGS84" ellipsoid model uses the geocentric geodetic coordinate system (referred to as the geodetic coordinate system), such as Figure 2 As shown. The center of the ellipsoid coincides with the center of mass of the earth. The Z axis of its geocentric space rectangular coordinate system points to the direction of the agreed earth pole (CTP) defined by BIH (International Time Service) 1984.0, the X axis points to the intersection of the zero meridian plane of BIH 1984.0 and the CTP equator, and the Y axis is perpendicular to the Z axis and the X axis to form a right-handed coordinate system. The position of any point is represented by (B, L, H) coordinates. The geodetic latitude B is the angle between the normal line of the ellipsoid surface passing through the point and the equatorial plane. Starting from the equatorial plane, it is positive to the north and negative to the south, with a value range of (±90 degrees); the geodetic longitude L is the dihedral angle formed by the geodetic starting meridian plane and the meridian plane where the point is located. Starting from the starting meridian plane, it is positive to the east and negative to the west, with a value range of (±180 degrees); the geodetic height H is the distance from the ground point to the ellipsoid surface along the normal line of the ellipsoid.

[0155] In the geodetic coordinate system, because the normal of point P and the equatorial plane do not necessarily intersect at the centroid, the calculation of latitude, longitude and elevation in space is very complicated. In the rectangular coordinate system, it is very convenient to calculate angles and distances in space.

[0156] Using the method of geodesy, the target point T (B, L, H) in the geodetic coordinate system is converted into the point T (R, A, Z) in the site coordinate system, so as to calculate the azimuth and elevation angle of the target point T relative to the reference point P. Because the site coordinate system is a local Cartesian coordinate system, and the geodetic coordinate system is a world coordinate system, the global Cartesian coordinate system - the earth-centered earth-fixed coordinate system (referred to as the geocentric coordinate system) is introduced as an auxiliary coordinate system for coordinate transformation, such as Figure 3 shown.

[0157] The definition of the geocentric coordinate system is: the origin O is the center of mass of the earth, the Z axis coincides with the earth's axis and points to the North Pole, the X axis points to the intersection of the prime meridian and the equatorial plane, the Y axis is perpendicular to the XOZ plane (that is, the intersection of 90 degrees east longitude and the equator) and forms a right-handed coordinate system with the X and Z axes. The position of any point is represented by (X, Y, Z) coordinates.

[0158] The above disclosure is only a preferred embodiment of the weather radar clearance condition calculation method based on geographic surveying and mapping technology of the present invention. Of course, this cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiments are implemented, and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for calculating weather radar clearance conditions based on geographic surveying and mapping technology, characterized in that: The following steps are involved: Convert geodetic coordinates to site coordinates; Based on the conversion results, the distance, azimuth and elevation angle from the target to the station center are calculated; The distance, azimuth and elevation angle from the target to the station center are used to draw a polar coordinate diagram of the occlusion distribution; Convert the site coordinate system to the geodetic coordinate system; Iteratively calculate the latitude and altitude to obtain the geodetic coordinates including the clearance condition; The geodetic coordinates including the clearance conditions are transformed from WGS84 to UTM projection to obtain the radar coverage plane.

2. The method for calculating weather radar clearance conditions based on geographic surveying and mapping technology according to claim 1, characterized in that: In "Converting Geodetic Coordinates to Site Coordinates", the following steps are included: Through mathematical transformation and iterative calculation, the geodetic coordinates of the points on the ellipsoid are converted into geocentric coordinates; According to the association rules of rotation matrix and coordinate axis projection, the geocentric coordinates are converted into station coordinates with the radar feed as the station center.

3. The method for calculating weather radar clearance conditions based on geographic surveying and mapping technology according to claim 1, characterized in that: In "Drawing a polar coordinate diagram of the occlusion distribution based on the distance, azimuth and elevation angle from the target to the center of the station", the following steps are included: Traverse the geographic information data, calculate the distance, azimuth and elevation angle of each grid point relative to the radar feed, and form polar coordinate data; Group by azimuth angle, and select the data with the largest pitch angle in each group as valid data; Organize the valid data and draw the polar coordinate diagram of occlusion distribution.

4. The method for calculating weather radar clearance conditions based on geographic surveying and mapping technology according to claim 1, characterized in that: In "Converting the Site Coordinate System to the Geodetic Coordinate System", the following steps are included: Convert the site coordinate system to the auxiliary coordinate system; Convert the auxiliary coordinate system to the geodetic coordinate system.

5. The method for calculating weather radar clearance conditions based on geographic surveying and mapping technology as claimed in claim 1, characterized in that: In "Iteratively calculating latitude and elevation to obtain geodetic coordinates including clearance conditions", the following steps are included: Convert valid data into rectangular coordinates; convert rectangular coordinates into geodetic coordinates including clearance conditions.

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