A radar initial orientation method

Abstract

This invention discloses a radar initial orientation method. The method is easy to implement, meets the accuracy requirements for engineering applications, and requires minimal additional equipment to achieve initial orientation. It also assists in the processing of subsequent radar monitoring results. Compared to existing technologies, if RTK is used, in addition to a mobile station, a base station and communication equipment are also required. If CORS is used, many projects are located in remote mountainous areas without CORS signals. If a total station is used, an additional total station weighing tens of kilograms needs to be carried. If the project is located in rugged mountainous areas or at altitudes of several thousand meters, there are also expensive additional costs.

Description

Technical Field

[0001] This invention relates to the field of radar monitoring technology, and more specifically to a radar initial orientation method. Background Technology

[0002] Ground-based circular arc synthetic aperture radar can achieve large-area deformation monitoring. Its monitoring range is a fan shape. The radar monitoring range is divided into several small fan-shaped cells by the resolution in the range and angle directions. The monitoring result is the cumulative deformation within the small fan-shaped cells relative to the initial monitoring time.

[0003] To better demonstrate the deformation at various locations on the actual terrain, it is usually necessary to overlay the radar's two-dimensional deformation field with the three-dimensional terrain. For example, Chinese patent (application number: CN202011110192.3) has achieved rapid calculation of the overlay of the radar's two-dimensional deformation field with the three-dimensional terrain. However, in practical applications, in order to accurately overlay the radar, it is necessary to determine the radar's initial azimuth angle. Existing conventional azimuth angle measurements can generally be performed using RTK or total station, but due to external limitations, these devices are sometimes not available.

[0004] In summary, there is an urgent need for a radar initial orientation method to solve the problems of existing technologies that rely on external equipment to determine the initial azimuth and cannot accurately determine the radar's initial azimuth angle. Summary of the Invention

[0005] The purpose of this invention is to provide a radar initial orientation method to solve the problems in the prior art that require external equipment to determine the initial azimuth and cannot accurately determine the radar's initial azimuth angle. The specific technical solution is as follows:

[0006] A radar initial orientation method includes the following steps:

[0007] Step S1: Establish a plane coordinate system, with the north direction as the positive X-axis and the east direction as the positive Y-axis; Step S2: Install the radar and deploy K corner reflectors along the radar scanning angle at the location to be monitored. Define the angle between the line connecting the corner reflector and the radar and the positive X-axis as the azimuth angle α of the corner reflector.

[0008] Step S3: Use 3D modeling technology to model the entire project area and generate a 3D model expressed in the planar coordinate system of Step S1. Select the planar coordinates of the corner reflector through the 3D model.

[0009] Step S4: Calculate the correction value of the azimuth angle of the corner reflector based on the plane coordinates of the selected corner reflector;

[0010] Step S5: Calculate the initial azimuth angle of the corner reflector based on the azimuth correction value, and determine the initial azimuth angle of the radar using the initial azimuth angle of the corner reflector.

[0011] In the preferred embodiment of the above technical solution, in step S2,

[0012] Before the radar is installed, a forced centering device is buried in the center of the monitoring pier. A GNSS antenna is installed on the forced centering device to receive GNSS signals for no less than 2 hours. The GNSS data is then post-processed to obtain the coordinates of the radar installation point, and the radar is then installed on the monitoring pier.

[0013] The K corner reflectors are numbered sequentially along the radar's angular direction, where K ≥ 2, and the corner reflector placement rule must meet the following conditions:

[0014] In the radar range direction, there are at least two corner reflectors distributed at a distance of not less than 1 / 2 of the radar range direction monitoring range;

[0015] In the direction of radar monitoring, there are at least two corner reflectors distributed at an angle not less than 1 / 2 of the radar angle in the monitoring range.

[0016] The distribution of any two corner reflectors in the range direction is no less than 100 times the radar range resolution;

[0017] The distribution of any two corner reflectors in the angular direction is no less than 100 times the radar angular resolution.

[0018] In the preferred embodiment of the above technical solution, step S4 includes:

[0019] Step S4.1: Based on the planar coordinates of the corner reflectors selected in step S3, calculate the closure error of the angle formed by the radar and two adjacent corner reflectors in the angular direction;

[0020] Step S4.2: Calculate the correction value of the included angle mentioned in step S4.1 based on the closure error, and calculate the corrected angle of the included angle using the correction value;

[0021] Step S4.3: Calculate the correction value of the azimuth angle α corresponding to the corner reflector using the corrected angle.

[0022] In the preferred embodiment of the above technical solution, the closure error Δβ in step S4.1 is as shown in Equation 1):

[0023]

[0024] Where βi(i+1) represents the angle formed by the i-th and i+1-th adjacent corner reflectors and the radar in the angular direction; β1K represents the angle formed by the 1-th and K-th corner reflectors and the radar.

[0025] In the preferred embodiment of the above technical solution, in step S4.2, the correction value Δβ of the included angle...i As shown in equation 2):

[0026]

[0027] In the preferred embodiment of the above technical solution, the corrected angle βi(i+1)' in step S4.2 is as shown in equation 3):

[0028] βi(i+1)'=βi(i+1)+Δβ' i 3);

[0029] Where i takes the values ​​1, 2, ..., K-1 in sequence.

[0030] In the preferred embodiment of the above technical solution, step S4.3,

[0031] The correction values ​​for the azimuth angle α corresponding to all corner reflectors are calculated using the corrected angles, as shown in Equation 4):

[0032]

[0033] Where, α i ' represents the correction value for the azimuth angle of the i-th corner reflector; α i βj(j+1)' represents the azimuth angle of the i-th corner reflector; βj(j+1)' represents the corrected angle between the radar and the adjacent j-th and (j+1)-th corner reflectors in the angular direction.

[0034] In the preferred embodiment of the above technical solution, when calculating the angle formed by two adjacent corner reflectors and the radar each time, the planar coordinates of the corner reflectors are reselected in the three-dimensional model for calculation.

[0035] In the preferred embodiment of the above technical solution, in step S5, the initial azimuth angle of the corner reflector i... As shown in equation 5):

[0036]

[0037] c i Δθ represents the angular index of the cell containing the i-th corner reflector in the radar scan results; Δθ represents the angular resolution of the radar.

[0038] In the preferred embodiment of the above technical solution, the initial azimuth angle α0 of the radar in step S5 is as shown in Equation 6):

[0039]

[0040] Where K represents the total number of corner reflectors.

[0041] The application of the technical solution of the present invention has the following beneficial effects:

[0042] (1) The initial orientation method provided by the present invention is easy to implement, can meet the accuracy requirements of engineering use, and can achieve initial orientation without too much additional equipment. It can help with the processing of subsequent radar monitoring results. Compared with the prior art, if RTK is used, in addition to the need for a mobile station, a base station and communication equipment are also required. If CORS is used, many projects are in remote mountainous areas without CORS signals. If a total station is used, an additional total station equipment weighing tens of kilograms is required. If the project is in rugged mountainous areas or mountainous areas at an altitude of several thousand meters, expensive additional costs are also required.

[0043] (2) Using RTK or total station requires measuring the baseline, but often the radar is deployed in places such as mountain tops with a very small range, making it impossible to measure the baseline. If an automatic gyroscope is used for orientation, on the one hand, the accuracy cannot meet the requirements, and on the other hand, the external environment has too much influence on the gyroscope. However, the method of this invention uses GNSS to measure the center coordinates of the radar axis when conducting UAV aerial surveys. After the aerial survey three-dimensional model is generated, the initial orientation angle can be calculated immediately, which saves both engineering costs and time costs.

[0044] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0045] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0046] In the attached diagram:

[0047] Figure 1 This is a schematic diagram of the cell division of the radar monitoring range in this embodiment;

[0048] Figure 2 This is a structural diagram of the corner reflector in this embodiment;

[0049] Figure 3 This is a diagram showing the positions of the radar and corner reflectors in this embodiment;

[0050] Among them, 1. Radar monitoring range; 2. Cell; 3. Corner reflector. Detailed Implementation

[0051] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0052] Example:

[0053] A radar initial orientation method includes steps S1 to S5, such as... Figures 1 to 3 As shown, the details are as follows:

[0054] First, the monitoring range of the radar (ground-based circular arc synthetic aperture radar) will be explained:

[0055] In this embodiment, the ground-based circular arc synthetic aperture radar (SAR) acquires a fan-shaped radar monitoring range, which is divided into fan-shaped grids. Each cell is a fan-shaped unit, and the entire radar monitoring range has M rows × N columns of cells. M is the number of cells in the range direction (i.e., range axis), and N is the number of cells in the angular direction (i.e., angular axis). The values ​​of M and N are jointly determined by the angular resolution Δθ, the range resolution Δr, and the radar monitoring range (in this embodiment, the radar's angular resolution Δθ is 0.12°, and the range resolution Δr is 0.3m). The cell number in the i-th row and j-th column is (i, j), where 1 ≤ i ≤ M and 1 ≤ j ≤ N. The row number increases from near to far along the radar wave emission direction, and the column number increases clockwise along the radar rotation direction. The radar monitoring results are divided into deformation data and signal strength data.

[0056] Step S1: Establish a plane coordinate system. The north direction is the positive X-axis and the east direction is the positive Y-axis. Of course, if there is a local plane coordinate system, the local plane coordinate system can also be used.

[0057] Step S2: This includes installing the radar and deploying corner reflectors, as detailed in steps S2.1 and S2.2:

[0058] Step S2.1: Install the radar. In this embodiment, the radar is installed on the monitoring pier. The monitoring pier is square and its size is the same as that of the radar base. A forced centering device is buried in the center of the monitoring pier.

[0059] Before installing the radar, a GNSS antenna is installed on the forced centering device to receive GNSS signals for at least 2 hours. The GNSS data is then post-processed to obtain coordinates in the WGS84 (a coordinate system established for use by the GPS global positioning system) coordinate system. The coordinates in the WGS84 coordinate system are converted to the plane coordinate system in step S1, represented by the ordinate X, abscissa Y, and geodetic height H. In this embodiment, they are converted to the coordinates R in the UTM coordinate system. Then the radar is installed on the monitoring pier, which allows the coordinates of the radar observation center to be obtained.

[0060] Step S2.2: Deploy K corner reflectors. At least K corner reflectors (K is greater than or equal to 2, preferably K=3 in this embodiment) are evenly deployed at the location to be monitored (e.g., on the slope to be monitored). The K corner reflectors are deployed sequentially along the angular direction monitored by the radar, and the deployment rules are as follows:

[0061] In the radar range direction, there are at least two corner reflectors distributed at a distance not less than 1 / 2 of the radar range direction monitoring range. Specifically, at least two corner reflectors are located at a distance greater than 1 / 2 of the radar range direction monitoring range from the radar.

[0062] In the angular direction monitored by the radar, there are at least two corner reflectors distributed at an angle not less than 1 / 2 of the radar's angular monitoring range. Specifically, the angle formed by the lines connecting the two corner reflectors to the radar (e.g., the angle between the two corner reflectors and the radar) is... Figure 3 The radar angular monitoring range where A1RA3 (i.e., angle β13) is greater than 1 / 2;

[0063] The distribution of any two corner reflectors in the range direction is not less than 100 times the radar range resolution. Specifically, the distance between any two corner reflectors in the range direction is not less than 100 times the radar range resolution (range resolution is Δr).

[0064] The distribution of any two corner reflectors in the angular direction is not less than 100 times the radar angular resolution. Specifically, the included angle formed by any two corner reflectors in the angular direction is not less than 100 times the radar angular resolution (angular resolution is Δθ).

[0065] Furthermore, the above deployment rules can be simply explained as follows: at least two corner reflectors are distributed at a distance of not less than 1 / 2 of the range monitoring range in the range direction monitored by the radar; at least two corner reflectors are distributed at a distance of not less than 1 / 2 of the angular monitoring range monitored by the radar; the distribution of any two corner reflectors in the range direction is not less than 100 times the range resolution; and the distribution in the angular direction is not less than 100 times the angular resolution.

[0066] After the corner reflectors (i.e., angle reflectors) are deployed, they are numbered sequentially in a clockwise direction. In this embodiment, three corner reflectors A1, A2, and A3 are set up. The angle between the positive X-axis of the plane coordinate system and the positive X-axis is the azimuth angle of the corner reflector, and the azimuth angle ranges from [0° to 360°].

[0067] In this embodiment, the angle (clockwise angle) between the line connecting the corner reflector and the radar and the positive X-axis is defined as the azimuth angle α of the corner reflector.

[0068] The corner reflector structure in this embodiment is as follows: the corner reflector is made of three identical isosceles right-angled triangular iron pieces spliced ​​together, and the hypotenuse of the triangle is not less than 50cm.

[0069] Step S3: Use 3D modeling technology to model the entire project area and generate a 3D model expressed in the planar coordinate system of Step S1. Select the planar coordinates of the corner reflector through the 3D model. Specifically, use UAV aerial photography 3D modeling technology to take aerial photos of the entire project area and finally generate a 3D model of the entire area. The 3D model is expressed in the planar coordinate system described in Step S1.

[0070] By selecting the center position of the corner reflector on the 3D model, the planar coordinates of the three corner reflectors can be obtained.

[0071] Step S4: Based on the selected plane coordinates of the corner reflector, calculate the correction value of the azimuth angle α of the corner reflector. Step S4 specifically includes steps S4.1 to S4.3, as follows:

[0072] Step S4.1: Based on the planar coordinates of the corner reflectors selected in step S3, calculate the closure error of the angle formed by the radar and two adjacent corner reflectors in the angular direction;

[0073] First, calculate the angle between the two adjacent corner reflectors and the radar in the angular direction. That is, the angle between corner reflectors A1 and A2 and the vertex (i.e., radar R) is β12. Similarly, the angle between corner reflectors A2 and A3 and the vertex radar R is β23. The angle between the corner reflector A1 closest to the radar initial direction and the corner reflector AK closest to the radar cutoff direction and the radar coordinates is β1K. That is, the angle between A1, A3 and the vertex radar R is β13.

[0074] Preferably, in order to reduce the error caused by selecting points on the three-dimensional model, when calculating the above-mentioned angles (i.e., β12, β23 and β13), the coordinate values ​​are obtained by re-selecting points on the three-dimensional model for each calculation.

[0075] The closure error Δβ is calculated as shown in Equation 1):

[0076]

[0077] Where βi(i+1) represents the angle formed by the i-th and i+1-th adjacent corner reflectors and the radar in the angular direction; β1K represents the angle formed by the 1-th and K-th (K=3) corner reflectors and the radar, that is, β1K=β13.

[0078] Step S4.2: Calculate the correction value of the included angle mentioned in step S4.1 based on the closure error, and calculate the corrected angle of the included angle using the correction value;

[0079] Calculate the correction Δβ for the angle formed by the coordinates of two adjacent corner reflectors and the radar coordinates. i As shown in Equation 2):

[0080]

[0081] In equation 2), for β1K,

[0082] The corrected angle βi(i+1)' is obtained by calculating the correction value, as shown in Equation 3):

[0083] βi(i+1)'=βi(i+1)+Δβ' i 3);

[0084] Where i takes values ​​of 1, 2, ..., K-1 in sequence; for β1K, the corrected angle β1K' = β1K + Δβ' 1K .

[0085] Step S4.3: Calculate the correction value of the azimuth angle α corresponding to the corner reflector using the corrected angle;

[0086] Let the correction value of the azimuth angle of the line connecting corner reflector A1 (i.e., the first corner reflector) to the radar be α'1 = α1 (i.e., the correction value of the first corner reflector is equal to the azimuth angle of that reflector). For corner reflector Ai (i = 2, 3, ..., K), the correction value of the azimuth angle of its line connecting to the radar is α'1. i As can be seen from the above, the correction value of the azimuth angle α calculated from the corrected angle can be expressed by the following formula 4):

[0087]

[0088] Where, α' i α represents the correction value for the azimuth angle of the i-th corner reflector. i βj(j+1) represents the azimuth angle of the i-th corner reflector; βj(j+1) represents the angle formed by the radar with the adjacent j-th and (j+1)-th corner reflectors in the angular direction.

[0089] The azimuth angle of the line connecting the corner reflector and the radar, calculated at this point, has undergone adjustment calculations, which reduces the error to a certain extent and makes the result closer to the true value.

[0090] Step S5: Calculate the initial azimuth angle of the corner reflector based on the correction value corresponding to the corner reflector, and determine the initial azimuth angle of the radar by using the initial azimuth angles of all corner reflectors;

[0091] Initial azimuth angle of the corner reflector:

[0092] The radar begins normal operation, acquiring scan results. Within the scan image, locate the signal strength data corresponding to the corner reflector (this can be done manually or using existing technology). Since corner reflectors are strong reflectors, it's easy to find the corresponding sector cell. Obtain the row and column number U of the cell containing corner reflector i. i (r i ,c i ), i = 1, 2, 3, where r is the row number and c is the column number;

[0093] Since the radar's angular resolution is known, the initial azimuth angle of corner reflector i can be calculated from the correction value of the azimuth angle corresponding to corner reflector i and the radar's scanning results. As shown in equation 5):

[0094]

[0095] Among them, c i Δθ represents the angular index of the cell containing the i-th corner reflector in the radar scan results (i.e., the column number of corner reflector i); Δθ represents the angular resolution of the radar.

[0096] The initial azimuth angle α0 of the radar is determined by the initial azimuth angles of all corner reflectors, as shown in Equation 6):

[0097]

[0098] in, The initial azimuth angle of corner reflector i is represented; K represents the total number of corner reflectors.

[0099] The initial radar azimuth angle calculated at this point, after undergoing multiple adjustment calculations as described above, reduces errors caused by the UAV aerial survey generating the 3D model, point selection errors on the model, and radar angular resolution, ensuring that the result meets the accuracy requirements of engineering applications. Furthermore, it is easy to implement on a computer, making it simple and fast.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A radar initial orientation method, characterized in that, Includes the following steps: Step S1: Establish a plane coordinate system, with the north direction as the positive X-axis and the east direction as the positive Y-axis. Step S2: Install the radar and deploy it along the radar scanning angle at the location to be monitored. For a corner reflector, the angle between the line connecting the corner reflector and the radar and the positive X-axis is defined as the azimuth angle of the corner reflector. ; Step S3: Use 3D modeling technology to model the entire project area and generate a 3D model expressed in the planar coordinate system of Step S1. Select the planar coordinates of the corner reflector through the 3D model. Step S4: Calculate the correction value of the azimuth angle of the corner reflector based on the selected plane coordinates of the corner reflector; Step S5: Calculate the initial azimuth angle of the corner reflector based on the azimuth correction value, and determine the initial azimuth angle of the radar using the initial azimuth angle of the corner reflector; Step S4 includes: Step S4.1: Based on the planar coordinates of the corner reflectors selected in step S3, calculate the closure error of the angle formed by the radar and two adjacent corner reflectors in the angular direction; Step S4.2: Calculate the correction value of the included angle mentioned in step S4.1 based on the closure error, and calculate the corrected angle of the included angle using the correction value; Step S4.3: Calculate the azimuth angle corresponding to the corner reflector using the corrected angle. The correction value.

2. The radar initial orientation method according to claim 1, characterized in that, In step S2, before the radar is installed, a forced centering device is buried in the center of the monitoring pier, a GNSS antenna is installed on the forced centering device, and GNSS signals are received for no less than 2 hours. The GNSS data is post-processed to obtain the coordinates of the radar installation point, and the radar is installed on the monitoring pier. Along the radar angle forward time target The corner reflectors are numbered sequentially, among which Furthermore, the placement rules for corner reflectors must meet the following conditions: In the radar range direction, there are at least two corner reflectors distributed at a distance of not less than 1 / 2 of the radar range direction monitoring range; In the direction of radar monitoring, there are at least two corner reflectors distributed at an angle not less than 1 / 2 of the radar angle in the monitoring range. The distribution of any two corner reflectors in the range direction is no less than 100 times the radar range resolution; The distribution of any two corner reflectors in the angular direction is no less than 100 times the radar angular resolution.

3. The radar initial orientation method according to claim 1, characterized in that, In step S4.1, the closure error As shown in Equation 1): 1）； in, Indicates the angle towards the adjacent first The corner reflector and the first The angle formed by the corner reflector and the radar; Indicates the first The corner reflector and the first The angle formed by the corner reflector and the radar.

4. The radar initial orientation method according to claim 3, characterized in that, In step S4.2, the correction number of the included angle As shown in equation 2): 2）。 5. The radar initial orientation method according to claim 4, characterized in that, In step S4.2, the corrected angle As shown in equation 3): 3）； in, Take in sequence .

6. The radar initial orientation method according to any one of claims 3-5, characterized in that, In step S4.3, Calculate the azimuth angles corresponding to all corner reflectors using the corrected angles. The correction values ​​are shown in Equation 4): 4）； in, Indicates the first Correction value for the azimuth angle of the corner reflector; Indicates the first The azimuth angle of the corner reflector; Indicates the angle towards the adjacent first The corner reflector and the first The angle formed by the corner reflector and the radar is the corrected angle.

7. The radar initial orientation method according to claim 6, characterized in that, Each time the angle between two adjacent corner reflectors and the radar is calculated, the planar coordinates of the corner reflectors are reselected in the three-dimensional model for calculation.

8. The radar initial orientation method according to claim 6, characterized in that, In step S5, the corner reflector initial azimuth angle As shown in equation 5): 5）； This indicates that in the radar scan results, the first... The angle of the cell where the corner reflector is located is numbered; This indicates the angular resolution of the radar.

9. The radar initial orientation method according to claim 8, characterized in that, In step S5, the initial azimuth angle of the radar As shown in equation 6): 6）； in, This indicates the total number of corner reflectors.

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