A ship radar calibration method and system of an active beacon

Abstract

The application provides a ship radar calibration method and system of an active beacon machine, a differential RTK GPS reference station is erected at a position with a view to a radar to be calibrated and a distance of 0.5 Km-3 Km, a reference point is selected to erect a differential RTK GPS mobile station; measurement data and a three-dimensional offset of a radar antenna installation point relative to the reference point in a ship coordinate system are acquired, a true value slant range and a true value azimuth angle of the radar antenna installation point relative to the reference point are calculated; a transmission power and a frequency of the active beacon machine are adjusted so that a signal of the active beacon machine can be received by the radar to be calibrated; an active beacon machine target is determined, and a target distance and an azimuth measured by the radar are recorded; and the target distance and the azimuth are compared with the true value slant range and the true value azimuth angle. The technical scheme of the application can overcome the defects of a fixed calibration tower calibration method, such as serious building obstruction, large clutter interference and uncontrollable calibration period, and solve the problems of a true value measurement, target recognition and heart correction calculation in an active calibration method.

Description

Technical Field

[0001] This invention belongs to the field of radar calibration technology, and specifically relates to a method and system for calibrating ship radar for an active beacon. Background Technology

[0002] Shipborne radar is a critical piece of equipment in ship navigation, maritime target detection, aerospace telemetry and control, and maritime combat systems. Its measurement accuracy directly affects ship navigation safety and mission execution effectiveness. As radar usage time increases, its systematic errors accumulate, leading to greater measurement errors and severely impacting radar performance. Therefore, regular radar calibration is essential. This involves calibrating and adjusting the radar's systematic errors using targets at known precise locations to eliminate or reduce these errors in radar observations.

[0003] The core of radar calibration lies in obtaining accurate target true values, comparing these true values ​​with the actual measured values ​​of the radar, calculating the radar's system error, and finally correcting the radar's zero range and zero angle values ​​to complete the radar calibration.

[0004] Therefore, how to provide a ship radar calibration method and system for active beacon machines that can overcome the shortcomings of existing fixed calibration tower calibration methods, such as severe obstruction by buildings, large clutter interference, and uncontrollable calibration cycle, and solve the problems of complex true value measurement, difficult target identification, and lack of standardized calculation of centering correction in existing active calibration methods, has become an urgent technical problem to be solved. Summary of the Invention

[0005] This invention provides a method and system for calibrating ship radar using an active beacon, which overcomes the shortcomings of existing fixed calibration tower calibration methods, such as severe obstruction by buildings, large clutter interference, and uncontrollable calibration cycle. It also solves the problems of complex true value measurement, difficult target identification, and lack of standardized calculation for centering correction in existing active calibration methods.

[0006] In one embodiment of the present invention, a method for calibrating a ship's radar using an active beacon is provided, comprising: S101. Set up the differential RTK GPS base station at a location that is in line with the radar to be calibrated and at a distance of 0.5Km to 3Km. At the same time, select a reference point on the bow-stern line of the ship where the radar to be calibrated is located, and set up the differential RTK GPS mobile station at the reference point. S102. Obtain measurement data through the differential RTK GPS base station and the differential RTK GPS rover station. The measurement data includes the slant distance R1, azimuth angle α1, and elevation angle β1 between the base station and the rover station. S103. Obtain the three-dimensional offsets ΔX, ΔY, and ΔZ of the radar antenna mounting point relative to the reference point in the ship's coordinate system, and calculate the true slant range R2 and true azimuth angle α2 of the radar antenna mounting point relative to the reference station according to the following formulas:

[0007]

[0008] Where c is the ship's heading angle, X B Y B These are the coordinates of the tested radar relative to the differential RTK GPS mobile station; S104. An active beacon is installed at the differential RTK GPS base station, and the transmission power and frequency of the active beacon are adjusted so that its signal can be received by the radar to be calibrated. S105. Start the radar to be calibrated, detect the signal emitted by the active beacon, and confirm the target as an active beacon by controlling the active beacon to intermittently stop transmitting signals and observing the synchronous disappearance and reappearance of the radar echo signal. Record the target distance and azimuth measured by the radar. S106. Compare the target distance and azimuth recorded in S105 with the true slant range R2 and true azimuth angle α2 calculated in S103. If the difference is within the preset error range, the calibration is deemed qualified; otherwise, adjust the system parameters of the radar to be calibrated and repeat S101 to S105 until the calibration is qualified.

[0009] Furthermore, before calculating the true slant distance R2 and the true azimuth angle α2 in S103, the step of establishing a temporary rectangular coordinate system with the differential RTK GPS mobile station as the origin is also included: setting the positive direction of the X-axis to the bow, the positive direction of the Y-axis to the starboard side, and the positive direction of the Z-axis vertically upward, and expressing the three-dimensional offsets ΔX, ΔY, and ΔZ in this coordinate system.

[0010] Furthermore, the specific method described in S105 for confirming a target by intermittently stopping the active beacon's signal transmission and observing the synchronous disappearance and reappearance of the radar echo signal is as follows: The active beacon is made to alternate between transmitting and stopping at fixed time intervals, with each transmission and stop duration being no less than one scan cycle of the radar antenna.

[0011] Furthermore, S105 also employs a delayed confirmation method: After turning off the active beacon, delay for a preset time window and observe whether the radar echo signal completely disappears within that time window to eliminate interference from multipath reflections or fixed clutter.

[0012] Furthermore, the reference point mentioned in S101 is a position on the bow and stern line of the ship near the radar antenna mounting point, and the line connecting the reference point and the radar antenna mounting point is parallel to the bow and stern line of the ship.

[0013] In another embodiment of the present invention, a ship radar calibration system for an active beacon is provided, for implementing the ship radar calibration method for an active beacon as described in any of the above claims, the system comprising: Differential RTK GPS base station is fixedly installed on a land-based or fixed platform that is in line with the radar to be calibrated; The differential RTK GPS mobile station can be detachably installed on the bow and stern reference points of the ship where the radar to be calibrated is located; An active beacon is installed at the same geographical location as the differential RTK GPS base station, and its antenna is located on the same pole or at the same erection point as the antenna of the differential RTK GPS base station. The data processor is communicatively connected to the differential RTK GPS base station and the differential RTK GPS mobile station, respectively, and is used to receive measurement data and perform the calculations described in S103; A comparator is used to compare the measured value output by the radar to be calibrated with the true value output by the data processor, and output the error amount; The display unit is used to display the error amount and the pass / fail determination result.

[0014] Furthermore, the active beacon includes a programmable controller and an RF transmission module. The programmable controller controls the RF transmission module to operate according to a preset stop-transmission sequence, which includes at least two operating modes: continuous transmission mode and intermittent transmission mode.

[0015] Furthermore, the differential RTK GPS base station and the differential RTK GPS mobile station transmit differential correction data in real time via a radio data link, enabling the mobile station to achieve centimeter-level positioning accuracy.

[0016] Furthermore, the data processor has a built-in calibration truth data calculation table, which receives the following input data in tabular form: horizontal distance D1, azimuth α1, and elevation β1 measured by the differential RTK GPS base station, heading c provided by the heading device, and the three-dimensional coordinates X of the tested radar relative to the differential RTK GPS rover station. B Y B Z B The calculation table automatically outputs the true slant range R2, true elevation angle β2, true hull angle q2, and true azimuth angle α2 of the radar relative to the beacon.

[0017] Furthermore, the differential RTK GPS base station and the active beacon are jointly mounted on a movable tripod or portable base, which has a leveling mechanism and a north dial for quick setup and orientation.

[0018] The beneficial effects of this invention are as follows: As can be seen from the above scheme, the embodiments of the present invention provide a method and system for calibrating ship radar using an active beacon. A differential RTK GPS reference station is set up at a location with line of sight to the radar to be calibrated and a distance of 0.5 km to 3 km. A reference point is selected on the bow-stern line of the ship where the radar to be calibrated is located, and a differential RTK GPS mobile station is set up at this reference point. Measurement data is acquired, including the three-dimensional offset of the radar antenna mounting point relative to the reference point in the ship's coordinate system. The true slant range and true azimuth angle of the radar antenna mounting point relative to the reference point are calculated. The differential RTK GPS system is then used to calibrate the radar antenna mounting point. An active beacon is installed at the GPS reference station. The transmission power and frequency of the active beacon are adjusted so that its signal can be received by the radar to be calibrated. The signal transmitted by the active beacon is detected. By intermittently controlling the active beacon to stop transmitting the signal and observing the synchronous disappearance and reappearance of the radar echo signal, the target is confirmed to be an active beacon. The target distance and azimuth measured by the radar are recorded. The target distance and azimuth are compared with the calculated true slant range and true azimuth angle. If the difference is within the preset error range, the calibration is deemed successful. The technical solution of this invention can overcome the shortcomings of the existing fixed calibration tower calibration method, which is severely blocked by buildings, has large clutter interference, and has an uncontrollable calibration cycle. It also solves the problems of complex true value measurement, difficult target identification, and lack of standardized calculation of centering correction in the existing active calibration methods. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the active beacon equipment calibration setup for the ship radar calibration method of the active beacon described in this invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] like Figure 1 As shown, Figure 1 This is a schematic diagram of the active beacon equipment calibration setup for the ship radar calibration method of the active beacon described in this invention.

[0022] Figure 1A method for calibrating a ship's radar using an active beacon includes: S101. Set up the differential RTK GPS base station at a location that is in line with the radar to be calibrated and at a distance of 0.5Km to 3Km. At the same time, select a reference point on the bow-stern line of the ship where the radar to be calibrated is located, and set up the differential RTK GPS mobile station at the reference point. S102. Obtain measurement data through the differential RTK GPS base station and the differential RTK GPS rover station. The measurement data includes the slant distance R1, azimuth angle α1, and elevation angle β1 between the base station and the rover station. S103. Obtain the three-dimensional offsets ΔX, ΔY, and ΔZ of the radar antenna mounting point relative to the reference point in the ship's coordinate system, and calculate the true slant range R2 and true azimuth angle α2 of the radar antenna mounting point relative to the reference station according to the following formulas:

[0023]

[0024] Where c is the ship's heading angle, X B Y B These are the coordinates of the tested radar relative to the differential RTK GPS mobile station; S104. An active beacon is installed at the differential RTK GPS base station, and the transmission power and frequency of the active beacon are adjusted so that its signal can be received by the radar to be calibrated. S105. Start the radar to be calibrated, detect the signal emitted by the active beacon, and confirm the target as an active beacon by controlling the active beacon to intermittently stop transmitting signals and observing the synchronous disappearance and reappearance of the radar echo signal. Record the target distance and azimuth measured by the radar. S106. Compare the target distance and azimuth recorded in S105 with the true slant range R2 and true azimuth angle α2 calculated in S103. If the difference is within the preset error range, the calibration is deemed qualified; otherwise, adjust the system parameters of the radar to be calibrated and repeat S101 to S105 until the calibration is qualified.

[0025] In this embodiment of the invention, a radar calibration method for an active beacon can quickly perform calibration work for various types of ship radars, greatly improving the efficiency of ship radar calibration, reducing environmental interference in traditional calibration methods, simplifying calculation steps, and effectively improving the accuracy and precision of radar calibration.

[0026] A differential RTK GPS base station is set up at a distance of 0.5 km to 3 km from the radar under test, and within line of sight of the radar. A point is selected on the bow-stern line of the ship on which the radar is being calibrated as the reference point for this calibration, and a rover is set up at the reference point. The differential GPS true value is read and recorded, and the range-azimuth true value of the radar under test is calculated through coordinate transformation. A source beacon is set up at the base station, and the transmission parameters are adjusted. After the radar under test is powered on and detects the transmission signal, the accuracy of the target is determined by techniques such as stopping transmission and delaying, the data is recorded, and compared with the true value. If the accuracy requirement is met, the calibration is completed. If the requirement is not met, the above steps are repeated, and the radar parameters are adjusted until the requirement is met.

[0027] In another embodiment of the present invention, before calculating the true slant distance R2 and the true azimuth angle α2 in S103, the method further includes the step of establishing a temporary rectangular coordinate system with the differential RTK GPS mobile station as the origin: setting the positive direction of the X-axis to the bow, the positive direction of the Y-axis to the starboard side, and the positive direction of the Z-axis vertically upward, and expressing the three-dimensional offsets ΔX, ΔY, and ΔZ in this coordinate system.

[0028] In another embodiment of the present invention, the specific method for confirming the target by controlling the active beacon to intermittently stop transmitting signals and observing the synchronous disappearance and reappearance of the radar echo signal in S105 is as follows: The active beacon is made to alternate between transmitting and stopping at fixed time intervals, with each transmission and stop duration being no less than one scan cycle of the radar antenna.

[0029] In another embodiment of the present invention, a delayed confirmation method is also employed in S105: After turning off the active beacon, delay for a preset time window and observe whether the radar echo signal completely disappears within that time window to eliminate interference from multipath reflections or fixed clutter.

[0030] In another embodiment of the present invention, the reference point mentioned in S101 is a position on the bow and stern line of the ship near the radar antenna mounting point, and the line connecting the reference point and the radar antenna mounting point is parallel to the bow and stern line of the ship.

[0031] In another embodiment of the present invention, a ship radar calibration system for an active beacon is provided, for implementing the ship radar calibration method for an active beacon as described in any of the above claims, the system comprising: Differential RTK GPS base station is fixedly installed on a land-based or fixed platform that is in line with the radar to be calibrated; The differential RTK GPS mobile station can be detachably installed on the bow and stern reference points of the ship where the radar to be calibrated is located; An active beacon is installed at the same geographical location as the differential RTK GPS base station, and its antenna is located on the same pole or at the same erection point as the antenna of the differential RTK GPS base station. The data processor is communicatively connected to the differential RTK GPS base station and the differential RTK GPS mobile station, respectively, and is used to receive measurement data and perform the calculations described in S103; A comparator is used to compare the measured value output by the radar to be calibrated with the true value output by the data processor, and output the error amount; The display unit is used to display the error amount and the pass / fail determination result.

[0032] In another embodiment of the present invention, the active beacon includes a programmable controller and an RF transmission module. The programmable controller controls the RF transmission module to operate according to a preset stop-transmission sequence, which includes at least two operating modes: continuous transmission mode and intermittent transmission mode.

[0033] In another embodiment of the present invention, the differential RTK GPS base station and the differential RTK GPS mobile station transmit differential correction data in real time via a radio data link, enabling the mobile station to obtain centimeter-level positioning accuracy.

[0034] In another embodiment of the present invention, the data processor has a built-in calibration truth data calculation table, which receives the following input data in tabular form: horizontal distance D1, azimuth α1, and elevation β1 measured by the differential RTK GPS base station, heading c provided by the heading device, and the three-dimensional coordinates X of the tested radar relative to the differential RTK GPS rover station. B Y B Z B The calculation table automatically outputs the true slant range R2, true elevation angle β2, true hull angle q2, and true azimuth angle α2 of the radar relative to the beacon.

[0035] As shown in Table 1, Table 1 is a calculation table of calibration true value data in an embodiment of the present invention.

[0036] Table 1. Calculation Table of Calibration True Value Data

[0037] By filling the measured values ​​into the "Coordinates of True Value Equipment, Heading Equipment, and Test Equipment" columns in the table, the true value of the test equipment relative to the target can be calculated. Therefore, the radar true value can be calculated simply by inputting the true value equipment data recorded during calibration, and can be directly used for calibration work.

[0038] In another embodiment of the present invention, the differential RTK GPS base station and the active beacon are jointly mounted on a movable tripod or portable base, which has a leveling mechanism and a north dial for quick setup and orientation.

[0039] In this embodiment of the invention, differential RTK GPS technology is employed. Differential correction data is transmitted in real time between the base station and the rover station via a radio data link, achieving centimeter-level positioning accuracy and ensuring the accuracy of the calibration true value. Simultaneously, this invention uses centering correction calculations to convert the true value from the GPS rover station reference point to the radar antenna installation point, eliminating systematic errors introduced by the inconsistency between the GPS antenna and radar antenna positions. Mathematical derivation and engineering verification show that this calculation model can achieve centimeter-level accuracy in obtaining the true value, ensuring the reliability of the radar calibration results. Compared to the shortcomings of fixed calibration towers, which are susceptible to building obstruction and clutter interference, this invention uses an active beacon as the calibration target. Its transmitted signal has clear signal characteristics and is easily distinguishable from environmental clutter. In particular, the intermittent stop signal confirmation method adopted in this invention—which allows the active beacon to alternately transmit and stop at a fixed time period, and ensures that the duration of each transmission and stop is not less than one scan cycle of the radar antenna—allows operators to accurately confirm the target by observing the synchronous disappearance and reappearance of the radar echo signal. This dual confirmation mechanism of stop and delay can effectively eliminate multipath reflection signals and fixed clutter interference, ensuring the accurate identification of the calibration target.

[0040] Existing active calibration solutions mostly rely on optical equipment such as laser theodolites for true value measurement, requiring the construction of optical paths and alignment with targets, resulting in high operational complexity. This invention utilizes differential RTK GPS to automatically acquire high-precision position information and directly calculates the true distance and azimuth values ​​of the radar relative to the beacon using a pre-set centering correction formula, eliminating the need for complex optical measurements and coordinate transformation calculations. The calibration true value data calculation table further simplifies and automates the calculation process; operators only need to input the original measurement data to directly obtain the true values ​​for calibration work, significantly reducing the computational complexity at the calibration site. Traditional fixed calibration tower methods are limited by berth locations, making calibration nodes uncontrollable and easily affecting the calibration cycle. This invention uses portable active beacons and differential GPS equipment, which can be erected at any location with line of sight to the radar under test, without relying on fixed calibration towers or specific berths. Calibration work can be arranged at any time, and calibration nodes are fully controllable, greatly shortening the calibration cycle and facilitating production node control.

[0041] Compared to fixed calibration towers that require large-scale civil engineering and long-term maintenance, this invention uses a portable tripod base to erect the reference station and beacon, making setup and dismantling convenient and allowing for repeated use in different situations. The active beacon is small and lightweight, easy to carry and maintain, and requires no dedicated target vessel, significantly reducing calibration costs. The system architecture of this invention supports radar parameter adjustment assistance, automatically generating radar system parameter correction suggestions (including range zero-point correction values, azimuth zero-point correction values, and antenna leveling adjustment) based on the error, assisting operators in quickly completing radar calibration. Simultaneously, the active beacon's transmission power and frequency are adjustable, enabling it to match different models and operating frequency bands of the radar under test, demonstrating good versatility.

[0042] This invention provides a method and system for calibrating a ship's radar using an active beacon. A differential RTK GPS reference station is set up at a location with line of sight to the radar to be calibrated, at a distance of 0.5 km to 3 km. A reference point is selected on the bow-stern line of the ship where the radar to be calibrated is located, and a differential RTK GPS rover station is set up at this reference point. Measurement data is acquired, including the three-dimensional offset of the radar antenna mounting point relative to the reference point in the ship's coordinate system. The true slant range and true azimuth angle of the radar antenna mounting point relative to the reference point are calculated. The differential RTK GPS rover station is then used to calibrate the radar antenna mounting point. An active beacon is set up at the GPS base station. The transmission power and frequency of the active beacon are adjusted so that its signal can be received by the radar to be calibrated. The signal transmitted by the active beacon is detected. The target is confirmed as an active beacon by intermittently stopping the transmission of the active beacon and observing the synchronous disappearance and reappearance of the radar echo signal. The target distance and azimuth measured by the radar are recorded. The target distance and azimuth are compared with the calculated true slant range and true azimuth angle. If the difference is within the preset error range, the calibration is deemed qualified.

[0043] The technical solution of this invention can overcome the shortcomings of existing fixed calibration tower calibration methods, such as severe building obstruction, large clutter interference, and uncontrollable calibration period. It also solves the problems of complex true value measurement, difficult target identification, and lack of standardized calculation of centering correction in existing active calibration methods.

[0044] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for calibrating ship radar using an active beacon, characterized in that, The calibration method includes: S101. Set up the differential RTK GPS base station at a location that is in line with the radar to be calibrated and at a distance of 0.5Km to 3Km. At the same time, select a reference point on the bow-stern line of the ship where the radar to be calibrated is located, and set up the differential RTK GPS mobile station at the reference point. S102. Obtain measurement data through the differential RTK GPS base station and the differential RTK GPS rover station. The measurement data includes the slant distance R1, azimuth angle α1, and elevation angle β1 between the base station and the rover station. S103. Obtain the three-dimensional offsets ΔX, ΔY, and ΔZ of the radar antenna mounting point relative to the reference point in the ship's coordinate system, and calculate the true slant range R2 and true azimuth angle α2 of the radar antenna mounting point relative to the reference station according to the following formulas: Where c is the ship's heading angle, X B Y B These are the coordinates of the tested radar relative to the differential RTK GPS mobile station; S104. An active beacon is installed at the differential RTK GPS base station, and the transmission power and frequency of the active beacon are adjusted so that its signal can be received by the radar to be calibrated. S105. Start the radar to be calibrated, detect the signal emitted by the active beacon, and confirm the target as an active beacon by controlling the active beacon to intermittently stop transmitting signals and observing the synchronous disappearance and reappearance of the radar echo signal. Record the target distance and azimuth measured by the radar. S106. Compare the target distance and azimuth recorded in S105 with the true slant range R2 and true azimuth angle α2 calculated in S103. If the difference is within the preset error range, the calibration is deemed qualified; otherwise, adjust the system parameters of the radar to be calibrated and repeat S101 to S105 until the calibration is qualified.

2. The method for calibrating a ship's radar using an active beacon as described in claim 1, characterized in that, Before calculating the true slant distance R2 and the true azimuth angle α2 in S103, the step of establishing a temporary rectangular coordinate system with the differential RTK GPS mobile station as the origin is also included: setting the positive direction of the X-axis to the bow, the positive direction of the Y-axis to the starboard side, and the positive direction of the Z-axis to the vertical upward, and expressing the three-dimensional offsets ΔX, ΔY, and ΔZ in this coordinate system.

3. The method for calibrating a ship's radar using an active beacon as described in claim 1, characterized in that, The specific method described in S105 for confirming a target by intermittently stopping the transmission of signals by controlling the active beacon and observing the synchronous disappearance and reappearance of the radar echo signal is as follows: The active beacon is made to alternate between transmitting and stopping at fixed time intervals, with each transmission and stop duration being no less than one scan cycle of the radar antenna.

4. The method for calibrating a ship's radar using an active beacon as described in claim 1, characterized in that, S105 also employs a delayed confirmation method: After turning off the active beacon, delay for a preset time window and observe whether the radar echo signal completely disappears within that time window to eliminate interference from multipath reflections or fixed clutter.

5. The method for calibrating a ship's radar using an active beacon as described in claim 1, characterized in that, The reference point mentioned in S101 is a position on the bow and stern line of the ship near the radar antenna mounting point, and the line connecting the reference point and the radar antenna mounting point is parallel to the bow and stern line of the ship.

6. A ship radar calibration system for an active beacon, used to implement the ship radar calibration method for an active beacon according to any one of claims 1 to 5, characterized in that, The system includes: Differential RTK GPS base station is fixedly installed on a land-based or fixed platform that is in line with the radar to be calibrated; The differential RTK GPS mobile station can be detachably installed on the bow and stern reference points of the ship where the radar to be calibrated is located; An active beacon is installed at the same geographical location as the differential RTK GPS base station, and its antenna is located on the same pole or at the same installation point as the antenna of the differential RTK GPS base station. The data processor is communicatively connected to the differential RTK GPS base station and the differential RTK GPS mobile station, respectively, and is used to receive measurement data and perform the calculations described in S103; A comparator is used to compare the measured value output by the radar to be calibrated with the true value output by the data processor, and output the error amount; The display unit is used to display the error amount and the pass / fail determination result.

7. A ship radar calibration system for an active beacon as described in claim 6, characterized in that, The active beacon includes a programmable controller and an RF transmission module. The programmable controller controls the RF transmission module to operate according to a preset stop-transmission sequence, which includes at least two operating modes: continuous transmission mode and intermittent transmission mode.

8. A ship radar calibration system for an active beacon as described in claim 6, characterized in that, The differential RTK GPS base station and the differential RTK GPS mobile station transmit differential correction data in real time via a radio data link, enabling the mobile station to achieve centimeter-level positioning accuracy.

9. A ship radar calibration system for an active beacon as described in claim 6, characterized in that, The data processor has a built-in calibration truth data calculation table, which receives the following input data in tabular form: horizontal distance D1, azimuth α1, and elevation β1 measured by the differential RTK GPS base station, heading c provided by the heading device, and the three-dimensional coordinates X of the tested radar relative to the differential RTK GPS rover station. B Y B Z B The calculation table automatically outputs the true slant range R2, true elevation angle β2, true hull angle q2, and true azimuth angle α2 of the radar relative to the beacon.

10. A ship radar calibration system for an active beacon as described in claim 6, characterized in that, The differential RTK GPS base station and the active beacon are mounted together on a movable tripod or portable base, which has a leveling mechanism and a north dial for quick setup and orientation.

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