Method and system for measuring due north direction based on solar azimuth solution

Abstract

The invention relates to the technical field of measurement engineering, and particularly provides a true north direction measurement method and system based on solar azimuth solution, the true north direction measurement method is suitable for a measurement system equipped with a total station and a data processing terminal, and the measurement system is used for true north direction measurement. Comprising the following steps: manually positioning a solar facula by adopting the total station, and after the positioning is completed, enabling a horizontal dial of the total station to be in an observation locking state; calculating a solar azimuth angle at an observation moment on the basis of a sun position algorithm at a data processing terminal, wherein the observation moment is the observation time recorded when the total station completes positioning; and after the horizontal dial reversely rotates the dial reading by the degree of the solar azimuth angle, determining that the pointing direction of the collimation axis of the total station is the true north reference. According to the method, high-precision measurement of the geographical due north direction is realized through solar azimuth calculation, and the precision requirement of precise engineering such as a concentrating solar photo-thermal project on due north reference is met.

Description

A method and system for determining true north based on solar azimuth calculation Technical Field

[0001] This application relates to the field of measurement engineering technology, and in particular to a method and system for determining true north based on solar azimuth calculation. Background Technology

[0002] Concentrated Solar Power (CSP) technology, as one of the core directions of renewable energy utilization, concentrates solar radiation energy into heat-absorbing devices through equipment such as heliostats, trough concentrators, and dish concentrators, realizing the conversion of light energy into heat energy. Its energy conversion efficiency directly depends on the installation accuracy of the concentrator equipment. In CSP project engineering practice, the tracking and pointing accuracy of heliostats and the azimuth calibration of the concentrator's reflector surface are based on geographic true north. The industry generally requires that the installation angle error of such equipment be controlled within 1 mrad (approximately 0.0573°), which places extremely high demands on the accuracy of determining the true north reference.

[0003] Among the commonly used north-pointing methods in existing engineering fields, astronomical observation relies on favorable weather conditions, and the operation process is complex, requiring professional astronomical surveyors and having a long data processing cycle, making it difficult to meet the needs of rapid deployment and efficient construction on CSP project sites. Magnetic compass methods are easily affected by geomagnetic interference, and large construction machinery, high-voltage transmission lines, and metal structures around CSP project sites can all cause magnetic field distortion, resulting in a significant decrease in positioning accuracy and failing to meet the precision installation requirement of 1 mrad. The gyro theodolite method is not economically viable when applied on a large scale in CSP projects.

[0004] With the development of solar trajectory calculation technology, the Solar Position Algorithm (SPA) has become a mature tool for accurately calculating the solar azimuth and altitude angles. However, currently, the SPA algorithm is only used as an independent software calculation model for solar trajectory simulation and has not yet been deeply integrated with the optical measurement system of a total station. On the one hand, the total station lacks built-in support for the SPA algorithm and cannot directly call the theoretical solar azimuth angle output by the algorithm as a measurement reference. On the other hand, the algorithm system errors, total station leveling errors, aiming errors, and other errors that exist in the process of combining the two have not been systematically analyzed and corrected by a model, resulting in the inability to form a complete solution from theoretical calculation to field measurement to precise positioning. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method and system for determining true north based on solar azimuth angle calculation. By calculating the solar azimuth angle, it achieves high-precision determination of geographic true north, meeting the accuracy requirements of true north reference for precision engineering projects such as concentrated solar thermal projects.

[0006] To achieve the objectives of this application, the following technical solution is provided: Firstly, this application provides a method for determining true north based on solar azimuth angle calculation, applicable to a measurement system equipped with a total station and a data processing terminal. The measurement system is used for determining true north. The method includes: manually locating a solar spot using the total station, and after completing the location, locking the horizontal circle of the total station in an observation lock state; calculating the solar azimuth angle at the observation time using the data processing terminal based on a solar position algorithm; the observation time being the observation time recorded when the total station completes the location; and after rotating the horizontal circle reading in the opposite direction by the degree of the solar azimuth angle, determining the direction of the total station's line of sight as the true north reference.

[0007] A further improvement of the present invention is that the data processing terminal is configured with the solar position algorithm; the step of calculating the solar azimuth angle at the observation time based on the solar position algorithm at the data processing terminal includes: inputting the observation time under Coordinated Universal Time, the geodetic latitude and longitude of the station, and the local real-time air pressure and real-time temperature values ​​into the calculation program of the solar position algorithm to obtain the solar azimuth angle at the observation time.

[0008] A further improvement of the present invention is that a planar target ring perpendicular to the optical axis of the objective lens is installed at a distance greater than or equal to a preset threshold from the rear end of the total station. The manual positioning of the solar spot using the total station includes: calibrating and compensating the total station for the zero point error of the horizontal circle, the standard deviation of the vertical circle, and the error of the horizontal axis; after completing the calibration and compensation, adjusting the total station so that the imaging spot formed by the sun after filtering falls into the target area of ​​the planar target ring, thereby achieving the positioning of the imaging spot.

[0009] A further improvement of the present invention is that the surface of the planar target ring is etched with a concentric circle structure based on minimum interval, and the target area refers to the annular area formed by any two adjacent concentric circles with the minimum interval in the concentric circle structure of the planar target ring.

[0010] A further improvement of the present invention is that the preset threshold is 600mm and the minimum interval is 0.5mm.

[0011] A further improvement of the present invention is that the planar target ring is made of a material with a low coefficient of thermal expansion, which is either microcrystalline glass or fused silica.

[0012] A further improvement of the present invention is that the observation time is the observation time based on the coordinated time.

[0013] A further improvement of the present invention is that the angle measurement accuracy of the total station is better than 5″.

[0014] A further improvement of this invention is that the formula for calculating the total positioning error is: In the formula, This represents the total positioning error; This refers to the systematic error of the SPA algorithm. This refers to the angle measurement error of the total station; This refers to the target ring positioning error. ,in, For target ring resolution. The objective lens focal length is greater than or equal to 600 mm.

[0015] Secondly, this application provides a system for determining true north based on solar azimuth angle calculation, used to implement the method for determining true north based on solar azimuth angle calculation as described above, comprising: a spot positioning module, used to manually position a solar spot using the total station, and after positioning is completed, to lock the horizontal circle of the total station in an observation lock state; an azimuth angle calculation module, used to calculate the solar azimuth angle at the observation time based on a solar position algorithm at a data processing terminal; the observation time is the observation time recorded when the total station completes positioning; and a true north determination module, used to determine the direction of the line of sight of the total station as the true north reference after the horizontal circle rotates the reading of the solar azimuth angle in the opposite direction.

[0016] Compared with existing technologies, the present invention has the following advantages: The method for determining true north based on solar azimuth angle calculation provided in this application involves manually locating the solar spot using a total station. After positioning, the horizontal circle of the total station is locked in observation mode. Then, the solar azimuth angle at the observation time is calculated using a solar position algorithm at the data processing terminal. This observation time is the time recorded when the total station completes positioning. Finally, after rotating the horizontal circle reading in the opposite direction by the degree of the solar azimuth angle, the direction of the total station's line of sight is determined as the true north reference. This method achieves high-precision positioning using conventional equipment improvements, significantly reducing equipment investment and human aiming errors. It also improves operational consistency and repeatability, offering high reliability, sufficient accuracy margin, and suitability for rapid on-site deployment. Attached Figure Description

[0017] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. Figure 1 is a schematic flowchart of an optional method for determining the due north direction based on solar azimuth angle calculation provided by an embodiment of this application. Figure 2 is a schematic diagram of the positioning structure of the solar imaging spot on the planar target ring provided by an embodiment of this application. Figure 3 is a schematic diagram of the structure of adding a planar target ring to the rear end of the total station eyepiece provided by an embodiment of this application.

[0018] Attached image labels: 1. Sun; 2. Total station; 3. Eyepiece; 4. Opaque light tube; 5. Planar target ring. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this application, unless otherwise stated, "multiple" means two or more.

[0021] In CSP project engineering practice, the installation accuracy of equipment such as heliostats and concentrators directly affects the light energy collection efficiency. The industry typically requires an installation angle error of less than 1 mrad (approximately 0.0573°), which places extremely high demands on the determination of true north. Traditionally, commonly used methods for determining true north include astronomical orientation, magnetic compass, and gyro-theodolite methods. Astronomical orientation, a classic method, utilizes the known motion patterns of celestial bodies such as stars or the sun, combined with the station's location and precise time information, to calculate the azimuth angle of the celestial body relative to a point on the ground, thus deriving geographic true north. This method has unique advantages in passive, interference-resistant scenarios, and there are already some application examples using sundials or photoelectric tracking devices for solar azimuth measurement. The magnetic compass method achieves azimuth positioning based on the Earth's magnetic field pointing to magnetic north, and then converts to true north through magnetic declination correction. The gyro-theodolite method utilizes the stability of the gyroscope rotor's rotation axis to detect the ground... The angular velocity component of the sphere's rotation determines true north, offering a high degree of automation and on-site adaptability. Traditional methods for determining true north have the following limitations: 1) Astronomical observation method: relies on favorable weather conditions, is complex to operate, and is unsuitable for rapid deployment on engineering sites; 2) Magnetic compass method: is susceptible to geomagnetic interference and has limited accuracy (usually >0.5°); large construction machinery, high-voltage transmission lines, and metal structures around the CSP project site can all cause magnetic field distortion, significantly reducing positioning accuracy; 3) Gyro theodolite method: expensive equipment, cumbersome operation, high maintenance costs, and difficult to promote and popularize; 4) Conventional total station method: lacks astronomical reference, and its accuracy is insufficient to meet the requirements of concentrated solar power projects.

[0022] In the existing technology, although the solar position algorithm SPA has been used for solar trajectory calculation, it has not yet been deeply integrated with the total station optical system, and a complete error analysis model has not been established to form a high-precision, quantifiable north-direction positioning solution.

[0023] To address the aforementioned technical problems, the present invention proposes the following technical solutions and corresponding embodiments.

[0024] The technical solution of the present invention is described below with reference to the embodiments shown in Figures 1 to 3: Embodiment 1 A method for determining the due north direction based on the calculation of the solar azimuth angle according to an embodiment of this application, as shown in Figure 1, includes the following steps S101 to S103: Step S101: Manually locate the solar spot using the total station, and after completing the positioning, put the horizontal circle of the total station in the observation lock state.

[0025] In this embodiment, the total station is manually adjusted so that its lens is precisely aligned with the sun, i.e., the center of the sunspot is found, and the line of sight is exactly pointing towards the sun. After alignment, the horizontal circle of the total station is locked (i.e., the observation is locked). In this embodiment, to match the high precision of the SPA algorithm, a high-precision total station with an angular measurement accuracy better than 5″ (i.e., 0.0014°) is required.

[0026] In this embodiment, the total station undergoes optical modification. A planar target ring perpendicular to the objective lens optical axis is added to the rear end of the total station eyepiece. Specifically, this planar target ring is made of a low-expansion-coefficient material, with its surface etched with a precision concentric circle structure with a minimum spacing of 0.5 mm. This planar target ring is installed at a position no less than 600 mm from the rear end of the total station eyepiece. This transforms the subjective operation of "aligning with the center of the sun" into an objective judgment mechanism of "the imaging spot falling within a specific concentric ring," thereby reducing human aiming errors and standardizing the alignment operation of the solar imaging spot. This enables the total station of this embodiment to possess a low-cost, easy-to-operate, and accurate solar spot interpretation capability.

[0027] The 600mm installation distance from the planar target ring to the rear end of the total station eyepiece ensures a sufficiently long optical lever to amplify minute angular changes and improve the ability of the human eye or image recognition system to distinguish the position of the light spot.

[0028] As a feasible implementation method, the operator locates the sun using a total station telescope and fine-tunes it so that the image spot formed by the sun after passing through the objective lens and filter precisely falls within the target area on the planar target ring. Once the image spot stabilizes within the target area, the position of the total station's optical tube is immediately locked (i.e., the horizontal circle reading of the total station is locked at this time (i.e., the observation azimuth angle reading of the sun in the instrument coordinate system)). Here, the synchronously recorded observation time must be accurate to the second to minimize time synchronization errors. In this embodiment, the target area refers to the annular area formed by any two adjacent concentric circles with a 0.5mm interval in the concentric circle structure of the planar target ring, that is, fine-tuning until the outer edge of the sun's image spot completely falls within the annular area formed by two adjacent circles spaced 0.5mm apart, as shown by the annular area where the bold line is located in Figure 2.

[0029] As a feasible implementation, the planar target ring can be made of a material with a low coefficient of thermal expansion, such as microcrystalline glass or fused silica. Referring to FIG3, the planar target ring of this embodiment can be fixed to the rear end of the eyepiece via an extension tube.

[0030] In this embodiment of the application, before manually locating the sunspot using a total station, the total station needs to be calibrated for the zero point error of the horizontal circle to eliminate the initial deviation of the circle; compensate for the vertical circle index difference to correct the vertical angle measurement error; and calibrate the horizontal axis error of the total station to ensure the perpendicularity of the horizontal axis to the vertical axis, thereby eliminating or reducing the systematic error of the total station itself and ensuring the initial reliability of the angle observation value.

[0031] Step S102: The data processing terminal calculates the solar azimuth angle at the observation time based on the solar position algorithm; the observation time is the observation time recorded when the total station completes positioning.

[0032] In this embodiment, the solar azimuth angle at the observation time is accurately calculated using a data processing terminal. The data processing terminal is equipped with a high-precision solar position algorithm. By inputting the observation time, observation location (station latitude and longitude information), local air pressure, and temperature into the data processing terminal, the solar position algorithm's dedicated program automatically calculates the solar azimuth angle (true azimuth angle) at the observation time using a celestial motion model and atmospheric refraction correction formula. The high-precision solar position algorithm in this embodiment uses the SPA released by NREL (National Renewable Energy Laboratory), which has the highest accuracy among various solar position positioning algorithms. It has been developed into a dedicated calculation interface, with a calculation accuracy within ±0.0003°, providing a reliable astronomical benchmark for direction calculation.

[0033] In this embodiment of the application, the observation time is the local observation time accurate to milliseconds, which is converted to UTC (Universal Time Coordinated) time within the SPA algorithm program; the geodetic latitude and longitude of the station can be determined based on the WGS-84 coordinate system.

[0034] As a feasible implementation method, after obtaining the solar azimuth angle from the data processing terminal, the solar azimuth angle is manually recorded.

[0035] Step S103: After rotating the horizontal circle reading in the opposite direction by the degree of the solar azimuth angle, determine the direction of the line of sight of the total station as the true north reference.

[0036] In this embodiment, after calculating the solar azimuth angle using the solar position algorithm, the horizontal circle reading is manually rotated. The total station's horizontal circle reading, which is in the observation-locked state in step S101, is then rotated in the opposite direction to the solar azimuth angle calculated in step S102. At this point, the total station's line of sight points to true north, which can be used as a reference for CSP project positioning. Compared to directly reading the solar azimuth angle and then manually calculating north, this feature provides a direct, intuitive, and error-proof operation path, improving engineering practicality.

[0037] For example, if the calculated solar azimuth angle is 80°, and the total station's horizontal circle is locked to the sun, the circle reading is 120°. Then, rotate it 80° in the opposite direction, and the circle reading becomes 120° - 80° = 40°. At this time, the lens direction corresponding to 40° is due north.

[0038] Therefore, this embodiment integrates a high-precision solar position algorithm with a total station hardware system to construct a high-precision north direction determination scheme that can be deployed on-site. By defining error sources and control measures, the operation process is standardized, and different personnel can obtain consistent results. This achieves a high-precision, low-cost, and standardized operation process, enabling rapid on-site deployment of high-precision north direction determination.

[0039] The method for determining true north based on solar azimuth angle calculation provided in this embodiment involves manually locating the solar spot using a total station. After positioning, the horizontal circle of the total station is locked in observation mode. Then, the solar azimuth angle at the observation time is calculated based on the solar position algorithm at the data processing terminal. This observation time is the observation time recorded when the total station completes positioning. Finally, after rotating the horizontal circle reading in the opposite direction by the degree of solar azimuth angle, the direction of the line of sight of the total station is determined as the true north reference. This method achieves high-precision positioning by improving conventional equipment, significantly reducing equipment investment, and significantly reducing human aiming errors. It also improves operational consistency and repeatability, has high reliability, and sufficient accuracy margin, making it suitable for rapid on-site deployment.

[0040] Example 2 Based on the above examples, this example also provides a method for determining true north based on solar azimuth angle calculation. The technical solution of this example includes two parts: system configuration and observation calculation.

[0041] The system configuration includes software preparation, hardware selection, and hardware optics modification. Specifically, in terms of software preparation, this embodiment develops a dedicated calculation program based on the high-precision solar position algorithm (SPA). The core input parameters of this program include: the precise observation time based on local time, the geodetic latitude and longitude of the station, and local air pressure and temperature. The program solves a series of celestial mechanical equations to output the true azimuth and altitude angles of the sun at the observation time, with a calculation accuracy within ±0.0003°, providing a reliable astronomical benchmark for direction calculation. In terms of hardware selection, to match the high precision of the SPA algorithm, this embodiment requires the selection of a total station with an angle measurement accuracy better than 5″. The internal encoder and shaft stability of such a total station ensure the accuracy and repeatability of angle readings, which is key to reducing instrument errors. In terms of hardware optics modification, this embodiment adds a [device name missing] at a position no less than 600mm behind the total station eyepiece. A planar target ring perpendicular to the objective lens's optical axis. Referring to Figure 2, this target ring is made of a material with a low coefficient of thermal expansion (such as microcrystalline glass), and its surface is etched with a precise concentric circle structure with a minimum spacing of 0.5 mm. The purpose of this design is to transform the subjective operation of "aligning with the center of the sun" into the objective judgment of "the imaging spot falling within a specific concentric circle." The 600 mm mounting distance ensures a sufficiently long optical lever, so that a tiny linear displacement (0.5 mm) on the target ring corresponds to a very small angle in the field of view, thus significantly reducing aiming error.

[0042] During the observation and calculation, the method for determining true north based on solar azimuth angle calculation in this embodiment is as follows: (I) First, before observation, the total station undergoes a rigorous initial calibration; this includes, but is not limited to, using the built-in program to detect and compensate for the zero-point error of the horizontal circle, the vertical circle index difference, and the horizontal axis error. This step aims to eliminate or reduce the instrument's own systematic errors and ensure the initial reliability of the angle observation values. (II) The operator uses the total station telescope to locate the sun and, through fine adjustments, ensures that the image spot formed by the sun after passing through the objective lens and filter precisely falls within the annular area formed by two adjacent 0.5mm-spaced concentric circles on the plane target ring after hardware optical modification; once the spot stabilizes within the preset range, the locking operation is immediately triggered: the total station's horizontal circle reading is kept in the observation locked state (i.e., the position of the total station's optical tube is manually locked), and the observation time is recorded synchronously. The recorded observation time must be accurate to the second level to minimize time synchronization errors. (III) Input the station coordinates (geodetic latitude and longitude of the station, based on the WGS-84 coordinate system), environmental parameters (local air pressure and temperature), and the observation time obtained above into the SPA calculation program to calculate the accurate solar azimuth. (IV) Manually rotate the horizontal circle reading of the total station, which is in the observation locked state, in the opposite direction to the reading A. This reading A is the solar azimuth value obtained by the SPA calculation above. At this time, lock the horizontal brake screw of the total station again. The direction indicated by the line of sight is the desired high-precision true north reference. This operation is mathematically equivalent to subtracting the azimuth from the solar direction vector (the direction in which the total station's optical tube points at the time of spot positioning and recording, which is also the actual measured solar position of the total station at the recording time), so that the line of sight of the eyepiece points to geographic true north.

[0043] In this embodiment, a complete error analysis and synthesis model is constructed for the north direction determination method of this embodiment, wherein the total positioning error is calculated using the following formula: In the formula, This represents the total positioning error; This refers to the systematic error of the SPA algorithm. This refers to the angle measurement error of the total station, i.e., the nominal accuracy of the instrument; This refers to the target ring positioning error. ,in, For target ring resolution. The objective lens focal length is not less than 600mm.

[0044] The error analysis and synthesis model in this embodiment can pre-estimate the positioning accuracy, ensuring that the total positioning error of the north direction determination method in this embodiment is less than 0.0513°, meeting the accuracy requirement of 1 mrad (0.0573°) for concentrated solar thermal projects. In this embodiment, the error can be further reduced by increasing the installation distance of the eyepiece rear end plane target ring.

[0045] Example 3 Based on the above examples, this example provides a method for determining true north based on solar azimuth angle calculation applied to CSP project sites. The equipment configuration includes a total station (Leica TS16 (angle measurement accuracy 2″)), a plane target ring (custom heat-resistant glass, concentric circle spacing 0.5mm), and a SPA calculation program (a small computer program integrating GPS / BeiDou positioning and network time synchronization functions).

[0046] During on-site operation, 1) Station setup: Center position of the power station, coordinates (N37.37°, E97.37°); 2) Environmental parameters: Air temperature 25℃, air pressure 905hPa, humidity 40%; 3) Observation time: Local time 10:30:25; 4) Solar imaging: The solar spot is stably located within the ring formed by two adjacent concentric circles. During data processing and direction determination, the observation parameters were input into the SPA calculation node, yielding a solar azimuth angle of 125.3648°. The total station was then rotated 125.3648° in the reverse direction to lock onto true north, thus establishing a reference point: A laser pointer was set to mark the direction, serving as the overall installation reference point.

[0047] In the process of quantitative analysis of each error source, =±0.0003° (systematic error) =±0.0006° (instrument nominal accuracy). =±0.0477° (optical resolution); therefore, the total error is calculated as follows: Verification showed that the directional consistency error was <0.05° in three consecutive repeated measurements, meaning that each measurement recorded a true north point, and the horizontal angle difference between the three points was <0.05°, which met the heliostat's 0.0573° installation accuracy requirement.

[0048] The method for determining true north based on solar azimuth angle calculation applied in this embodiment to CSP project sites saves 400,000 yuan in costs and increases work efficiency by 3 times compared to the gyro theodolite solution.

[0049] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0050] The units described in the embodiments of the present invention can be implemented in software or hardware, and the described units can also be located in a processor. The names of these units do not necessarily limit the specific unit itself.

[0051] It should be noted that although several modules or units of the device for performing actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0052] In the several embodiments provided in this application, it should be understood that the disclosed systems, modules, and methods can be implemented in other ways. For example, the module embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between modules or units, and may be electrical, mechanical, or other forms.

[0053] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. This application is not limited to the exact structures described above and illustrated in the accompanying drawings, and it should not be considered that the specific implementation of this application is limited to these descriptions. For those skilled in the art, various changes and modifications made without departing from the concept of this application should be considered to fall within the protection scope of this application.

Claims

1. A method for determining true north based on solar azimuth calculation, characterized in that, A measurement system equipped with a total station and a data processing terminal is used to determine true north. The method includes: manually locating a solar spot using the total station, and locking the horizontal circle of the total station after locating the spot; calculating the solar azimuth angle at the observation time using the data processing terminal based on a solar position algorithm; the observation time being the observation time recorded when the total station completes locating the spot; and determining the direction of the line of sight of the total station as the true north reference after rotating the horizontal circle reading in the opposite direction by the degree of the solar azimuth angle.

2. The method for determining true north based on solar azimuth angle calculation according to claim 1, characterized in that, The data processing terminal is equipped with the solar position algorithm; the step of calculating the solar azimuth angle at the observation time based on the solar position algorithm in the data processing terminal includes: inputting the observation time under Coordinated Universal Time, the geodetic latitude and longitude of the station, and the local real-time air pressure and real-time temperature values ​​into the calculation program of the solar position algorithm to obtain the solar azimuth angle at the observation time.

3. The method for determining true north based on solar azimuth angle calculation according to claim 2, wherein a planar target ring perpendicular to the objective lens optical axis is installed at a distance greater than or equal to a preset threshold from the rear end of the eyepiece of the total station, characterized in that... The method of manually locating the solar spot using the total station includes: calibrating and compensating the total station for the horizontal circle zero point error, vertical circle standard deviation, and horizontal axis error; after completing the calibration and compensation, adjusting the total station so that the image spot formed by the sun after filtering falls into the target area of ​​the planar target ring, thereby achieving the positioning of the image spot.

4. The method for determining true north based on solar azimuth angle calculation according to claim 3, characterized in that, The planar target ring surface is etched with a concentric circle structure based on minimum spacing, and the target region is the annular region formed by any two adjacent concentric circles with the minimum spacing in the concentric circle structure of the planar target ring.

5. The method for determining true north based on solar azimuth angle calculation according to claim 4, characterized in that, The preset threshold is 600mm; the minimum interval is 0.5mm.

6. The method for determining true north based on solar azimuth angle calculation according to claim 4, characterized in that, The planar target ring is made of a material with a low coefficient of thermal expansion, which can be either microcrystalline glass or fused silica.

7. The method for determining true north based on solar azimuth angle calculation according to claim 1, characterized in that, The observation time is based on Coordinated Universal Time (UTC).

8. The method for determining true north based on solar azimuth angle calculation according to claim 1, characterized in that, The total station has an angle measurement accuracy better than 5″.

9. A method for determining true north based on solar azimuth calculation according to any one of claims 1-8, characterized in that, Also includes: The formula for calculating the total positioning error is: In the formula, This represents the total positioning error; This refers to the systematic error of the SPA algorithm. This refers to the angle measurement error of the total station; This refers to the target ring positioning error. ,in, For target ring resolution. The objective lens focal length is greater than or equal to 600 mm.

10. A system for determining true north based on solar azimuth angle calculation, used to implement the method for determining true north based on solar azimuth angle calculation as described in any one of claims 1-9, characterized in that, include: The solar spot positioning module is used to manually position the solar spot using the total station, and after positioning is completed, to lock the horizontal circle of the total station in the observation lock state. An azimuth angle calculation module is used to calculate the solar azimuth angle at the observation time based on a solar position algorithm at the data processing terminal; the observation time is the observation time recorded when the total station completes positioning. The north determination module is used to determine the direction of the line of sight of the total station as the north reference after the horizontal circle rotates the reading of the circle in the opposite direction by the degree of the solar azimuth angle.

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