Magnetic declination measuring and calculating method based on target positioning system

Abstract

The invention discloses a magnetic declination measuring and calculating method and equipment based on a target positioning system, and relates to the field of multifunctional telescopes. The method comprises the following steps: firstly, inputting known target coordinates, adjusting equipment to aim at a target, measuring a measured distance, and recording a magnetic azimuth angle and a pitch angle; the distance is calculated according to the coordinates of the compass and the target, whether the difference between the distance and the actually measured distance is within the error range is judged, it is ensured that the target to be aimed is the target expected to be aimed, if yes, the true north included angle is calculated, then the actual magnetic declination angle is obtained, and the zero declination angle can be calculated in the pitching direction of the compass assembly to improve the elevation precision; and finally, obtaining a real-time true north included angle by using the actual magnetic declination and the real-time magnetic azimuth angle. According to the method, a geomagnetic field model is not used, the measured magnetic declination is real and accurate, errors can be reduced, and target positioning precision is improved. A known target needs to be in an intervisibility range, the coordinates of the known target can be obtained in various modes, and various geodetic coordinate solution back calculation formulas can be adopted for calculating the distance and the true north included angle.

Description

Technical Field

[0001] This proposal relates to the field of multifunctional telescopes, and specifically to a method for measuring magnetic declination based on a target positioning system. Background Art

[0002] A handheld target positioning system, also known as a multi-function telescope or multi-function handheld, consists of an imaging component, a rangefinder component, a compass component, a positioning component, a power supply component, a display component, a storage component, and a control component. The system's target positioning function is achieved through the combination of these components, enabling it to acquire the location data of the observed target.

[0003] When the device locates a target, it needs to use the true north angle for calculation, while the compass component in the device outputs the magnetic north angle. The difference between the true north angle and the magnetic north angle is called magnetic declination.

[0004] The magnetic declination used in the prior art is obtained by inputting geographic coordinates into a geomagnetic field model (such as WMM, IGRF, etc.) (i.e., obtained by looking up a table). However, in real-world applications, there may be deviations between the actual magnetic declination and the declination output by the geomagnetic field model. The reason is that the geomagnetic field model is modeled after observing the magnetic field conditions at multiple locations around the world, and cannot completely cover every area of ​​use. In addition, the actual geomagnetic field in the actual area of ​​use is often not completely consistent with the model due to human development, such as the presence of new buildings, vehicles, metals, and electronic equipment. At this time, the true north angle calculated by combining the deviated magnetic declination and the magnetic azimuth output by the compass component also has deviations, which in turn leads to deviations in the calculation of the target positioning coordinates, resulting in large errors in the target positioning data ultimately obtained by the device. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a more accurate method for calculating magnetic declination.

[0006] The specific technical solution of the present invention to solve the above technical problems is:

[0007] S1. Input the known target’s coordinates Q, such as latitude, longitude, and elevation.

[0008] S2. Adjust the device posture so that the optical axis of the ranging component is aimed at the known target, operate the ranging component to emit laser to measure the actual distance SL to the known target, and simultaneously record the magnetic azimuth ∠AM and pitch angle ∠B output by the compass component during measurement;

[0009] S3. The self-coordinate P obtained by the positioning component is combined with the known target coordinate Q, and the calculated distance DL between the two coordinates is calculated using the geodetic coordinate solution inverse calculation formula;

[0010] S4. Determine whether the difference between the calculated distance DL and the measured distance SL is within the error range. If so, it indicates that the known target is consistent with the aiming target, and proceed to calculate the true north angle in S5.

[0011] S5. Calculate the true north angle ∠AT between the own coordinate P and the known target coordinate Q using the geodetic coordinate solution inverse calculation formula;

[0012] S6. Subtract the magnetic azimuth ∠AM from the calculated true north angle ∠AT to obtain the actual magnetic declination ∠M = ∠AT - ∠AM. Record the actual magnetic declination ∠M in the device.

[0013] S7. Add the actual magnetic declination ∠M to the real-time magnetic azimuth ∠AM' of the compass component to obtain the real-time true north angle ∠AT' of the device.

[0014] During the above operation, when measuring the actual magnetic declination through a known target, the actual distance SL is first measured based on the laser rangefinder, and the distance DL is calculated by reverse calculation based on the coordinates of the known target and the coordinates of the device itself. Only when the difference between the calculated distance DL and the actual distance SL is checked to be within the set error, is it confirmed that there is no problem with the selection and observation of this known target. Then, based on the coordinates of the two places, the true north angle ∠AT between the two places is reverse calculated, and then combined with the magnetic azimuth ∠AM read by the compass component, the actual local magnetic declination ∠M is obtained. This avoids the introduction of errors caused by wrong target selection or improper instrument adjustment into the subsequent correction link, thereby ensuring the accuracy of subsequent measurements.

[0015] This solution calculates magnetic declination by subtracting the true north angle from the magnetic azimuth obtained from the actual magnetic environment. This calculation avoids the use of an idealized geomagnetic field model and remains completely consistent with the actual environment, resulting in a true and accurate declination. By incorporating the actual declination into the geodetic coordinate calculation formula comprised of the compass, positioning, and ranging components, the true coordinates of the measured target are obtained, minimizing the impact of declination errors and improving target positioning accuracy.

[0016] Furthermore, in step S4, if the difference between the calculated distance DL and the measured distance SL exceeds the set threshold, it means that the aiming target is incorrect or the aiming operation is incorrect, and it is necessary to return to S1, readjust the device posture to aim at the correct target, or reselect a known target and repeat the ranging operation to ensure that the aimed target is indeed the known target selected previously, so as to avoid mistaking the adjacent A for B and calculating the magnetic declination based on the measurement of A.

[0017] Furthermore, the known target needs to be able to be observed by the imaging component within the line of sight, and the latitude, longitude, and elevation of the target can be measured by historical data, maps, or third-party equipment (such as differential GPS, etc.);

[0018] Furthermore, in step S3, the calculation is specifically performed using one of the following calculation methods: Vincenty orthogonal calculation, Karney algorithm, geodetic thematic orthogonal calculation, geodesic calculation, great circle navigation formula, or small distance approximation. The Vincenty geodetic coordinate solution inverse calculation formula calculates the straight-line distance DL between two coordinates. The Vincenty geodetic coordinate solution method is a set of precise formulas for solving geodetic problems proposed by Austrian geodesist Thomas Vincenty in 1975. It is used to solve geodetic calculation problems such as the distance and azimuth between two points on the Earth's ellipsoid and is widely used in surveying and mapping, geographic information, navigation, and other fields.

[0019] Furthermore, in step 5), the pitch angle between the local coordinates P and the known target coordinates Q can be calculated using spatial geometry formulas. This difference is then compared with the pitch angle output by the compass assembly. The difference between the two is the installation zero deflection angle of the compass assembly in the device's pitch direction. This installation zero deflection angle is stored in the device and superimposed with the real-time pitch angle output by the compass assembly for calculation. Eliminating the installation zero deflection angle further improves the accuracy of the target coordinates' mid-elevation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of measuring and locating unknown targets for a handheld target positioning system;

[0021] Figure 2 Schematic diagram of the magnetic declination angle calculation method based on the target positioning system of the present invention;

[0022] Figure 3 Schematic diagram of calculating magnetic declination based on a known target according to the present invention. DETAILED DESCRIPTION

[0023] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0024] like Figure 1 As shown, to obtain the coordinate data Q' of the unknown target being aimed at, the device needs to use its own coordinates P, the true north angle ∠AT' and the pitch angle ∠B' between the unknown target being aimed at and itself, and the straight-line distance L' between the target and itself. The coordinates Q' of the unknown target being aimed at can be obtained by using the geodetic coordinate solution formula (such as Vincenty calculation, Karney algorithm, geodetic thematic calculation, geodesic calculation, great circle navigation formula or small distance approximation calculation method).

[0025] The true north angle ∠AT'=the magnetic azimuth ∠AM' output by the compass component + the actual magnetic declination ∠M. The actual magnetic declination ∠M is calculated by the following steps: Figure 2This is the flow chart for calculating the actual magnetic declination. Figure 3 This is a measurement diagram for calculating the actual magnetic declination.

[0026] 1) Identify a known target and input its latitude, longitude, elevation, and other coordinates Q into the device through the control component. The known target must be visible through the imaging component within the line of sight. The latitude, longitude, and elevation of the known target can be measured using historical data, maps, or third-party equipment (such as differential GPS).

[0027] 2) Adjust the device posture so that the optical axis of the ranging component is aimed at the known target, keep the device stable, operate the ranging component to emit laser to measure the measured straight-line distance SL between its own coordinates P and the known target, and simultaneously record the magnetic azimuth ∠AM and pitch angle ∠B output by the compass component;

[0028] 3) The device performs calculations internally, using the self-coordinates P obtained by the positioning component and the known target coordinates Q input, and uses the geodetic coordinate solution inverse calculation formula (such as Vincenty inverse calculation) to calculate the calculated straight-line distance DL between the two coordinates.

[0029] 4) Determine whether the error between the measured straight-line distance SL and the calculated straight-line distance DL meets the accuracy requirements of the ranging component, such as a distance error of ≤1m (within the effective range of the ranging component, generally 3-15km). If the distance error meets the error requirement, it indicates that the known target and the aiming target are consistent, and the next step is to calculate the true north angle. If they are inconsistent, it indicates that the aiming target is incorrect, and it is necessary to readjust the device attitude to aim at the correct target, or reselect the known target and repeat the ranging operation.

[0030] 5) Using the local coordinates P and the known target coordinates Q, calculate the true north angle ∠AT between the two using the geodetic coordinate solution inverse calculation formula (such as Vincenty inverse calculation).

[0031] 6) Subtract the magnetic azimuth ∠AM recorded in step 2) from the true north angle ∠AT to obtain the actual magnetic declination ∠M = ∠AT - ∠AM. Record the actual magnetic declination ∠M in the device.

[0032] 7) Add the actual magnetic declination ∠M to the magnetic azimuth ∠AM' output by the compass component to obtain the real-time true north angle ∠AT' between the device's coordinates and the target. When operating the ranging component, use the geodetic coordinate solution formula to calculate the coordinates of other unknown targets.

[0033] During the above operation, magnetic declination is calculated by subtracting the true north angle from the magnetic azimuth obtained from the actual magnetic environment. This means that an ideal geomagnetic field model is not used in the calculation and the calculation is completely consistent with the actual environment, resulting in a true and accurate magnetic declination. By incorporating the actual magnetic declination into the geodetic coordinate calculation formula composed of the compass, positioning, and ranging components, the true coordinates of the measured target are obtained, reducing the impact of magnetic declination errors and improving target positioning accuracy.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for calculating magnetic declination based on a target positioning system, characterized in that: The following steps are involved: S1. Input the known target's latitude, longitude, elevation and other coordinates Q; S2. Adjust the device posture so that the optical axis of the ranging component is aimed at the known target, operate the ranging component to emit laser to measure the actual measured distance SL to the known target, and simultaneously record the magnetic azimuth ∠AM and pitch angle ∠B output by the compass component; S3, S3, the own coordinates P obtained by the positioning component, combined with the known target coordinates Q, use the geodetic coordinate solution inverse calculation formula to calculate the calculated distance DL between the two coordinates; S4. Determine whether the difference between the calculated distance DL and the measured distance SL is within the error range. If so, it indicates that the known target is consistent with the aiming target, and proceed to calculate the true north angle in S5. S5. Calculate the true north angle ∠AT between the own coordinate P and the known target coordinate Q using the geodetic coordinate solution inverse calculation formula; S6. Subtract the recorded magnetic azimuth ∠AM from the calculated true north angle ∠AT to obtain the actual magnetic declination ∠M = ∠AT - ∠AM. Record the actual magnetic declination in the device. S7. Add the actual magnetic declination ∠M to the real-time magnetic azimuth ∠AM' of the compass component to obtain the real-time true north angle ∠AT' of the device.

2. The magnetic declination angle calculation method based on the target positioning system according to claim 1, characterized in that: In step S4, if there is any inconsistency, it means that the aiming target is wrong or the aiming operation is wrong, and it is necessary to return to S1, readjust the device posture to aim at the correct target, or reselect a known target and repeat the ranging operation.

3. The magnetic declination angle calculation method based on the target positioning system according to claim 2, characterized in that: The known target needs to be able to be observed by the imaging component within the line of sight, and the latitude, longitude and elevation of the target can be measured through historical data, maps, or third-party equipment (such as differential GPS, etc.).

4. The method for calculating magnetic declination based on a target positioning system according to any one of claims 1 to 3, wherein: In the step S3, specifically, the calculated distance DL between the known target and its own coordinates is calculated using one of Vincenty orthogonal calculation, Karney algorithm, geodetic thematic orthogonal calculation, geodesic calculation, great circle navigation formula or small distance approximate calculation method.

5. The method for calculating magnetic declination based on a target positioning system according to any one of claims 1 to 3, characterized in that: In step S5, the pitch angle between the local coordinate P and the known target coordinate Q is calculated using a spatial geometry formula and compared with the pitch angle output by the compass component. The difference between the two is the installation zero deflection angle of the compass component in the pitch direction of the device. The installation zero deflection angle is stored in the device and superimposed with the pitch angle output in real time by the compass component to participate in the calculation, thereby further improving the accuracy of obtaining the elevation of the target coordinates.

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