A method and device for calibrating the normal direction of an ellipsoid based on GNSS technology

Abstract

The present invention relates to a method and device for calibrating the normal direction of an ellipsoid based on GNSS technology, and belongs to the technical field of measuring the normal direction of the earth's reference ellipsoid surface; it is composed of an equipment tripod, a GNSS antenna array, a GNSS dual-antenna receiver, and an electronic handbook; the GNSS antenna array includes an upper antenna and a lower antenna, the upper antenna and the lower antenna are connected to each other through an antenna tube, the upper antenna and the lower antenna are connected to the GNSS dual-antenna receiver, and the GNSS dual-antenna receiver is connected to the electronic handbook. The beneficial effect is that the dual-antenna GNSS receiver is directly used to measure the normal direction of the approaching ellipsoid, the measurement accuracy is high, the measurement method is simple and direct, and the result can be solved in real time; the efficiency and accuracy are greatly improved compared with the traditional method, and at the same time, the measurement device is simple and compact, and the measurement operation can be completed by one person, which greatly saves the relevant labor costs.

Description

Technical Field

[0001] The invention relates to a method and a device for calibrating the normal direction of an ellipsoid based on the GNSS technology, and belongs to the technical field of measuring the normal direction of the earth reference ellipsoid surface. Background Art

[0002] With the increasing maturity of satellite geodetic technology, GNSS related industries have also been vigorously developed. As the basic reference surface of satellite geodetic related technologies, the calibration and measurement of relevant parameters of the earth reference ellipsoid have become increasingly important. Since the earth reference ellipsoid is extremely large, in a certain local area, the main parameter that can be actually measured is the normal direction of the earth reference ellipsoid at a certain point. At present, there are no instruments and equipment specifically for measuring this parameter at home and abroad. The equipment that is slightly closer to it is a plumb bob, which is an instrument that uses optical and gravity means to transmit the direction of the plumb bob. At present, the known plumb bob uses a visible laser that coincides with the sighting axis to generate an upward plumb line, which is used to measure small deviations relative to the plumb line and to position and transmit the plumb line. Plumb bobs are widely used in the construction and installation of high-rise buildings, towers, chimneys, elevators, and large-scale institutional equipment. Plumb bobs can provide a plumb base line with extremely high accuracy, which can be used for various construction measurements or special engineering measurements and deformation measurements. The plumb line is mainly used in high-rise buildings. Generally, a small hole is reserved in the middle of each floor, and the control point is led to the downstairs. The plumb line is set up, strictly leveled, and the laser is turned on, so that it is convenient to build a station and lay out lines on the floor. However, the plumb line is mainly used to transmit the plumb direction, which is not completely equivalent to the normal direction of the earth's reference ellipsoid. The angle u between the plumb line and the ellipsoid surface normal at the same measuring station is the vertical deviation. u is usually represented by the north-south component ζ and the east-west component η. There are not many studies on the joint solution of the plumb line and GNSS in the industry. For example, the process of GPS measurement and verticality calculation mentioned in "Discussion on the Verticality Detection Method of High-rise Buildings" also provides a good reference idea for the present invention, but the general GPS equipment and solution software used in the article are used for verticality calculation. Its operation steps are cumbersome, data processing is complex, and timeliness is not high. The same problem also appears in "CN102080960A GPS-based Super High-rise Building Verticality Measurement and Control Method". It can be seen that the demand for using GNSS technology for verticality and normal measurement objectively exists and has engineering application value, and there is a large room for optimization.

[0003] Combining many years of R&D and engineering experience in the field of GNSS and geodesy, the inventor has innovatively proposed a method and device for calibrating the normal direction of the earth reference ellipsoid based on GNSS technology, hoping to solve the problem of measuring and calibrating the normal direction of the earth reference ellipsoid in one fell swoop, and provide convenience for subsequent GNSS-based engineering applications and theoretical research in the field of satellite geodesy. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for calibrating the normal direction of an ellipsoid based on GNSS technology, so as to overcome the deficiencies in the prior art.

[0005] The present invention is implemented by the following technical solution, which specifically comprises the following steps:

[0006] Step 1.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration;

[0007] Step 1.2: Roughly level the calibration equipment tripod, including leveling the total station tripod and the base connector;

[0008] Step 1.3: Install and calibrate the GNSS antenna array, perform horizontal north-seeking measurement, and rotate the base connector according to the true north direction;

[0009] Step 1.4: Vertically erect the GNSS antenna array and use the locking buckle to fix the GNSS antenna array so that it is perpendicular to the base connector;

[0010] Step 1.5: Start the GNSS dual-antenna receiver, complete satellite search and initial positioning, and calculate the baseline vectors of the upper antenna and the lower antenna in the GNSS antenna array;

[0011] Step 1.6, using the phase center of the lower antenna in the GNSS antenna array as the starting reference, convert the phase center position of the upper antenna in the GNSS antenna array into ENU coordinates, i.e., “northeast sky” coordinates, in real time;

[0012] Step 1.7: Calibrate the embedded program in the electronic notebook, perform mean and standard deviation calculations on the baseline solution results of the GNSS dual-antenna receiver within the set time range. When the standard deviations of the three directions of ENU converge to the tolerance range within the specified time, proceed to the next step; otherwise, a prompt will pop up, requiring the surveyor to check the surrounding environment to avoid obvious obstruction of the GNSS antenna or being too close to the electromagnetic interference source;

[0013] Step 1.8, calibrate the U value of the electronic handbook. The U value is based on the phase center of one of the antennas of the GNSS dual-antenna receiver as the reference point. The baseline vector of the line connecting the phase center of the other antenna and the reference point is projected in the normal direction of the reference ellipsoid. After stable convergence, the judgment is made. If the deviation between the U value and the antenna tube length is less than the specified value, proceed to the next step; if not, the surveyor is prompted to re-level the equipment tripod;

[0014] Step 1.9, compare the EN value, i.e. the northeast value, in the embedded program. If the E value is larger, it will prompt you to adjust the two fine adjustment knobs perpendicular to the true north direction first to make the E value smaller than the specified value, and then adjust the single fine adjustment knob parallel to the true north direction to make the N value smaller than the specified value;

[0015] Step 1.10: At this time, if the U value is less than the set value, the adjustment and calibration operation is completed, and the antenna tube points to the direction of the reference ellipsoid normal. If not, return to step 1.3 and repeat the operation.

[0016] The present invention also includes a method for calibrating the azimuth and elevation angles of a GNSS dual-antenna receiver:

[0017] Step 2.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration;

[0018] Step 2.2: Roughly level the calibration equipment tripod, including leveling the total station tripod and the base connector;

[0019] Step 2.3: Install and calibrate the GNSS antenna array, perform horizontal north-seeking measurement, and rotate and place the leveling base connector according to the true north direction;

[0020] Step 2.4: Vertically erect the GNSS antenna array and use the locking buckle to make it perpendicular to the leveled base connector. At this time, read the pitch angle in the electronic handbook. If the value is within the set value range, that is, 89.5° to 90°, proceed to step 2.5; otherwise, repeat steps 2.2-2.3;

[0021] Step 2.5, adjust the east-west fine adjustment knob so that the azimuth reading in the electronic handbook is within the range of 355.5° to 360° and 0° to 0.5°;

[0022] Step 2.6. Observe the pitch angle reading in the electronic handbook. If the value is within the set value range, that is, 89.5° to 90°, the calibration step is completed. If not, fine-tune the north-south fine-tuning knob to bring the pitch angle value back to the set value range.

[0023] The device of the present invention is composed of an equipment tripod, a GNSS antenna array, a GNSS dual-antenna receiver and an electronic handbook;

[0024] The equipment tripod includes a base connector arranged on the total station tripod; and also includes a 90° flip bracket arranged on the base connector, and the GNSS antenna array is hingedly connected to the 90° flip bracket; a locking buckle is also fixedly arranged in the vertical direction of the 90° flip bracket, and the GNSS antenna array is limited by the locking buckle;

[0025] The GNSS antenna array includes an upper antenna and a lower antenna, and the upper antenna and the lower antenna are connected to each other through an antenna tube.

[0026] The upper antenna and the lower antenna are connected to the GNSS dual-antenna receiver via a data cable.

[0027] The GNSS dual-antenna receiver is connected to the electronic handbook via a data cable.

[0028] The locking buckle is an opening and closing sleeve of a two-half structure, and two hanging ears are arranged opposite to each other at the opening and closing part of the outer wall of the opening and closing sleeve, and are fixed by a pin penetrating through the through hole on the hanging ear.

[0029] The electronic notebook is a hardware device required to run the embedded program, and uses a general-purpose portable PC, a reinforced tablet computer or an iPad.

[0030] The beneficial effects of the present invention are that a dual-antenna GNSS receiver is directly used to measure the direction of the approximate ellipsoid normal, the measurement accuracy is high, the measurement method is simple and direct, and the results can be solved in real time; the efficiency and accuracy are greatly improved compared with the traditional method, and at the same time, the measuring device is simple and small, and the measurement operation can be completed by one person, which greatly saves the relevant labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a structural diagram of the present invention.

[0032] Figure 2 This is a structural diagram of the equipment tripod and GNSS antenna array.

[0033] Figure 3 Schematic diagram of baseline vector.

[0034] Figure 4 Flowchart for baseline data processing. DETAILED DESCRIPTION

[0035] The following is combined with Figures 1 to 4 To further illustrate the preferred embodiment of the present invention, the device of the present invention is composed of a device stand 1, a GNSS antenna array 2, a GNSS dual-antenna receiver 4 and an electronic handbook 4;

[0036] The equipment tripod 1 includes a base connector 12 arranged on a total station tripod 11; and also includes a 90° flip bracket 13 arranged on the base connector 12, and the GNSS antenna array 2 is hingedly connected to the 90° flip bracket 13; a locking buckle 14 is also fixedly arranged in the vertical direction of the 90° flip bracket 13, and the GNSS antenna array 2 is limited by the locking buckle 14;

[0037] The GNSS antenna array 2 includes an upper antenna 21 and a lower antenna 22, and the upper antenna 21 and the lower antenna 22 are connected to each other through an antenna tube 23.

[0038] The upper antenna 22 and the lower antenna 23 are connected to the GNSS dual-antenna receiver 3 via a data line.

[0039] The GNSS dual-antenna receiver 3 is connected to the electronic handbook 4 .

[0040] The locking buckle 14 is an opening and closing sleeve of a two-half structure, and two hanging ears 141 are arranged opposite to each other at the opening and closing part of the outer wall of the opening and closing sleeve, and fixed by a latch 142 that penetrates through the through hole of the hanging ear 141. When in use, the GNSS antenna array 2 is vertically erected upward, and then the opening and closing sleeve of the two-half structure is put on the outer wall of the GNSS antenna array 2 and fixed by the latch 142; the bottom of the locking buckle 14 is pressed on the 90° flip bracket 13 under the action of gravity, thereby ensuring that the GNSS antenna array 2 will not fall down.

[0041] The electronic notebook 4 is a hardware device required to run the embedded program, and uses a general-purpose portable PC, a reinforced tablet computer (Android system) or an iPad.

[0042] The present invention comprises the following steps:

[0043] Step 1.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration;

[0044] Step 1.2, roughly leveling the calibration equipment tripod 1, including leveling the total station tripod 11 and the base connector 12;

[0045] Step 1.3, install and calibrate the GNSS antenna array 2, perform horizontal north-seeking measurement, and rotate and set the base connector 12 according to the true north direction;

[0046] Step 1.4, vertically erect the GNSS antenna array 2, and use the locking buckle 14 to fix the GNSS antenna array 2 so that it is perpendicular to the base connector 12;

[0047] Step 1.5, start the GNSS dual-antenna receiver 3, complete satellite search and initialization positioning, and solve the baseline vector of the upper antenna 21 and the lower antenna 22 in the GNSS antenna array 2;

[0048] Step 1.6, taking the phase center of the lower antenna 22 in the GNSS antenna array 2 as the starting reference, convert the phase center position of the upper antenna 21 in the GNSS antenna array 2 into ENU coordinates, i.e., “northeast sky” coordinates, in real time;

[0049] Step 1.7, calibrate the embedded program in the electronic notebook 4, and perform mean and standard deviation calculations on the baseline solution results of the GNSS dual-antenna receiver 3 within the set time range, with the initial value of the time range set to 1 minute. When the standard deviations of the three directions of ENU converge to the tolerance range within the specified time, with the initial value of the tolerance range set to 5 cm, proceed to the next step; otherwise, a prompt will pop up, requiring the surveyor to check the surrounding environment to avoid obvious obstruction of the GNSS antenna or being too close to the electromagnetic interference source;

[0050] Step 1.8, calibrate the U value of the electronic handbook 4. The U value is based on the phase center of one of the antennas of the GNSS dual-antenna receiver as the reference point. The baseline vector of the line connecting the phase center of the other antenna and the reference point is projected in the normal direction of the reference ellipsoid. After stable convergence, the judgment is made. If the U value and the length of the antenna tube 23 are 0.5m long, and the deviation is less than the specified value range: 0.01m-0.02m, proceed to the next step; if not, the surveyor is prompted to re-level the equipment tripod 1;

[0051] Step 1.9, compare the EN value, i.e. the northeast value, in the embedded program. If the E value is larger, it is prompted to adjust the two fine adjustment knobs perpendicular to the true north direction first, so that the E value is less than the specified value, ranging from 0.005m to 0.01m, and then adjust the single fine adjustment knob parallel to the true north direction, so that the N value is less than the specified value, ranging from 0.005m to 0.01m;

[0052] Step 1.10 At this time, if the U value is less than the set value, the range is 0.02m-0.025m, then the adjustment and calibration operation is completed, and the antenna tube 23 points to the direction of the reference ellipsoid normal. If not, return to step 1.3 and repeat the operation in sequence.

[0053] Considering that some types of GNSS dual-antenna receivers 3 do not have the function of outputting the baseline vector ENU value between the master and slave antennas, the present invention also includes a method for calibrating the azimuth and elevation angles of the GNSS dual-antenna receiver 3:

[0054] Step 2.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration;

[0055] Step 2.2, roughly level the calibration equipment tripod 1, including leveling the total station tripod 11 and the base connector 12;

[0056] Step 2.3, install and calibrate the GNSS antenna array 2, perform horizontal north-seeking measurement, and rotate and place the leveling base connector 12 according to the true north direction;

[0057] Step 2.4, vertically erect the GNSS antenna array 2, use the locking buckle 14 to make it perpendicular to the leveled base connector 12, and then read the pitch angle in the electronic handbook 4. If the value is within the set value range, that is, within 89.5° to 90°, proceed to step 2.5; otherwise, repeat steps 2.2-2.3;

[0058] Step 2.5, adjust the east-west fine adjustment knob so that the azimuth reading in the electronic handbook 4 is within the range of 355.5° to 360° and 0° to 0.5°;

[0059] Step 2.6, now observe the pitch angle reading in the electronic handbook 4, if the value is within the set value range, that is, 89.5° to 90°, the calibration step is completed, if not, fine-tune the north-south fine adjustment knob to make the pitch angle value return to the set value range.

[0060] The technical principles on which the present invention is based include:

[0061] 1. Determination of the normal of the earth reference ellipsoid

[0062] 1. The concept of the shape of the earth. Since the natural surface of the earth is irregular, calculations cannot be performed on it. The geoid is a closed surface extending from the mean sea level, which is closest to the natural surface of the earth. The advantages of the geoid include: (1) The vertical line (direction of gravity) at any point on the geoid is orthogonal to the tangent plane at that point. Gravity is the combined force of centrifugal force and gravity (the ratio of centrifugal force to gravity is about 1:300), and the gravity at each point on the geoid is different, resulting in different directions of the vertical lines at each point. (2) The curved surface composed of the tangent planes at each point - the geoid is also irregular, with slight undulations, and is a curved surface with physical properties. Both practice and theory can prove that: 1) the horizontal angle measured on each level surface (the non-parallelism with the geoid is not very obvious), because the correction when normalized to the geoid is very small, can be regarded as the angle value on the geoid; 2) the side length measured on each elevation surface can also be calculated on the geoid; 3) the elevation of the ground point is also calculated from the geoid. Conclusion: The geoid is the reference surface for field measurement; but it is a physical surface rather than a mathematical surface, so it cannot be used as a reference surface for measurement and calculation.

[0063] 2. Geometric elements and parameters of the ellipsoid

[0064] (1) Elements of the ellipsoid: major radius: a, minor radius: b;

[0065] (2) Ellipsoid parameters: Flattening: ,

[0066] First eccentricity: ,

[0067] Second eccentricity: ,

[0068] Where: Represents the focal length of the ellipse, that is, the distance from the focus of the ellipse to the center of the ellipse;

[0069] (3) Relational formula

[0070]

[0071]

[0072]

[0073]

[0074] e is the first eccentricity of the earth reference ellipsoid, and its calculation formula is: , α is the flattening rate, and its calculation formula is , where the major radius is a, the minor radius is b. The values ​​of the above parameters are given when the reference ellipsoid is defined. Taking the CGCS2000 ellipsoid parameters, which are currently the most widely used in my country, as an example,

[0075] a=6378137m, α=1 / 298.257222101, from the above formula we can calculate b=6356752.31414m,

[0076] e=0.08181919104.

[0077] 3. Definition of normal direction, the normal of the reference ellipsoid at a certain point is calculated as the vector perpendicular to the tangent plane at that point, which is the existing technology.

[0078] 2. Derivation of local coordinate system conversion formula

[0079] 1. WGS84 coordinate system, also known as longitude and latitude coordinate system (LLA coordinate system of longitude, latitude and altitude).

[0080] Global geographic coordinate system, geodetic coordinate system. It can be said to be the most widely used earth coordinate system. It gives the geodetic latitude, geodetic longitude and geodetic elevation of a point and tells us the position of the point in the earth more intuitively, so it is also called the latitude, longitude and altitude coordinate system. The X-axis of the WGS-84 coordinate system points to the intersection of the zero meridian plane (Greenwich) defined by BIH (International Time Service) 1984.0 and the equator of the agreement earth pole (CTP). The Z-axis points to the direction of CTP. The Y-axis, X-axis and Z-axis form a right-handed coordinate system.

[0081] Explanation: The ECEF coordinate system is used in GPS, which is the WGS-84 coordinate system.

[0082] (1): Geodetic latitude is the angle between the normal of the reference ellipsoid passing through the user point P and the equatorial plane. The latitude value is between -90° and +90°. It is positive in the northern hemisphere and negative in the southern hemisphere;

[0083] (2): Geodetic longitude is the angle between the meridian plane passing through the user point P and the prime meridian. The longitude value is between -180° and +180°;

[0084] (3): The geodetic height h is the normal distance from the user point P to the reference ellipsoid. It is negative inside the reference ellipsoid and positive outside it.

[0085] 2. The Northeastern Universe (ENU) coordinate system, also called the station center coordinate system, takes the user's location P as the coordinate origin:

[0086] The coordinate system is defined as: E axis: points to the east N axis: points to the north U axis: points to the zenith. The ENU local coordinate system uses a three-dimensional rectangular coordinate system to describe the earth's surface. The calculation formula is as follows:

[0087]

[0088] Among them, Δe, Δn, Δu are the deviations in the northeast celestial direction to be determined, a is the major radius of the reference ellipsoid, lat is the latitude of the point, Δlat, Δlon, Δalt are the latitude, longitude, and geodetic height deviations between the point to be measured and the reference point.

[0089] 3. GNSS relative positioning technology

[0090] 1. Baseline solution principle

[0091] The baseline vector is described by the three-dimensional relative position between the measuring stations and is obtained by differential analysis of synchronous observation data. The baseline vector is represented by the side length and three-dimensional relative coordinates, such as Figure 3 As shown, in order to intuitively reflect the relative position characteristics of the baseline vector and combine it with actual needs, the station center coordinates are usually used to represent the three-dimensional coordinates of the baseline vector:

[0092]

[0093] The baseline solution process mainly includes data preprocessing, differential observation value formation, cycle slip detection, parameter estimation and integer ambiguity processing.

[0094] The process of baseline data processing is as follows: Figure 4As shown in the figure, the main task of data preprocessing is to provide pseudorange and carrier phase that can be directly solved after decoding, and to perform single-point positioning of the reference value position as the initial value of the parameter to be estimated; then a double-difference observation model is constructed, and the errors related to the satellite and the receiver can be effectively eliminated through differentiation; then the measurement value needs to be cycle-slip detected, and when a cycle slip occurs, the initial value of the subsequent parameter estimation needs to be reset; with the completion of the cycle slip detection, the extended Kalman filter method is then used to perform parameter estimation to obtain the floating-point solution of the Kalman filter state vector; for the floating-point solution of the state vector, a suitable integer ambiguity processing strategy (LAMBDA method) needs to be adopted to restore the true carrier phase between the satellite and the receiver, and an accurate baseline vector solution can be obtained after the fixed ambiguity is obtained.

[0095] In summary, the use of a dual-antenna GNSS receiver to measure the direction of the approximate ellipsoid normal has high measurement accuracy, a simple and direct measurement method, and can solve the results in real time; the efficiency and accuracy are greatly improved compared to traditional methods. At the same time, the measurement device is simple and compact, and one person can complete the measurement operation, which greatly saves related labor costs.

Claims

1. A method for calibrating the normal direction of an ellipsoid based on GNSS technology, characterized in that The following steps are involved: Step 1.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration; Step 1.2: Roughly level the calibration equipment tripod, including leveling the total station tripod and the base connector; Step 1.3: Install and calibrate the GNSS antenna array, perform horizontal north-seeking measurement, and rotate the base connector according to the true north direction; Step 1.4: Vertically erect the GNSS antenna array and use the locking buckle to fix the GNSS antenna array so that it is perpendicular to the base connector; Step 1.5: Start the GNSS dual-antenna receiver, complete satellite search and initial positioning, and calculate the baseline vectors of the upper antenna and the lower antenna in the GNSS antenna array; Step 1.6, using the lower antenna phase center in the GNSS antenna array as the starting reference, convert the upper antenna phase center position in the GNSS antenna array into ENU coordinates, i.e., "northeast sky" coordinates, in real time; Step 1.7: Calibrate the embedded program in the electronic notebook, perform mean and standard deviation calculations on the baseline solution results of the GNSS dual-antenna receiver within the set time range. When the standard deviations of the three directions of ENU converge to the tolerance range within the specified time, proceed to the next step; otherwise, a prompt will pop up, requiring the surveyor to check the surrounding environment to avoid obvious obstruction of the GNSS antenna or being too close to the electromagnetic interference source; Step 1.8, calibrate the U value of the electronic handbook. The U value is based on the phase center of one of the antennas of the GNSS dual-antenna receiver as the reference point. The baseline vector of the line connecting the phase center of the other antenna and the reference point is projected in the normal direction of the reference ellipsoid. After stable convergence, the judgment is made. If the deviation between the U value and the antenna tube length is less than the specified value, proceed to the next step. If not, the surveyor is prompted to re-level the equipment stand; Step 1.9, compare the EN value, i.e. the northeast value, in the embedded program. If the E value is larger, it will prompt you to adjust the two fine adjustment knobs perpendicular to the true north direction first to make the E value smaller than the specified value, and then adjust the single fine adjustment knob parallel to the true north direction to make the N value smaller than the specified value; Step 1.10: At this time, if the U value is less than the set value, the adjustment and calibration operation is completed, and the antenna tube points to the direction of the reference ellipsoid normal. If not, return to step 1.3 and repeat the operation in sequence.

2. The ellipsoid normal direction calibration method based on GNSS technology according to claim 1, characterized in that: Also included is a method for calibrating the azimuth and elevation angles of a GNSS dual-antenna receiver: Step 2.1: Perform a preliminary screening of the observation environment for GNSS technology before calibration; Step 2.2: Roughly level the calibration equipment tripod, including leveling the total station tripod and the base connector; Step 2.3: Install and calibrate the GNSS antenna array, perform horizontal north-seeking measurement, and rotate and place the leveling base connector according to the true north direction; Step 2.4: Vertically erect the GNSS antenna array and use the locking buckle to make it perpendicular to the leveled base connector. At this time, read the pitch angle in the electronic handbook. If the value is within the set value range, that is, 89.5° to 90°, proceed to step 2.5; otherwise, repeat steps 2.2-2.3; Step 2.5, adjust the east-west fine adjustment knob so that the azimuth reading in the electronic handbook is within the range of 355.5° to 360° and 0° to 0.5°; Step 2.

6. Observe the pitch angle reading in the electronic handbook. If the value is within the set value range, that is, 89.5° to 90°, the calibration step is completed. If not, fine-tune the north-south fine-tuning knob to bring the pitch angle value back to the set value range.

3. A device for calibrating the normal direction of an ellipsoid based on GNSS technology, characterized in that: It consists of a device tripod, a GNSS antenna array, a GNSS dual-antenna receiver and an electronic handbook; The equipment tripod includes a base connector arranged on the total station tripod; and also includes a 90° flip bracket arranged on the base connector, and the GNSS antenna array is hingedly connected to the 90° flip bracket; a locking buckle is also fixedly arranged in the vertical direction of the 90° flip bracket, and the GNSS antenna array is limited by the locking buckle; The GNSS antenna array includes an upper antenna and a lower antenna, and the upper antenna and the lower antenna are connected to each other through an antenna tube. The upper antenna and the lower antenna are connected to the GNSS dual-antenna receiver via a data cable; The GNSS dual-antenna receiver is connected to the electronic handbook via a data cable.

4. The device for calibrating the ellipsoid normal direction based on GNSS technology according to claim 3 is characterized by: The locking buckle is an opening and closing sleeve of a two-half structure, and two hanging ears are arranged opposite to each other at the opening and closing part of the outer wall of the opening and closing sleeve, and are fixed by a pin penetrating through the through hole on the hanging ear.

5. The device for calibrating the ellipsoid normal direction based on GNSS technology according to claim 3 is characterized in that: The electronic notebook is a hardware device required to run the embedded program, and uses a general-purpose portable PC, a reinforced tablet computer or an iPad.

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