A single-term difference solution method and compensation method for photoelectric theodolite

Abstract

The present invention relates to the technical field of photoelectric theodolites, and specifically provides a method for solving and compensating a single error of a photoelectric theodolite. The sky area is divided into 60 sub-areas by star selection software, and a star is selected in each sub-area as a reference star, one of the theodolite points is controlled to point to the reference star, and the azimuth deviation and elevation deviation corresponding to each reference star are calculated respectively, and an axis system error pointing model of the electric theodolite, an azimuth error equation and an elevation error equation of the photoelectric theodolite are established, and the least squares estimate of the azimuth single error and the least squares estimate of the elevation single error are solved by the least squares method, and the reference stars with large fitting residuals are eliminated and repeatedly iterated to obtain the final single error of the photoelectric theodolite and compensate for it. The method of the present invention effectively reduces the influence of the theoretical position deviation of individual reference stars on the calculation results, ensures the consistency of the single error in multiple measurement results, and thus improves the compensation accuracy of the single error of the photoelectric theodolite.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric theodolites, and specifically provides a single-term difference solving method and a compensation method for a photoelectric theodolite. Background Art

[0002] When photoelectric measurement equipment is used in the field, the principle system error of the equipment needs to be calibrated. As the aperture of the telescope increases, various adjustment errors will also increase. The main sources of the system error of photoelectric measurement equipment include vertical axis tilt error, collimation error, horizontal axis tilt error, encoder zero point deviation, line of sight disturbance, etc. Among them, the vertical axis tilt is mainly affected by the level of the foundation, the collimation error is affected by the change of the camera installation position, the encoder zero point is affected by the north accuracy, and the line of sight disturbance is mainly the change of the optical axis of the lens barrel at different pitch angles.

[0003] In principle, if the random accuracy of the photoelectric measurement device is high enough, once the photoelectric measurement device is fixed, the system error of the photoelectric measurement device is basically fixed and will not change significantly. How to obtain the accurate system error of the photoelectric measurement device in the field is a key factor affecting the angle measurement accuracy of the photoelectric measurement device.

[0004] Star calibration is a method of solving the system errors of photoelectric theodolites based on stars. This method has been used in various optical measurement equipment since the late 1980s. This method selects the latest star library (with an accuracy of up to 0.01 arc seconds), selects 40 to 60 stars at uniform azimuth and elevation angles, and obtains the measurement error of the stars, that is, the deviation between the real-time theoretical value of the encoder and the actual measurement value. The deviation between the real-time theoretical value and the actual measured value of the miss distance , according to the pointing model of the photoelectric theodolite, a single difference fitting is performed to obtain the optimal estimated pointing error of each axis of the theodolite.

[0005] The current traditional single-item difference solution method based on star calibration can improve the measurement accuracy of optoelectronic equipment to a certain extent. However, in actual use, it is found that the single-item differences measured multiple times in the same time period have large differences, and the consistency of the single-item differences in multiple measurement results cannot be guaranteed. In response to this problem, the present invention proposes a single-item difference solution method based on multiple iterations. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a single-term difference solving method and compensation method for a photoelectric theodolite, which automatically selects reference stars for single-term difference solving according to star selection software, ensures high consistency of single-term difference, and improves the pointing accuracy of the photoelectric theodolite.

[0007] The single-term difference solution method of the photoelectric theodolite provided by the present invention comprises:

[0008] S1: Divide the sky area evenly into multiple sub-areas, and select a star in each sub-area as the reference star of the area;

[0009] S2: Calculate the guidance data of the photoelectric theodolite based on the theoretical position of the reference star;

[0010] S3: According to the guidance data, guide the photoelectric theodolite to point to the reference star, and record the encoder value and the miss value of the photoelectric theodolite;

[0011] S4: Fit the encoder value and the miss value to the actual pointing of the photoelectric theodolite, and calculate the azimuth deviation of the photoelectric theodolite based on the actual pointing and guidance data and pitch deviation ;

[0012] S5: Based on the position deviation and pitch deviation , establish the axis system error pointing model of the photoelectric theodolite;

[0013] S6: Based on the error pointing model of the photoelectric theodolite axis system, the azimuth error equation and elevation error equation of the photoelectric theodolite are established, which are:

[0014] ;

[0015] ;

[0016] in, It represents the horizontal component of the vertical axis tilt error of the photoelectric theodolite. It represents the component of the vertical axis tilt error of the photoelectric theodolite in the vertical direction. represents the measured azimuth of the corresponding reference star, represents the measured elevation angle of the corresponding reference star, represents the number of reference stars, represents the orientation error of the photoelectric theodolite, Indicates the collimation error of the electric theodolite. Indicates the horizontal axis tilt error of the electric theodolite, The coefficient representing the pitch error due to gravity sag, Indicates the zero position error of the electric theodolite, , , , and All are single errors of photoelectric theodolite;

[0017] S7: Calculate the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference based on the azimuth error equation and the elevation error equation of the photoelectric theodolite;

[0018] S8: Based on the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference, recalculate the pointing fitting residual of each reference star position, calculate the standard deviation based on the pointing fitting residual, and determine whether each pointing fitting residual is greater than three times the standard deviation one by one:

[0019] If it is greater than three times the standard deviation, the reference star is removed, and S1 to S8 are re-executed based on the remaining reference stars until the pointing fitting residuals of all reference stars are no greater than three times the standard deviation, and the final least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference are obtained.

[0020] Preferably, the number of sub-areas is 60.

[0021] Preferably, the reference star is the brightest star in the sub-region.

[0022] Preferably, the orientation deviation The difference between the actual pointing azimuth and the guidance data azimuth, the pitch deviation It is the difference between the actual pointing pitch angle and the guidance data pitch angle.

[0023] Preferably, the axis system error pointing model is:

[0024] ;

[0025] Preferably, the method further includes evaluating the accuracy of the least squares estimate of the azimuth single-term difference and the least squares estimate of the elevation single-term difference solved by S8:

[0026] A new reference star is selected in the sub-area, new guidance data is recalculated based on the new reference star, the new guidance data is compensated based on the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference to obtain corrected guidance data, the photoelectric theodolite is guided to point to the new reference star by the corrected guidance data, and the new encoder value and miss value are recorded;

[0027] The new azimuth deviation and pitch deviation are calculated based on the new encoder value and the miss value. When the new azimuth deviation and pitch deviation distribution satisfy the root mean square error less than 5 arc seconds, it is considered that the accuracy of the least squares estimate of the azimuth single difference and the least squares estimate of the pitch single difference meets the requirements.

[0028] Preferably, the new reference star is the second brightest star in the sub-region.

[0029] A single-term difference compensation method for a photoelectric theodolite is used to compensate the single-term difference of the photoelectric theodolite according to the least squares estimation value of the final azimuth single-term difference and the least squares estimation value of the elevation single-term difference.

[0030] Preferably, the method further comprises performing secondary compensation for the single-term error of the photoelectric theodolite by using a span correction method, an astronomical coordinate vertical line deviation correction method or an atmospheric error correction method.

[0031] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0032] The embodiment of the present invention automatically selects reference stars according to the sky region through the star selection software, ensuring that the selection range of reference stars covers different sky regions and is evenly distributed in azimuth and elevation, avoiding the uneven density of the sky region caused by manual star selection, making the selected reference stars more valuable for reference, thereby making the execution accuracy of the photoelectric theodolite higher and the consistency of the calculated single difference higher.

[0033] When calculating the single difference of the photoelectric theodolite, the embodiment of the present invention performs iterative calculation based on the fitting residuals of the reference stars, and eliminates the reference stars with abnormal fitting residuals, so that the single difference finally solved has high consistency and accuracy, which can further improve the compensation accuracy.

[0034] In addition, for some special targets at close range and low elevation angles, after solving the single-term difference and compensating it by the method of the embodiment of the present invention, a secondary correction is performed on it by correction means such as span correction, astronomical coordinate vertical line deviation correction, and atmospheric error correction, which can further improve the measurement accuracy of the photoelectric theodolite. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of single-term difference solution of a photoelectric theodolite provided in an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the star selection software operation interface provided according to an embodiment of the present invention;

[0037] Figure 3 is a single-term difference iteration flow chart of a photoelectric theodolite provided according to an embodiment of the present invention;

[0038] Figure 4 It is a data diagram of single-term difference solution results of a photoelectric theodolite provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0041] like Figure 1 As shown, the present invention provides a single-term difference solving method and compensation method for a photoelectric theodolite, comprising:

[0042] S1: Before performing the single-term difference solution of the photoelectric theodolite, it is necessary to select some stars as reference stars. To ensure the accuracy of the single-term difference solution, the reference stars in the selected area should be distributed as evenly as possible in all areas of the entire sky. The traditional solution method relies on manual selection of some stars in the sky area as reference stars, which cannot guarantee the uniformity of the reference stars. Figure 2 As shown, the embodiment of the present invention uses star selection software to select reference stars.

[0043] By using the star selection software, the sky area with a pitch angle between 20° and 65° is evenly divided into multiple sub-areas. represents the number of sub-regions, and in each sub-region, the brightest star is selected as the reference star of the region, and Reference stars are used to calculate the single error of the photoelectric theodolite. The value is 60, that is, the sky area with a pitch angle between 20° and 65° is evenly divided into 60 sub-areas, and the corresponding number of selected reference stars is 60.

[0044] When selecting reference stars, you do not have to choose the brightest star, but the brightest star is easy to observe, so choosing the brightest star as the reference star is the best method for selecting reference stars.

[0045] S2: After determining the reference star, according to the star catalog epoch (The embodiment of the present invention adopts the standard epoch J2000.0), the theoretical positions of the selected 60 reference stars are calculated in real time, and the reference stars are assumed to be in the star catalog epoch The position and proper motion in the astronomical reference frame of the reference star are expressed as (radians), the declination of the reference star is expressed as (radians), the proper motion velocity of the reference star in the right ascension direction is (hours / seconds / Julian century), the proper motion velocity of the reference star in the declination direction is (arc seconds / Julian century), and the astronomical longitude and latitude of the station in the Earth's reference system are (radians) and (radians), referenced to sidereal time in Coordinated Universal Time The observation epoch under The corresponding Julian day (including the fraction of the day) is .

[0046] Q2: Calculate the instantaneous astronomical longitude and latitude of a reference star and :

[0047] ;

[0048] ;

[0049] in, and They are all parameters of the Earth's rotation, used to describe the phenomenon of polar shift during the Earth's rotation. They are the motion components of the instantaneous rotation angular velocity direction relative to a fixed point near the Earth's North Pole (usually the International Agreement Origin CIO). represents the component of polar motion in the X-axis direction, represents the component of polar motion in the Y-axis direction, , and Published by the International Earth Rotation Service (IERS).

[0050] Q3: Stars move in space, which is called stellar proper motion. The magnitude and direction of stellar proper motion can be obtained through astronomical observation and calculation. Stellar proper motion reflects the lateral motion of stars relative to the observer, and is the combined result of the star's intrinsic motion and visual motion.

[0051] Consider the proper motion of the reference star and make the corresponding reference proper motion correction as follows:

[0052] ;

[0053] ;

[0054] in, represents the corrected right ascension of the reference star, Indicates the corrected declination of the reference star.

[0055] Q4: Calculate the epoch mean position of a reference star :

[0056] ;

[0057] Q5: Due to the movement of the Earth's rotation axis (precession) and the gravitational effects of the Moon, Sun, etc. on the Earth (nutation), the positions of stars on the celestial sphere will change slightly over time. Therefore, when calculating the theoretical positions of stars, it is necessary to apply precession and nutation corrections.

[0058] Calculate the precession of a reference star and the nutation matrix :

[0059] ;

[0060] ;

[0061] in, They represent the first precession, the second precession and the third precession respectively, and the calculation method is as follows:

[0062] ;

[0063] ;

[0064] ;

[0065] in, is the obliquity of the ecliptic, , They represent the momentum (radians) in Chapter 1 and the momentum (radians) in Chapter 2, respectively.

[0066] ;

[0067] The spatial position is The rotation matrix about the axis.

[0068] Then the position vector of the star relative to the true equator and the true equinox at the time of observation is for:

[0069] ;

[0070] Q6: Since the Earth is always moving around the Sun, it will cause parallax in the position of stars, namely the annual aberration. When calculating the theoretical position of the reference star, the annual aberration needs to be corrected:

[0071] Calculate the position vector of the sun relative to the true equator and true equinox at the time of observation ,but and The angle between for:

[0072] ;

[0073] remember is the position vector of the reference star after annual aberration correction, then

[0074] ;

[0075] This is the apparent position of the reference star at the true equinox and true equator at the time of observation. Since the maximum diurnal aberration is 0.39 arc seconds, no diurnal aberration correction is performed here.

[0076] Q7: Calculate the position vector of the reference star in the horizontal coordinate system :

[0077] First calculate the Greenwich true sidereal time at the time of observation :

[0078] ;

[0079] in, , for Fraction of a day, , , It is the movement of Huang Jing Zhang.

[0080] The local sidereal time of the station is for:

[0081] ;

[0082] ;

[0083] in,

[0084] ;

[0085] Depend on Get the calculated values ​​of the azimuth and elevation of the star and , and This is the required theoretical position of the reference star.

[0086] Due to atmospheric refraction, the observed position of a star is different from its true position. The observed height of a star should be subtracted from the atmospheric difference to obtain the true height of the star. The greater the zenith distance of the star, the greater the atmospheric difference. When the temperature and pressure change, the magnitude of the atmospheric difference will be different. The theoretical value of the position of a star should be corrected with the atmospheric difference when used as guidance data. And perform the air gap correction:

[0087] ;

[0088] ;

[0089] in, and represent the air pressure and temperature at the measuring station, respectively. and They respectively represent the azimuth and elevation angles of the theoretical position of the reference star after correction for atmospheric aberration.

[0090] After obtaining the theoretical position of the reference star, it is used as the guidance data of the photoelectric theodolite to guide the photoelectric theodolite to point to the reference star. Theoretically, when the error-free photoelectric theodolite is guided with the theoretical position of the reference star as the guidance data, its actual encoder value and off-target value should be consistent with the theoretical position of the reference star. If they are inconsistent, it means that there is a single error in the photoelectric theodolite. Therefore, the single error of the photoelectric theodolite can be calculated by this principle.

[0091] The theoretical position of the reference star is the value in the horizontal coordinate system, that is, the azimuth and elevation angle of the observed star, based on The theoretical positions of the reference stars correspond to the calculation of the photoelectric theodolite The bootstrap data is calculated as follows:

[0092] First, convert the horizon polar coordinates of the theoretical position of the reference star into horizon rectangular coordinates:

[0093] ;

[0094] in, , , Represents the spatial rectangular coordinate of the reference star relative to the center of the earth.

[0095] Then convert the horizontal rectangular coordinates to polar coordinates:

[0096] ;

[0097] in, , , Represents the spatial rectangular coordinates and azimuth values ​​of the reference star relative to the observatory site , Pitch value Directly used as guidance data for the photoelectric theodolite, guiding the servo tracking system to point to the reference star.

[0098] S3: Each reference star has its own theoretical position, so the number of guiding moments of the photoelectric theodolite calculated is the same as the number of reference stars, which is also Guide the photoelectric theodolite according to The guide data points to reference stars, and record them separately with The encoder value and the miss-value corresponding to each guide data are used to calculate the single error of the photoelectric theodolite.

[0099] S4: Match the encoder value and the miss distance value recorded in S3 one by one, and fit them into The actual direction of the photoelectric theodolite is The actual response of the guided data. The actual direction and The guide data is calculated to obtain the photoelectric theodolite Azimuth Deviation and Pitch deviation , azimuth deviation The difference between the actual pointing azimuth and the guidance data azimuth, the pitch deviation It is the difference between the actual pointing pitch angle and the guidance data pitch angle.

[0100] The position of each reference star can store multiple frames of data, and the average value can be used to eliminate random errors in image extraction. Generally, a total of 40 to 60 reference stars are selected, with a pitch distribution of 25 to 70 degrees (mainly considering reducing the influence of the atmospheric difference), and the theoretical pointing and actual pointing deviation values ​​of each reference star are obtained for calibration.

[0101] S5: The axis system error of the photoelectric theodolite mainly includes azimuth error and pitch error. According to the azimuth deviation calculated above and pitch deviation , the error pointing model of the photoelectric theodolite axis system is established as follows:

[0102] ;

[0103] in, It represents the horizontal component of the vertical axis tilt error of the photoelectric theodolite. It represents the component of the vertical axis tilt error of the photoelectric theodolite in the vertical direction. represents the measured azimuth of the corresponding reference star, represents the measured elevation angle of the corresponding reference star, represents the orientation error of the photoelectric theodolite, Indicates the collimation error of the electric theodolite. Indicates the horizontal axis tilt error of the electric theodolite, The coefficient representing the pitch error due to gravity sag, represents the zero position error of the electric theodolite, where , , , and All are single errors of photoelectric theodolite.

[0104] S6: Based on the error pointing model of the photoelectric theodolite axis system, the azimuth error equation and elevation error equation of the photoelectric theodolite are established, which are:

[0105] ;

[0106] ;

[0107] Among them, the orientation deviation and pitch deviation are the theoretical values ​​of azimuth error and pitch error respectively. The closer the azimuth error and pitch error are to the azimuth deviation and pitch deviation The closer the single-term difference obtained by solving the azimuth error equation and the pitch error equation is to the actual situation, the more accurate it is.

[0108] S7: Transform the solution of the above equation into a linear regression problem, and establish the linearized regression equation as follows: , you can Understand as a set of observations, is understood as a set of independent variables, represents the coefficient matrix, and the goal is to find the linear model parameters that best fit these libraries. Using the least squares rule, solve The estimated value of is: , then the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference are:

[0109] ;

[0110] ;

[0111] in, and That is, the least squares estimate of the azimuth single difference and the least squares estimate of the elevation single difference.

[0112] In order to ensure the accuracy of the solved single-term difference, the least squares estimate of the azimuth single-term difference and the least squares estimate of the elevation single-term difference are also evaluated for accuracy. The specific evaluation method is as follows:

[0113] In each sub-area, another new set of reference stars is re-selected. The selection method of the new reference stars is similar to that of the reference stars selected in S1, but they are not repeated in S1. The second brightest star can be selected as the new reference star. The new guidance data is recalculated based on the new reference stars. The calculation method is the same as S2. The new guidance data is compensated based on the least squares estimate of the azimuth single difference and the least squares estimate of the elevation single difference to obtain the corrected guidance data. At this time, if the least squares estimate of the azimuth single difference and the least squares estimate of the elevation single difference are accurate and error-free, the compensated and corrected new guidance data should be the guidance data in the ideal state. Guide the photoelectric theodolite to point to the new reference stars one by one through the corrected guidance data, and record the new encoder value and the miss-target value;

[0114] The new azimuth deviation and pitch deviation are calculated based on the new encoder value and the miss value. When the new azimuth deviation and pitch deviation distribution satisfy the root mean square error less than 5 arc seconds, it is considered that the accuracy of the least squares estimate of the azimuth single difference and the least squares estimate of the pitch single difference meet the requirements.

[0115] S8: Figure 3 As shown, after solving the single difference coefficient, the pointing fitting residual of each reference star position can be recalculated, and the standard deviation can be calculated based on the pointing fitting residual. When the pointing fitting residual of a reference star is large, it is considered that the theoretical position of the reference star may be biased. The embodiment of the present invention uses three times the standard deviation as the threshold. If the pointing fitting residual is greater than three times the standard deviation, it is considered that the pointing fitting residual of the reference star is large. At this time, the relevant data of the reference star is discarded, and the single difference of the remaining reference stars is recalculated. The calculation is iterated repeatedly until the pointing fitting residual of each remaining star is less than three times the standard deviation. At this point, the single difference solution result is considered reasonable and reliable, and can be used for real-time correction of photoelectric theodolites and the calculation of post-measurement accuracy of observed targets. The specific process is as follows:

[0116] Based on the least squares estimate of the single differences of the orientation The least squares estimate of the single difference between , recalculate the pointing fitting residual of each reference star position, and calculate the standard deviation based on the pointing fitting residual, and judge whether the pointing fitting residual is greater than three times the standard deviation one by one:

[0117] If it is greater than three times the standard deviation, the reference star is removed, and steps S1 to S8 are re-executed based on the remaining reference stars until the pointing fitting residuals of all reference stars are no greater than three times the standard deviation, and the final least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference are obtained.

[0118] When verifying the embodiment of the present invention, the following is obtained: Figure 4 The single difference solution result data graph is shown.

[0119] The photoelectric theodolite single-term difference compensation can be performed based on the final least squares estimate of the azimuth single-term difference and the least squares estimate of the elevation single-term difference.

[0120] For most of the observation targets, after solving the single difference and compensating by the above method, a higher angle measurement accuracy of the photoelectric theodolite can be generally obtained. However, for special observation targets at low elevation and close distance, the angle measurement error may be large. After compensation by the above method, a higher angle measurement accuracy may still not be achieved. The reasons affecting the error may be the site accuracy, the calculation accuracy of the atmospheric difference, etc. Therefore, the photoelectric theodolite after the single difference correction by the above method can be corrected twice. The embodiment of the present invention further proposes correction means such as span correction, astronomical coordinate vertical deviation correction and atmospheric difference correction to perform secondary correction of the single difference of the photoelectric theodolite, which can further improve the measurement accuracy of the photoelectric theodolite.

[0121] The span of span correction refers to the position deviation between the main axis optical path and the paraxial optical path of the photoelectric theodolite. In actual observation, the photoelectric theodolite uses a multi-channel detector to obtain the target image. When calculating the measurement accuracy of the paraxial image, it is necessary to calculate the real-time position of the paraxial optical path based on the current observation station site according to the angle of the photoelectric theodolite encoder, and use this position as the new site position to calculate the angle measurement position. After adding span correction, the measurement accuracy of the photoelectric theodolite can be further improved.

[0122] The coordinates of the observatory site generally use the geodetic coordinate system (CGCS2000), while the theoretical position calculation of general celestial targets (stars, planets, etc.) uses the astronomical coordinate system. There will be slight deviations between the two coordinate systems. The astronomical coordinate system is a coordinate system that uses the celestial pole and the vernal equinox as the celestial orientation reference, indicating the position of ground points on the geoid. Its reference is the plumb line and the geoid. For long-distance targets greater than 20 kilometers, the coordinate system error can be ignored, while for close-range targets, the station site needs to be converted into astronomical coordinates by correcting the plumb line deviation when measuring angles. The specific correction method is to multiply the geodetic coordinates of the current station site by the plumb line deviation correction matrix to obtain the astronomical and geographical coordinates of the station site.

[0123] Atmospheric error refers to the difference between the observed target direction and the actual target direction due to atmospheric refraction, which mainly affects the observed pitch angle. Atmospheric error is mainly related to atmospheric pressure, temperature and humidity, and the observed pitch angle. In the case of low elevation angles, there is currently no unified formula for calculating the atmospheric error, and there are large differences between different atmospheric error calculation formulas. In actual use, the specific value of the atmospheric error is calibrated through multiple azimuth marks at low elevation angles, and the atmospheric error value at the current pitch angle is estimated based on empirical data.

[0124] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0125] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for solving single-term difference of photoelectric theodolite, characterized in that: include: S1: Divide the sky area evenly into multiple sub-areas, and select a star in each sub-area as the reference star of the area; S2: Calculating guidance data for guiding the photoelectric theodolite according to the theoretical position of the reference star; S3: guiding the photoelectric theodolite to point to the reference star according to the guidance data, and recording the encoder value and the miss value of the photoelectric theodolite; S4: Fitting the encoder value and the miss value into the actual pointing direction of the photoelectric theodolite, and calculating the azimuth deviation of the photoelectric theodolite according to the actual pointing direction and the guidance data and pitch deviation ; The bearing deviation is the difference between the azimuth of the actual pointing direction and the azimuth of the guidance data, and the pitch deviation is the difference between the actual pointing pitch angle and the guidance data pitch angle; S5: Based on the position deviation and pitch deviation , establish the axis system error pointing model of the photoelectric theodolite; The axis system error pointing model is: ； S6: According to the photoelectric theodolite axis system error pointing model, establish the photoelectric theodolite azimuth error equation and the pitch error equation, which are: ； ； in, It represents the horizontal component of the vertical axis tilt error of the photoelectric theodolite. It represents the component of the vertical axis tilt error of the photoelectric theodolite in the vertical direction. represents the measured azimuth of the corresponding reference star, represents the measured elevation angle of the corresponding reference star, represents the number of reference stars, represents the orientation error of the photoelectric theodolite, Indicates the collimation error of the electric theodolite. Indicates the horizontal axis tilt error of the electric theodolite, The coefficient representing the pitch error due to gravity sag, Indicates the zero position error of the electric theodolite, , , , and All are single errors of photoelectric theodolite; S7: Calculate the least squares estimated value of the azimuth single term difference and the least squares estimated value of the elevation single term difference according to the azimuth error equation and the elevation error equation of the photoelectric theodolite; S8: Recalculate the pointing fitting residual of each reference star position according to the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference, calculate the standard deviation according to the pointing fitting residual, and determine whether each pointing fitting residual is greater than three times the standard deviation one by one: If it is greater than three times the standard deviation, the reference star is removed, and S1 to S8 are re-executed based on the remaining reference stars until the pointing fitting residuals of all reference stars are no greater than three times the standard deviation, and the final least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference are obtained.

2. The single-term difference solution method of the photoelectric theodolite according to claim 1, characterized in that: The number of the sub-areas is 60.

3. The single-term difference solution method of the photoelectric theodolite according to claim 1, characterized in that: The reference star is the brightest star in the sub-region.

4. The single-term difference solution method of the photoelectric theodolite according to claim 1, characterized in that: It also includes the accuracy evaluation of the least squares estimate of the azimuth single-term difference and the least squares estimate of the elevation single-term difference solved by S8: Selecting a new reference star in the sub-region, recalculating new guidance data according to the new reference star, compensating the new guidance data according to the least squares estimate of the azimuth single term difference and the least squares estimate of the elevation single term difference to obtain corrected guidance data, guiding the photoelectric theodolite to point to the new reference star by means of the corrected guidance data, and recording new encoder values ​​and miss-value values; New azimuth deviation and pitch deviation are calculated based on the new encoder value and the miss value. When the new azimuth deviation and pitch deviation distribution satisfy the root mean square error less than 5 arc seconds, it is considered that the accuracy of the least squares estimate of the azimuth single difference and the least squares estimate of the pitch single difference meets the requirement.

5. The single-term difference solution method of the photoelectric theodolite as claimed in claim 4, characterized in that: The new reference star is the second brightest star in the sub-region.

6. A single-term difference compensation method for a photoelectric theodolite, characterized in that: According to the final least squares estimation value of the azimuth single-term difference and the least squares estimation value of the elevation single-term difference solved as claimed in claims 1 to 4, single-term difference compensation is performed on the photoelectric theodolite.

7. The single-term difference compensation method of the photoelectric theodolite as claimed in claim 6, characterized in that: It also includes the use of span correction method, astronomical coordinate vertical deviation correction method or atmospheric error correction method to perform secondary compensation for the single error of the photoelectric theodolite.

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