CN115218861A - Astronomical azimuth measurement method based on automatic theodolite - Google Patents
Astronomical azimuth measurement method based on automatic theodolite Download PDFInfo
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Abstract
The invention relates to an astronomical azimuth measurement method based on an automatic theodolite. The method is characterized in that: the method comprises six steps of solving fixed star declination, solving fixed star right ascension, matching and identifying fixed stars, calculating fixed star visual positions, calculating the astronomical azimuth angle of the ground target, and selecting stars again to solve the astronomical azimuth angle of the ground target. The overall work flow is as follows: firstly, erecting an automatic theodolite at an observation station position, and performing rough leveling and fine leveling through a leveling device on the automatic theodolite; then, selecting an observation fixed star for collimation and calculating the right ascension and the declination of the fixed star; then, matching and identifying the observation fixed star by adopting a hash searching method and calculating the visual position of the fixed star; and finally, measuring for multiple times to obtain a final astronomical azimuth angle of the ground target. The method solves the limitation problem of the traditional azimuth angle measuring method, and has wider application range on the basis of keeping good measuring precision.
Description
Technical Field
The invention belongs to the technical field of geodetic astronomical measurement, and relates to an astronomical azimuth measurement method based on an automatic theodolite.
Background
The automatic theodolite is a high-precision astronomical observation instrument used on the ground, is used for completing astronomical measurement of ground point location information, solves the problems that an optical theodolite is complex in operation process, complex in links, tedious in calculation, incapable of automatically recording data and the like, and achieves a good effect in the national defense field and the civil field. The most reliable reference datum for the external field operation of the automatic theodolite is a star, and the positioning and orientation realized by observing the star is an effective method with higher precision. The final purpose of the astronomical azimuth measurement is to calculate the accurate azimuth angle from the measuring station to the ground target to be measured, namely the included angle between the meridian plane of the measuring station and the plumb surface of the passing measuring station and the target. At present, when an automatic theodolite is adopted to measure an astronomical azimuth, an arbitrary time angle method of a polaris is mainly used. First, an automatic theodolite at a survey station aims at a ground target to measure a horizontal scale reading R of the ground target 1 (ii) a Then, since the north celestial pole cannot be directly aimed by the automatic theodolite, the azimuth angle of the ground target needs to be indirectly calculated by the azimuth angle of the north star, that is, the reading R of the horizontal scale at the moment of aiming at the north star is recorded 2 And calculating the azimuth A of the instant Polaris, so that the azimuth of the ground target can be determined from R 1 、R 2 And A is obtained. However, the above-mentioned automatic theodolite azimuth angle measurement method has certain disadvantages in practical use: when the measuring station is in the northern hemisphere, if the altitude angle is too large when the polaris is observed, the measuring range of the instrument cannot be met necessarily, and if the altitude angle is too small when the polaris is observed, the polaris is easily shielded by an obstacle and cannot be observed; when the survey station is in the southern hemisphere, the arctic star will never be observed by the automatic theodolite.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an astronomical azimuth measurement method based on an automatic theodolite, which solves the limitation problem of the traditional azimuth measurement method and has wider application range on the basis of keeping good measurement precision.
The technical solution of the present invention is now described as follows:
the invention relates to an astronomical azimuth measurement method based on an automatic theodolite, which is characterized by comprising the following steps of: comprises the following steps of (a) preparing a solution,
step 1: resolution of sidereal declination
After the instrument is debugged at the survey station, a fixed star meeting the star selection condition is randomly selected in the whole day area and observed by an automatic theodolite. Because the prior information does not comprise an accurate value of astronomical north, an included angle exists between the 0-degree direction and the south direction of the automatic theodolite dial, the azimuth angle of the fixed star is calculated to be A by utilizing relevant information such as collimation instantaneous zenith distance, observation station astronomical latitude, observation angle value of the fixed star and the like, and then declination delta is solved;
step 2: resolution of the sidereal Chin meridian
After calculating the declination delta of the randomly selected bright star, solving a unique time angle t by using the corner relation in the spherical triangle, and obtaining the declination alpha of the randomly selected bright star by using the relation among the time angle, the observation instant Greenwich mean time, the right ascension and the survey station astronomical longitude;
and step 3: match identification of stars
The declination and declination values of the fixed stars, which are obtained by calculation in the first two steps, are coupled with errors in each measurement link, the result is not the real position of the fixed stars in the celestial sphere, and the astronomical measurement precision requirement of the automatic theodolite is high, so that the automatic theodolite cannot be directly used for calculating the subsequent astronomical azimuth angle of the ground target. Therefore, the fixed star observed in the star table must be matched and identified to obtain the accurate right ascension and declination values, i.e. the characteristic data of the observed fixed star is compared with the characteristic data of the fixed star in the star table in a series. According to the method, the matching identification of the fixed stars is finished by adopting a hash examination method, and the data to be searched can be directly obtained from a database through one-time calculation without any comparison;
and 4, step 4: sidereal apparent position calculation
So far, finding out the corresponding fixed stars and obtaining the accurate right ascension and declination values; however, the position of the star in the celestial coordinate system is not a dust, and the right ascension and declination values in the star chart are values under a certain epoch, and are not the right ascension and declination values at the current observation time, but the calculation of the astronomical measurement uses the right ascension and declination values for observing the instantaneous star. Therefore, the right ascension and declination values in the star catalogue need to be converted to obtain accurate right ascension alpha 'and declination delta' values for observing the instantaneous fixed stars, and the conversion process is the visual position calculation process;
and 5: calculation of astronomical azimuth of ground target
In practice, the astronomical north direction is different from the ground object and cannot be directly aligned by the automatic theodolite, so the astronomical azimuth angle of the ground object can be obtained only indirectly by aligning a certain star to read the horizontal dial reading of the star and calculating the azimuth angle of the star. Knowing the precise right ascension alpha 'and declination delta' of the fixed star, the precise azimuth angle of the fixed star at the moment when the automatic theodolite aims at the observation fixed star can be obtained according to the corner relationship in the spherical triangle;
therefore, the randomly selected star lights are observed for multiple times in a disk left observation mode to obtain the azimuth angle of the star lights at each time of collimation and the dial reading, and finally the true north direction value is measured in a disk left observation mode. And observing the ground target for multiple times by using a left-hand observation mode to obtain the dial reading of the ground target. The difference between the north direction value and the ground target dial reading is the astronomical azimuth angle of the ground target measured by using the left-hand observation mode. And similarly, the astronomical azimuth angle of the ground target is calculated by using a disk right observation mode, and the final astronomical azimuth angle of the ground target is obtained by taking the mean value.
And 6: reselecting satellite to resolve astronomical azimuth of ground target
In order to improve the final measurement accuracy, the geometric position relation of the fixed star in the celestial coordinate system needs to be considered during star selection. I.e. a higher star is reselected, which must satisfy the corresponding star selection conditions (altitude angle and azimuth angle in the horizontal coordinate system with the origin of the survey station) in altitude and azimuth. And then repeating the operation from the first step to the fourth step, and obtaining a new astronomical azimuth angle of the ground target by relying on the bright star. Then, another higher bright star, such as a star, is selected, and the bright star must satisfy the same star selection condition. The terrestrial target astronomical azimuth of the bright star is obtained according to the same measurement method as before. And taking the average value of the three measurement results as the measurement result of the astronomical azimuth angle of the ground target. The process of measuring the astronomical azimuth angle is finished;
in order to improve the final azimuth angle measurement accuracy, the measurement process needs to be repeated by selecting a plurality of proper time periods according to the measurement accuracy requirement during measurement, and then the average value of the measurement results of a plurality of times is obtained to obtain the final ground target astronomical azimuth angle.
Drawings
FIG. 1: astronomical triangular geometric model
FIG. 2 is a schematic diagram: sidereal apparent position calculation model
FIG. 3: astronomical azimuth measurement model
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings.
The invention provides an astronomical azimuth measurement method based on an automatic theodolite, which comprises six steps of star declination calculation, star right ascension calculation, star matching identification, star visual position calculation, ground target astronomical azimuth calculation and star reselection for calculating the ground target astronomical azimuth. The overall work flow is as follows: firstly, erecting an automatic theodolite at a survey station position, and performing rough leveling and fine leveling through a leveling device on the automatic theodolite; then, selecting an observation fixed star for collimation and calculating the right ascension and the declination of the fixed star; then, matching and identifying the observation fixed star by adopting a hash searching method and calculating the visual position of the fixed star; and finally, measuring for multiple times to obtain a final ground target astronomical azimuth angle.
Referring to fig. 1:
step 1: resolution of sidereal declination
The astronomical triangle is also called as a positioning triangle and is widely applied in astronomical navigation, namely, a spherical triangle which is formed by taking a certain celestial body sigma, a north celestial pole P and a zenith Z of a measuring station as vertexes, the direction of a dotted line is a ground axis, a circular plane passing through points L and W is an equatorial plane, a circular plane passing through points Q and W is a measuring station horizontal plane and is vertical to a plumb line of the measuring station, M point represents the intersection point of the measuring station horizontal plane and a large circular arc passing through the zenith Z and the celestial body sigma, and N point represents the intersection point of the equatorial plane and the large circular arc passing through the north celestial pole P and the celestial body sigma. According to the geometric relationship among the horizontal coordinate system, the time-angle coordinate system and the equatorial coordinate system, the following relationship exists among the corners in the spherical triangle:
wherein z is the distance between the zenith and the zenith,
the method is characterized in that the method is used for measuring station astronomical latitude, lambda is measuring station astronomical longitude, alpha is fixed star right ascension, delta is fixed star declination, A is fixed star azimuth, t is time angle, t = S-alpha-lambda, and S is observing instantaneous Greenwich mean time of true constellations.
Leveling the automatic theodolite at the observation station to ensure that a rotating shaft of the automatic theodolite is coincident with a plumb line, randomly selecting a high bright star with a height angle of 40-45 degrees, such as stars and the like in a whole sky area, observing the high bright star by using the automatic theodolite, and assuming that the randomly selected bright star is observed twice, obtaining the corner relationship derived from a spherical triangle:
wherein ,
is the astronomical latitude of the survey station, delta is the declination of the fixed star, A is the azimuth of the fixed star, and z 1 、z 2 Is zenith distance, A' is observation angle value of fixed star, delta A is included angle between 0 deg. direction of automatic theodolite dial and south direction, t is time angle, t = S-alpha-lambda, lambda is astronomical longitude of survey station, and S is instantaneous observation Greenwich meanIn the case of stars, α is the right ascension of the stars.
Since the prior information does not include an accurate value of the astronomical north direction, it is impossible to accurately indicate the north to the dial direction of the automatic theodolite. Therefore, an included angle exists between the 0-degree direction and the south direction of the automatic theodolite dial, the included angle is assumed to be delta A, the automatic theodolite is used for aiming at the instant of a certain fixed star, the observation angle value of the fixed star is A', the azimuth angle of the fixed star is A calculated through a corner relation formula derived from an astronomical triangle, and the relationship among the three is as follows: a = a' + Δ a.
The cos (A' + Δ A) term is expanded to yield:
combining and sorting the two formulas to obtain the following formula:
wherein m = sinz 1 cosA 1 ′,n＝sinz 2 cosA 2 ′，z 1 、A 1 ′、z 2 、A 2 ' both are data observed by the automatic theodolite, and m and n are known quantities. Therefore, the formula only contains two unknowns of sin delta and sin delta A, and only 4 times of observation are needed to be carried out on the randomly selected bright star, so that the written software program simultaneous equation can be used for solving the sin delta and further solving the declination delta.
Step 2: resolution of the Chi meridian of the Star
After calculating the declination delta of the randomly selected bright star, the declination alpha of the bright star can be easily obtained, and the relationship of the corners in the spherical triangle can be known as follows:
and respectively solving cost and sint, and further solving a unique time angle t by utilizing a written software program, wherein t = S-alpha-lambda, S is a known quantity when an instantaneous Greenwich mean star is observed, and the right ascension alpha of the randomly selected bright star can be obtained.
And 3, step 3: match identification of stars
The matching identification of the fixed stars is a key link of the astronomical azimuth measurement of the automatic theodolite, and directly determines the precision of the astronomical measurement method. The values of the right ascension and the declination of the fixed star obtained by calculation in the step 1 and the step 2 are coupled with errors in each measuring link and cannot be directly used for calculating the astronomical azimuth of a subsequent ground target, so that the fixed star observed in the star catalogue must be matched and identified to obtain the accurate values of the right ascension and the declination; the star matching identification process actually carries out a series of comparison on the characteristic data of the observed star and the characteristic data of the stars in the star catalogue. The star catalogue has a large amount of data, and a linear checking method and a binary checking method, which have time complexity of o (n) and o (log), respectively, are commonly used 2 n ) These searching methods all require multiple comparisons to accurately find the data position, and are inefficient. Therefore, the invention adopts a hash checking method to complete the matching identification of the fixed stars, and the method can directly obtain the data to be searched from the database by one-time calculation without any comparison, thereby greatly improving the searching speed. The basic principle is to establish a mapping relation H between the storage Location of the data and the data, so that on the premise of knowing the data, the corresponding storage Location can be quickly located through the mapping relation, that is, location = H (date), where represents the storage Location of the data, and date represents the data. The time complexity of the hash check is o (1);
based on the idea of hash search, the data in the star table is arranged in an ascending order of the right ascension, curve fitting is performed by using the right ascension as an argument (namely the date of the hash function) and the position index as a dependent variable (namely the Location of the hash function), and the hash function is obtained. Since the independent variable (right ascension) and the dependent variable (storage location) of the hash function are strictly increased, the constructed hash function has no problem of address conflict (namely one address corresponds to a plurality of right ascensions). Based on a hash searching method, when the fixed star matching identification is carried out, a written software program is utilized to quickly reduce the fixed star matching identification area to a small range, and then other characteristic data (declination, stars and the like) are utilized to carry out comparison screening on the data in the small range one by one, so as to obtain a final result;
referring to fig. 2:
and 4, step 4: sidereal apparent position calculation
After the step 1 and the step 2 work out the right ascension alpha, the declination delta, the sketch star and the like containing errors of the observed fixed star, the step 3 uses a hash search method to carry out matching identification on the observed fixed star in the fixed star table, finds out the fixed star corresponding to the observed fixed star, and obtains the accurate right ascension and declination values of the observed fixed star. However, the position of the star in the celestial coordinate system is not a dust, and the right ascension and declination values in the star chart are values under a certain epoch, and are not the right ascension and declination values at the current observation time, but the calculation of the astronomical measurement uses the right ascension and declination values for observing the instantaneous star. Therefore, the declination and the declination values in the star catalogue need to be converted to obtain the accurate declination alpha 'and declination delta' values for observing the instantaneous fixed stars, the conversion process is a visual position calculation process, and the accuracy degree of the visual position calculation directly influences the calculation accuracy of the astronomical measurement.
In apparent position calculation, two main factors influencing the stellar ray difference are the movement speed and the light speed of an observer. The optical aberration mainly comprises sunday optical aberration, anniversary optical aberration and long-term optical aberration, and the sunday optical aberration is mainly caused by the rotation motion of the earth; annual optical aberration is mainly caused by the revolution motion of the earth; long-term photoperiod is mainly caused by the motion of the solar system. The influence of the sunday light row difference and the long-term light row difference on the star position is generally negligible, and the influence of the annual light row difference on the star position is mainly considered. The light travel difference correction value of the star position can be obtained by dividing the speed component of the earth's center in the inertial system by the speed of light, and the value can be directly inquired in a star table. And (3) coordinate rotations corresponding to the time offset correction, wherein the expression is shown as the formula (6). The nutation correction generally adopts a simplified model, the calculation of the nutation delta psi and the inclination nutation delta epsilon of the yellow longitude is shown as a formula (8), based on the above-mentioned time difference-nutation model, the written software program is used for calculating the apparent position of the fixed star, the precision of the simplified model can reach milli-second level,
P＝R x (-z)·R y (θ)·R z (-ζ) (6)
wherein ,Rx 、R y 、R z Is a rotation matrix rotated about the X, Y, Z axes; the z, theta and zeta calculation method is as follows:
wherein, when the time T is the mechanics calculated by the standard epoch of J2000.0, taking the Ru's century as a unit, the rest coefficients can be obtained by inquiring in the related international terrestrial rotation parameter service organization, which is not listed here.
Referring to fig. 3: the method specifically comprises the following steps:
and 5: calculation of astronomical azimuth of ground target
The essence of measuring the astronomical azimuth angle of a ground target is to measure the angle between the meridian plane of the survey station and the plumb plane of the survey station and the target, i.e. the horizontal angle a between OA and OP in fig. 3. Wherein, the point O is a survey station, the point A is a ground target, the point P is a north celestial pole and also represents the north direction of astronomy,
in order to obtain the horizontal angle a between OA and OP, it is necessary to measure the horizontal circle readings of the ground target in the direction a and the direction P of the north celestial pole, and the difference between the two readings is the astronomical azimuth angle of the ground target. Therefore, in the first step, a high bright star such as a star is selected and the rough position of the bright star is solved, and then the bright star is matched and identified by combining the star catalogue, and finally the accurate right ascension and declination values of the bright star at the observation time are obtained;
the accurate right ascension alpha 'and declination delta' of the randomly selected bright star are solved, and the azimuth angle of the automatic theodolite at the moment of observing the fixed star can be solved by the following formula according to the corner relation in the spherical triangle:
wherein ,
measuring station astronomical latitude, delta is declination of a fixed star, A is azimuth angle of the fixed star, t is time angle, and t = S-alpha' -lambda; the accurate azimuth angle A of the randomly selected bright star can be solved by using the formula;
and observing the randomly selected star by using a disk left observation mode for n times, wherein the azimuth angles of the star at the moment of each aiming of the automatic theodolite are respectively as follows: a. The 1 、A 2 ……A n ；
And observing the randomly selected star by using a left-hand observation mode for n times, wherein the dial reading of the automatic theodolite at each aiming moment is respectively as follows: w 1 、W 2 ……W n ；
Observing the randomly selected star for n times by using a left-hand observation mode, wherein the reading of a horizontal scale in the due north direction is respectively as follows: n is a radical of 1 、N 2 ……N n ，N i ＝W i -A i ；
The true north direction value measured by the disk left observation mode is:
the ground target is observed for n times by using a left-hand observation mode, and the dial reading of the automatic theodolite at the moment of each collimation is respectively as follows: m 1 、M 2 ……M n 。
The ground target scale readings measured using the pan left view are:
the astronomical azimuth angle of the ground target measured by the disk left observation mode is as follows:
a L ＝M L -N L (12)
in the same way, the astronomical azimuth angle of the ground target measured by the disk right observation mode is as follows:
a R ＝M R -N R (13)
then the measured terrestrial target astronomical azimuth angle by relying on the randomly selected bright star is as follows:
step 6: re-star-selecting and resolving ground target astronomical azimuth angle by considering geometric distribution characteristics of fixed stars in celestial sphere system
Reselecting a higher bright star 2 (the former selected bright star is abbreviated as bright star 1), wherein the bright star satisfies the following conditions: the elevation angle is around 40 ° and the difference in azimuth angle to the bright star 1 is around 120 °. Then, the operation from the first step to the fourth step is repeated, and the astronomical azimuth angle of the ground target measured by the star 2 is a 2 . And then a high bright star 3 such as a star is selected, and the bright star satisfies the following conditions: the elevation angle is around 40 ° and the difference between the azimuth angles of the bright stars 1, 2 is around 120 °. And then repeating the operation from the first step to the fourth step, wherein the astronomical azimuth angle of the ground target measured by relying on the bright star 2 is a 3 . So far, the process of measuring the astronomical azimuth angle is finished, and the astronomical azimuth angle of the ground target is as follows:
in order to improve the final azimuth angle measurement accuracy, the measurement process needs to be repeated by selecting a plurality of proper time periods according to the measurement accuracy requirement during measurement, and then the average value of the measurement results of a plurality of times is taken to obtain the final terrestrial target astronomical azimuth angle.
In summary, according to the automatic theodolite astronomical azimuth measurement method based on the embodiment, the astronomical azimuth is measured by using a plurality of fixed stars with better geometric distribution characteristics to replace the arbitrary time angle method of the arctic star, so that the applicability of astronomical azimuth measurement is stronger, the influence of weather factors, geographic factors and the like is avoided, and the defect of the arbitrary time angle method of the arctic star is overcome; moreover, a better time difference-nutation model is introduced in the conversion of the position of the fixed star, so that the fixed star can be ensured to have milli-angular-second-level position accuracy; in addition, the whole data processing process is based on a program written by software, so that the automatic processing level of the system is improved, and the requirements of the real-time performance and the accuracy of the system are met.
Claims (5)
1. An astronomical azimuth measurement method based on an automatic theodolite is characterized by comprising the following steps: comprises the following steps of (a) preparing a solution,
step 1: resolution of sidereal declination
After an instrument is debugged at a survey station, randomly selecting a fixed star meeting the star selection condition in the whole sky area, observing the fixed star by using an automatic theodolite, wherein an included angle exists between the 0-degree direction of an automatic theodolite dial and the south direction, and calculating the azimuth angle of the fixed star to be A by using relevant information such as the collimation instantaneous zenith distance, the astronomical latitude of the survey station, the observation angle value of the fixed star and the like so as to solve the declination delta;
step 2: resolution of the sidereal Chin meridian
After calculating the declination delta of the randomly selected bright star, solving a unique time angle t by using the corner relation in the spherical triangle, and obtaining the declination alpha of the randomly selected bright star by using the relation among the time angle, the observation instant Greenwich mean time, the right ascension and the survey station astronomical longitude;
and step 3: match identification of stars
The declination and declination values of the stars calculated in the first two steps are coupled with errors in each measuring link, the result is not the real position of the stars in the celestial sphere, and the astronomical measurement precision of the automatic theodolite is very high, so that the automatic theodolite cannot be directly used for calculating the astronomical azimuth angle of a subsequent ground target, therefore, the stars to be observed must be matched and identified in the star table to obtain the accurate declination and declination values of the stars, namely, a series of comparisons are carried out on the characteristic data of the observed stars and the characteristic data of the stars in the star table, the invention adopts a hash examination finding method to complete the matching and identification of the stars, and the method can directly obtain the data to be searched from a database by one-time calculation without any comparison;
and 4, step 4: sidereal apparent position calculation
So far, finding out the corresponding fixed stars and obtaining the accurate right ascension and declination values; however, the position of the star in the celestial coordinate system is not dust-free, the right ascension and declination values in the star catalogue are values under a certain epoch, and are not the right ascension and declination values at the current observation time, and the right ascension and declination values of the instantaneous star are observed in the calculation of astronomical measurement, so the right ascension and declination values in the star catalogue need to be converted to obtain the accurate right ascension alpha 'and declination delta' values of the instantaneous star, and the conversion process is the apparent position calculation process;
and 5: calculation of astronomical azimuth of ground target
Step 5.1: the astronomical north direction is different from the ground target, cannot be directly aimed by an automatic theodolite, and only can indirectly obtain the astronomical azimuth angle of the ground target by aiming at a certain star to read the reading of a horizontal scale and calculating the azimuth angle of the star; knowing the precise right ascension alpha 'and declination delta' of the fixed star, the precise azimuth angle of the fixed star at the moment when the automatic theodolite aims at the observation fixed star can be calculated according to the corner relationship in the spherical triangle;
step 5.2: observing the randomly selected star lights for multiple times by using a disk left observation mode to obtain the azimuth angle of the star lights at each time of collimation and the disk reading, and finally measuring the true north direction value by using the disk left observation mode;
step 5.3: then, observing the ground target for multiple times by using a disc left observation mode to obtain a reading of a ground target dial, wherein the difference between the due north direction value and the reading of the ground target dial is the astronomical azimuth angle of the ground target measured by using the disc left observation mode; similarly, a ground target astronomical azimuth angle is calculated by using a disc right observation mode, and then the mean value is taken to obtain a final ground target astronomical azimuth angle;
step 6: re-satellite-selection resolving astronomical azimuth angle of ground target
Step 6.1: in order to improve the measurement accuracy, the geometric position relationship of the fixed star in the celestial coordinate system needs to be considered during star selection, namely, a high star such as a star is selected again, and the high star needs to meet corresponding star selection conditions (the height angle and the azimuth angle in the horizontal coordinate system with the measurement station as the origin) in the height angle and the azimuth angle;
step 6.2: then repeating the operation from the step 1 to the step 4, and obtaining a new astronomical azimuth angle of the ground target by relying on the bright star;
step 6.3: selecting another bright star with higher height, wherein the bright star needs to meet the same star selection condition, obtaining the ground target astronomical azimuth angle of the bright star according to the same measurement method as the previous measurement method, and taking the average value of the three measurement results as the measurement result of the ground target astronomical azimuth angle;
step 6.4: in order to improve the final azimuth angle measurement precision, the measurement process needs to be repeated by selecting a plurality of proper time periods according to the measurement precision requirement during measurement, and the final ground target astronomical azimuth angle is obtained by averaging the measurement results of a plurality of times.
2. The method of claim 1 for measuring astronomical directions based on an automatic theodolite, wherein: the step 1 of calculating the azimuth angle of the fixed star as A by using relevant information such as collimation instantaneous zenith distance, observation station astronomical latitude, observation angle value of the fixed star and the like so as to solve the declination delta specifically comprises the following steps:
step 1.1: a spherical triangle which is formed by taking a certain celestial body sigma, a north celestial pole P and a zenith Z of a measuring station as vertexes, wherein the direction of a dotted line is a ground axis, a circular plane passing through points L and W is an equatorial plane, a circular plane passing through points Q and W is a measuring station horizontal plane and is vertical to a plumb line of a measuring station, a point M represents an intersection point of the measuring station horizontal plane and a great arc passing through the zenith Z and the celestial body sigma, and a point N represents an intersection point of the equatorial plane and a great arc passing through the north celestial pole P and the celestial body sigma; according to the geometric relationship among the horizontal coordinate system, the time-angle coordinate system and the equatorial coordinate system, the following relationship exists among the corners in the spherical triangle:
wherein z is the distance between the zenith and the zenith,
the method comprises the following steps of (1) measuring station astronomical latitude, lambda is measuring station astronomical longitude, alpha is fixed star right ascension, delta is fixed star declination, A is fixed star azimuth, t is time angle, t = S-alpha-lambda, and S is observing instantaneous Greenwich mean time of true constellations;
step 1.2: leveling the automatic theodolite at the survey station to enable the rotation axis of the automatic theodolite to coincide with the plumb line, randomly selecting a high bright star with a height angle of 40-45 degrees, such as stars and the like in the whole sky area, observing the bright star by using the automatic theodolite, and assuming that the randomly selected bright star is observed twice, obtaining the corner relation derived from the spherical triangle:
wherein ,
is the astronomical latitude of the survey station, delta is the declination of the fixed star, A is the azimuth of the fixed star, and z 1 、z 2 The zenith distance is used, A' is an observation angle value of a fixed star, delta A is an included angle between the 0-degree direction and the south direction of an automatic theodolite dial, t is a time angle, t = S-alpha-lambda, lambda is a survey station astronomical longitude, and S is the observation instant Greenwich mean time when the fixed star is observed, and alpha is the akashin of the fixed star;
step 1.3: an included angle exists between the 0-degree direction and the south direction of the automatic theodolite dial, the included angle is supposed to be delta A, the automatic theodolite is used for aiming at the instant of a certain fixed star, the observation angle value of the fixed star is A', the azimuth angle of the fixed star is calculated to be A through a corner relation formula derived from an astronomical triangle, and the relationship among the three is as follows: a = a '+ Δ a, developing the cos (a' + Δ a) term:
combining and sorting the two formula items to obtain:
wherein m = sinz 1 cosA 1 ′,n＝sinz 2 cosA 2 ′，z 1 、A 1 ′、z 2 、A 2 The data obtained by observation of the automatic theodolite is known, and m and n are known quantities, so that the formula only contains two unknowns of sin delta and sin delta A, only 4 times of observation needs to be carried out on the randomly selected bright star, and the sin delta can be solved by utilizing a written software program simultaneous equation so as to solve the declination delta.
3. The method of claim 1 for measuring astronomical directions based on an automatic theodolite, wherein: the relation among the time angle, the observation instant Greenwich mean time, the right ascension and the observation station astronomical longitude in the step 2 can obtain the randomly selected right ascension alpha of the bright star as follows:
after calculating the declination delta of the randomly selected bright star, the declination alpha of the bright star can be easily obtained, and the relationship of the corners in the spherical triangle can be known as follows:
and respectively solving cost and sint, and further solving a unique time angle t by utilizing a written software program, wherein t = S-alpha-lambda, S is a known quantity when an instantaneous Greenwich mean star is observed, and the right ascension alpha of the randomly selected bright star can be obtained.
4. The method of claim 1 for astronomical azimuth measurements based on automatic theodolites, characterized in that: the "matching identification method for completing stars by using the hash checking method" described in step 3 is specifically as follows:
step 3.1: establishing a mapping relation H between the storage position of the data and the data, so that the corresponding storage position, namely Location = H (date), can be quickly located through the mapping relation on the premise that the data is known, wherein the Location represents the storage position of the data, the date represents the data, and the time complexity of the hash check is o (1);
step 3.2: based on the idea of hash search, arranging the data in the star table in an ascending manner of the right ascension, and performing curve fitting by taking the right ascension as an independent variable (namely the date of a hash function) and taking the position index as a dependent variable (namely the Location of the hash function) to obtain the hash function;
step 3.3: the independent variable (right ascension) and the dependent variable (storage position) of the hash function are strictly increased, and the constructed hash function has no problem of address conflict (namely one address corresponds to a plurality of right ascensions); based on a hash searching method, when the fixed star matching identification is carried out, a written software program is utilized to quickly reduce the fixed star matching identification area to a small range, and then the data in the small range are compared and screened item by utilizing other characteristic data (declination, star and the like) to obtain a final result.
5. The method of claim 1 for astronomical azimuth measurements based on automatic theodolites, characterized in that: the calculation of the apparent position of the fixed star in the step 4 is specifically as follows:
step 4.1: converting the right ascension and declination values in the star catalogue to obtain accurate right ascension alpha 'and declination delta' values for observing the instantaneous stars;
step 4.2: in the calculation of the apparent position, the light travel difference correction value of the fixed star position is obtained by dividing the speed component of the geocentric in an inertial system by the light speed, and the value can be directly inquired in a star table;
step 4.3: correcting the corresponding 3 times of coordinate rotation according to the years, wherein the expression is shown as a formula (6); based on the above-mentioned time difference-nutation model, the written software program can be used for calculating apparent position of fixed star, and the accuracy of said simplified model can be up to milli-gonic-second level,
P＝R x (-z)·R y (θ)·R z (-ζ) (6)
wherein Rx 、R y 、R z Is a rotation matrix rotated about the X, Y, Z axes;
step 4.4: the z, theta and zeta calculation method is as follows:
step 4.5: the nutation correction generally adopts a simplified model, the yellow longitude nutation delta psi and the inclination nutation delta epsilon are calculated as the formula (8),
wherein, when the time T is the mechanics calculated by the J2000.0 standard epoch, the rest coefficients can be obtained by inquiring related international terrestrial rotation parameter service organizations by taking the Confucian century as a unit.
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