A Fast Method for Determining GNSS Integer Ambiguity Based on Solution Verification Update

Abstract

This invention relates to a rapid determination method for GNSS integer ambiguity based on solution verification and updating. The method includes: screening and classifying all observed satellites in a single epoch into reference satellites, Class I satellites, and Class II satellites; establishing double-difference carrier phase observation equations for Class I and Class II satellite pairs; solving and verifying the double-difference integer ambiguity of the Class I satellite pairs to obtain the double-difference integer ambiguity of the verified Class I satellite pairs, and then solving for the local solutions usable for positioning of the Class I satellite pairs; substituting the local solutions used for positioning of the Class I satellite pairs into the double-difference carrier phase observation equations of the Class II satellite pairs, rounding to calculate the double-difference integer ambiguity of the Class II satellite pairs; and determining the GNSS single-epoch double-difference integer ambiguity based on the double-difference integer ambiguities of the Class I and Class II satellite pairs.

Description

[0001] This application is a divisional application of the invention patent application with the application date of June 28, 2020, the application number of 202010599437.7, and the invention name of "GNSS single epoch double difference integer ambiguity fast determination method". TECHNICAL FIELD

[0002] The present application relates to the technical field of GNSS single epoch double difference integer ambiguity fast determination, and in particular to the application of GNSS receiver in the field of safety monitoring of construction tower crane (construction tower crane or tower crane). BACKGROUND

[0003] In the field of high-precision satellite positioning, the GNSS carrier phase measurement method is generally used. The carrier phase signal is a periodic sinusoidal signal, and the phase measurement can only measure the part less than one wavelength, so there is the problem of integer ambiguity (also known as integer unknown). The fast determination of integer ambiguity is one of the keys to high-precision satellite real-time kinematic positioning.

[0004] In order to quickly determine the integer unknown, the workers in the field have made various efforts, developed various methods, and achieved a lot of achievements. However, in actual engineering application practice, especially in the construction tower crane system, in the case of requiring higher precision real-time positioning, the current method still needs to be improved to reduce the amount of calculation and improve the determination efficiency. SUMMARY

[0005] The present application is made in view of the above situation of the prior art, to solve one or more problems existing in the prior art, and at least provide a beneficial option.

[0006] According to one aspect of the present application, there is provided a GNSS single epoch double-difference integer ambiguity fast determination method based on solution check and update, which comprises: satellite screening and grading processing step, screening and grading all observed satellites in a single epoch, and dividing into reference satellites, class I satellites and class II satellites, the class I satellites are a predetermined number of satellites with relatively better spatial geometric distribution, and the class II satellites are satellites other than the reference satellites and the class I satellites, and are satellites with relatively poor spatial geometric distribution; double-difference carrier phase observation equation establishment step, establishing double-difference carrier phase observation equations of the class I satellite pairs and double-difference carrier phase observation equations of the class II satellite pairs; class I satellite pair local solution step, solving and checking double-difference integer ambiguities of the class I satellite pairs to obtain double-difference integer ambiguities of the class I satellite pairs that pass the check, and then solving local solutions of the class I satellite pairs that can be used for positioning; class II satellite pair double-difference integer ambiguity determination step, substituting the local solutions of the class I satellite pairs that can be used for positioning into the double-difference carrier phase observation equations of the class II satellite pairs, and rounding to solve double-difference integer ambiguities of the class II satellite pairs; and determining GNSS single epoch double-difference integer ambiguities according to the double-difference integer ambiguities of the class I satellite pairs and the double-difference integer ambiguities of the class II satellite pairs.

[0007] According to another aspect of the present application, there is provided a construction tower crane satellite positioning intelligent monitoring system, which comprises GNSS receivers of reference stations and monitoring stations and communication links, and the GNSS receivers use the aforementioned construction tower crane (tower crane) GNSS single epoch double-difference integer ambiguity fast determination method.

[0008] The GNSS receivers are installed on the reference station GNSS receivers near the construction site of the tower crane and the monitoring station GNSS receivers on the tower arm or tower body.

[0009] According to some embodiments of the present application, the integer unknowns can be solved more quickly and efficiently without affecting the positioning accuracy and reliability of the GNSS system.

[0010] According to some embodiments of the present application, all observed satellites in a single epoch are screened and graded, a predetermined number of class I satellites are controlled, and then the search space of satellite pair double-difference ambiguities is greatly compressed, the GNSS single epoch double-difference integer ambiguity solution efficiency is accelerated, and thus the GNSS receiver sampling rate can be appropriately increased. For example, the GNSS receiver sampling rate is increased to 10 Hz. BRIEF DESCRIPTION OF DRAWINGS

[0011] The present application can be better understood in conjunction with the accompanying drawings, which are schematic and not a limitation on the scope of protection of the present application.

[0012] Figure 1A schematic flow of a GNSS single-epoch double-difference integer ambiguity fast determination method according to an embodiment of the present application is shown.

[0013] Figure 2 A schematic flow of a double-difference integer ambiguity resolution check method for a satellite pair of class I according to an embodiment of the present application is shown.

[0014] Figure 3 A schematic block diagram of a GNSS single-epoch double-difference integer ambiguity fast determination apparatus according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0015] Figure 1 A schematic flow of a GNSS single-epoch double-difference integer ambiguity determination method according to an embodiment of the present application is shown.

[0016] As shown in Figure 1 A schematic flow of a GNSS single-epoch double-difference integer ambiguity fast determination method according to an embodiment of the present application is shown. First, satellite screening and grading processing is performed in step S10, i.e. all observation satellites of a single epoch are screened and graded, divided into reference satellites, satellites of class I and satellites of class II, satellites of class I are a predetermined number of satellites with relatively better spatial geometric distribution, satellites of class II are satellites other than reference satellites and satellites of class I, which are satellites with relatively poor spatial geometric distribution.

[0017] According to an embodiment, in step S10, first, the satellite with the largest elevation angle is determined as the reference satellite; then, for satellites other than the reference satellite, the satellite azimuth angle difference is compared according to two adjacent satellites, the two satellites with the smallest satellite azimuth angle difference are obtained, the satellite with the smaller elevation angle among the two satellites is retained, and then repeated to obtain a predetermined number of satellites determined as satellites of class I; finally, the remaining satellites are determined as satellites of class II.

[0018] According to an embodiment, the predetermined number is predetermined to be 5-7 satellites. According to another embodiment, the predetermined number can be determined according to the GNSS receiver sampling interval as follows:

[0019]

[0020] wherein SatNum is the predetermined number, T is the GNSS receiver sampling interval,

[0021] wherein F is the GNSS receiver sampling rate.

[0022] Then, in the double-difference carrier phase observation equation establishing step of step S20, double-difference carrier phase observation equations of the satellite pair of the first type and double-difference carrier phase observation equations of the satellite pair of the second type are established.

[0023] According to an embodiment, in step S20, the double-difference carrier phase observation equations of the satellite pair of the first type are established as follows:

[0024]

[0025] and the double-difference carrier phase observation equations of the satellite pair of the second type are established as follows:

[0026]

[0027] where s is the total number of the satellite pair of the first type, j1 represents the satellite of the first type, j1 = 1, 2, …, s, k is the total number of the satellite pair of the second type, j2 represents the satellite of the second type, j2 = 1, 2, …, k, i represents the reference satellite, λ is the wavelength of the frequency signal, the subscript b represents the base station, the subscript m represents the monitoring station, represents the double-difference carrier phase observation value of the satellite pair of the first type, represents the difference between the inter-station distance observation value and the satellite-earth distance difference of the satellite pair of the first type, represents the satellite-earth distance direction cosine coefficient of the satellite pair of the first type, represents the double-difference integer ambiguity of the satellite pair of the first type, represents the double-difference carrier phase observation value of the satellite pair of the second type, represents the difference between the inter-station distance observation value and the satellite-earth distance difference of the satellite pair of the second type, represents the satellite-earth distance direction cosine coefficient of the satellite pair of the second type, represents the double-difference integer ambiguity of the satellite pair of the second type, and is the three-dimensional coordinate correction of the monitoring station m, and 1 + s + k is a positive integer, indicating the total number of satellites observed in the current epoch.

[0028] Next, in the satellite pair of the first type local solution step of step S30, the double-difference integer ambiguity of the satellite pair of the first type is solved, and the double-difference integer ambiguity of the satellite pair of the first type that passes the check is obtained, and then the local solution of the satellite pair of the first type that can be used for positioning is solved.

[0029] According to an embodiment, as shown in Figure 2 the double-difference integer ambiguity of the satellite pair of the first type is solved as follows in S30:

[0030] Step S1, determining a main frequency signal and an auxiliary frequency signal. In an embodiment, a first frequency signal of a GPS, GLONASS, BDS or Galileo system, or a combined frequency signal formed by linear combination of the first frequency signal and a second frequency signal and / or a third frequency signal of the GPS, GLONASS, BDS or Galileo system, is determined as the main frequency signal, and the second frequency signal or the third frequency signal or the combined frequency signal other than the main frequency signal is determined as the auxiliary frequency signal, the first frequency signal of the GPS, GLONASS, BDS or Galileo system being a primary frequency signal of the GPS, GLONASS, BDS or Galileo system;

[0031] Step S2, establishing a double-difference carrier phase observation equation of the main frequency signal and a double-difference carrier phase observation equation of the auxiliary frequency signal.

[0032] According to an embodiment, the double-difference carrier phase observation equation of the main frequency signal and the double-difference carrier phase observation equation of the auxiliary frequency signal are established as follows:

[0033]

[0034] wherein λ is the wavelength of the frequency signal, including the wavelength of the main frequency signal and the wavelength of the auxiliary frequency signal, when λ is the wavelength of the main frequency signal, the double-difference carrier phase observation equation of the main frequency signal is established, and when λ is the wavelength of the auxiliary frequency signal, the double-difference carrier phase observation equation of the auxiliary frequency signal is established,

[0035] wherein subscript b represents a reference station, subscript m represents a monitoring station, superscript i represents a reference satellite with the largest satellite elevation angle, superscript j represents a satellite other than the reference satellite, j1=1, 2, …, s, is a double-difference carrier phase observation value of a satellite pair of the first type, is a difference between an inter-station-satellite distance observation value of the satellite pair of the first type and a satellite-earth distance difference, and is a satellite-earth distance direction cosine coefficient of the satellite pair of the first type, is a double-difference integer ambiguity of the satellite pair of the first type, and is a three-dimensional coordinate correction number of the monitoring station m, s is a positive integer, and represents the total number of the satellite pair of the first type observed at the current epoch;

[0036] Step S3, determining a candidate group of double-difference integer ambiguities of the main frequency signal by using the double-difference carrier phase observation equation of the auxiliary frequency signal.

[0037] According to an embodiment, the candidate group of double-difference integer ambiguities of the main frequency signal is determined as follows:

[0038] First, calculate the initial value of the double-difference integer ambiguity of the secondary frequency signal as follows:

[0039]

[0040] in, Auxiliary frequency signal f Fu The initial value of the double-difference integer ambiguity. Auxiliary frequency signal f Fu The difference between the observed inter-satellite distance and the satellite-to-Earth distance. Auxiliary frequency signal f Fu Double-difference carrier phase observations, Auxiliary frequency signal f Fu The wavelength;

[0041] Secondly, using the initial value, candidate values ​​for the double-difference integer ambiguity of the auxiliary frequency signal are determined:

[0042] For satellite pairs i and j1,

[0043]

[0044] Where i is the reference satellite, j1 is a Class I satellite, j1 = 1, 2, ..., s, E Length This refers to the band length of the error band for Class I satellites, i and j1. Where: σ is the standard error of the GNSS single-epoch pseudorange difference observation, and λ is... fFu The wavelength of the secondary frequency signal is l = 2 to 5, and int(·) represents the integer operation. Auxiliary frequency signal f Fu Candidate values ​​for double-difference integer ambiguity. w is the number of candidate values;

[0045] Secondly, using the following relational formula, of Determine the main frequency signal f Zhu Candidate values ​​for double-difference integer ambiguity:

[0046]

[0047] in:

[0048] Where u represents the error band. Main frequency signal f Zhu Residual error and measurement noise after inter-satellite double difference Auxiliary frequency signal f Fu Residual error and measurement noise after inter-satellite double difference The wavelength of the main frequency signal. The wavelength of the secondary frequency signal. candidate value of double-difference integer ambiguity of the main frequency signal f Fu Wide bandwidth of error band of the satellite pair i and j1 of the category I satellite, in an embodiment, E Wide may be determined as follows:

[0049] wherein L bm is the baseline length L bm formed between the reference station b and the monitoring station m,

[0050] candidate value of double-difference integer ambiguity of the main frequency signal f Zh v is the number of candidate values;

[0051] Finally, the candidate value of double-difference integer ambiguity of the main frequency signal of the satellite pair of the category I satellite is expressed as follows:

[0052]

[0053] The candidate values are subjected to group permutation combination to obtain candidate groups of double-difference integer ambiguity of the main frequency signal of all satellite pairs in a single epoch, and t represents the total number of candidate groups;

[0054] Step S4, the candidate groups are subjected to significance test by using the double-difference carrier phase observation equation of the main frequency signal, and the candidate group passing the significance test is determined as the optimal group. According to an embodiment, the optimal group of double-difference integer ambiguity of the main frequency signal is determined as follows:

[0055] Firstly, the t groups of candidate groups of double-difference integer ambiguity of the main frequency signal are substituted into the double-difference carrier phase observation equation of the main frequency signal in turn, and according to the least square indirect adjustment principle, the error equation of the corresponding double-difference carrier phase observation equation of the main frequency signal is as follows:

[0056]

[0057] which is written in matrix form as:

[0058]

[0059] wherein,

[0060] the subscript b represents the reference station, the subscript m represents the monitoring station, the superscript i represents the reference satellite with the largest satellite elevation angle, and the superscript j1 represents the satellite other than the reference satellite, j1 = 1, 2, …, s, is the double-difference carrier phase observation value of the satellite pair of the category I satellite, ​​​The wavelength of the main frequency signal. Candidate groups for the double-difference integer ambiguity of the main frequency signal of Class I satellite pairs; This represents the difference between the observed inter-satellite distance and the satellite-to-ground distance for a Class I satellite pair. and The cosine coefficient of the satellite-to-Earth distance direction. The residuals of the double-difference carrier phase observations for a Class I satellite pair. The constant term in the double-difference carrier phase observation equation for the main frequency signal. and Let m be the correction value for the three-dimensional coordinates of monitoring station m;

[0061] Secondly, based on the least squares parameter estimation method, the unit weight variance factor of the double-difference carrier phase observation equation of the main frequency signal is calculated as follows:

[0062]

[0063] Where: s is the total number of Class I satellite pairs, and P is the weight matrix of the double-difference carrier phase observations of Class I satellite pairs;

[0064] From t candidate groups, t unit weight variance factors can be calculated, which can be represented by a set.

[0065] Next, sort the elements in set {Ω} in ascending order to obtain set {Ω} = {Ω1 Ω2 …Ω}. t Construct significance test values:

[0066]

[0067] The candidate group of double-difference integer ambiguities corresponding to Ω1 with ratio > R is determined as the optimal group, i.e. Where R = 1.8 to 3;

[0068] Step S5: Using the double-difference carrier phase observation equation of the main frequency signal, determine the rounding group of the double-difference integer ambiguity of the main frequency signal. According to one embodiment, the rounding group of the double-difference integer ambiguity of the main frequency signal is determined as follows:

[0069] First, the optimal group of double-difference integer ambiguities of the determined main frequency signal is... Substituting the double-difference carrier phase observation equation of the main frequency signal, the three-dimensional coordinate correction of monitoring station m is calculated using the least squares parameter indirect adjustment method. The three-dimensional coordinate correction is then substituted back into the double-difference carrier phase observation equation of the main frequency signal to solve the real solution of the double-difference integer ambiguity of the main frequency signal as follows:

[0070]

[0071] Then, the real number solution is rounded according to the principle of "rounding up six and rounding down five, rounding even number and not rounding odd number", and the rounding set of the double-difference integer ambiguity of the main frequency signal is obtained as follows:

[0072]

[0073] wherein, is the rounding set of the double-difference integer ambiguity of the main frequency signal;

[0074] Step S6, checking the consistency of the optimal set and the rounding set. According to an embodiment, the consistency of the optimal set and the rounding set of the double-difference integer ambiguity of the main frequency signal is checked as follows:

[0075] For the double-difference integer ambiguity of the satellite pair i and j1 of the first type, it is judged whether the optimal set is equal to the rounding set, j1 = 1, 2, …, s.

[0076] If , it is determined that the double-difference integer ambiguity solution of the satellite pair of the first type passes the check, indicating that the double-difference integer ambiguity solution of the satellite pair i and j1 is successful.

[0077] If , it is determined that the double-difference integer ambiguity solution of the satellite pair of the first type fails the check, indicating that the double-difference integer ambiguity solution of the satellite pair i and j1 fails.

[0078] Step S7, obtaining the double-difference integer ambiguity of the satellite pair of the first type that passes the check, i.e.

[0079] According to an embodiment, if the double-difference integer ambiguity solution of the satellite pair of the first type fails the check in step S6, it further includes updating the first type satellite and the second type satellite and updating the double-difference carrier phase observation equation of the satellite pair of the first type and the satellite pair of the second type, and solving with the updated equation.

[0080] According to an embodiment, the first type satellite and the second type satellite are updated as follows: the satellite j1 whose double-difference integer ambiguity solution is successful is retained in the first type satellite, and otherwise, the satellite j1 whose double-difference integer ambiguity solution fails is excluded from the first type satellite and is included in the second type satellite.

[0081] According to an embodiment, the double-difference carrier phase observation equation of the satellite pair of the first type is updated as follows:

[0082]

[0083] wherein: s1≤s

[0084] ​​and the double-difference carrier phase observation equation of the class II satellite pair is updated as follows:

[0085]

[0086] wherein k2≥k

[0087] wherein s1 is the total number of the updated class I satellite pairs, s is the total number of the original class I satellite pairs, j1 represents the class I satellite, j1 = 1, 2, …, s1, k1 is the total number of the updated class II satellite pairs, k is the total number of the original class II satellite pairs, j2 represents the class II satellite, j2 = 1, 2, …, k2, i represents the reference satellite, λ is the wavelength of the frequency signal, the subscript b represents the base station, the subscript m represents the monitoring station, represents the double-difference carrier phase observation value of the class I satellite pair, represents the difference between the inter-station distance observation value and the satellite-earth distance difference of the class I satellite pair, and represents the satellite-earth distance direction cosine coefficient of the class I satellite pair, represents the double-difference integer ambiguity of the class I satellite pair, represents the double-difference carrier phase observation value of the class II satellite pair, represents the difference between the inter-station distance observation value and the satellite-earth distance difference of the class II satellite pair, and represents the satellite-earth distance direction cosine coefficient of the class II satellite pair, represents the double-difference integer ambiguity of the class II satellite pair, and is the three-dimensional coordinate correction of the monitoring station m, 1 + s1 + k2 is a positive integer, 1 + s1 + k2 represents the total number of satellites observed in the current epoch, and 1 + s1 + k2 = 1 + s + k.

[0088] Then, in the class II satellite pair double-difference integer ambiguity determination step of step S40, the partial solution of the class I satellite pair used for positioning is substituted into the double-difference carrier phase observation equation of the class II satellite pair, and the double-difference integer ambiguity of the class II satellite pair is calculated by rounding.

[0089] In one embodiment, the real solution of the double-difference integer ambiguity of the class II satellite pair is calculated as follows:

[0090]

[0091] Then, the real solution is rounded according to the principle of “rounding up for four and rounding down for six, rounding in for five and rounding out for even”, and the rounding set of the double-difference integer ambiguity of the frequency signal is obtained as follows:

[0092]

[0093] wherein, integer resolution of double-difference integer ambiguity of class II satellite pairs.

[0094] Then, in step S50, GNSS single-epoch double-difference integer ambiguity is determined according to double-difference integer ambiguity of class I satellite pairs and double-difference integer ambiguity of class II satellite pairs.

[0095] According to an embodiment, the double-difference integer ambiguity of class I satellite pairs and the double-difference integer ambiguity of class II satellite pairs are combined to directly determine GNSS single-epoch double-difference integer ambiguity, i.e.:

[0096] According to an embodiment of the present application, in the method, real-time positioning can be applied to GNSS receiver data sampling rate not lower than 1 Hz.

[0097] The aforementioned method of the present application can be applied to a construction tower satellite positioning intelligent monitoring system, which comprises GNSS receivers of reference stations and monitoring stations and communication links, and the GNSS receivers use the aforementioned construction tower (tower crane) GNSS single-epoch double-difference integer ambiguity fast determination method. The GNSS receivers are installed on reference station GNSS receivers near the construction site of the tower crane and monitoring station GNSS receivers on the tower arm or tower body.

[0098] The construction tower satellite positioning intelligent monitoring system can comprise a GNSS single-epoch double-difference integer ambiguity fast determination device. Figure 3 A schematic block diagram of a GNSS single-epoch double-difference integer ambiguity fast determination device according to an embodiment of the present application is shown. As Figure 3 shown, the device comprises:

[0099] A satellite screening and grading processing unit 100 screens and grades all observation satellites of a single epoch, and divides them into reference satellites, class I satellites and class II satellites. The class I satellites are a predetermined number of satellites with relatively better spatial geometric distribution, and the class II satellites are satellites other than the reference satellites and the class I satellites, which are satellites with relatively poor spatial geometric distribution.

[0100] A double-difference carrier phase observation equation establishing unit 200 establishes double-difference carrier phase observation equations of class I satellite pairs and double-difference carrier phase observation equations of class II satellite pairs.

[0101] A class I satellite pair local solution unit 300 solves double-difference integer ambiguity of the class I satellite pairs, obtains double-difference integer ambiguity of the class I satellite pairs that passes the check, and further solves a local solution of the class I satellite pairs that can be used for positioning.

[0102] The second-class satellite pair double-difference integer ambiguity determination unit 400 substitutes the local solution of the first-class satellite pair for positioning into the double-difference carrier phase observation equation of the second-class satellite pair, and takes the integer to solve the double-difference integer ambiguity of the second-class satellite pair.

[0103] The GNSS single-epoch double-difference integer ambiguity fast determination unit 500 determines the GNSS single-epoch double-difference integer ambiguity according to the double-difference integer ambiguity of the first-class satellite pair and the double-difference integer ambiguity of the second-class satellite pair.

[0104] The above units respectively perform the operations of the aforementioned satellite screening and grading processing step S10, the double-difference carrier phase observation equation establishment step S20, the first-class satellite pair local solution step S30, the second-class satellite pair double-difference integer ambiguity determination step S40, and the GNSS single-epoch double-difference integer ambiguity fast determination step S50. Specifically, reference can be made to the foregoing descriptions of the corresponding steps. The above units and devices can be respectively or combinedly realized by a programmed independent chip, a specially manufactured chip, a field programmable gate array, or the like hardware alone. Alternatively, the above units and devices can be realized by a machine with a computing processing capability in combination with software.

[0105] The foregoing detailed description of the application merely gives further belief to those skilled in the art for implementing the preferred aspects of the application, and does not limit the scope of the application. Only the claims are used to determine the protection scope of the application. Therefore, the combination of the features and steps in the foregoing detailed description is not necessary for implementing the application in the broadest scope, and alternatively only gives teaching to the representative embodiments of the application which are particularly described in detail. Furthermore, in order to obtain additional useful embodiments of the application, the various features taught in the specification can be combined in various ways, however, these ways are not particularly exemplified.

Claims

1. A GNSS single epoch double-difference integer ambiguity fast determination method based on solving and checking update, the method comprising: a satellite screening and grading processing step, screening and grading all observed satellites of a single epoch, into reference satellites, class I satellites and class II satellites, the class I satellites being a predetermined number of satellites with relatively better spatial geometric distribution, and the class II satellites being satellites other than the reference satellites and the class I satellites, and being satellites with relatively poor spatial geometric distribution; a double-difference carrier phase observation equation establishment step, establishing double-difference carrier phase observation equations for pairs of class I satellites and pairs of class II satellites; a class I satellite pair local solving step, solving double-difference integer ambiguities for the pairs of class I satellites, obtaining double-difference integer ambiguities for pairs of class I satellites that pass the check, and then solving local solutions for positioning of the pairs of class I satellites; a class II satellite pair double-difference integer ambiguity determination step, substituting the local solutions for positioning of the pairs of class I satellites into the double-difference carrier phase observation equations for pairs of class II satellites, and solving double-difference integer ambiguities for the pairs of class II satellites; and a GNSS single epoch double-difference integer ambiguity fast determination step, determining GNSS single epoch double-difference integer ambiguities based on the double-difference integer ambiguities for the pairs of class I satellites and the double-difference integer ambiguities for the pairs of class II satellites, wherein the satellite screening and grading processing step comprises: first, determining the satellite with the largest elevation angle as the reference satellite; second, for satellites other than the reference satellite, comparing the azimuth angles of every two adjacent satellites to obtain two satellites with the smallest azimuth angle difference, retaining the satellite with the smaller elevation angle among the two satellites, and then repeating the process to obtain a predetermined number of satellites as the class I satellites; finally, determining the remaining satellites as the class II satellites, wherein the predetermined number is determined according to the sampling interval of the GNSS receiver as follows: wherein, is the predetermined number, is the GNSS receiver sampling interval, , is the GNSS receiver sampling rate, wherein the local solution for positioning of the pairs of class I satellites is solved as follows: substituting the double-difference integer ambiguities for the pairs of class I satellites that pass the check into the double-difference carrier phase observation equations for the pairs of class I satellites that are re-established, and using the least squares parameter estimation method to solve the local solution for positioning of the pairs of class I satellites, characterized in that in the class II satellite pair double-difference integer ambiguity determination step, the real solution for the double-difference integer ambiguities for the pairs of class II satellites is solved as follows: then, rounding the real solution according to the principle of "rounding up for six and rounding down for five, and rounding up for even and rounding down for odd", to obtain a set of rounded double-difference integer ambiguities for the frequency signals as follows: wherein is the integer solution of the double-difference integer ambiguity for a pair of class II satellites.

2. The method of claim 1, wherein, in the class I satellite pair local solving step, the double-difference integer ambiguities for the pairs of class I satellites are solved as follows: step S1, determining the primary frequency signal and the secondary frequency signal, The first frequency signal of the GPS, GLONASS, BDS or Galileo system, or a combined frequency signal formed by linear combination of the first frequency signal and a second frequency signal and / or a third frequency signal, is determined as a main frequency signal, and a second frequency signal or a third frequency signal or a combined frequency signal other than the main frequency signal is determined as an auxiliary frequency signal, the first frequency signal of the GPS, GLONASS, BDS or Galileo system being a main frequency signal of the GPS, GLONASS, BDS or Galileo system; Step S2, establishing double-difference carrier phase observation equations of the main frequency signal and double-difference carrier phase observation equations of the auxiliary frequency signal, The double-difference carrier phase observation equations of the main frequency signal and the double-difference carrier phase observation equations of the auxiliary frequency signal are established as follows: wherein, is the wavelength of the frequency signal, including the wavelength of the primary frequency signal and the wavelength of the secondary frequency signal, when is the wavelength of the primary frequency signal, the double-difference carrier phase observation equation for the primary frequency signal is established, when is the wavelength of the secondary frequency signal, the double-difference carrier phase observation equation for the secondary frequency signal is established, wherein subscript represents a reference station, subscript represents a monitoring station, superscript represents a reference satellite with the largest satellite elevation angle, superscript represents a satellite other than the reference satellite, , is a double-difference carrier phase observation value of a satellite pair of Class I, is a difference between a station-satellite distance observation value of the satellite pair of Class I and a satellite-earth distance difference, , and is a satellite-earth distance direction cosine coefficient of the satellite pair of Class I, is a double-difference integer ambiguity of the satellite pair of Class I, , and is a three-dimensional coordinate correction of the monitoring station m, is a positive integer, indicating the total number of the satellite pair of Class I observed at the current epoch. Step S3, determining a candidate group of double-difference integer ambiguity of the main frequency signal by using the double-difference carrier phase observation equations of the auxiliary frequency signal, The candidate group of double-difference integer ambiguity of the main frequency signal is determined as follows: Firstly, the initial value of the double-difference integer ambiguity of the auxiliary frequency signal is calculated as follows: wherein is a double-difference integer ambiguity initial value for the secondary frequency signal is a double-difference integer ambiguity initial value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal is a double-difference carrier phase observation value for the secondary frequency signal Secondly, the initial value is used to determine the candidate value of the double-difference integer ambiguity of the auxiliary frequency signal: For satellites pair i and , wherein i denotes a reference satellite, is a class I satellite, , denotes a band length of an error band of the class I satellite for i and , is a candidate value of a double-difference integer ambiguity of a secondary frequency signal , , is a number of candidate values; Again, the candidate value of the double-difference integer cycle ambiguity of the primary frequency signal is determined by using the following relation: Again, the candidate value of the double-difference integer cycle ambiguity of the primary frequency signal is determined by using the following relation:​​ ， wherein, is the error band, is the primary frequency signal is the residual error and measurement noise after station- inter- satellite double difference, is the secondary frequency signal is the residual error and measurement noise after station- inter- satellite double difference, is the wavelength of the primary frequency signal, is the wavelength of the secondary frequency signal, is the secondary frequency signal is the double-difference integer ambiguity candidate value, denotes the error band of the primary satellite pair i and is the bandwidth of the error band, is the double-difference integer ambiguity candidate value of the primary frequency signal , , is the number of candidate values; Finally, the candidate value of the double-difference integer ambiguity of the main frequency signal of the satellite pair of the first type is expressed as follows: performing the following operations on the candidate values obtaining a candidate set of double-difference integer ambiguity of the main frequency signal of the satellite pair of the first type, t represents the total number of candidate sets; Step S4, performing significance test on the candidate group by using the double-difference carrier phase observation equations of the main frequency signal, and determining the candidate group passing the significance test as an optimal group, The optimal group of the double-difference integer ambiguity of the main frequency signal is determined as follows: Firstly, the t candidate groups of the double-difference integer ambiguity of the main frequency signal are sequentially substituted into the double-difference carrier phase observation equations of the main frequency signal, and the error equation of the corresponding double-difference carrier phase observation equation of the main frequency signal is calculated according to the least square indirect adjustment principle: The matrix form is as follows: wherein , , , , subscript denotes a reference station, subscript m denotes a monitoring station, superscript denotes a reference satellite with the largest satellite elevation angle, superscript denotes a satellite of class I, , is a double-difference carrier phase observation of a pair of satellites of class I, is a wavelength of a primary frequency signal, is a candidate set of double-difference integer ambiguities of the primary frequency signal of the pair of satellites of class I; is a difference between a station-satellite range observation and a satellite-earth distance difference of the pair of satellites of class I, , and are satellite-earth distance direction cosine coefficients, is a residual of the double-difference carrier phase observation of the pair of satellites of class I, is a constant term of a double-difference carrier phase observation equation of the primary frequency signal, , and are three-dimensional coordinate corrections of the monitoring station m; Secondly, the unit weight variance factor of the double-difference carrier phase observation equation of the main frequency signal is calculated according to the least square parameter estimation method as follows: wherein: is the total number of pairs of class I satellites, is the weight matrix of the double-difference carrier phase observations of pairs of class I satellites. From the t sets of candidate groups, t unit-weight variance factors can be computed, denoted by the set ; Next, the elements in the set are sorted from small to large, obtaining the set , and the significance test value is constructed: ， Will of The candidate group corresponding to the double-difference integer ambiguity is determined as the optimal group, i.e. ,in =1.8~3; Step S5, determining the rounding group of the double-difference integer ambiguity of the main frequency signal by using the double-difference carrier phase observation equations of the main frequency signal, The rounding group of the double-difference integer ambiguity of the main frequency signal is determined as follows: First, the optimal group of double-difference integer ambiguity of the determined main frequency signal is calculated The double-difference carrier phase observation equation of the main frequency signal is substituted, the least square parameter indirect adjustment method is adopted, the three-dimensional coordinate correction number of the monitoring station m is calculated and obtained, and the three-dimensional coordinate correction number is substituted back to the double-difference carrier phase observation equation of the main frequency signal. The real solution of the double-difference integer ambiguity of the main frequency signal is calculated as follows: Then, the real solution is rounded according to the principle of "rounding off six and rounding in, rounding off five and rounding in, and rounding off even and not rounding in", and the rounding group of the double-difference integer ambiguity of the main frequency signal is obtained as follows: wherein an integer number of double-difference cycle slips for the primary frequency signal; Step S6, checking the consistency of the optimal group and the rounding group, The consistency of the optimal group and the rounding group of the double-difference integer ambiguity of the main frequency signal is checked as follows: For the double-difference integer ambiguity of the I-class satellite pair i and , judge whether the in the optimal group is equal to the in the rounding group, ; If , it is determined that the double-difference integer ambiguity resolution check of the satellite pair of class I is passed, indicating that the double-difference integer ambiguity resolution of the satellite pair i and is successful; If , then it is determined that the double-difference integer ambiguity resolution check for the class I satellite pair fails, indicating that the double-difference integer ambiguity resolution for the satellite pair i and has failed. Step S7, obtain the double-difference integer ambiguity of the Class I satellite pair that passes the check, that is: .

3. The method of claim 2, wherein, If the double-difference integer ambiguity solution of the satellite pair of the first type fails to pass the checking in step S6, the method further comprises: updating the class I satellites and class II satellites, the satellites for which the double-difference integer ambiguity resolution was successful leaving in the class I satellites, the satellites for which the double-difference integer ambiguity resolution was unsuccessful classifying into the class II satellites, updating the double-difference carrier phase observation equation of the satellite pair of the first type: ， and updating the double-difference carrier phase observation equation of the satellite pair of the second type: ， wherein is the total number of updated Class-I satellite pairs, is the total number of original Class-I satellite pairs, denotes a Class-I satellite, , is the total number of updated Class-II satellite pairs, is the total number of original Class-II satellite pairs, denotes a Class-II satellite, , denotes a reference satellite, is the wavelength of the frequency signal, subscript denotes a base station, subscript denotes a monitoring station, denotes a double-difference carrier phase observation of a Class-I satellite pair, denotes the difference between a station-satellite range observation and a satellite-ground range difference of a Class-I satellite pair, , and denotes a satellite-ground range direction cosine factor of a Class-I satellite pair, denotes a double-difference integer ambiguity of a Class-I satellite pair, denotes a double-difference carrier phase observation of a Class-II satellite pair, denotes the difference between a station-satellite range observation and a satellite-ground range difference of a Class-II satellite pair, , and denotes a satellite-ground range direction cosine factor of a Class-II satellite pair, denotes a double-difference integer ambiguity of a Class-II satellite pair, , and is a three-dimensional coordinate correction of the monitoring station m, is a positive integer, indicating the total number of satellites observed at the current epoch, .

4. The method of claim 2, wherein, is determined as follows : ， wherein: is the baseline length formed between the reference station b and the monitoring station m.

5. The method of claim 2, wherein, is determined as follows : ， wherein: is the mean error of the GNSS single-epoch pseudorange difference observation, is the wavelength of the secondary frequency signal, = 2 ~ 5, denotes the rounding operation.

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