A GNSS partial ambiguity fixing method and system based on element-by-element ratio test

Abstract

The present invention discloses a GNSS partial ambiguity fixing method and system based on element-by-element ratio test. By constructing an element-by-element ratio test method, quality checks are carried out on the elements in the integer ambiguity alternative group one by one using the ratio test method, so as to judge the reliability of all ambiguity elements at one time, solve the key problem of quickly and effectively selecting a reliable ambiguity subset in high-dimensional ambiguity fixing, require lower computing power compared with the classical partial ambiguity fixing method, and ensure the stability of the method at the same time. The present invention solves the problem that high-dimensional ambiguities are difficult to be quickly and reliably fixed as a whole in the fields of existing GNSS high-precision positioning, satellite orbit determination, etc., has the characteristics of rigorous theory, simple model, easy implementation, etc., and can be applied to high-precision position service fields such as autonomous driving.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite navigation, and particularly relates to a method and system for GNSS (Global Navigation Satellite System) partial ambiguity fixing based on element-by-element ratio test. Background Art

[0002] Integer ambiguity fixing is an important technology for high-precision GNSS data processing, which can effectively improve the accuracy of GNSS positioning, satellite orbit determination, etc. In recent years, GNSS has been developing increasingly maturely. The number of observable satellites for users is increasing, and the satellite geometric configuration has been significantly improved. However, at the same time, the ambiguity dimension has also increased greatly, bringing challenges to the overall fast and reliable fixing. High-speed moving carriers such as vehicles, aircraft, and low-earth orbit satellites have high requirements for positioning real-time performance. The inability to quickly solve and fix high-dimensional ambiguities may reduce the overall performance of the system or even lead to system failure. Constructing a fast and effective ambiguity fixing method is the key to solving high-precision real-time GNSS positioning.

[0003] Partial ambiguity fixing is an effective means to solve the problem of high-dimensional ambiguity fixing. By fixing some of the elements rather than all of them, the positioning result can be improved. Compared with the integer ambiguity fixing strategy of accepting or rejecting all ambiguities completely, partial ambiguity fixing can exclude the influence of poorly qualified ambiguity elements on the whole, only fix reliable ambiguity elements, and is more flexible to use. Moreover, the number of ambiguity elements to be fixed is less, and the timeliness is higher. However, in the high-dimensional ambiguity scenario, the overall search of ambiguities takes a long time, and the computing power consumption is even more severe when using iterative strategies to eliminate / select some ambiguity elements, making it difficult to meet the requirements of real-time high-precision positioning. At the same time, the correlation between ambiguity elements is strong, and the reliability judgment of a single ambiguity element is easily affected by the remaining elements, making it difficult to select an effective subset of ambiguities. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a partial ambiguity fixing method that not only does not require iterative search to reduce the time-consuming of ambiguity fixing, but also can reliably screen the elements of the ambiguity subset. By performing element-by-element ratio test to judge the reliability of each element in the integer ambiguity candidate group, the fast and effective selection of the partial ambiguity subset is realized, and the calculation time is less.

[0005] According to one aspect of the specification of the present invention, a method for GNSS partial ambiguity fixing based on element-by-element ratio test is provided, including:

[0006] Solving the constructed GNSS hybrid integer parameter estimation model by using real number least squares estimation to obtain the floating-point solutions of GNSS integer ambiguity parameters and other real parameters;

[0007] Using the element-by-element ratio test method, a subset of ambiguities that meets the element-by-element ratio test criteria is selected to obtain reliable floating-point ambiguities;

[0008] The obtained floating-point ambiguities are fixed to integer ambiguities, and the fixed solutions of other real parameters are updated and obtained.

[0009] As a further technical solution, using the element-by-element ratio test method, a subset of ambiguities that meets the element-by-element ratio test criteria includes:

[0010] While obtaining the optimal solution of the ambiguities At the same time, the sub-optimal solutions for all individual ambiguity elements are obtained , , that is, the sub-optimal solution Among all the integer ambiguity alternative groups in which the i-th element has the closest Mahalanobis distance to the i-th element of the floating-point ambiguity; if the Mahalanobis distances of the i-th elements in multiple alternative groups to the i-th element of the floating-point ambiguity are the same, the alternative group with the smallest Mahalanobis distance to the floating-point ambiguity Is selected as the sub-optimal solution; thus, a total of n groups of ratio test relationships between the sub-optimal and optimal solutions for the i-th element are constructed to achieve quality control of individual ambiguity elements and serve as the basis for selecting the ambiguity subset.

[0011] As a further technical solution, the ambiguity subset Is defined in the following manner:

[0012]

[0013] Wherein Represents a sub-optimal ambiguity alternative group, in which the i-th element cannot be the same as the i-th element in the optimal solution, and in addition, it satisfies the condition of the smallest Mahalanobis distance; Represents the variance-covariance information of the integer ambiguity parameter; Represents any n-dimensional integer vector, where the i-th element is different from the i-th element in the optimal solution ; Represents the ratio of the Mahalanobis distances.

[0014] As a further technical solution, when using real number least squares estimation to solve the constructed GNSS mixed integer parameter estimation model, it further includes: obtaining the variance-covariance matrix between the integer ambiguity parameter and other real parameters.

[0015] As a further technical solution, the method further includes: when obtaining the fixed solution of the real parameter, updating its variance-covariance information.

[0016] As a further technical solution, fixing the obtained floating-point ambiguity to an integer ambiguity includes:

[0017] Define the ambiguity number set as a subset of , representing the ambiguity set corresponding to the subset number, and the corresponding floating-point solution and fixed solution are respectively expressed as and , and the projection function with some ambiguities fixed is expressed as ; using the domain to give the definition of the projection function :

[0018] ,

[0019] The domain contains any , where obtains the integer vector through the action of the partial ambiguity fixed projection function .

[0020] As a further technical solution, the constructed GNSS hybrid integer parameter estimation model is as follows:

[0021] ,

[0022] where represents the m-dimensional observation vector; represents the n-dimensional integer parameter to be estimated; represents the -dimensional real parameter to be estimated; the design matrices and are full-rank matrices determined by the observations; is the observation noise.

[0023] According to one aspect of the specification of the present invention, a GNSS partial ambiguity fixing system based on element-by-element ratio test is provided, and the system includes:

[0024] A first calculation module for solving the constructed GNSS hybrid integer parameter estimation model using real number least squares estimation to obtain the floating-point solutions of GNSS integer ambiguity parameters and other real parameters;

[0025] A second calculation module for selecting the ambiguity subset that meets the element-by-element ratio test index using the element-by-element ratio test method to obtain reliable floating-point ambiguities;

[0026] A third calculation module for fixing the obtained floating-point ambiguities to integer ambiguities and updating to obtain the fixed solutions of other real parameters.

[0027] According to one aspect of the specification of the present invention, there is provided a GNSS partial ambiguity fixing device based on element-by-element ratio test, including a memory and a processor. The memory stores program instructions executed by the processor, and the processor calls the program instructions to execute the steps of the method for GNSS partial ambiguity fixing based on element-by-element ratio test.

[0028] According to one aspect of the specification of the present invention, there is provided a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the steps of the method for GNSS partial ambiguity fixing based on element-by-element ratio test.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The method and system for GNSS partial ambiguity fixing based on element-by-element ratio test of the present invention judge the reliability of each element in the integer ambiguity candidate group through element-by-element ratio test. Compared with the classical integer ambiguity fixing method, it can quickly and effectively select a partial ambiguity subset without iteration, and the calculation time consumption is less. The present invention solves the key problem of ambiguity subset selection in high-dimensional integer ambiguity fixing, and has the characteristics of strict theory, simple model, easy to implement, etc., and can be applied to multiple fields such as GNSS high-precision positioning and precise satellite orbit determination. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings used in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic flow chart of the method provided by the embodiment of the present invention.

[0033] Figure 2 It is a two-dimensional schematic diagram of the aperture space of the element-by-element ratio test provided by the embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of the cumulative distribution function of the partial ambiguity fixed orbit error 3DRMS in the real-time orbit determination of low-earth orbit satellites provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] In view of the current situation of difficult screening of ambiguity subset elements and time-consuming ambiguity fixing in the prior art, the present invention proposes a GNSS partial ambiguity fixing method and system with low computing power requirements and strong stability, which can achieve fast and reliable fixing of real-time ambiguities in the multi-GNSS background, and is of great significance for high-precision real-time positioning of carriers, high-precision position services such as autonomous driving, etc.

[0036] The terms "comprising" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0037] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention. In addition, the technical features in each embodiment or a single embodiment provided by the present invention can be combined with each other arbitrarily to form a new technical solution. Such combination is not restricted by the order of steps and / or the pattern of structural composition, but must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions conflicts with each other or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0038] The embodiment of the present invention provides a GNSS partial ambiguity fixing method based on element-by-element ratio test. First, the floating-point solutions of GNSS integer ambiguity parameters and other real parameters are obtained by using real number least squares estimation to solve the constructed GNSS mixed integer parameter estimation model; then, the element-by-element ratio test method is used to select the ambiguity subset that meets the element-by-element ratio test index to obtain reliable floating-point ambiguities; finally, the obtained floating-point ambiguities are fixed to integer ambiguities, and the fixed solutions of other real parameters are updated.

[0039] Specifically, when constructing the GNSS mixed integer parameter estimation model, the GNSS observation equation is written in a linear form:

[0040] ,

[0041] where, represents an m-dimensional observation vector; represents an n-dimensional integer parameter to be estimated; Denote the m-dimensional real-valued parameter to be estimated; the design matrix and are full-rank matrices determined by the observations; is the observation noise, which follows a zero-mean Gaussian distribution when the observation model is accurate, and its variance-covariance matrix can be written as .

[0042] According to the application scenario and positioning mode, the GNSS observations can be carrier phase observations in the form of undifferenced, single-differenced, double-differenced, etc. At this time represents the integer ambiguity or its linear combination, can refer to other real-valued parameters to be estimated such as station coordinates / baseline vectors, satellite clock biases, receiver clock biases, ionospheric parameters, tropospheric parameters, etc.

[0043] Solve the above model according to the following steps:

[0044] (1) Ignoring the integer nature of the integer parameters, solve using a real-valued least squares estimator to obtain the parameters to be estimated and :

[0045]

[0046] where , , . and The two orthogonal projection matrices in and are written as:

[0047]

[0048] where represents the m-dimensional identity matrix.

[0049] The obtained parameters and follow a Gaussian distribution, written as:

[0050]

[0051] represents the variance-covariance matrix between elements, represents the variance-covariance matrix between elements, , represents the variance-covariance matrix between the parameters and and are transposes of each other.

[0052] (2) The floating-point ambiguity Mapped to corresponding integers through an integer estimator , the projection function is denoted as , where . . The ambiguity fixing process is written as:

[0053]

[0054] (3) Taking as the prior value, update the parameter , and obtain :

[0055]

[0056] , , represent a p-dimensional real vector, an n-dimensional real vector, and an m-dimensional integer vector respectively.

[0057] The obtained real vector is the fixed solution.

[0058] In the embodiment of the present invention, the GNSS partial ambiguity fixing process further includes constructing an integer least squares optimal solution.

[0059] Since the parameter estimation can be fixed to any integer vector through the projection function , first define the optimal solution. Solved using the real least squares criterion, the objective function can be written as:

[0060]

[0061] The above extreme value problem has been proven to be convertible to an integer least squares problem, and the solution criterion is , written as (XU P, CANNON E, LACHAPELLE G. Mixed integer programming for the resolution of GPS carrier phase ambiguities [M], IUGG95 Assembly; 1995, Boulder: 2-14):

[0062]

[0063] where , that is, the Mahalanobis Distance. Denote the number field satisfying the above condition as , then for any real vector , except for the unique integer vector All other integer vectors have a Mahalanobis distance to this real vector greater than the Mahalanobis distance to this real vector, that is:

[0064]

[0065] At this time, this integer vector is called the optimal solution. At the same time, a sub-optimal solution is defined, that is, except the integer vector with the second smallest Mahalanobis distance to any real vector .

[0066] In the embodiment of the present invention, the GNSS partial ambiguity fixing process further includes constructing a GNSS partial ambiguity fixing projection function .

[0067] For the n-dimensional ambiguity , the ambiguity fixing solution obtained by the projection function is the fixing of all ambiguities, while the partial ambiguity fixing means only fixing some elements in. Define the ambiguity number set as a subset of, represents the ambiguity set corresponding to the subset number, and the corresponding floating-point solution and fixed solution are respectively represented as and , and the projection function for partial ambiguity fixing is represented as ; using the domain to give the definition of the projection function :

[0068] ,

[0069] That is, the domain contains any , where obtains an integer vector through the action of the partial ambiguity fixing projection function . Through describing the relationship between the n-dimensional integer ambiguity and the floating-point ambiguity , we can get:

[0070] .

[0071] Among them, the ambiguity vector of the fixed partial ambiguity elements can be written as an improvement to the real vector :

[0072]

[0073]

[0074] Fixing different ambiguity subsets Fixing the real number fixed solution has different effects. The more ambiguities are fixed, the higher the accuracy of the fixed solution, but the reliability of the fixed ambiguity will also be affected. Therefore, a corresponding test method needs to be constructed to determine the ambiguity subset to be fixed.

[0075] The element-by-element ratio test method described in the embodiments of the present invention, that is, the construction of the element-by-element ratio test index and the subset selection method are as follows. The classical ratio test method controls the quality of the optimal solution by setting the empirical threshold of the Mahalanobis distance ratio of the optimal solution and the sub-optimal solution. If the threshold requirement cannot be met, the fixed solution is considered unreliable, and all integer ambiguity elements are discarded, and the accuracy of the floating-point solution cannot be further improved. The element-by-element ratio test method proposed by the present invention determines the reliability of the ambiguity elements one by one, thereby constructing an ambiguity subset selection method to achieve partial ambiguity fixing.

[0076] Specifically, while obtaining the optimal ambiguity solution , obtain the sub-optimal solution for all single ambiguity elements , that is the Mahalanobis distance between the i-th element in all integer ambiguity alternative groups in and the i-th element of the floating-point ambiguity is the closest. If the Mahalanobis distance between the i-th element in multiple alternative groups and the i-th element of the floating-point ambiguity is the same, select the alternative group with the smallest Mahalanobis distance between as the sub-optimal solution. Thus, a total of n groups of ratio test relationships between the sub-optimal and optimal solutions for the i-th element are constructed, so as to realize the quality control of individual ambiguity elements and serve as the basis for subset selection.

[0077] Define the ambiguity subset in the following way:

[0078]

[0079] The above formula is the element-by-element ratio test method constructed by the invention, where represents a sub-optimal ambiguity alternative group, and the i-th element in this alternative group cannot be the same as the i-th element in the optimal solution, and in addition, it satisfies the condition of the smallest Mahalanobis distance.

[0080] Please refer to Figure 1, in the embodiment of the present invention, taking the real-time precise orbit determination of the GRACE-D satellite as an example, a method for fixing GNSS partial ambiguities based on element-by-element ratio test is provided, which specifically includes the following steps:

[0081] Step 1, establish the observation equation for the real-time precise orbit determination of the GRACE-D satellite, and obtain the floating-point solutions of the GNSS integer ambiguity parameters and the floating-point solutions of the GRACE-D satellite orbit and receiver clock error parameters , and at the same time obtain the variance-covariance matrix between the integer ambiguity parameters and other parameters .

[0082] Step 2, use the element-by-element ratio test method disclosed in the present invention, input and , select the ambiguity subset that meets the element-by-element ratio test index , and finally obtain a reliable ambiguity vector . .

[0083] Step 3, fix the floating-point ambiguity to the integer ambiguity , then update other real parameters , obtain the fixed solutions of the real parameters , and update their variance-covariance information , thereby obtaining the fixed solutions for the real-time precise orbit determination of the final low-earth orbit satellite.

[0084] The two-dimensional schematic diagram of the aperture space corresponding to the element-by-element ratio test in the embodiment of the present invention (representing the two-dimensional integer domain) is shown in Appendix Figure 2 , and the cumulative distribution function of the 3DRMS of the partial ambiguity fixed orbit error in the real-time orbit determination of the low-earth orbit satellite is shown in Appendix Figure 3 .

[0085] The implementation basis of each embodiment of the present invention is realized through programmed processing by a device with processor functions. Therefore, in engineering practice, the technical solutions and functions of each embodiment of the present invention are encapsulated into various modules. Based on this actual situation, on the basis of the above embodiments, the embodiment of the present invention provides a GNSS partial ambiguity fixing system based on element-by-element ratio test, which is used to execute a GNSS partial ambiguity fixing method based on element-by-element ratio test in the above method embodiment.

[0086] The system includes: a first calculation module, which is used to solve the constructed GNSS mixed-integer parameter estimation model by using real number least squares estimation to obtain the floating-point solutions of GNSS integer ambiguity parameters and other real parameters; a second calculation module, which is used to select the ambiguity subset that meets the element-by-element ratio test index by using the element-by-element ratio test method to obtain reliable floating-point ambiguities; a third calculation module, which is used to fix the obtained floating-point ambiguities to integer ambiguities and update to obtain the fixed solutions of other real parameters.

[0087] A GNSS partial ambiguity fixing system based on element-by-element ratio test provided by an embodiment of the present invention faces the current situation of difficult selection of elements in the existing ambiguity subset and time-consuming ambiguity fixing. By using the several modules described above, it judges the reliability of each element in the integer ambiguity alternative group through the element-by-element ratio test. Compared with the classical integer ambiguity fixing method, it can quickly and effectively select a partial ambiguity subset without iteration and takes less calculation time.

[0088] It should be noted that the system embodiment provided by the present invention, in addition to being used to implement the method in the above method embodiment, is also used to implement the methods in other method embodiments provided by the present invention. The difference is only in setting the corresponding functional modules, and its principle is basically the same as the principle of the above system embodiment provided by the present invention. As long as those skilled in the art, on the basis of the above system embodiment, refer to the specific technical solutions in other method embodiments, obtain the corresponding technical means by combining technical features, and the technical solutions composed of these technical means, and on the premise of ensuring the practicability of the technical solutions, improve the modules in the above system embodiment to obtain the corresponding system-like embodiments for implementing the methods in other method-like embodiments.

[0089] Based on the same inventive concept as the above embodiment, an embodiment of the present invention also provides a GNSS partial ambiguity fixing device based on element-by-element ratio test, including a memory and a processor. The memory stores program instructions executed by the processor, and the processor calls the program instructions to execute the steps of a GNSS partial ambiguity fixing method based on element-by-element ratio test.

[0090] In an embodiment of the present invention, the memory may be a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), etc., or may also be a volatile memory, such as a random-access memory (RAM). The memory is any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory in the embodiment of the present invention may also be a circuit or any other device capable of implementing a storage function, for storing program instructions and / or data.

[0091] In an embodiment of the present invention, the processor may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and can implement or execute the various methods, steps and logic block diagrams disclosed in the embodiments of the present invention. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present invention can be directly embodied as being executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

[0092] Based on the same inventive concept as the above embodiments, an embodiment of the present invention further provides a non-transitory computer-readable storage medium storing computer instructions that cause the computer to execute the steps of a method for GNSS partial ambiguity fixing based on element-by-element ratio test.

[0093] In summary of the above embodiments, the present invention discloses a method and system for GNSS partial ambiguity fixing based on element-by-element ratio test. By constructing an element-by-element ratio test method, the elements in the integer ambiguity candidate group are checked for quality one by one using the ratio test method, so as to judge the reliability of all ambiguity elements at one time, solving the key problem of quickly and effectively selecting a reliable ambiguity subset in high-dimensional ambiguity fixing. Compared with the classical partial ambiguity fixing method, the computing power requirement is lower, and at the same time, the stability of the method is ensured. The present invention solves the problem that high-dimensional ambiguities are difficult to be reliably fixed as a whole quickly in the fields of existing GNSS high-precision positioning, satellite orbit determination, etc., and has the characteristics of strict theory, simple model, easy implementation, etc., and can be applied to high-precision position service fields such as autonomous driving.

[0094] It should be understood that the parts not elaborated in this specification all belong to the prior art.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A GNSS partial ambiguity fixing method based on element-by-element ratio test, characterized in that Comprising: Solving a constructed GNSS mixed integer parameter estimation model by using real number least squares estimation to obtain floating point solutions of GNSS integer ambiguity parameters and other real parameters; Using an element-by-element ratio test method to select an ambiguity subset that meets the element-by-element ratio test index to obtain reliable floating point ambiguities; The method of using element-by-element ratio test to select the ambiguity subset that meets the element-by-element ratio test index includes: while obtaining the optimal solution of the ambiguity simultaneously, obtaining the sub-optimal solutions for all individual ambiguity elements , , that is, the sub-optimal solution in which the i-th element in all integer ambiguity alternative groups has the closest Mahalanobis distance to the i-th element of the floating-point ambiguity; if the Mahalanobis distances of the i-th elements in multiple alternative groups to the i-th element of the floating-point ambiguity are the same, select the alternative group with the smallest Mahalanobis distance to the floating-point ambiguity as the sub-optimal solution; thus, a total of n groups of ratio test relationships between the sub-optimal and optimal solutions for the i-th element are constructed to achieve quality control of individual ambiguity elements and serve as the basis for selecting the ambiguity subset. Fixing the obtained floating point ambiguities to integer ambiguities and updating to obtain fixed solutions of other real parameters.

2. The GNSS partial ambiguity fixing method based on element-by-element ratio test according to claim 1, characterized in that Ambiguity subset is defined as follows: ， wherein represents a sub - optimal ambiguity candidate group, in which the i - th element cannot be the same as the i - th element in the optimal solution, and in addition satisfies the condition of the minimum Mahalanobis distance; represents the variance - covariance information of the integer ambiguity parameter; represents an arbitrary n - dimensional integer vector, where the i - th element is different from the i - th element in the optimal solution ; represents the ratio of the Mahalanobis distances.

3. The GNSS partial ambiguity fixing method based on element-by-element ratio test according to claim 1, characterized in that, When solving a constructed GNSS mixed integer parameter estimation model by using real number least squares estimation, it further includes: obtaining a variance-covariance matrix between integer ambiguity parameters and other real parameters.

4. The GNSS partial ambiguity fixing method based on element-by-element ratio test according to claim 2, wherein, The method further includes: updating its variance-covariance information when obtaining the fixed solution of the real parameter.

5. The GNSS partial ambiguity fixing method based on element-by-element ratio test according to claim 1, characterized in that Fixing the obtained floating point ambiguities to integer ambiguities includes: Define the ambiguity number set as a subset of which represents the ambiguity set corresponding to the subset number, and the corresponding floating-point solution and fixed solution are respectively represented as and , and the projection function with some ambiguities fixed is represented as ; using the domain gives the definition of the projection function as follows: ， field contains any , where obtains an integer vector through the action of a partial ambiguity-fixed projection function .​ 6. The GNSS partial ambiguity fixing method based on element-by-element ratio test according to claim 1, characterized in that, The constructed GNSS mixed integer parameter estimation model is as follows: , in, represents the m-dimensional observation vector; Represents the n-dimensional integer parameter to be estimated; represents the real number parameter to be estimated; the design matrix and is a full rank matrix determined by the observations; is the observation noise.

7. A GNSS partial ambiguity fixing system based on element-by-element ratio test, characterized in that, The system includes: A first calculation module, configured to solve a constructed GNSS mixed integer parameter estimation model by using real number least squares estimation to obtain floating point solutions of GNSS integer ambiguity parameters and other real parameters; A second calculation module, configured to select a subset of ambiguities that meet the element-by-element ratio test index by using the element-by-element ratio test method, so as to obtain reliable floating-point ambiguities; the step of selecting a subset of ambiguities that meet the element-by-element ratio test index by using the element-by-element ratio test method includes: when obtaining the optimal solution of the ambiguities meanwhile, obtaining the sub-optimal solutions for all individual ambiguity elements , , that is, the sub-optimal solution in which the i-th element in all integer ambiguity alternative groups has the closest Mahalanobis distance to the i-th element of the floating-point ambiguity; if the Mahalanobis distances between the i-th elements in multiple alternative groups and the i-th element of the floating-point ambiguity are the same, select the alternative group with the smallest Mahalanobis distance from the floating-point ambiguity as the sub-optimal solution; thus, a total of n groups of ratio test relationships between the sub-optimal and optimal solutions for the i-th element are constructed to implement the quality control of individual ambiguity elements and serve as the basis for selecting the ambiguity subset A third calculation module, configured to fix the obtained floating point ambiguities to integer ambiguities and update to obtain fixed solutions of other real parameters.

8. A GNSS partial ambiguity fixing device based on element-by-element ratio test, characterized in that, Including a memory and a processor, the memory stores program instructions executed by the processor, and the processor calls the program instructions to execute the steps of a method for fixing partial GNSS ambiguities based on element-by-element ratio test according to any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the steps of a method for fixing partial GNSS ambiguities based on element-by-element ratio test according to any one of claims 1 to 6.

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