Reset-free RTK base station switching method and system, medium and product

Abstract

The invention discloses a reference station switching method and system without resetting RTK, a medium and a product, and belongs to the field of RTK positioning switching, and the method comprises the steps: obtaining carrier phase observation values and coordinates of all satellites at the current moment of a new reference station and at the previous moment of an old reference station, corresponding to double-difference pseudo-range observation values, the moving station constructs a double-difference carrier observation value vector according to the carrier phase observation values and coordinates of the new and old reference stations based on the ambiguity state vector of the old reference station, and calculates a double-difference ambiguity state vector by combining the double-difference pseudo-range observation value; obtaining a floating-point double-difference ambiguity solution through filtering estimation, and fixing the floating-point double-difference ambiguity solution as an integer solution by adopting a reduced correlation integer least square method; and carrying out difference on the fixed solution and the ambiguity state vector of the moving station to generate an updated ambiguity state vector based on a new reference station so as to realize reference switching. According to the invention, the problem of positioning interruption or flying spot caused by resetting the ambiguity state when the RTK moving station switches the base station in the prior art can be solved.

Description

Technical Field

[0001] This invention belongs to the field of RTK positioning and switching, and relates to a method, system, medium and product for switching base stations without resetting RTK. Background Technology

[0002] Real-time dynamic carrier phase differential (RTK) technology is widely used in fields such as autonomous driving, precision agriculture, and surveying, achieving centimeter-level high-precision positioning through double-difference observations between the rover and the base station. In practical applications, the rover often needs to switch to a new base station to maintain continuous positioning service because it moves beyond the service range of the original base station.

[0003] Existing technologies typically employ a reset strategy when switching base stations. This involves clearing the existing ambiguity and filter states within the rover station and re-initializing and converging from scratch based on the observation data from the new base station. While this method is simple to implement, it results in a significant decrease in positioning accuracy during re-convergence. Furthermore, the risk of integer errors due to ambiguity recalculation can easily lead to coordinate jumps (flying points), making it difficult to meet the application requirements for high-reliability continuous positioning. Summary of the Invention

[0004] This application provides a method, system, medium, and product for switching base stations without resetting RTK, which can solve the problem of positioning interruption or flying points caused by resetting ambiguity state when switching base stations in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a base station handover method without resetting RTK, comprising:

[0006] Obtain the carrier phase observations and coordinates of each satellite at the current time from the new reference station, the carrier phase observations and coordinates of each satellite at the previous time from the old reference station, the double-difference pseudorange observations corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station.

[0007] Based on the carrier phase observations and coordinates of the old and new reference stations, a double-difference carrier observation vector is constructed, and combined with the double-difference pseudorange observations, a double-difference ambiguity state vector is calculated.

[0008] Based on the double-difference carrier observation vector and the double-difference ambiguity state vector, a floating-point double-difference ambiguity solution is obtained through filtering estimation, and a reduced correlation integer least squares method is performed on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution.

[0009] The fixed double-difference ambiguity solution is differentially analyzed with the current ambiguity state vector of the rover station based on the old reference station to generate an updated ambiguity state vector based on the new reference station, thus completing the reference switching.

[0010] Compared to existing technologies, the embodiments of this application have the following beneficial effects: A double-difference carrier observation vector is constructed based on the carrier phase observations and coordinates of the old and new reference stations. A vector reflecting the observation differences between the reference stations is generated using a mathematical combination of the carrier phase observations and coordinates of the same group of satellites from the two reference stations. This vector does not depend on the rover's state and only characterizes the observation relationship between the old and new reference stations themselves. Based on this, a double-difference ambiguity state vector is calculated by combining the double-difference pseudorange observations. Since the double-difference pseudorange observations provide unambiguous but low-precision distance information, while the double-difference carrier observations provide high-precision but integer-cycle-ambiguous phase information, the combination of the two can solve for a floating-point initial ambiguity value, thereby establishing the ambiguity correlation between the old and new reference stations. Subsequently, a floating-point double-difference ambiguity solution is obtained through filtering estimation based on the double-difference carrier observation vector and the double-difference ambiguity state vector. The observed values ​​and initial state value are used for estimation processing to suppress noise, and then the floating-point... The double-difference ambiguity solution is obtained by performing a fixed operation using the reduced correlation integer least squares method. The floating-point solution is then transformed into a deterministic integer solution through integer search and reliability checks, ensuring that this solution is a reliable and unique ambiguity difference. Finally, the fixed double-difference ambiguity solution is differentially analyzed with the rover's current ambiguity state vector based on the old reference station. Since the fixed double-difference ambiguity solution represents the ambiguity change from the old reference station to the new reference station, and the rover's original state is based on the old reference station, the difference yields an updated ambiguity state vector corresponding to the new reference station. This allows for reference switching without discarding the original state. This process avoids resetting the rover's ambiguity state by constructing a fixed ambiguity difference between the old and new reference stations and using it to update the original state. Therefore, it eliminates the need for re-initialization and convergence, directly maintaining the continuity of the positioning solution and solving the positioning interruption or flying point problem caused by resetting in traditional switching methods.

[0011] In some embodiments of the first aspect of this application, the step of constructing a double-difference carrier observation vector based on the carrier phase observations and coordinates of the old and new reference stations includes:

[0012] Based on the carrier phase observations and coordinate data of the old and new reference stations, the difference between the satellite-to-ground distance vectors from the old and new reference stations to each satellite is calculated to obtain the inter-station single-difference satellite-to-ground distance vector.

[0013] For each satellite and each observed signal frequency observed by the old and new reference stations, the carrier phase observation value of the new reference station is subtracted from the carrier phase observation value of the old reference station, and the corresponding inter-station single-difference satellite-to-ground distance vector is subtracted to obtain the corresponding inter-station single-difference carrier observation value.

[0014] Select one satellite from the common observations of the old and new reference stations as the reference satellite, and subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

[0015] Compared with existing technologies, the above embodiments have the following beneficial effects: By calculating the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observations and coordinate data of the old and new reference stations, the inter-station single-difference satellite-to-ground distance vector is obtained, which accurately compensates for the geometric distance changes caused by the difference in the position of the reference stations and the Earth's rotation; furthermore, by subtracting the carrier phase observations of the old and new reference stations from the corresponding inter-station single-difference satellite-to-ground distance vector for each satellite and each observation signal frequency, the inter-station single-difference carrier observation value is obtained, which effectively eliminates the common error term and retains the pure observations related to ambiguity; at the same time, by selecting one of the commonly observed satellites as a reference satellite, the inter-station single-difference carrier observation values ​​of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observation value vector, which further eliminates residual common errors such as receiver clock bias, improves the accuracy and stability of the observation values, and provides high-quality input for subsequent ambiguity resolution.

[0016] In some embodiments of the first aspect of this application, the step of calculating the double-difference ambiguity state vector by combining the double-difference pseudorange observations includes:

[0017] For each observed signal frequency, subtract the corresponding double-difference pseudorange observation value from the element corresponding to that frequency in the double-difference carrier observation vector to obtain the double-difference pseudorange residual at that frequency, and divide it by the signal wavelength at that frequency to obtain the double-difference ambiguity at that frequency.

[0018] Arrange the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector.

[0019] Compared with existing technologies, the above embodiments have the following beneficial effects: By subtracting the corresponding double-difference pseudorange observation value from the element of the double-difference carrier observation vector at each observed signal frequency to obtain the double-difference pseudorange residual, and dividing it by the signal wavelength at that frequency to obtain the double-difference ambiguity, the pseudorange observation value provides coarse but unambiguous geometric information to assist in carrier phase resolution, thus alleviating the ambiguity of the initial value of pure carrier ambiguity; furthermore, by arranging the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector, a structured, multi-frequency compatible initial state representation is formed, laying the foundation for joint ambiguity resolution of multi-frequency RTK systems and improving initialization speed and robustness.

[0020] In some embodiments of the first aspect of this application, obtaining the floating-point double-difference ambiguity solution through filtering estimation based on the double-difference carrier observation vector and the double-difference ambiguity state vector includes:

[0021] For each satellite and each observation signal frequency, the standard deviation of the inter-station single difference ambiguity corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and the preset pseudorange observation noise standard deviation. Based on the standard deviation of the inter-station single difference ambiguity, an initial covariance matrix is ​​constructed.

[0022] Based on the wavelength of each observed signal frequency, construct the observation equation matrix;

[0023] For each satellite and each observation signal frequency observed by the old and new reference stations, the inter-station single-difference carrier observation noise standard deviation corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and the preset carrier phase observation noise standard deviation. Based on the inter-station single-difference carrier observation noise standard deviation, the observation noise covariance matrix is ​​constructed.

[0024] Substitute the observation equation matrix, the double-difference carrier observation vector, the observation noise covariance matrix, the double-difference ambiguity state vector, and the initialization covariance matrix into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix.

[0025] Compared with the prior art, the above embodiments have the following beneficial effects: By calculating the inter-station single-difference ambiguity standard deviation for each satellite and each observation signal frequency based on the satellite's elevation angle, the signal wavelength of the frequency, and the preset pseudorange observation noise standard deviation, and constructing an initial covariance matrix based on the inter-station single-difference ambiguity standard deviation, the uncertainty of the initial ambiguity value is reasonably quantified, enabling the filter to dynamically adjust the weights according to the satellite's geometric distribution; furthermore, by constructing an observation equation matrix based on the wavelength of each observation signal frequency, an accurate linear mapping relationship between the observed quantity and the state quantity is established. Simultaneously, by calculating the standard deviation of single-difference carrier observation noise between stations based on the elevation angle, signal wavelength, and preset carrier phase observation noise standard deviation for each satellite and each observation signal frequency observed at both old and new reference stations, and constructing an observation noise covariance matrix, the statistical characteristics of observation noise are accurately characterized. Finally, the observation equation matrix, double-difference carrier observation vector, observation noise covariance matrix, double-difference ambiguity state vector, and initial covariance matrix are substituted into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix, achieving optimal weighted fusion of state estimation and significantly improving the accuracy and convergence stability of the floating-point solution.

[0026] In some embodiments of the first aspect of this application, the fixed double-difference fuzzy solution is obtained by performing a reduced correlation integer least squares method on the floating-point double-difference fuzzy solution, and the reliability of the fixation is determined based on the ratio of the best integer solution to the second-best integer solution. When the ratio is greater than a preset threshold, the fixation is confirmed to be successful.

[0027] Compared with the prior art, the above embodiments have the following beneficial effects: by using downcorrelation transformation to compress the ambiguity search space to improve search efficiency, and by using a ratio test mechanism to quantitatively evaluate the uniqueness and reliability of integer solutions, the positioning deviation caused by incorrect fixing is effectively avoided, and the integer correctness and high confidence of the ambiguity solutions after switching are ensured.

[0028] In some embodiments of the first aspect of this application, after generating the updated ambiguity state vector based on the new reference station, the method further includes:

[0029] Based on the carrier phase observations of each satellite by the rover station at the previous moment and the carrier phase observations of each satellite by the new reference station at the current moment, calculate the inter-station single-difference carrier observations from the rover station to the new reference station.

[0030] Select one satellite jointly observed by the rover station and the new reference station as the reference satellite. Subtract the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to each of the other non-reference satellites from the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to the reference satellite to obtain the double-difference carrier observation value.

[0031] For each observed signal frequency and each non-reference satellite, the reference transformation residual corresponding to the satellite at that frequency is calculated based on the signal wavelength at that frequency, the corresponding double-difference carrier observation value, and the updated ambiguity state vector.

[0032] If the statistical characteristics of all benchmark transformation residuals conform to a normal distribution with zero expectation and a preset covariance matrix as variance, then the benchmark switching is confirmed to be successful; otherwise, the switching is rejected.

[0033] Compared to existing technologies, the above embodiments have the following advantages: By acquiring the carrier phase observations of each satellite from the rover station at the previous moment and the carrier phase observations of each satellite from the new reference station at the current moment, and calculating the inter-station single-difference carrier observations from the rover station to the new reference station accordingly, a direct observation correlation between the rover station and the new reference station after the switch is established, providing the original data basis for verification; furthermore, one satellite is selected as a reference satellite from the satellites jointly observed by the rover station and the new reference station, and the inter-station single-difference carrier observations of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observations, thus eliminating receiver clock errors through inter-satellite single-difference. Differential common errors are eliminated to improve the accuracy of observations. Based on this, for each observation signal frequency and each non-reference satellite, the reference transformation residual corresponding to the satellite at that frequency is calculated according to the signal wavelength of that frequency, the corresponding double-difference carrier observation value, and the updated ambiguity state vector, so as to realize the quantitative comparison between the observation value and the theoretical state. Finally, the success of the reference switching is confirmed by judging whether the statistical characteristics of all reference transformation residuals conform to a normal distribution with zero expectation and a preset covariance matrix as variance. Statistical hypothesis testing is used to objectively verify the switching results, effectively identify unreliable switching, and prevent positioning failure caused by erroneous switching.

[0034] Secondly, the present invention also provides a base station switching system that does not require resetting RTK, comprising: a data acquisition module, a calculation module, a filtering and fixing module, and a result output module;

[0035] The data acquisition module is used to acquire the carrier phase observation values ​​and coordinates of each satellite at the current time of the new reference station, the carrier phase observation values ​​and coordinates of each satellite at the previous time of the old reference station, the double-difference pseudorange observation values ​​corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station.

[0036] The calculation module is used to construct a double-difference carrier observation vector based on the carrier phase observation values ​​and coordinates of the old and new reference stations, and to calculate the double-difference ambiguity state vector by combining the double-difference pseudorange observation values.

[0037] The filtering and fixing module is used to obtain a floating-point double-difference ambiguity solution by filtering and estimating based on the double-difference carrier observation vector and the double-difference ambiguity state vector, and to perform a reduced correlation integer least squares fixing operation on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution.

[0038] The result output module is used to perform a difference operation between the fixed double-difference ambiguity solution and the current ambiguity state vector of the rover station based on the old reference station, generate an updated ambiguity state vector based on the new reference station, and complete the reference switching.

[0039] Compared with the prior art, the above embodiments of this application have the following beneficial effects: A double-difference carrier observation vector is constructed based on the carrier phase observations and coordinates of the old and new reference stations. A vector reflecting the observation differences between the reference stations is generated using the mathematical combination of the carrier phase observations and coordinates of the two reference stations for the same group of satellites. This vector does not depend on the rover's state and only characterizes the observation relationship between the old and new reference stations themselves. Based on this, a double-difference ambiguity state vector is calculated by combining the double-difference pseudorange observations. Since the double-difference pseudorange observations provide unambiguous but low-precision distance information, while the double-difference carrier observations provide high-precision but integer-cycle ambiguity phase information, the combination of the two can solve for a floating-point initial ambiguity value, thereby establishing the ambiguity correlation between the old and new reference stations. Subsequently, a floating-point double-difference ambiguity solution is obtained by filtering estimation based on the double-difference carrier observation vector and the double-difference ambiguity state vector. The observations and initial state value are used for estimation processing to suppress noise, and then the floating-point ambiguity solution is further processed. The fixed double-difference ambiguity solution is obtained by performing a fixed operation using the reduced correlation integer least squares method. The floating-point solution is then transformed into a deterministic integer solution through integer search and reliability checks, ensuring that this solution is a reliable and unique ambiguity difference. Finally, the fixed double-difference ambiguity solution is differentially analyzed with the rover's current ambiguity state vector based on the old reference station. Since the fixed double-difference ambiguity solution represents the ambiguity change from the old reference station to the new reference station, and the rover's original state is based on the old reference station, the difference yields an updated ambiguity state vector corresponding to the new reference station. This allows for reference switching without discarding the original state. This process avoids resetting the rover's ambiguity state by constructing a fixed ambiguity difference between the old and new reference stations and using it to update the original state. Therefore, it eliminates the need for re-initialization and convergence, directly maintaining the continuity of the positioning solution and solving the positioning interruption or flying point problem caused by resetting in traditional switching methods.

[0040] In some embodiments of the second aspect of this application, the calculation module includes: a vector calculation unit, a single difference calculation unit, and a double difference calculation unit;

[0041] The vector calculation unit is used to calculate the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observation values ​​and coordinate data of the old and new reference stations, so as to obtain the inter-station single difference satellite-to-ground distance vector.

[0042] The single-difference calculation unit is used to subtract the carrier phase observation value of the new reference station from the carrier phase observation value of the old reference station for each satellite and each observation signal frequency observed by the new and old reference stations, and subtract the corresponding inter-station single-difference satellite-to-ground distance vector to obtain the corresponding inter-station single-difference carrier observation value.

[0043] The double-difference calculation unit is used to select one satellite as a reference satellite from the satellites jointly observed by the old and new reference stations, and to subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

[0044] Compared with existing technologies, the above embodiments have the following beneficial effects: By calculating the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observations and coordinate data of the old and new reference stations, the inter-station single-difference satellite-to-ground distance vector is obtained, which accurately compensates for the geometric distance changes caused by the difference in the position of the reference stations and the Earth's rotation; furthermore, by subtracting the carrier phase observations of the old and new reference stations from the corresponding inter-station single-difference satellite-to-ground distance vector for each satellite and each observation signal frequency, the inter-station single-difference carrier observation value is obtained, which effectively eliminates the common error term and retains the pure observations related to ambiguity; at the same time, by selecting one of the commonly observed satellites as a reference satellite, the inter-station single-difference carrier observation values ​​of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observation value vector, which further eliminates residual common errors such as receiver clock bias, improves the accuracy and stability of the observation values, and provides high-quality input for subsequent ambiguity resolution.

[0045] Thirdly, the present invention also provides a computer program product, including a computer program or instructions, characterized in that, when the computer program or instructions are executed, they implement any one of the base station switching methods of the present invention that does not require resetting RTK.

[0046] Fourthly, embodiments of this application also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, implements any one of the base station switching methods of the present invention for non-reset RTK. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating a base station switching method for RTK without resetting provided in some embodiments of the present invention.

[0048] Figure 2 This is a schematic diagram of the verification process for a base station switching method without resetting RTK provided in some embodiments of the present invention.

[0049] Figure 3 This is a schematic diagram of a base station switching system that does not require resetting RTK, provided in some embodiments of the present invention.

[0050] Figure 4 This is a schematic diagram of a location provided in some embodiments of the present invention.

[0051] Figure 5 This is a flowchart of a base station switching process provided in some embodiments of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Example 1:

[0054] Please refer to Figure 1 To address the problem of positioning interruption or flying points caused by resetting ambiguity state when switching base stations in RTK rover technology, an embodiment of the present invention provides a base station switching method for RTK without resetting, comprising steps S1 to S4:

[0055] Step S1: Obtain the carrier phase observation values ​​and coordinates of each satellite at the current time from the new reference station, the carrier phase observation values ​​and coordinates of each satellite at the previous time from the old reference station, the double-difference pseudorange observation values ​​corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station.

[0056] Step S2: Based on the carrier phase observations and coordinates of the old and new reference stations, construct a double-difference carrier observation vector, and combine it with the double-difference pseudorange observations to calculate the double-difference ambiguity state vector.

[0057] Furthermore, step S2 can be implemented through the following preferred embodiments, including steps S21-S25, as detailed below:

[0058] S21: Based on the carrier phase observations and coordinate data of the old and new reference stations, calculate the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite, and obtain the inter-station single-difference satellite-to-ground distance vector.

[0059] S22: For each satellite and each observed signal frequency observed by the new and old reference stations, the carrier phase observation value of the new reference station is subtracted from the carrier phase observation value of the old reference station, and the corresponding inter-station single difference satellite-to-ground distance vector is subtracted to obtain the corresponding inter-station single difference carrier observation value.

[0060] S23: Select one satellite from the common observations of the old and new reference stations as the reference satellite, and subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

[0061] In this preferred embodiment, the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite is calculated based on the carrier phase observations and coordinate data of the old and new reference stations, resulting in an inter-station single-difference satellite-to-ground distance vector. This accurately compensates for the geometric distance changes caused by the differences in the reference station positions and the Earth's rotation. Furthermore, by subtracting the carrier phase observations of the old and new reference stations for each satellite and each observation signal frequency, and subtracting the corresponding inter-station single-difference satellite-to-ground distance vector, an inter-station single-difference carrier observation value is obtained. This effectively eliminates common error terms and retains the pure observations related to ambiguity. Simultaneously, by selecting one of the commonly observed satellites as a reference satellite, the inter-station single-difference carrier observation values ​​of the non-reference satellite and the reference satellite are subtracted to obtain a double-difference carrier observation value vector. This further eliminates residual common errors such as receiver clock bias, improves the accuracy and stability of the observation values, and provides high-quality input for subsequent ambiguity resolution.

[0062] S24: For each observed signal frequency, subtract the corresponding double-difference pseudorange observation value from the element corresponding to that frequency in the double-difference carrier observation vector to obtain the double-difference pseudorange residual at that frequency, and divide it by the signal wavelength at that frequency to obtain the double-difference ambiguity at that frequency.

[0063] S25: Arrange the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector.

[0064] In this preferred embodiment, for each observed signal frequency, the double-difference pseudorange residual is obtained by subtracting the double-difference pseudorange observation value corresponding to that frequency from the element corresponding to that frequency in the double-difference carrier observation vector. This residual is then divided by the signal wavelength at that frequency to obtain the double-difference ambiguity. The pseudorange observation value provides coarse but unambiguous geometric information to assist in carrier phase resolution, alleviating the ambiguity of the initial value of pure carrier ambiguity. Furthermore, by arranging the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector, a structured, multi-frequency compatible initial state representation is formed. This lays the foundation for joint ambiguity resolution of the multi-frequency RTK system and improves the initialization speed and robustness.

[0065] Step S3: Based on the double-difference carrier observation vector and the double-difference ambiguity state vector, a floating-point double-difference ambiguity solution is obtained by filtering estimation, and a reduced correlation integer least squares method is performed on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution.

[0066] Furthermore, the filtering estimation can be implemented through the following preferred embodiments, including steps S31-S34, as follows:

[0067] S31: For each satellite and each observation signal frequency, calculate the standard deviation of the inter-station single difference ambiguity corresponding to the old and new reference stations based on the satellite's elevation angle, the signal wavelength of the frequency and the preset pseudorange observation noise standard deviation, and construct an initial covariance matrix based on the standard deviation of the inter-station single difference ambiguity.

[0068] S32: Construct the observation equation matrix based on the wavelength of each observed signal frequency;

[0069] S33: For each satellite and each observation signal frequency observed by the old and new reference stations, calculate the inter-station single-difference carrier observation noise standard deviation corresponding to the old and new reference stations based on the elevation angle of the satellite, the signal wavelength of the frequency and the preset carrier phase observation noise standard deviation, and construct the observation noise covariance matrix based on the inter-station single-difference carrier observation noise standard deviation of each station.

[0070] S34: Substitute the observation equation matrix, double-difference carrier observation vector, observation noise covariance matrix, double-difference ambiguity state vector, and initialization covariance matrix into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix.

[0071] In this preferred embodiment, for each satellite and each observation signal frequency, the standard deviation of the inter-station single-difference ambiguity corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and a preset pseudorange observation noise standard deviation. An initial covariance matrix is ​​then constructed based on these inter-station single-difference ambiguity standard deviations to reasonably quantify the uncertainty of the initial ambiguity values, enabling the filter to dynamically adjust weights according to the satellite's geometric distribution. Furthermore, an observation equation matrix is ​​constructed based on the wavelength of each observation signal frequency, establishing an accurate linear mapping relationship between observations and state variables. Simultaneously, the standard deviation of the inter-station single-difference carrier observation noise is calculated for each satellite and each observation signal frequency observed by the old and new reference stations based on the elevation angle, signal wavelength, and a preset carrier phase observation noise standard deviation, and an observation noise covariance matrix is ​​constructed to accurately characterize the statistical properties of the observation noise. Finally, the observation equation matrix, the double-difference carrier observation vector, the observation noise covariance matrix, the double-difference ambiguity state vector, and the initial covariance matrix are substituted into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix, achieving optimal weighted fusion of state estimation and significantly improving the accuracy and convergence stability of the floating-point solution.

[0072] Furthermore, the fixed double-difference fuzzy solution is obtained by performing a reduced correlation integer least squares method on the floating-point double-difference fuzzy solution, and the reliability of the fixation is determined based on the ratio of the optimal integer solution to the second-best integer solution. When the ratio is greater than a preset threshold, the fixation is confirmed to be successful.

[0073] In this preferred embodiment, the ambiguity search space is compressed by using a downcorrelation transformation to improve search efficiency. At the same time, the uniqueness and reliability of the integer solution are quantitatively evaluated by a ratio test mechanism, which effectively avoids the positioning deviation caused by incorrect fixation and ensures the integer correctness and high confidence of the ambiguity solution after switching.

[0074] Step S4: Perform a difference operation between the fixed double-difference ambiguity solution and the current ambiguity state vector of the rover station based on the old reference station to generate an updated ambiguity state vector based on the new reference station, thus completing the reference switching.

[0075] Further, refer to Figure 2 The diagram illustrates the verification process of a base station handover method without resetting RTK. After generating the updated ambiguity state vector based on the new base station in step S4, steps S5-S8 are also included, as follows:

[0076] Step S5: Obtain and calculate the inter-station single-difference carrier observation value between the rover station and the new reference station based on the carrier phase observation values ​​of each satellite at the previous moment and the carrier phase observation values ​​of each satellite at the current moment.

[0077] Step S6: Select one satellite from the satellites jointly observed by the rover station and the new reference station as the reference satellite. Subtract the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to each of the other non-reference satellites from the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to the reference satellite to obtain the double-difference carrier observation value.

[0078] Step S7: For each observed signal frequency and each non-reference satellite, calculate the reference transformation residual corresponding to the satellite at that frequency based on the signal wavelength at that frequency, the corresponding double-difference carrier observation value, and the updated ambiguity state vector;

[0079] Step S8: If the statistical characteristics of all benchmark transformation residuals conform to a normal distribution with zero as the expectation and a preset covariance matrix as the variance, then the benchmark switching is confirmed to be successful; otherwise, the switching is rejected.

[0080] In this preferred embodiment, by acquiring the carrier phase observations of each satellite from the rover station at the previous moment and the carrier phase observations of each satellite from the new reference station at the current moment, and calculating the inter-station single-difference carrier observations from the rover station to the new reference station accordingly, a direct observational correlation between the rover station and the new reference station after the handover is established, providing the original data basis for verification. Furthermore, one satellite jointly observed by the rover station and the new reference station is selected as a reference satellite, and the inter-station single-difference carrier observations of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observations. The inter-satellite single-difference observations eliminate common errors such as receiver clock bias. To improve the accuracy of observations, for each observed signal frequency and each non-reference satellite, the reference transformation residual corresponding to the satellite at that frequency is calculated based on the signal wavelength, the corresponding double-difference carrier observation, and the updated ambiguity state vector. This enables a quantitative comparison between the observed values ​​and the theoretical state. Finally, the success of the reference switching is confirmed by judging whether the statistical characteristics of all reference transformation residuals conform to a normal distribution with zero expectation and a preset covariance matrix as the variance. Statistical hypothesis testing is used to objectively verify the switching results, effectively identify unreliable switching, and prevent positioning failure caused by erroneous switching.

[0081] In practical implementation, if the rover station's fixed ambiguity remains unchanged and no cycle slip occurs when switching reference stations, then they are only switching the reference for the double-difference ambiguity. Before the switch, it is based on the old reference station, and after the switch, it is based on the new reference station. In the traditional scheme, the technical problem of some useful information being discarded due to resetting the RTK algorithm, which fails to suppress potential flypoints, is transformed into three main steps: first, find the reference difference between the old and new reference observations so that the RTK algorithm can run continuously; second, complete the reference transformation; and third, verify the accuracy of this reference transfer, as follows:

[0082] Step 1: Baseline Calculation

[0083] To calculate the double-difference ambiguity difference between the old and new reference stations, VRS technology typically divides the service area into 2*2km sections. When the distance between the old and new reference stations is 4km, it is considered a short baseline, and the effects of ionospheric and tropospheric delays do not need to be considered. Let's assume that the switch to the new reference station occurs at time k, and the GNSS carrier observation value of the new reference station b1 at this time is... The corresponding coordinates are The GNSS carrier observations cached at the old base station b0 are The corresponding coordinates are

[0084] Calculate the baseline vectors of the old and new reference stations, where the Δ operator represents the single difference between stations. This baseline vector, when substituted into the carrier wave observations, needs to be corrected for Earth's rotation. (The last part is a typo and can be left as is.) Let the position of the j-th satellite at time k be:

[0085]

[0086] Where ω is the Earth's rotational angular velocity, c is the speed of light, and the third and fourth terms on the right side of the equation are the Earth's rotation corrections corresponding to the signals received from the j-th satellite by the new and old reference stations, respectively. At time k... It is the x-component of the coordinates of the j-th satellite in ECEF. It is the y-component of the new reference station b1 coordinates at ECEF. It is the y-component of the coordinates of the j-th satellite in ECEF. It is the x-component of the new reference station b1 coordinates at ECEF, at time k-1. It is the x-component of the coordinates of the j-th satellite in ECEF. It is the y-component of the old base station b0 coordinates at ECEF. It is the y-component of the coordinates of the j-th satellite in ECEF. It is the x component of the old base station b0 coordinates in ECEF; It is the single-difference baseline vector between the old and new reference stations b1 and b0 after the coordinates of the j-th satellite are corrected for Earth rotation, or the single-difference satellite-to-ground distance vector between the stations.

[0087] Calculate the inter-station single-difference carrier observations of the j-th satellite at time k between the old and new reference stations.

[0088] Where the subscript i represents the i-th frequency, It is the carrier wave observation of the j-th satellite at time k at the new reference station b1. It is the carrier observation of the j-th satellite at the old reference station b0 at time k-1. The modulus of the single-difference satellite-to-ground distance between the j-th satellite and the station is given, where o(ΔI) represents the negligible ionospheric delay and o(ΔT) represents the negligible tropospheric delay. This represents the observation noise of a single-difference carrier observation.

[0089] Construct observation equations for double-difference ambiguity of n satellites, denote the first satellite as the reference satellite, perform inter-satellite single-difference, and obtain double-difference carrier observations.

[0090]

[0091] Calculate the initial double-difference ambiguity for the i-th frequency using the 1-th satellite as the reference satellite. λ i Let be the wavelength of the i-th frequency. For the pseudorange observation of the i-th frequency with double difference:

[0092]

[0093] To calculate the initial double-difference ambiguity state vector X0 and variance-covariance matrix P0, the weighting results of the inter-station single-difference variances are first required, where E j It is the elevation angle of the j-th satellite. The initial inter-station single-difference ambiguity standard deviation for the i-th frequency and j-th satellite:

[0094]

[0095] Calculate the variance-covariance matrix R of the observations L:

[0096]

[0097] Substituting the observation equation matrix H, observation vector L, observation noise covariance matrix R, initialization parameter X0, and initial variance covariance matrix P0 obtained above into the Kalman filter equation, we can obtain the floating-point solution of the double-difference ambiguity following the formula... The expected value is a normal distribution with variance P: Kalman filter update formula:

[0098]

[0099] The superscript ^ indicates a floating-point solution. P is substituted into the least squares method of decreasing correlation (LAMBDA) for fixing; when ratio > 3, it is determined to be a fixed double-difference ambiguity. Top Mark This indicates a fixed level of ambiguity.

[0100] Step 2, Baseline Switching:

[0101] The fixed double-difference ambiguity obtained in step one represents the reference difference between the old and new reference stations. Applying this ambiguity to the Kalman filter of the floating-point ambiguity and the ambiguity preservation parameter completes the reference switching. Given the (n-1)th double-difference ambiguity at the i-th frequency of the old and new reference stations... as follows:

[0102]

[0103] Kalman filtering for floating-point ambiguity commonly uses two filter configurations: single-difference Kalman filtering (denoted by subscript SD) and double-difference Kalman filtering (denoted by subscript DD). The reference switching method differs slightly. and These are the single-difference Kalman filter ambiguity states based on reference stations b0 and b1, respectively. and These are the ambiguity states of the double-difference Kalman filter based on reference stations b0 and b1, respectively.

[0104]

[0105] The following equation can be used to... or Switch to or

[0106] This completes the baseline switching.

[0107] Step 3, Benchmark Verification:

[0108] refer to Figure 4 The diagram shows a point location, and Figure 5 The diagram shows a base station switching process.

[0109] At time k, a total of three copies of data were cached:

[0110] Old base station data at time k-1 Let it be point A;

[0111] New base station data at time k Let this be point B;

[0112] The rover data L at time k-1 r,k-1 Let it be point C;

[0113] The rover data L at time k r,k Let it be point D;

[0114] Baseline operation is defined as:

[0115] At this point, after step one baseline Its double-difference ambiguity is known, and the baseline is obtained after calculation in the (k-1)th epoch. The ambiguity is also known; points A, B, and C form a triangular network. Using the property that the sum of the double-difference ambiguities within the triangular network is zero, the accuracy of the reference switching can be checked. The calculated coordinates are r. k-1 The baseline vector from the rover to the new reference station at coordinate b1, with Earth rotation correction:

[0116]

[0117] in Let r represent the single-difference satellite-to-ground distance vector between the j-th satellite and the rover and the base station. r,k-1 These are the coordinates of the rover at time k-1. These are the coordinates of the new reference station. The third and fourth terms on the right side of the equation are the Earth's rotation corrections.

[0118] Calculate the inter-station single-difference carrier observations from the rover to the new reference station at time k-1. Using its first satellite as the reference satellite, double-difference carrier observations are obtained.

[0119]

[0120] Record the baseline The fixed double difference ambiguity is Baseline The fixed double difference ambiguity is At this point, the baseline can be obtained. Fixed double difference ambiguity

[0121] The residual V from the benchmark transformation can be calculated:

[0122] Where λ i V is the wavelength of the i-th frequency point. At this time, V follows a normal distribution with expectation of 0 and variance of R: V ~ N(0,R).

[0123] If no outliers are found in the residual vector V, the baseline transformation is considered successful, and the new baseline station b1 can be used directly in the next epoch.

[0124] In summary, compared with the prior art, the above embodiments of this application have the following beneficial effects: A double-difference carrier observation vector is constructed based on the carrier phase observations and coordinates of the old and new reference stations. A vector reflecting the observation differences between the reference stations is generated using the mathematical combination of the carrier phase observations and coordinates of the two reference stations for the same group of satellites. This vector does not depend on the rover's state and only characterizes the observation relationship between the old and new reference stations themselves. Based on this, a double-difference ambiguity state vector is calculated by combining the double-difference pseudorange observations. Since the double-difference pseudorange observations provide unambiguous but low-precision distance information, while the double-difference carrier observations provide high-precision but integer-cycle ambiguity phase information, the combination of the two can solve for a floating-point initial ambiguity value, thereby establishing the ambiguity correlation between the old and new reference stations. Subsequently, based on the double-difference carrier observation vector and the double-difference ambiguity state vector, a floating-point double-difference ambiguity solution is obtained through filtering estimation. The observed values ​​and initial state values ​​are used for estimation processing to suppress noise, and then the solution is further processed... The floating-point double-difference ambiguity solution is subjected to a fixed operation using the reduced-correlation integer least squares method to obtain a fixed double-difference ambiguity solution. Through integer search and reliability checks, the floating-point solution is transformed into a deterministic integer solution, ensuring that this solution is a reliable and unique ambiguity difference quantity. Finally, the fixed double-difference ambiguity solution is differentially analyzed with the rover's current ambiguity state vector based on the old reference station. Since the fixed double-difference ambiguity solution represents the ambiguity change from the old reference station to the new reference station, and the rover's original state is based on the old reference station, the difference yields an updated ambiguity state vector corresponding to the new reference station. This allows for reference switching without discarding the original state. This process avoids resetting the rover's ambiguity state by constructing a fixed ambiguity difference quantity between the old and new reference stations and using it to update the original state. Therefore, it eliminates the need for re-initialization and convergence, directly maintaining the continuity of the positioning solution and solving the positioning interruption or flying point problem caused by resetting in traditional switching methods.

[0125] Example 2:

[0126] Please refer to Figure 3 Based on the same inventive concept, the present invention discloses a base station switching system for RTK without resetting, comprising: a data acquisition module M1, a calculation module M2, a filtering and fixing module M3, and a result output module M4;

[0127] The data acquisition module M1 is used to acquire the carrier phase observation values ​​and coordinates of each satellite at the current time of the new reference station, the carrier phase observation values ​​and coordinates of each satellite at the previous time of the old reference station, the double-difference pseudorange observation values ​​corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station.

[0128] The calculation module M2 is used to construct a double-difference carrier observation vector based on the carrier phase observation values ​​and coordinates of the old and new reference stations, and to calculate the double-difference ambiguity state vector by combining the double-difference pseudorange observation values.

[0129] Furthermore, the calculation module M2 includes: a vector calculation unit, a single difference calculation unit, and a double difference calculation unit;

[0130] The vector calculation unit is used to calculate the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observation values ​​and coordinate data of the old and new reference stations, so as to obtain the inter-station single difference satellite-to-ground distance vector.

[0131] The single-difference calculation unit is used to subtract the carrier phase observation value of the new reference station from the carrier phase observation value of the old reference station for each satellite and each observation signal frequency observed by the new and old reference stations, and subtract the corresponding inter-station single-difference satellite-to-ground distance vector to obtain the corresponding inter-station single-difference carrier observation value.

[0132] The double-difference calculation unit is used to select one satellite as a reference satellite from the satellites jointly observed by the old and new reference stations, and to subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

[0133] By calculating the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observations and coordinate data, the inter-station single-difference satellite-to-ground distance vector is obtained, which accurately compensates for the geometric distance changes caused by the difference in the position of the reference stations and the Earth's rotation. Furthermore, by subtracting the carrier phase observations of the old and new reference stations for each satellite and each observation signal frequency, and subtracting the corresponding inter-station single-difference satellite-to-ground distance vector, the inter-station single-difference carrier observation value is obtained, which effectively eliminates common error terms and retains the pure observations related to ambiguity. At the same time, by selecting one of the commonly observed satellites as a reference satellite, the inter-station single-difference carrier observation values ​​of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observation value vector, which further eliminates residual common errors such as receiver clock bias, improves the accuracy and stability of the observation values, and provides high-quality input for subsequent ambiguity resolution.

[0134] Furthermore, the calculation module M2 also includes: a double-difference ambiguity calculation unit and an arrangement unit;

[0135] The double-difference ambiguity calculation unit is used to subtract the double-difference pseudorange observation value corresponding to the frequency from the element corresponding to the frequency in the double-difference carrier observation value vector for each observation signal frequency, to obtain the double-difference pseudorange residual at that frequency, and divide it by the signal wavelength at that frequency to obtain the double-difference ambiguity at that frequency.

[0136] The arrangement unit is used to arrange the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector.

[0137] In this preferred embodiment, for each observed signal frequency, the double-difference pseudorange residual is obtained by subtracting the double-difference pseudorange observation value corresponding to that frequency from the element corresponding to that frequency in the double-difference carrier observation vector. This residual is then divided by the signal wavelength at that frequency to obtain the double-difference ambiguity. The pseudorange observation value provides coarse but unambiguous geometric information to assist in carrier phase resolution, alleviating the ambiguity of the initial value of pure carrier ambiguity. Furthermore, by arranging the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector, a structured, multi-frequency compatible initial state representation is formed. This lays the foundation for joint ambiguity resolution of the multi-frequency RTK system and improves the initialization speed and robustness.

[0138] The filtering and fixing module M3 is used to obtain a floating-point double-difference ambiguity solution by filtering and estimating based on the double-difference carrier observation vector and the double-difference ambiguity state vector, and to perform a reduced correlation integer least squares fixing operation on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution.

[0139] Furthermore, the filtering fixing module M3 includes: a first matrix construction unit, a second matrix construction unit, a third matrix construction unit, and a filtering estimation unit;

[0140] The first matrix construction unit is used to calculate the inter-station single difference ambiguity standard deviation corresponding to the old and new reference stations for each satellite and each observation signal frequency, based on the satellite's elevation angle, the signal wavelength of the frequency and the preset pseudorange observation noise standard deviation, and to construct an initial covariance matrix based on the inter-station single difference ambiguity standard deviation.

[0141] The second matrix construction unit is used to construct the observation equation matrix based on the wavelength of each observed signal frequency;

[0142] The third matrix construction unit is used to calculate the inter-station single-difference carrier observation noise standard deviation corresponding to the old and new reference stations for each satellite and each observation signal frequency observed by the old and new reference stations, based on the elevation angle of the satellite, the signal wavelength of the frequency and the preset carrier phase observation noise standard deviation, and to construct the observation noise covariance matrix based on the inter-station single-difference carrier observation noise standard deviation.

[0143] The filtering estimation unit is used to substitute the observation equation matrix, the double-difference carrier observation vector, the observation noise covariance matrix, the double-difference ambiguity state vector, and the initialization covariance matrix into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix.

[0144] In this preferred embodiment, for each satellite and each observation signal frequency, the standard deviation of the inter-station single-difference ambiguity corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and a preset pseudorange observation noise standard deviation. An initial covariance matrix is ​​then constructed based on these inter-station single-difference ambiguity standard deviations to reasonably quantify the uncertainty of the initial ambiguity values, enabling the filter to dynamically adjust weights according to the satellite's geometric distribution. Furthermore, an observation equation matrix is ​​constructed based on the wavelength of each observation signal frequency, establishing an accurate linear mapping relationship between observations and state variables. Simultaneously, the standard deviation of the inter-station single-difference carrier observation noise is calculated for each satellite and each observation signal frequency observed by the old and new reference stations based on the elevation angle, signal wavelength, and a preset carrier phase observation noise standard deviation, and an observation noise covariance matrix is ​​constructed to accurately characterize the statistical properties of the observation noise. Finally, the observation equation matrix, the double-difference carrier observation vector, the observation noise covariance matrix, the double-difference ambiguity state vector, and the initial covariance matrix are substituted into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix, achieving optimal weighted fusion of state estimation and significantly improving the accuracy and convergence stability of the floating-point solution.

[0145] Furthermore, the fixed double-difference fuzzy solution is obtained by performing a reduced correlation integer least squares method on the floating-point double-difference fuzzy solution, and the reliability of the fixation is determined based on the ratio of the optimal integer solution to the second-best integer solution. When the ratio is greater than a preset threshold, the fixation is confirmed to be successful.

[0146] In this preferred embodiment, the ambiguity search space is compressed by using a downcorrelation transformation to improve search efficiency. At the same time, the uniqueness and reliability of the integer solution are quantitatively evaluated by a ratio test mechanism, which effectively avoids the positioning deviation caused by incorrect fixation and ensures the integer correctness and high confidence of the ambiguity solution after switching.

[0147] The result output module M4 is used to perform a difference operation between the fixed double-difference ambiguity solution and the current ambiguity state vector of the rover station based on the old reference station, generate an updated ambiguity state vector based on the new reference station, and complete the reference switching.

[0148] Furthermore, the aforementioned base station switching system for RTK without reset also includes: an inter-station single difference calculation module M5, a double difference calculation module M6, a residual calculation module M7, and a verification module M8;

[0149] The inter-station single-difference calculation module M5 is used to acquire and calculate the inter-station single-difference carrier observation value from the rover station to the new reference station based on the carrier phase observation values ​​of each satellite at the previous moment and the carrier phase observation values ​​of each satellite at the current moment of the new reference station.

[0150] The double-difference calculation module M6 is used to select one satellite as a reference satellite from the satellites jointly observed by the rover station and the new reference station, and to subtract the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to each of the other non-reference satellites from the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to the reference satellite, so as to obtain each double-difference carrier observation value.

[0151] The residual calculation module M7 is used to calculate the reference transformation residual corresponding to the satellite at each frequency for each observed signal frequency and each non-reference satellite, based on the signal wavelength of that frequency, the corresponding double-difference carrier observation value, and the updated ambiguity state vector.

[0152] The verification module M8 is used to confirm that the benchmark switching is successful if the statistical characteristics of all benchmark transformation residuals conform to a normal distribution with zero as the expectation and a preset covariance matrix as the variance; otherwise, the switching is rejected.

[0153] In this preferred embodiment, by acquiring the carrier phase observations of each satellite from the rover station at the previous moment and the carrier phase observations of each satellite from the new reference station at the current moment, and calculating the inter-station single-difference carrier observations from the rover station to the new reference station accordingly, a direct observational correlation between the rover station and the new reference station after the handover is established, providing the original data basis for verification. Furthermore, one satellite jointly observed by the rover station and the new reference station is selected as a reference satellite, and the inter-station single-difference carrier observations of the non-reference satellite and the reference satellite are subtracted to obtain the double-difference carrier observations. The inter-satellite single-difference observations eliminate common errors such as receiver clock bias. To improve the accuracy of observations, for each observed signal frequency and each non-reference satellite, the reference transformation residual corresponding to the satellite at that frequency is calculated based on the signal wavelength, the corresponding double-difference carrier observation, and the updated ambiguity state vector. This enables a quantitative comparison between the observed values ​​and the theoretical state. Finally, the success of the reference switching is confirmed by judging whether the statistical characteristics of all reference transformation residuals conform to a normal distribution with zero expectation and a preset covariance matrix as the variance. Statistical hypothesis testing is used to objectively verify the switching results, effectively identify unreliable switching, and prevent positioning failure caused by erroneous switching.

[0154] In summary, compared with the prior art, the embodiments of this application have the following beneficial effects: A double-difference carrier observation vector is constructed based on the carrier phase observations and coordinates of the old and new reference stations. A vector reflecting the observation differences between the reference stations is generated using the mathematical combination of the carrier phase observations and coordinates of the two reference stations for the same group of satellites. This vector does not depend on the rover's state and only characterizes the observation relationship between the old and new reference stations themselves. Based on this, a double-difference ambiguity state vector is calculated by combining the double-difference pseudorange observations. Since the double-difference pseudorange observations provide unambiguous but low-precision distance information, while the double-difference carrier observations provide high-precision but integer-cycle ambiguity phase information, the combination of the two can solve for a floating-point initial ambiguity value, thereby establishing the ambiguity correlation between the old and new reference stations. Subsequently, a floating-point double-difference ambiguity solution is obtained by filtering estimation based on the double-difference carrier observation vector and the double-difference ambiguity state vector. The observed values ​​and initial state values ​​are used for estimation processing to suppress noise, and then the solution is further processed... The floating-point double-difference ambiguity solution is fixed by performing a reduced-correlation integer least squares method to obtain a fixed double-difference ambiguity solution. This floating-point solution is then transformed into a deterministic integer solution through integer search and reliability checks, ensuring that the solution is a reliable and unique ambiguity difference. Finally, the fixed double-difference ambiguity solution is differentially analyzed with the rover's current ambiguity state vector based on the old reference station. Since the fixed double-difference ambiguity solution represents the ambiguity change from the old reference station to the new reference station, and the rover's original state is based on the old reference station, the difference yields an updated ambiguity state vector corresponding to the new reference station. This allows for reference switching without discarding the original state. This process avoids resetting the rover's ambiguity state by constructing a fixed ambiguity difference between the old and new reference stations and using it to update the original state. Therefore, it eliminates the need for re-initialization and convergence, directly maintaining the continuity of the positioning solution and solving the positioning interruption or flying point problem caused by resetting in traditional switching methods.

[0155] Example 3:

[0156] This invention also provides a computer program product, including a computer program or instructions, capable of running on a computing device or stored in any available medium. When the computer program product is run on at least one computing device, it causes the at least one computing device to execute any of the reset-free RTK base station handover methods of this invention.

[0157] Example 4:

[0158] This invention also provides a computer-readable storage medium storing at least one executable instruction that, when executed on a non-reset RTK base station handover system, causes the non-reset RTK base station handover system to perform one of the non-reset RTK base station handover methods described in any of the above method embodiments.

[0159] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. Similarly, for the purpose of simplification and aiding understanding of one or more aspects of the invention, in the above description of exemplary embodiments of this application, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0160] Those skilled in the art will understand that the modules in the system of the embodiments can be adaptively changed and placed in one or more systems different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

Claims

1. A base station handover method without resetting RTK, characterized in that, include: Obtain the carrier phase observations and coordinates of each satellite at the current time from the new reference station, the carrier phase observations and coordinates of each satellite at the previous time from the old reference station, the double-difference pseudorange observations corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station. Based on the carrier phase observations and coordinates of the old and new reference stations, a double-difference carrier observation vector is constructed, and combined with the double-difference pseudorange observations, a double-difference ambiguity state vector is calculated. Based on the double-difference carrier observation vector and the double-difference ambiguity state vector, a floating-point double-difference ambiguity solution is obtained through filtering estimation, and a reduced correlation integer least squares method is performed on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution. The fixed double-difference ambiguity solution is differentially analyzed with the current ambiguity state vector of the rover station based on the old reference station to generate an updated ambiguity state vector based on the new reference station, thus completing the reference switching.

2. The base station handover method without resetting RTK as described in claim 1, characterized in that, The step of constructing a double-difference carrier observation vector based on the carrier phase observations and coordinates of the old and new reference stations includes: Based on the carrier phase observations and coordinate data of the old and new reference stations, the difference between the satellite-to-ground distance vectors from the old and new reference stations to each satellite is calculated to obtain the inter-station single-difference satellite-to-ground distance vector. For each satellite and each observed signal frequency observed by the old and new reference stations, the carrier phase observation value of the new reference station is subtracted from the carrier phase observation value of the old reference station, and the corresponding inter-station single-difference satellite-to-ground distance vector is subtracted to obtain the corresponding inter-station single-difference carrier observation value. Select one satellite from the common observations of the old and new reference stations as the reference satellite, and subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

3. The base station handover method without resetting RTK as described in claim 2, characterized in that, The calculation of the double-difference ambiguity state vector by combining the double-difference pseudorange observations includes: For each observed signal frequency, subtract the corresponding double-difference pseudorange observation value from the element corresponding to that frequency in the double-difference carrier observation vector to obtain the double-difference pseudorange residual at that frequency, and divide it by the signal wavelength at that frequency to obtain the double-difference ambiguity at that frequency. Arrange the double-difference ambiguities corresponding to each non-reference satellite at all frequencies according to frequency and satellite number to form a double-difference ambiguity state vector.

4. The base station handover method without resetting RTK as described in claim 1, characterized in that, The step of obtaining the floating-point double-difference ambiguity solution through filtering estimation based on the double-difference carrier observation vector and the double-difference ambiguity state vector includes: For each satellite and each observation signal frequency, the standard deviation of the inter-station single difference ambiguity corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and the preset pseudorange observation noise standard deviation. Based on the standard deviation of the inter-station single difference ambiguity, an initial covariance matrix is ​​constructed. Based on the wavelength of each observed signal frequency, construct the observation equation matrix; For each satellite and each observation signal frequency observed by the old and new reference stations, the inter-station single-difference carrier observation noise standard deviation corresponding to the old and new reference stations is calculated based on the satellite's elevation angle, the signal wavelength of the frequency, and the preset carrier phase observation noise standard deviation. Based on the inter-station single-difference carrier observation noise standard deviation, the observation noise covariance matrix is ​​constructed. Substitute the observation equation matrix, the double-difference carrier observation vector, the observation noise covariance matrix, the double-difference ambiguity state vector, and the initialization covariance matrix into the Kalman filter equation to calculate the floating-point double-difference ambiguity solution and its covariance matrix.

5. The base station handover method without resetting RTK as described in claim 1, characterized in that, The fixed double-difference fuzzy solution is obtained by performing a reduced correlation integer least squares method on the floating-point double-difference fuzzy solution. The reliability of the fixation is determined by the ratio of the best integer solution to the second-best integer solution. When the ratio is greater than a preset threshold, the fixation is confirmed to be successful.

6. The base station handover method without resetting RTK as described in claim 1, characterized in that, After generating the updated ambiguity state vector based on the new reference station, the following steps are also included: Based on the carrier phase observations of each satellite by the rover station at the previous moment and the carrier phase observations of each satellite by the new reference station at the current moment, calculate the inter-station single-difference carrier observations from the rover station to the new reference station. Select one satellite jointly observed by the rover station and the new reference station as the reference satellite. Subtract the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to each of the other non-reference satellites from the inter-station single-difference carrier observation value from the rover station to the new reference station corresponding to the reference satellite to obtain the double-difference carrier observation value. For each observed signal frequency and each non-reference satellite, the reference transformation residual corresponding to the satellite at that frequency is calculated based on the signal wavelength at that frequency, the corresponding double-difference carrier observation value, and the updated ambiguity state vector. If the statistical characteristics of all benchmark transformation residuals conform to a normal distribution with zero expectation and a preset covariance matrix as variance, then the benchmark switching is confirmed to be successful; otherwise, the switching is rejected.

7. A base station handover system that eliminates the need for RTK reset, characterized in that, include: Data acquisition module, calculation module, filtering and fixing module, and result output module; The data acquisition module is used to acquire the carrier phase observation values ​​and coordinates of each satellite at the current time of the new reference station, the carrier phase observation values ​​and coordinates of each satellite at the previous time of the old reference station, the double-difference pseudorange observation values ​​corresponding to the new and old reference stations, and the ambiguity state vector of the rover station based on the old reference station. The calculation module is used to construct a double-difference carrier observation vector based on the carrier phase observation values ​​and coordinates of the old and new reference stations, and to calculate the double-difference ambiguity state vector by combining the double-difference pseudorange observation values. The filtering and fixing module is used to obtain a floating-point double-difference ambiguity solution by filtering and estimating based on the double-difference carrier observation vector and the double-difference ambiguity state vector, and to perform a reduced correlation integer least squares fixing operation on the floating-point double-difference ambiguity solution to obtain a fixed double-difference ambiguity solution. The result output module is used to perform a difference operation between the fixed double-difference ambiguity solution and the current ambiguity state vector of the rover station based on the old reference station, generate an updated ambiguity state vector based on the new reference station, and complete the reference switching.

8. A base station handover system for RTK without resetting as described in claim 7, characterized in that, The calculation module includes: a vector calculation unit, a single difference calculation unit, and a double difference calculation unit; The vector calculation unit is used to calculate the difference between the satellite-to-ground distance vectors of the old and new reference stations to each satellite based on the carrier phase observation values ​​and coordinate data of the old and new reference stations, so as to obtain the inter-station single difference satellite-to-ground distance vector. The single-difference calculation unit is used to subtract the carrier phase observation value of the new reference station from the carrier phase observation value of the old reference station for each satellite and each observation signal frequency observed by the new and old reference stations, and subtract the corresponding inter-station single-difference satellite-to-ground distance vector to obtain the corresponding inter-station single-difference carrier observation value. The double-difference calculation unit is used to select one satellite as a reference satellite from the satellites jointly observed by the old and new reference stations, and to subtract the inter-station single-difference carrier observation value of each of the other non-reference satellites from the inter-station single-difference carrier observation value of the reference satellite to obtain the double-difference carrier observation value vector.

9. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed, they implement a base station switching method for RTK without resetting as described in any one of claims 1-6.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements a base station switching method for a resetless RTK as described in any one of claims 1-6.

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