A GNSS cycle slip detection method combining doppler and phase observation information

Abstract

The application discloses a GNSS cycle slip detection method combining Doppler and phase observation information and belongs to the technical field of GNSS data processing, which comprises the following steps: acquiring carrier phase and Doppler observation value, performing smoothing and noise reduction processing on original Doppler observation value, constructing a phase GF model and a Doppler GF model, and calculating phase GF interepoch difference and Doppler GF interepoch difference. The two characteristics are used for judgment: when the absolute value of phase interepoch difference is greater than a second discrimination threshold, it is determined that there is a cycle slip, and when the absolute value of phase interepoch difference is less than or equal to a first discrimination threshold, it is determined that there is no cycle slip; for the fuzzy interval from the second discrimination threshold to the first discrimination threshold, the two are added to construct a secondary discrimination statistic to eliminate the influence of ionospheric delay; if the new statistic is less than a third discrimination threshold, it is determined that there is no cycle slip, otherwise, it is determined that there is a cycle slip. The application significantly reduces Doppler observation value noise, effectively distinguishes cycle slips in the fuzzy interval from ionospheric abnormal disturbances through hierarchical cycle slip detection.

Description

Technical Field

[0001] This invention belongs to the field of high-precision data processing technology for Global Navigation Satellite System (GNSS), specifically involving a GNSS cycle slip detection method that combines Doppler and phase observation information, and the application of this method in the network solution of reference stations for Network Real-Time Kinematic (NRTK) servers and the high-precision positioning solution of user terminals. Background Technology

[0002] In GNSS high-precision positioning, correctly fixing the integer ambiguity of carrier phase observations is a core prerequisite for achieving positioning accuracy at the millimeter to centimeter level. Integer ambiguity describes the number of unknown integer cycles in carrier phase observations, and correct ambiguity resolution depends on ambiguity continuity. However, in actual observations, interference factors such as signal obstruction, multipath effects, or severe ionospheric activity often cause integer cycle slips, leading to interruptions in ambiguity counting and requiring reinitialization, which seriously affects the continuity and reliability of positioning.

[0003] Commonly used cycle slip detection methods include the higher order difference method, polynomial fitting method, geometry-free (GF) model method, and ionospheric residual method. Among them, the GF model is widely used for real-time data preprocessing because it can eliminate the effects of geometric distance, clock error, and tropospheric delay. However, this method has significant drawbacks in ionospheric active environments:

[0004] (1) High misjudgment rate of cycle slip under active ionospheric conditions: During periods of active ionospheric conditions (such as high solar activity years and equatorial ionospheric anomaly regions), the GF model is easily misjudged as cycle slips due to the drastic changes in ionospheric delay and the significant increase in the difference between GF epochs.

[0005] (2) Difficulty in setting the threshold: In order to reduce the false judgment of cycle slip when the ionosphere is active, a large threshold usually needs to be set, but this will reduce the detection sensitivity of small cycle slips and cause the real small cycle slips to be missed.

[0006] (3) Impact of NRTK service on terminal positioning: On the NRTK service side, frequent cycle slip misjudgments will trigger repeated initialization of baseline resolution ambiguity, causing fluctuations or even interruptions in the number of differential satellites; on the terminal side, ambiguity initialization caused by cycle slip misjudgments will reduce the number of available satellites, thereby reducing the ambiguity fixation rate and affecting positioning accuracy and reliability. Summary of the Invention

[0007] This invention addresses the problems of high false alarm rates in traditional geometry-free (GF) cycle slip detection methods during periods of ionospheric activity due to their inability to distinguish between drastic ionospheric changes and small cycle slips, frequent initialization of ambiguity parameters in NRTK server baseline resolution, and decreased terminal positioning fixation rate and accuracy. It provides a GNSS cycle slip detection method that combines Doppler and phase observation information. The method acquires carrier phase and Doppler observations, and uses a Gaussian weighted moving average method to smooth and denoise the original Doppler observations. It then constructs phase GF models and Doppler GF models respectively, and calculates the inter-epoch difference between phase GF and Doppler GF models. This invention utilizes the combined characteristics of both Doppler and phase observations for a cycle slip determination: when the absolute value of the phase epoch difference is greater than a first discrimination threshold, it is determined to be a cycle slip; when it is less than a second discrimination threshold, it is determined to be a cycle slip-free. Focusing on the fuzzy interval between the second and first discrimination thresholds, it leverages the fact that the Doppler GF epoch difference is unaffected by cycle slips and has the opposite sign to the phase GF epoch difference. The two are added together to construct a secondary discrimination statistic to eliminate the influence of ionospheric delay. If the new statistic is less than a third discrimination threshold, it is determined to be a cycle slip-free; otherwise, it is a cycle slip. This invention significantly reduces Doppler observation noise through a Gaussian weighted moving average method. Furthermore, by combining Doppler and phase observations for hierarchical cycle slip detection, it effectively distinguishes cycle slips in fuzzy intervals from ionospheric anomalies, reducing the cycle slip misjudgment rate of Network Real-Time Kinematic (NRTK) in complex ionospheric environments and improving the continuity and reliability of positioning services. Using the cycle slip detection method proposed in this invention in an ionospheric active environment can significantly reduce the cycle slip misjudgment rate and ensure the stability of NRTK service and the continuity of terminal positioning.

[0008] According to one aspect of this specification, a GNSS cycle slip detection method combining Doppler and phase observation information is provided, comprising:

[0009] Acquire dual-frequency carrier phase observations from the GNSS receiver and calculate the epoch-free difference in carrier phase; acquire dual-frequency Doppler observations from the GNSS receiver and calculate the epoch-free difference in Doppler phase.

[0010] In the initial judgment stage, if the absolute value of the difference between geometric distance epochs of the carrier phase is greater than the second discrimination threshold, it is determined that a cycle slip has occurred; if the absolute value of the difference between geometric distance epochs of the carrier phase is less than or equal to the first discrimination threshold, it is determined that there is no cycle slip.

[0011] When the absolute value of the carrier phase epoch difference without geometric distance is greater than the first discrimination threshold and less than or equal to the second discrimination threshold, the process enters the re-discrimination stage; the re-discrimination stage includes: when the secondary discrimination statistic is less than or equal to the third discrimination threshold, it is determined that there is no cycle slip; when the secondary discrimination statistic is greater than the third discrimination threshold, it is determined that a cycle slip has occurred; wherein, the secondary discrimination statistic is the absolute value of the sum of the carrier phase epoch difference without geometric distance and the Doppler epoch difference without geometric distance.

[0012] As a further technical solution, the expression for the secondary discriminant statistic is:

[0013]

[0014] in, This represents the second-order discriminant statistic. This indicates that the carrier phase has no geometrical distance epoch difference. This indicates that there is no geometrical distance difference between Doppler epochs. This represents the integer ambiguity change caused by cycle slips. Geometrically inverse carrier phase observation noise representing the epoch difference. Geometric distance-free Doppler observation noise representing the difference between epochs.

[0015] As a further technical solution, calculating the carrier phase difference without geometric distance between epochs includes:

[0016] The epoch difference of the carrier phase observations is obtained by performing epoch difference on the dual-frequency carrier phase observations;

[0017] By constructing a geometrically distance-free combination using carrier phase observations, the geometrically distance-free epoch difference of carrier phase is calculated.

[0018] As a further technical solution, calculating the Doppler epoch difference without geometric distance includes:

[0019] The dual-frequency Doppler observations are smoothed and denoised to obtain smoothed Doppler observations.

[0020] Time integration is performed on the smoothed Doppler observations to restore the change in carrier phase between epochs;

[0021] The variation of carrier phase observations between epochs is discretized and approximated, and the Doppler non-geometric distance epoch difference is calculated based on the approximation results.

[0022] As a further technical solution, the carrier phase observations are differentially analyzed between epochs, as expressed by:

[0023]

[0024] in, Represents frequency The epochal difference between carrier phase observations, expressed in meters; Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference represents the satellite clock bias. This represents the epochal difference of tropospheric delay. Represents frequency The epochal difference of ionospheric delay on the surface Represents frequency wavelength, This represents the integer variation in ambiguity between epochs. Represents frequency The noise of carrier phase observations between epochs.

[0025] As a further technical solution, a geometrically distance-free combination is constructed using dual-frequency carrier phase observations, expressed as follows:

[0026]

[0027] in, This indicates that the carrier phase has no geometrical distance epoch difference. This represents the epochal difference in carrier phase observations at the first frequency, expressed in meters. This represents the epoch difference between carrier phase observations at the second frequency, expressed in meters. This represents the ionospheric delay variation between epochs at the first frequency. This indicates the ionospheric delay variation between epochs at the second frequency; The wavelength of the first frequency. The wavelength of the second frequency. This represents the integer ambiguity change over an epoch at the first frequency. This represents the integer ambiguity change between epochs at the second frequency. This represents the geometrically inverse carrier phase observation noise representing the epoch difference.

[0028] As a further technical solution, the smoothed Doppler observations are integrated over time, as shown in the expression:

[0029]

[0030] in, The change in carrier phase between epochs is the result of integrating Doppler observations. For frequency wavelength, The starting time of integration, The time when the integration ends, for The time is smoothed by Doppler observations. Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference represents the satellite clock bias. This represents the epochal difference of tropospheric delay. For frequency The epochal difference of ionospheric delay on the surface For frequency The noise in Doppler observations due to epochal differences.

[0031] As a further technical solution, the Doppler epoch-free distance difference is calculated based on approximate calculation results, and the expression is:

[0032]

[0033] in, For Doppler epochs with no geometric distance, This is the inter-epoch phase change obtained by integrating the Doppler observations at the first frequency. This is the interepochal phase change obtained by integrating the Doppler observations at the second frequency; This represents the ionospheric delay variation between epochs at the first frequency. This indicates the ionospheric delay variation between epochs at the second frequency. This is the geometrically insensitive Doppler observation noise between epochs.

[0034] According to one aspect of this specification, a GNSS cycle slip detection system combining Doppler and phase observation information is provided to implement the aforementioned GNSS cycle slip detection method combining Doppler and phase observation information, comprising:

[0035] The first processing module is used to acquire dual-frequency carrier phase observations from the GNSS receiver and calculate the epoch-free difference in carrier phase; and to acquire dual-frequency Doppler observations from the GNSS receiver and calculate the epoch-free difference in Doppler.

[0036] The second processing module is used to determine that a cycle slip has occurred when the absolute value of the difference between geometric distance epochs of the carrier phase is greater than the second discrimination threshold during the initial judgment stage; and to determine that there is no cycle slip when the absolute value of the difference between geometric distance epochs of the carrier phase is less than or equal to the first discrimination threshold.

[0037] The third processing module is used to enter a re-judgment stage when the absolute value of the carrier phase epoch difference without geometric distance is greater than the first discrimination threshold and less than or equal to the second discrimination threshold; the re-judgment stage includes: determining that there is no cycle slip when the secondary discrimination statistic is less than or equal to the third discrimination threshold; determining that a cycle slip has occurred when the secondary discrimination statistic is greater than the third discrimination threshold; wherein, the secondary discrimination statistic is the absolute value of the sum of the carrier phase epoch difference without geometric distance and the Doppler epoch difference without geometric distance.

[0038] According to one aspect of the present invention, an electronic device is provided, including a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of the GNSS cycle slip detection method with combined Doppler and phase observation information.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. This invention introduces Doppler integral phase recovery and Gaussian weighted moving average techniques, utilizing the characteristic that Doppler observations are unaffected by cycle slips to construct a secondary discriminant statistic. During periods of ionospheric activity, this statistic effectively reduces the interference of ionospheric delay changes on cycle slip detection, solving the technical problem of numerous cycle slip misjudgments caused by the reliance on fixed empirical thresholds in traditional GF cycle slip detection methods.

[0041] 2. This invention uses Doppler observations to determine cycle slips twice, effectively avoiding repeated initialization of baseline ambiguity caused by ionospheric fluctuations, ensuring the continuity and stability of the differential satellite count, and is applied to NRTK servers.

[0042] 3. This invention increases the number of available satellites by retaining satellites that are misjudged as cycle slips by GF detection due to ionospheric activity, thus significantly improving the ambiguity fixation rate and positioning accuracy in complex space environments, and can be applied to terminals. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 A flowchart of a GNSS cycle slip detection method that combines Doppler and phase observation information, provided in an embodiment of the present invention.

[0045] Figure 2 The reference station network diagram used in the experimental verification process provided in the embodiments of the present invention.

[0046] Figure 3 The phase and Doppler calculation GF epoch difference sequence diagram provided for embodiments of the present invention (taking VBJA as an example).

[0047] Figure 4 The diagram shows the terminal fixation rate and positioning accuracy results of the traditional GF cycle slip detection method provided in this embodiment of the invention.

[0048] Figure 5 The terminal fixation rate and positioning accuracy results are shown in the figure corresponding to the GNSS cycle slip detection method with combined Doppler and phase observation information provided in the embodiments of the present invention.

[0049] Figure 6 This diagram illustrates the terminal-fixed ratio results for the traditional GF cycle slip detection method and the GNSS cycle slip detection method combining Doppler and phase observation information proposed in this invention, as provided in the embodiments of the present invention. Detailed Implementation

[0050] 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.

[0051] like Figure 1 As shown, this embodiment of the invention proposes a GNSS cycle slip detection method that combines Doppler and phase observation information, including: Step S1, acquiring dual-frequency carrier phase observations from a GNSS receiver and calculating the epoch-free difference between carrier phase and geometric distance; acquiring dual-frequency Doppler observations from a GNSS receiver and calculating the epoch-free difference between Doppler and geometric distance; Step S2, performing cycle slip determination based on the epoch-free difference between carrier phase and geometric distance: when the absolute value of the epoch-free difference between carrier phase and geometric distance is greater than a first discrimination threshold, a cycle slip is determined to have occurred; when the absolute value of the epoch-free difference between carrier phase and geometric distance is less than a second discrimination threshold, no cycle slip is determined to have occurred; when the absolute value of the epoch-free difference between carrier phase and geometric distance is greater than the second discrimination threshold and less than the first discrimination threshold, constructing a secondary discrimination statistic for cycle slip determination: when the secondary discrimination statistic is less than a third discrimination threshold, no cycle slip is determined to have occurred; when the secondary discrimination statistic is greater than the third discrimination threshold, a cycle slip is determined to have occurred.

[0052] Specifically, step S1 includes the following:

[0053] 1. The expressions for the dual-frequency carrier phase observation equation and the dual-frequency Doppler observation equation are as follows:

[0054] (1)

[0055] in, For frequency Carrier phase observations in meters. For frequency Doppler observations in meters per second (mathematically defined as the rate of change of carrier phase). For frequency The dual-frequency carrier phase observations on a weekly basis. For frequency The above are dual-frequency Doppler observations in weeks per second. For frequency The wavelength; and These are the satellite-to-Earth distance and the rate of change of satellite-to-Earth distance, respectively. At the speed of light, For receiver clock bias, For satellite clock bias, For receiver clock drift, For satellite clock drift; and These are the tropospheric delay and the rate of change of tropospheric delay, respectively. and Frequency Ionospheric delay and rate of change of ionospheric delay; For frequency Integer blur on the top and Frequency carrier phase observation noise and frequency Doppler observation noise.

[0056] 2. Calculate the phase-free (GF) inter-epoch difference. Obtain the GNSS receiver's epoch. He Liyuan The dual-frequency carrier phase observations are first subjected to inter-epoch difference analysis to obtain:

[0057] (2)

[0058] in, Represents frequency The epochal difference between carrier phase observations, expressed in meters; Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference represents the satellite clock bias. This represents the epochal difference of tropospheric delay. For frequency The epochal difference of ionospheric delay on the surface For frequency wavelength, This represents the integer change in ambiguity between epochs; it is 0 when no cycle slip occurs, and not 0 when a cycle slip occurs. For frequency The noise of carrier phase observations between epochs.

[0059] Then, a GF combination is constructed using dual-frequency carrier phase observations to eliminate the geometric distance term. Receiver clock bias Satellite clock bias and tropospheric terms ,get:

[0060] (3)

[0061] in, This indicates that the carrier phase has no geometrical distance epoch difference. This represents the epochal difference in carrier phase observations at the first frequency, expressed in meters. This represents the epoch difference between carrier phase observations at the second frequency, expressed in meters. This represents the ionospheric delay variation between epochs at the first frequency. This indicates the ionospheric delay variation between epochs at the second frequency; The wavelength of the first frequency. The wavelength of the second frequency. This represents the integer ambiguity change over an epoch at the first frequency. This represents the integer ambiguity change between epochs at the second frequency; This represents the geometrically inverse carrier phase observation noise representing the epoch difference.

[0062] The simplified representation is as follows:

[0063] (4)

[0064] in, This represents the amount of ionospheric delay change between epochs. ; This represents the integer ambiguity change caused by cycle slips.

[0065] In the absence of cycle slip It mainly includes the interepochal ionospheric delay variation. and observation noise When a cycle slip occurs, It also includes the integer ambiguity change term caused by cycle slip. .

[0066] 3. Calculate the epoch difference of Doppler without geometric distance. .

[0067] Before calculating the Doppler GF inter-epoch difference, the dual-frequency Doppler observations from the GNSS receiver are smoothed and denoised using a Gaussian weighted moving average method:

[0068] (5)

[0069] in, These are smoothed Doppler observations; Indicates Doppler observations; Indicates the current epoch; This represents the Doppler observations within a sliding window starting from the current epoch; The width of the sliding window. For the first Gaussian weight coefficients corresponding to each epoch.

[0070] Gaussian weighting coefficients The calculation method is as follows:

[0071] (6)

[0072] in, The standard deviation of the Gaussian kernel function determines the smoothness of the filter; a value of 1-2 is recommended. This is a normalization coefficient used to ensure that the sum of all weights is 1; The summation index variable takes values ​​from 0 to M-1 and is used to iterate through all sample values ​​in the sliding window.

[0073] Due to Doppler observations Essentially, it is the derivative of the carrier phase with respect to time, and does not contain integer ambiguity information. By integrating the smoothed Doppler observations over time, the change in carrier phase between epochs can be reconstructed. :

[0074] (7)

[0075] in, The change in carrier phase between epochs is the result of integrating Doppler observations. for The time is smoothed by Doppler observations. The starting time of integration, This is the moment when the integration ends; Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference represents the satellite clock bias. This represents the epochal difference of tropospheric delay. For frequency The epochal difference of ionospheric delay on the surface For frequency The noise in Doppler observations due to epochal differences. It does not contain an ambiguity term, so theoretically it is not affected by cycle slip.

[0076] In practical calculations, the trapezoidal integral method is used to discretize and approximate the changes in phase observations between epochs:

[0077] (8)

[0078] in, and The start time is respectively and the end time Smoothed Doppler observations .

[0079] Calculate the epochal difference of Doppler GF :

[0080] (9)

[0081] in, This is the inter-epoch phase change obtained by integrating the Doppler observations at the first frequency. This is the interepochal phase change obtained by integrating the Doppler observations at the second frequency; This represents the ionospheric delay variation between epochs at the first frequency. This represents the ionospheric delay variation between epochs at the second frequency. Doppler GF epoch difference The simplified representation is as follows:

[0082] (10)

[0083] in, This represents the change in the ionosphere. Geometric distance-free Doppler observation noise due to epoch difference. Doppler GF epoch difference Unaffected by cycle slips, and the ionospheric influence and the phase GF epoch difference The absolute values ​​of the effects of the intermediate ionosphere are equal, but their signs are opposite. Since Doppler observations are unaffected by cycle slips... It only reflects ionospheric changes and Doppler observation noise, and does not include cycle slip information.

[0084] Specifically, step S2 includes the following:

[0085] 1. Preliminary judgment stage: based on Absolute value and first discrimination threshold Second discrimination threshold Determine whether a cycle slip has occurred.

[0086] like The condition is determined to be a cycle slip. Considering that the GF combination cannot detect cycle slips of specific combinations (e.g., a 9-cycle slip at the first frequency point and a 7-cycle slip at the second frequency point), relying solely on the GF combination may lead to missed detections. To compensate for this deficiency, this embodiment of the invention introduces the Melbourne-Wübbena (MW) combination as a supplementary determination; the second discrimination threshold... Used to identify significant cycle slips.

[0087] like If so, it is determined to be without cycle slip.

[0088] 2. Reassessment Stage (Handling Uncertain Intervals of Cycle Slips): If Traditional cycle slip detection often relies directly on the combination of GF and MW, which is easily affected by intense ionospheric activity, leading to false cycle slips. Therefore, this invention utilizes the characteristic that Doppler observations are unaffected by cycle slips to detect... and Perform combination operations to calculate the second-order discriminant statistic. The second-order discrimination statistic is the absolute value of the sum of the carrier phase epoch difference without geometric distance and the Doppler epoch difference without geometric distance:

[0089] (11)

[0090] Among them, statistics It is not affected by the ionosphere, but only by cycle slips and observation noise.

[0091] Comparison of second-order discriminant statistics With the third judgment threshold :like If it is determined to be without cycle slip, This is determined to be a cycle slip.

[0092] Specifically, the threshold , and The threshold setting method can be dynamically adjusted based on the receiver type, observation sampling rate, and current ionospheric background environment, or a reasonable fixed threshold can be selected based on a large number of engineering experimental statistics. The value range is 0.15m-0.25m, with 0.2m being preferred; The value range is 0.03m-0.06m, with 0.05m being preferred; The value range is 0.05m-0.10m, with 0.08m being preferred.

[0093] Specifically, when no cycle slip occurs, The value should only include phase observation noise and Doppler observation noise, and be less than the third judgment threshold. When a cycle slip occurs, Significantly increased and exceeding the third judgment threshold .

[0094] Specifically, this invention is applied to cycle slip detection in the baseline solution of Network Real-Time Kinematic (NRTK) servers, including: performing cycle slip classification detection by combining Doppler and phase observation information; accurately identifying and correcting cycle slip misjudgments caused by drastic fluctuations in ionospheric delay during active ionospheric periods by constructing a secondary discrimination statistic based on the GF phase epoch difference and the Doppler-reconstructed phase epoch difference; and avoiding frequent initialization of ambiguity parameters in the server baseline solution, thereby improving the stability and continuity of the number of differential satellites provided by the NRTK server.

[0095] Specifically, the embodiments of the present invention are applied to cycle slip detection in NRTK terminal positioning calculation, including: the cycle slip detection method of the present invention is also used in the terminal positioning calculation, in a complex ionospheric environment, to reduce the frequent initialization of ambiguity caused by cycle slip misjudgment, increase the number of available satellites, and improve the ambiguity fixation rate of the terminal and the reliability of the positioning results.

[0096] This invention, based on a company's independently developed NRTK solution software platform, elaborates in detail the implementation process of the GNSS cycle slip detection method combining Doppler and phase observation information in the entire process of NRTK server-side base station network solution and user terminal positioning. It mainly includes base station networking and data preprocessing, baseline solution and differential information broadcasting, and terminal positioning solution.

[0097] 1. NRTK server base station networking and data preprocessing.

[0098] 1.1 Base Station Networking and Raw Data Stream Access. This embodiment of the invention selects a CORS network consisting of six self-built base stations (VBZC, VBSZ, VBSJ, VBLH, VBJA, VBZS) from a certain company as the experimental environment. The data processing center establishes data links with each base station and receives real-time streaming data. The system first performs site configuration, determining the base station ID, antenna type, and coordinates, completing the base station network, as follows... Figure 2 As shown.

[0099] 1.2 Calculate the phase GF inter-epoch difference. The carrier phase observation equation and Doppler observation equation obtained by the GNSS receiver are expressed as follows:

[0100] (12)

[0101] in, For frequency The dual-frequency carrier phase observations, in meters. For frequency Dual-frequency Doppler observations in meters per second (mathematically defined as the rate of change of carrier phase). For frequency The dual-frequency carrier phase observations on a weekly basis. For frequency The above are dual-frequency Doppler observations in weeks per second. For frequency The wavelength; and These are the satellite-to-Earth distance and the rate of change of satellite-to-Earth distance, respectively. At the speed of light, For receiver clock bias, For satellite clock bias, For receiver clock drift, For satellite clock drift; and These are the tropospheric delay and the rate of change of tropospheric delay, respectively. and Frequency Ionospheric delay and rate of change of ionospheric delay; For frequency Integer blur on the top and Frequency carrier phase observation noise and frequency Doppler observation noise.

[0102] First, the carrier phase observations are differentially analyzed between epochs to obtain:

[0103] (13)

[0104] in, Represents frequency The epochal difference between dual-frequency carrier phase observations, expressed in meters; Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference represents the satellite clock bias. This represents the epochal difference of tropospheric delay. For frequency The epochal difference of ionospheric delay on the surface For frequency wavelength, This represents the integer change in ambiguity between epochs; it is 0 when no cycle slip occurs, and not 0 when a cycle slip occurs. For frequency The noise of carrier phase observations between epochs.

[0105] Then, a GF combination is constructed using dual-frequency observations to eliminate the geometric distance term. Receiver clock bias Satellite clock bias and tropospheric terms ,get:

[0106] (14)

[0107] The simplified representation is as follows:

[0108] (15)

[0109] in, , .

[0110] 1.3. Smoothing and Denoising Doppler Observations. The original Doppler observations were smoothed and denoised using a Gaussian weighted moving average method:

[0111] (16)

[0112] in, These are smoothed Doppler observations; Indicates Doppler observations; Indicates the current epoch; This represents the Doppler observations within a sliding window starting from the current epoch; The width of the sliding window. For the first Gaussian weight coefficients corresponding to each epoch.

[0113] Gaussian weighting coefficients The calculation method is as follows:

[0114] (17)

[0115] in, The standard deviation of the Gaussian kernel function determines the smoothness of the filter; a value of 1-2 is recommended. The denominator is the normalization coefficient, used to ensure that the sum of all weights is 1.

[0116] 1.4 Calculate the Doppler GF inter-epoch difference. Integrate the smoothed Doppler observations over time to reconstruct the carrier phase variation between epochs:

[0117] (18)

[0118] in, This is the epochal carrier phase change obtained by integrating Doppler observations. It is the starting moment of integration. This is the moment when the integration ends.

[0119] In practical calculations, the trapezoidal integral method is used to discretize and approximate the above integral:

[0120] (19)

[0121] in, and The start time is respectively and the end time Smoothed Doppler observations .

[0122] Calculate the epochal difference of Doppler GF :

[0123] (20)

[0124] The simplified representation is as follows:

[0125] (twenty one)

[0126] in, This represents the change in the ionosphere. This is for Doppler observation noise.

[0127] 1.5. Cycle slip detection using combined Doppler and phase observations. The initial threshold for determining whether a cycle slip has occurred includes a first discrimination threshold. Second discrimination threshold Based on extensive engineering experiments and statistics, the first discrimination threshold... The threshold is typically set between 0.03m and 0.06m, preferably 0.05m. This is the second discrimination threshold. The value used to identify significant cycle slips is typically between 0.15m and 0.25m, with 0.2m being preferred.

[0128] like If a cycle slip occurs, it is determined that a cycle slip has occurred. Considering that the GF combination cannot detect cycle slips of specific combinations (such as a 9-cycle slip at the first frequency point and a 7-cycle slip at the second frequency point), relying solely on the GF combination may lead to missed detections. To compensate for this deficiency, this embodiment of the invention introduces the Melbourne-Wübbena (MW) combination as a supplementary determination.

[0129] like If so, it is determined to be without cycle slip.

[0130] Table 1 presents the statistical results of the GF epoch difference during the 40-day (February 5 to March 16, 2026) quiescent period at six reference stations. During the ionospheric quiescent period, ionospheric fluctuations are very small, and the phase observations are calculated... If the change exceeds 0.05m, it is usually considered a cycle slip because ionospheric fluctuations alone are unlikely to cause such a large change in GF without a cycle slip. Table 1 shows the 40-day stationary period for the six stations. The number of satellites with a phase change greater than 0.05m exceeds 300. In comparison, the calculation after restoring the phase change using Doppler integration... The number of satellites with a value greater than 0.05m is less than 10 (e.g., 0 for VBJA station and only 2 for VBZC station). This result verifies that Doppler observations are largely unaffected by cycle slips. Figure 3 The difference sequence diagrams between phase GF epochs and Doppler GF epochs, calculated using the VBJA station as an example, are presented.

[0131] Table 1. Statistical results of the interepochal differences in GF calculated by the two methods during the 40-day ionospheric quiescence period.

[0132] like If the condition is not met, the system enters the ambiguous region for judgment. This embodiment of the invention utilizes the characteristic that Doppler observations are unaffected by cycle slips to construct a secondary discriminant statistic to distinguish between small cycle slips and ionospheric fluctuations. The phase change is reconstructed by integrating the Doppler observations over time. The Doppler GF epoch difference is then calculated. Constructing a second-order discriminant statistic :

[0133] (twenty two)

[0134] like If it is determined to be without cycle slip; This is determined to be a cycle slip.

[0135] 2. Baseline calculation and differential information broadcasting.

[0136] 2.1 Baseline Calculation. Using the cycle-slip-free data corrected in step S5, baseline calculation between reference stations is performed. Since the cycle-slip misjudgment caused by severe ionospheric fluctuations has been corrected, the ambiguity parameters do not need frequent initialization.

[0137] 2.2 Differential Data Broadcasting. After completing the baseline calculation on the server side, the system generates differential data and broadcasts it to the user. Specifically, the system uses virtual reference station technology to interpolate and generate error corrections (including ionospheric delay, tropospheric delay, etc.) and virtual observations at the approximate coordinates of the terminal. The virtual observations are then encoded into standard RTCM format data and broadcast to the terminal in real time via mobile communication network or radio link. During this process, because the server has corrected misjudged cycle slips using the aforementioned cycle slip detection method, the broadcast differential corrections have higher stability and continuity.

[0138] 3. Terminal positioning calculation.

[0139] The terminal first decodes the differential data provided by the server. Similarly, the GNSS cycle slip detection method based on the joint Doppler and phase observation information of this invention is used in data preprocessing. First, a double-difference observation equation is constructed. Then, the system uses a least-squares ambiguity decorrelation adjustment algorithm to search for the optimal integer solution and performs a ratio value check. Because this invention can retain satellites that are misjudged as cycle slips by GF detection due to ionospheric activity, increasing the number of available satellites, ambiguity parameters can be fixed quickly and accurately. Once ambiguity is successfully fixed, the terminal can calculate centimeter-level high-precision position information.

[0140] To visually demonstrate the optimization effect of the method of this invention in NRTK, this embodiment presents a comparison of the localization results of the traditional method and the method of this invention during the active period of the ionosphere (March 5, 2025, UTC 12:00-16:00), as follows. Figure 4 and Figure 5 As shown in the figure. The fixation rate is defined as the correct fixation rate (plane error less than 5 cm, elevation error less than 10 cm), and the terminal fixation Ratio (Ratio: a criterion for determining ambiguity fixation; a Ratio value greater than 3.0 usually indicates successful ambiguity fixation) is as follows. Figure 6 As shown, the cycle slip detection method of this invention significantly improves the terminal positioning accuracy.

[0141] The implementation of the various embodiments of the present invention is based on programmed processing by a device with processor functionality. Therefore, in practical engineering, the technical solutions and functions of the various embodiments of the present invention are encapsulated into various modules. Based on this reality, and building upon the above embodiments, the embodiments of the present invention provide a GNSS cycle slip detection system that combines Doppler and phase observation information. This system is used to execute a GNSS cycle slip detection method that combines Doppler and phase observation information from the above method embodiments.

[0142] The system includes: a first processing module for acquiring dual-frequency carrier phase observations from a GNSS receiver and calculating the epoch-free difference in carrier phase; acquiring dual-frequency Doppler observations from a GNSS receiver and calculating the epoch-free difference in Doppler; a second processing module for, in the initial judgment stage, determining a cycle slip as occurring when the absolute value of the epoch-free difference in carrier phase is greater than a second discrimination threshold; and determining no cycle slip when the absolute value of the epoch-free difference in carrier phase is less than or equal to a first discrimination threshold; a third processing module for, entering a re-judgment stage when the absolute value of the epoch-free difference in carrier phase is greater than the first discrimination threshold and less than or equal to the second discrimination threshold; the re-judgment stage includes: determining no cycle slip when the secondary discrimination statistic is less than or equal to a third discrimination threshold; and determining a cycle slip as occurring when the secondary discrimination statistic is greater than the third discrimination threshold; wherein the secondary discrimination statistic is the absolute value of the sum of the epoch-free difference in carrier phase and the epoch-free difference in Doppler.

[0143] This invention provides a GNSS cycle slip detection system that combines Doppler and phase observation information. This addresses the problems of traditional cycle slip detection methods without geometric distance, which suffer from high false positive rates during periods of ionospheric activity due to the inability to distinguish between drastic ionospheric changes and small cycle slips, as well as the frequent initialization of ambiguity parameters in NRTK server baseline resolution, leading to decreased terminal positioning stability and accuracy. The method acquires carrier phase and Doppler observations, performs smoothing and noise reduction on the original Doppler observations, constructs a phase GF model and a Doppler GF model, and calculates the phase GF epoch difference and the Doppler GF epoch difference. Combinatorial logic is used to determine whether the phase epoch difference is greater than a first discrimination threshold and less than a second discrimination threshold. For the ambiguity interval between the second and first discrimination thresholds, the two are added to construct a secondary discrimination statistic to eliminate the influence of ionospheric delay. If the new statistic is less than a third discrimination threshold, it is determined to be a cycle slip-free system; otherwise, it is a cycle slip. This invention significantly reduces the noise in Doppler observations and effectively distinguishes between cycle slips and ionospheric anomalous disturbances in ambiguous intervals through graded cycle slip detection.

[0144] Based on the same inventive concept as the foregoing embodiments, this embodiment of the invention also provides an electronic device, including a memory and a processor. The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize a GNSS cycle slip detection method that combines Doppler and phase observation information as proposed in the above embodiments.

[0145] Finally, it should be noted that the above specific embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above specific embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above specific embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A GNSS cycle slip detection method that combines Doppler and phase observation information, characterized in that, include: Obtain dual-frequency carrier phase observations from a GNSS receiver and calculate the carrier phase difference between geometric distance epochs. Acquire dual-frequency Doppler observations from a GNSS receiver and calculate the Doppler epoch-free distance difference; In the initial judgment stage, if the absolute value of the difference between geometric distance epochs of the carrier phase is greater than the second discrimination threshold, it is determined that a cycle slip has occurred; if the absolute value of the difference between geometric distance epochs of the carrier phase is less than or equal to the first discrimination threshold, it is determined that there is no cycle slip. When the absolute value of the epoch difference between the carrier phase and the geometric distance is greater than the first discrimination threshold and less than or equal to the second discrimination threshold, the re-discrimination stage is entered. The re-judgment stage includes: determining that there is no cycle slip when the secondary discrimination statistic is less than or equal to the third discrimination threshold; determining that a cycle slip has occurred when the secondary discrimination statistic is greater than the third discrimination threshold; wherein, the secondary discrimination statistic is the absolute value of the sum of the carrier phase epoch difference without geometric distance and the Doppler epoch difference without geometric distance; the expression for the secondary discrimination statistic is: ， in, This represents the second-order discriminant statistic. This indicates that the carrier phase has no geometrical distance epoch difference. This indicates that there is no geometric distance difference between Doppler epochs. This represents the integer ambiguity change caused by cycle slips. Geometrically inverse carrier phase observation noise representing the epoch difference. Geometric distance-free Doppler observation noise representing the difference between epochs.

2. The GNSS cycle slip detection method according to claim 1, characterized in that, Calculating the carrier phase epoch difference without geometric distance includes: The epoch difference of the carrier phase observations is obtained by performing epoch difference on the dual-frequency carrier phase observations; By constructing a geometrically distance-free combination using carrier phase observations, the geometrically distance-free epoch difference of carrier phase is calculated.

3. The GNSS cycle slip detection method combining Doppler and phase observation information according to claim 1, characterized in that, Calculating the Doppler epoch difference without geometric distance includes: The dual-frequency Doppler observations are smoothed and denoised to obtain smoothed Doppler observations. Time integration is performed on the smoothed Doppler observations to restore the change in carrier phase between epochs; The variation of carrier phase observations between epochs is discretized and approximated, and the Doppler non-geometric distance epoch difference is calculated based on the approximation results.

4. The GNSS cycle slip detection method combining Doppler and phase observation information according to claim 2, characterized in that, The inter-epoch difference of the carrier phase observations is expressed as follows: ， in, Represents frequency The epochal difference between carrier phase observations, expressed in meters; Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference representing satellite clock bias. This represents the epochal difference of tropospheric delay. Represents frequency The epochal difference of ionospheric delay on the surface Represents frequency wavelength, This represents the integer variation in ambiguity between epochs. Represents frequency The noise of carrier phase observations between epochs.

5. A GNSS cycle slip detection method combining Doppler and phase observation information according to claim 2, characterized in that, A geometrically distance-free combination is constructed using dual-frequency carrier phase observations, expressed as: ， in, This indicates that the carrier phase has no geometrical distance epoch difference. This represents the epochal difference in carrier phase observations at the first frequency, expressed in meters. This represents the epoch difference between carrier phase observations at the second frequency, expressed in meters. This represents the ionospheric delay variation between epochs at the first frequency. This indicates the ionospheric delay variation between epochs at the second frequency; The wavelength of the first frequency. The wavelength of the second frequency. This represents the integer ambiguity change over an epoch at the first frequency. This represents the integer ambiguity change between epochs at the second frequency. This represents the geometrically inverse carrier phase observation noise representing the epoch difference.

6. The GNSS cycle slip detection method according to claim 3, characterized in that, The time integral of the smoothed Doppler observations is expressed as: ， in, The change in carrier phase between epochs is the result of integrating Doppler observations. For frequency wavelength, The starting time of integration, The time when the integration ends, for The time is smoothed by Doppler observations. Represents the geometric distance term. Represents the speed of light. This represents the epoch difference of the receiver clock. The epoch difference representing satellite clock bias. This represents the epochal difference of tropospheric delay. For frequency The epochal difference of ionospheric delay on the surface For frequency The noise in Doppler observations due to epochal differences.

7. A GNSS cycle slip detection method combining Doppler and phase observation information according to claim 3, characterized in that, The Doppler epoch difference without geometric distance was calculated based on the approximate calculation results, and the expression is: ， in, For Doppler epochs with no geometric distance, This is the inter-epoch phase change obtained by integrating the Doppler observations at the first frequency. This is the interepochal phase change obtained by integrating the Doppler observations at the second frequency; This represents the ionospheric delay variation between epochs at the first frequency. This indicates the ionospheric delay variation between epochs at the second frequency. This is the geometrically insensitive Doppler observation noise between epochs.

8. A GNSS cycle slip detection system that combines Doppler and phase observation information, characterized in that, A GNSS cycle slip detection method for implementing the method of combining Doppler and phase observation information as described in any one of claims 1-7 includes: The first processing module is used to acquire dual-frequency carrier phase observations from the GNSS receiver and calculate the epoch-free difference in carrier phase; and to acquire dual-frequency Doppler observations from the GNSS receiver and calculate the epoch-free difference in Doppler. The second processing module is used to determine that a cycle slip has occurred when the absolute value of the difference between geometric distance epochs of the carrier phase is greater than the second discrimination threshold during the initial judgment stage; and to determine that there is no cycle slip when the absolute value of the difference between geometric distance epochs of the carrier phase is less than or equal to the first discrimination threshold. The third processing module is used to enter a re-judgment stage when the absolute value of the carrier phase epoch difference without geometric distance is greater than the first discrimination threshold and less than or equal to the second discrimination threshold; the re-judgment stage includes: determining that there is no cycle slip when the secondary discrimination statistic is less than or equal to the third discrimination threshold; determining that a cycle slip has occurred when the secondary discrimination statistic is greater than the third discrimination threshold; wherein, the secondary discrimination statistic is the absolute value of the sum of the carrier phase epoch difference without geometric distance and the Doppler epoch difference without geometric distance.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the GNSS cycle slip detection method according to any one of claims 1 to 7, which combines Doppler and phase observation information.

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