Ground GNSS differential data correction method and device
By combining TECR and MW wide-lane combined observations, an adaptive threshold model is constructed. The carrier phase is corrected using the ionospheric TEC change rate and MW combined function, which solves the problem of GNSS cycle slip detection and repair in dynamic environments, improves GNSS positioning accuracy, and is suitable for air flight tests.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINESE FLIGHT TEST ESTAB
- Filing Date
- 2025-12-27
- Publication Date
- 2026-04-17
AI Technical Summary
Under dynamic conditions, the GNSS observation environment is highly variable, with low signal-to-noise ratio, complex multipath effects, and large variations in ionospheric delay error. Existing technologies are unable to effectively detect and repair cycle slips, resulting in insufficient positioning accuracy.
Cycle slip detection and repair were performed using a combination of TECR and MW wide-lane observations. An adaptive threshold model was constructed, and the integer cycle slip value of the carrier phase was calculated using the ionospheric TEC rate of change and the MW combination function for accurate correction.
It improves the overall performance of cycle slip detection and repair, reduces false alarms and false alarms, and enhances GNSS positioning accuracy, making it suitable for precision positioning services in flight tests.
Smart Images
Figure CN121878744A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of aviation flight test technology and relates to a ground GNSS differential data correction method and device. Background Technology
[0002] Satellite navigation systems can quickly and reliably determine the position and velocity of a carrier, and have been widely used in spaceborne, airborne, vehicle-mounted, shipborne, and weapons testing and experimentation fields. Reducing GNSS measurement errors is one of the measures to improve GNSS positioning accuracy, and differential GNSS is an effective method to reduce or even eliminate various GNSS measurement errors.
[0003] A differential GNSS system comprises one or more GNSS receivers mounted at known coordinate points as reference stations. The reference station receivers measure GNSS satellite signals to calculate differential correction values, which are then used to correct the rover receiver, improving the positioning accuracy of the user receiver. Post-hoc GNSS differential is a precise positioning technique based on differential technology, typically employing a double-difference observation model, including intra-system double-difference models (loosely combined models) and inter-system double-difference models (tightly combined models). The double-difference model not only eliminates satellite clock errors and receiver clock errors but also significantly reduces satellite orbital errors, ionospheric delay errors, and tropospheric delay errors. Because ionospheric and tropospheric delay errors have strong spatial correlation, their residual effects cannot be ignored under medium- to long-baseline conditions. Therefore, error correction is necessary to improve the accuracy of differential positioning. Summary of the Invention
[0004] This invention provides a method and apparatus for correcting ground-based GNSS differential data. It employs a combination of TECR and MW wide-lane observations to detect and repair cycle slips, and constructs a threshold model to improve TurboEdit's real-time cycle slip detection. For dual-frequency GNSS data, a combination of MW and ionospheric TEC rate of change (TECR) is used to detect and repair cycle slips. Furthermore, in dynamic flight observation environments, cycle slips occur more frequently, and the complex and variable motion of the carrier leads to unclear patterns in phase observations. Using a fixed threshold in cycle slip detection easily results in false positives and false negatives. Therefore, an adaptive threshold model is constructed based on TurboEdit's cycle slip detection, thereby improving the overall performance of cycle slip detection and repair. The technical solution is as follows: Firstly, a ground-based GNSS differential data correction method is provided, which obtains pseudorange and carrier phase, calculates the integer jump value of carrier phase using the MW combination function and the ionospheric delay change rate, and corrects the carrier phase value using the calculated integer jump value of carrier phase.
[0005] In one possible implementation, the method specifically includes: Step 1: After preprocessing the base station observations, broadcast ephemeris, and user station observations, we obtain the pseudorange and carrier phase; Step 2: Construct the MW combination function using pseudorange and carrier phase, calculate the first cycle slip value of the carrier phase, and calculate the second cycle slip value of the carrier phase using the ionospheric delay change rate; Step 3: Calculate the integer phase jump value of the carrier based on the first and second cycle jump values; Step 4: Correct the carrier phase value using the calculated integer transition value of the carrier phase, and output the corrected carrier phase value.
[0006] In one feasible approach, in step 2, When calculating the first cycle jump value, a MW combination function is constructed using pseudorange and carrier phase to calculate wide-lane ambiguity. The expression for the MW combination function is:
[0007] In the formula, These are phase observations at different frequencies. These are pseudorange observations at different frequencies, L WL It is a combination of wide lanes. For wide-lane wavelength, The mean and variance of the wide-lane ambiguity are calculated using the following recursive formula:
[0008] in, represents the average value of the wide-lane ambiguity, and k and k-1 represent the current epoch and the previous epoch, respectively. Let represent the variance of the wide-lane ambiguity; when a cycle slip occurs, the wide-lane ambiguity will change abruptly, and this will be used to determine whether a cycle slip has occurred; the following cycle slip judgment formula is established:
[0009] when If the above equation is satisfied, then a cycle jump is considered to have occurred in epoch k.
[0010] In one feasible approach, during step 2, when calculating the second cycle jump value, the ionospheric rate of change (TECR) value can be considered a constant over a short period of time, and the ionospheric delay (TEC) at epoch k-1 is calculated using the following formula:
[0011] In the formula, , For the corresponding carrier frequency, The signal frequency offsets at the receiver and satellite ends, respectively, can be considered constant over a period of time. Therefore, the ionosphere at epoch k... The rate of change (TECR) is:
[0012] In the formula, the ambiguity parameter and the inter-frequency deviation parameter are eliminated. When a cycle slip occurs in epoch k, the calculated value will be affected by the cycle slip value. Assuming that the phase observations before epoch k have not experienced cycle slips or have been repaired, the TECR of all epochs before epoch k is calculated. Since the change in ionospheric TECR is gradual over a short period, the values calculated in previous epochs are used. The information predicts the TECR value of the current epoch k. Assuming the TECR values of epochs (k-1) and (k-1) have been calculated, the predicted TEC rate of change TECR(k) of epoch k is calculated using the following formula:
[0013]
[0014] In practice, It is also obtained by progressively smoothing the phase observations from previous epochs to reduce measurement noise and thus obtain higher accuracy. and ; When the difference between the two exceeds a certain threshold, it is considered that a cycle jump has occurred in that epoch. According to calculation Worth the weekly jump to epoch k: .
[0015] In one feasible approach, in step 3, The cycle slip value obtained from the MW combination function is 'a', and the cycle slip value obtained from TECR is 'a'. If the value is b, then the cycle slip of the carrier phase is calculated according to the following formula:
[0016] in, Let b be an integer and b be a real number. The real value obtained by applying the above formula is... Rounding up yields integer transition values at frequencies L1 and L2, which are then used to repair the carrier phase.
[0017] In a second aspect, a ground GNSS differential data correction apparatus is provided for performing any of the methods described in the first aspect, the apparatus comprising: The acquisition module is used to acquire pseudorange and carrier phase. The calculation module is used to calculate the integer phase jump value of the carrier using the MW combination function and the ionospheric delay change rate. The correction module is used to correct the carrier phase value using the calculated integer jump value of the carrier phase.
[0018] Thirdly, a ground GNSS differential data correction device is provided, comprising a processor and a memory, wherein the processor executes a program in the memory to implement the ground GNSS differential data correction method described in any of the first aspects.
[0019] Fourthly, a computer-readable storage medium is provided, wherein instructions are stored therein, which, when executed on a processing component of a computer, cause the processing component to perform any of the ground GNSS differential data correction methods described in the first aspect.
[0020] The beneficial effects of this invention are at least as follows: 1) Compared with similar technologies at home and abroad, the complexity of dynamic conditions lies in the variable GNSS observation environment, low signal-to-noise ratio, complex multipath effects, unclear station-satellite geometric variation patterns, and large variations in ionospheric delay error. The MW combination eliminates atmospheric delay errors (including ionospheric and tropospheric), station-satellite geometric distances, satellite and receiver clock errors, and has a wavelength of 86cm, making it very suitable for handling cycle slip problems in dynamic environments. However, the MW combination has the drawback of being unable to detect the same cycle slip occurring at different frequencies, and it cannot know the magnitude of the cycle slip at each frequency. Therefore, other methods are needed for auxiliary detection. Using continuous phase observations without cycle slips can calculate the ionospheric TEC rate of change. Since the ionospheric TEC rate of change changes smoothly over a short period, the occurrence of cycle slips will disrupt the smoothness of the calculated ionospheric TEC rate of change. Therefore, this characteristic can be used to detect cycle slips. This method also eliminates the influence of station-satellite geometric distances and takes into account the influence of ionospheric variations, making it suitable for cycle slip detection in dynamic environments.
[0021] 2) An adaptive threshold model was built on the basis of TurboEdit cycle slip detection under the dynamic flight observation environment, which reduced the cycle slip misjudgment at low satellite elevation angles and weakened the impact of low sampling rate on the performance of GF combined cycle slip detection to a certain extent.
[0022] 3) It provides technical support for the application of GNSS differential data in flight tests and provides precise positioning services directly for model research. Attached Figure Description
[0023] 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. 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.
[0024] Figure 1 Here is a flowchart of a method for correcting differential ground GNSS data. Figure 2 This is a flowchart of the cycle slip detection and repair algorithm. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.
[0026] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.
[0027] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0028] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.
[0029] The present invention provides a ground GNSS differential data correction method, which mainly includes: 1) A method for detecting and repairing cycle slips by combining TECR and MW wide-lane combined observations is proposed. The TECR rate of change can detect cycle slips as small as one cycle in phase observations and can detect cycle slips with the same value at two frequencies, thus making up for the deficiency of MW combination in that it cannot detect cycle slips of the same size at different frequencies.
[0030] 2) An adaptive threshold model based on root mean square variation is proposed, which can effectively reduce cycle slip false positives for single data. It also improves the detection performance for cycle slip underreporting when the root mean square is large, resulting in a significant improvement in detection performance compared to previous methods.
[0031] 3) A weighted threshold model for GF combined cycle slip detection is proposed. The weighted threshold model is obtained through statistical analysis based on a large number of tests on data from different regions, different sampling rates, and different satellite elevation angles. Therefore, the model can be basically applied to cycle slip detection of data under different observation environments.
[0032] See Figure 1 and Figure 2 The present invention provides a ground GNSS differential data correction method, comprising the following steps: Step 1: After preprocessing the base station observations, broadcast ephemeris, and user station observations, obtain the pseudorange and carrier phase.
[0033] Step 2: Calculate the cycle slip value of the carrier phase.
[0034] Calculating the cycle slip value of the carrier phase requires two operations. In the first operation, a MW combination function is constructed using the pseudorange and the carrier phase, and the cycle slip value of the carrier phase is calculated using the MW combination function.
[0035] A MW combination function is constructed using pseudorange and carrier phase. This MW combination function is used to calculate wide-lane ambiguity. The expression for the MW combination function is as follows:
[0036] In the formula, These are phase observations at different frequencies (unit: cycles). These are pseudorange observations at different frequencies (unit: meters), L WL For wide lane combinations (unit: meters). The wavelength is the wide-lane wavelength.
[0037] To mitigate the impact of noise, the following recursive algorithm is used to calculate the average and variance of the wide-lane ambiguity:
[0038] In the above formula, represents the average value of the wide-lane ambiguity, and k and k-1 represent the current epoch and the previous epoch, respectively. This represents the variance of the wide-lane ambiguity. When a cycle slip occurs, the wide-lane ambiguity will change abruptly, which can be used to determine whether a cycle slip has occurred. The cycle slip judgment formula is established as follows:
[0039] when If the above equation is satisfied, then a cycle jump is considered to have occurred in epoch k.
[0040] In the second operation, the cycle slip value of the carrier phase is calculated using the ionospheric change rate.
[0041] Over a short period, the rate of ionospheric change (TECR) can be considered a constant. The ionospheric delay TEC at epoch k-1 can be calculated using the following formula:
[0042] In the formula, , For the corresponding carrier frequency, The signal frequency offsets at the receiver and satellite ends, respectively, can be considered constant over a period of time. Therefore, the ionosphere at epoch k... rate of change The calculated value is:
[0043] In the formula, the ambiguity parameter and the inter-frequency deviation parameter are eliminated. Clearly, when a cycle slip occurs in epoch k, this calculated value will be affected by the cycle slip value.
[0044] Assuming that phase observations prior to epoch k have not experienced cycle slips or have been corrected, the TECR for all epochs prior to epoch k can also be calculated. Since the ionospheric TECR changes gradually over a short period, the TECR information calculated from previous epochs can be used to predict the current epoch. The TECR value. Assuming the TECR values for epochs (k-1) and (k-1) are calculated, then the predicted epoch k... The rate of change TECR(k) can be calculated using the following two formulas:
[0045]
[0046] In practice, It is also obtained by progressively smoothing the phase observations from previous epochs to reduce measurement noise and thus obtain higher accuracy. and .
[0047] Given that the change in ionospheric ETCR is relatively gradual over a short period, theoretically, the difference between the calculated and predicted ETCR values for the current epoch should be very small if no cycle slip occurs. Therefore, when the difference exceeds a certain threshold (0.15 ETCU / s), a cycle slip is considered to have occurred at that epoch.
[0048] According to calculation The value can be used to obtain the cycle jump of epoch k, and the calculation formula is as follows:
[0049] The calculation of the cycle slip value of the carrier phase involves two operations to ensure that the subsequent calculation of the integer cycle slip value of the carrier phase is more accurate, thus enabling precise correction of the carrier phase value.
[0050] Step 3: Calculate the integer cycle change value of the carrier phase using the cycle slip values detected by the above two operations.
[0051] Assuming the cycle slip value obtained by the MW combination function in the first operation described above is 'a', and the cycle slip value obtained by the TECR detection in the second operation is used... If the value is b, then the integer phase jump value of the carrier phase can be calculated according to the following formula:
[0052] in, Let b be an integer and b be a real number. The real value obtained by applying the above formula is... Rounding up yields integer transition values at frequencies L1 and L2, which can then be used to repair the carrier phase.
[0053] The above equations are solved to obtain... The value of .
[0054] Step 4: Correct the carrier phase value using the calculated integer transition value of the carrier phase, and output the corrected carrier phase value. This correction process can be found in relevant technologies and will not be elaborated upon here.
[0055] An embodiment of the present invention also provides a ground GNSS differential data correction device for performing the method described in the embodiment of the present invention, the device comprising: The acquisition module is used to acquire pseudorange and carrier phase. The calculation module is used to calculate the integer phase jump value of the carrier using the MW combination function and the ionospheric delay change rate. The correction module is used to correct the carrier phase value using the calculated integer jump value of the carrier phase.
[0056] An embodiment of the present invention also provides a ground GNSS differential data correction device, including a processor and a memory, wherein the processor executes a program in the memory to implement the ground GNSS differential data correction method described in the embodiment of the present invention.
[0057] An embodiment of the present invention also provides a computer-readable storage medium storing instructions that, when executed on a computer's processing component, cause the processing component to perform the ground GNSS differential data correction method described in this embodiment of the present invention.
[0058] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.
Claims
1. A method for correcting ground GNSS differential data, characterized in that, Obtain the pseudorange and carrier phase, calculate the integer jump value of the carrier phase using the MW combination function and the ionospheric delay change rate, and correct the carrier phase value using the calculated integer jump value of the carrier phase.
2. The method according to claim 1, characterized in that, The method specifically includes: Step 1: After preprocessing the base station observations, broadcast ephemeris, and user station observations, we obtain the pseudorange and carrier phase; Step 2: Construct the MW combination function using pseudorange and carrier phase, calculate the first cycle slip value of the carrier phase, and calculate the second cycle slip value of the carrier phase using the ionospheric delay change rate; Step 3: Calculate the integer phase jump value of the carrier based on the first and second cycle jump values; Step 4: Correct the carrier phase value using the calculated integer transition value of the carrier phase, and output the corrected carrier phase value.
3. The method according to claim 2, characterized in that, In step 2, When calculating the first cycle jump value, a MW combination function is constructed using pseudorange and carrier phase to calculate wide-lane ambiguity. The expression for the MW combination function is: In the formula, These are phase observations at different frequencies. These are pseudorange observations at different frequencies, L WL It is a combination of wide lanes. For wide-lane wavelength, The mean and variance of the wide-lane ambiguity are calculated using the following recursive formula: in, represents the average value of the wide-lane ambiguity, and k and k-1 represent the current epoch and the previous epoch, respectively. Let represent the variance of the wide-lane ambiguity; when a cycle slip occurs, the wide-lane ambiguity will change abruptly, and this will be used to determine whether a cycle slip has occurred; the following cycle slip judgment formula is established: when If the above equation is satisfied, then a cycle jump is considered to have occurred in epoch k.
4. The method according to claim 3, characterized in that, In step 2, when calculating the second cycle jump value, the ionospheric change rate TECR value can be considered as a constant over a short period of time. The ionospheric delay TEC at epoch k-1 is calculated using the following formula: In the formula, , For the corresponding carrier frequency, The signal frequency offsets at the receiver and satellite ends, respectively, can be considered constant over a period of time. Therefore, the ionosphere at epoch k... The rate of change (TECR) is: In the formula, the ambiguity parameter and the inter-frequency deviation parameter are eliminated. When a cycle slip occurs in epoch k, the calculated value will be affected by the cycle slip value. Assuming that the phase observations before epoch k have not experienced cycle slips or have been repaired, the TECR of all epochs before epoch k is calculated. Since the change in ionospheric TECR is gradual over a short period, the values calculated in previous epochs are used. The information predicts the TECR value of the current epoch k. Assuming the TECR values of epochs (k-1) and (k-1) have been calculated, the predicted TEC rate of change TECR(k) of epoch k is calculated using the following formula: In practice, It is also obtained by progressively smoothing the phase observations from previous epochs to reduce measurement noise and thus obtain higher accuracy. and ; When the difference between the two exceeds a certain threshold, it is considered that a cycle jump has occurred in that epoch. According to calculation Worth the weekly jump to epoch k: 。 5. The method according to claim 4, characterized in that, In step 3, The cycle slip value obtained from the MW combination function is 'a', and the cycle slip value obtained from TECR is 'a'. If the value is b, then the cycle slip of the carrier phase is calculated according to the following formula: in, Let b be an integer and b be a real number. The real value obtained by applying the above formula is... Rounding up yields integer transition values at frequencies L1 and L2, which are then used to repair the carrier phase.
6. A ground-based GNSS differential data correction device, characterized in that, The apparatus for performing the method according to any one of claims 1 to 5, the apparatus comprising: The acquisition module is used to acquire pseudorange and carrier phase. The calculation module is used to calculate the integer phase jump value of the carrier using the MW combination function and the ionospheric delay change rate. The correction module is used to correct the carrier phase value using the calculated integer jump value of the carrier phase.
7. A ground-based GNSS differential data correction device, characterized in that, It includes a processor and a memory, wherein the processor executes a program in the memory to implement the ground GNSS differential data correction method according to any one of claims 1 to 5.
8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed on a computer's processing component, cause the processing component to perform the ground GNSS differential data correction method according to any one of claims 1 to 5.