Double-difference carrier cycle slip repair and multipath suppression method, system and storable medium

Abstract

The present invention discloses a double-difference carrier cycle slip repair and multipath suppression method, system and storable medium, and relates to the field of satellite navigation. The present invention comprises: a double-difference observation input unit, a carrier phase cycle slip repair unit, a carrier-to-noise ratio-assisted multipath suppression unit, and an RTK positioning unit. The observation input unit is responsible for obtaining observation inputs of pseudorange, carrier phase and carrier-to-noise ratio from a terminal device; the carrier phase cycle slip repair unit is responsible for repairing the cycle slip problem existing in the carrier phase; the carrier-to-noise ratio-assisted multipath suppression unit is responsible for suppressing the multipath error in the pseudorange; and finally the RTK positioning unit is responsible for positioning and solving. The present invention uses the joint detection of double-difference carrier phase and composite observation to reduce the probability of false detection of cycle slip repair.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation, and in particular to a double-difference carrier cycle slip repair and multipath suppression method, system and storable medium. Background Art

[0002] In recent years, the manufacturing technology of electronic equipment has been continuously improved, and GNSS equipment has also developed towards miniaturization and low cost. More GNSS boards and chips are also emerging. Compared with surveying-level receivers, low-cost GNSS receiver terminals have a wider range of application scenarios, such as smartphone platforms, small drones and robot platforms, etc. In such scenarios, lightweight and low cost are almost necessary conditions. However, in comparison, the positioning accuracy of low-cost receivers is still far inferior to that of surveying-level receivers. The fundamental reason lies in the low-quality observation caused by hardware equipment. In an open environment without multipath, the positioning accuracy of low-cost receivers is generally 5 to 10 meters, while in a severe multipath environment, its positioning error may reach tens of meters. Carrier phase is one of the most important observations in satellite positioning. It has excellent characteristics such as low noise and small multipath error. After ambiguity resolution, it is often used in high-precision positioning algorithms. However, since the performance of the tracking loop of low-cost receivers is far inferior to that of surveying-level receivers, the probability of signal loss is increased, resulting in frequent carrier phase cycle jumps. The existence of carrier phase cycle slips affects the continuity of its observation, making it more difficult to apply algorithms that use carrier phase, such as carrier phase smoothing pseudorange and carrier phase ambiguity resolution technology. Using RTK or PPP technology, low-cost receivers can also achieve decimeter-level positioning accuracy, but the premise is that a long convergence process is required, and its application scenarios are greatly limited. Therefore, high-precision positioning of low-cost receivers is still a problem to be solved, among which carrier phase cycle slips and pseudorange multipath are the most critical technical difficulties.

[0003] Currently, cycle slip repair algorithms for low-cost receivers are still not perfect. Most traditional cycle slip detection and repair algorithms designed based on surveying-grade receivers have relatively high requirements for the quality of the receiver's pseudorange or Doppler observations, so that these observations can be used to detect jumps in the carrier phase. These algorithms are only applicable to surveying-grade receivers where the observation quality is guaranteed and cycle slips do not occur so frequently. For low-cost receivers, the noise and errors of pseudorange and Doppler observations are large, especially in some complex environments, where the carrier-to-noise ratio of the received signal is lower, further reducing the quality of the observation. Therefore, it is necessary to propose a practical strategy for cycle slip repair for low-cost receivers, and this strategy needs to have a certain degree of robustness in complex environments.

[0004] Many algorithms have been proposed for pseudo-range multipath suppression, but few are suitable for low-cost devices. Most of them require multi-frequency observation or 3D model data of the surrounding environment. A carrier phase multipath suppression method based on carrier-to-noise ratio assistance has also been proposed and is suitable for low-cost devices, but no corresponding method has been used for pseudo-range observation. Therefore, it is urgent to design a pseudo-range multipath suppression method, system and storable medium based on carrier-to-noise ratio assistance. Summary of the invention

[0005] In view of this, the present invention provides a double-difference carrier cycle slip repair and multipath suppression method, system and storable medium, which selects the most suitable cycle slip repair strategy according to the characteristics of low-cost equipment observations, and identifies invalid observations therein to reduce the probability of false detection and false repair; in the pseudo-range multipath suppression method, the carrier-to-noise ratio is innovatively used for auxiliary estimation, and the parameters of the multipath model are estimated in combination with the repaired carrier phase to achieve the purpose of estimating the pseudo-range multipath.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A double-difference carrier phase cycle slip repair and multipath suppression method comprises the following steps:

[0008] Receive pseudorange, carrier phase observation data and carrier-to-noise ratio observation data;

[0009] Generate double difference carrier phase according to carrier phase observation data and perform cycle slip repair;

[0010] Pseudorange multipath suppression is performed based on the pseudorange and carrier-to-noise ratio observation data of the mobile station and base station and the repaired double-difference carrier phase;

[0011] The repaired double-difference carrier phase and pseudo-range multipath results are used for positioning and the positioning results are output.

[0012] The cycle slip repair is as follows: after obtaining the carrier phase observations of the base station and the mobile station and performing differential processing, the carrier phase of the reference satellite is selected for differential processing to obtain double-difference carrier phase observations; composite observation data is obtained by adding the double-difference carrier phase to the inter-satellite differential distance of the base station; polynomial fitting is performed on the double-difference carrier phase and the composite observation data respectively to obtain the cycle slip; and cycle slip repair is performed on the observation data with cycle slips.

[0013] The suppression of pseudorange multipath is as follows: double-difference processing is performed on the base station pseudorange and the mobile station pseudorange to obtain double-difference pseudorange observation, and the carrier phase observation after cycle slip repair and the double-difference pseudorange observation are combined into CMP observation; the original carrier-to-noise ratio observation data input is analyzed, and the frequency component of the original carrier-to-noise ratio observation data is extracted by FFT transformation; the double-difference carrier phase ambiguity and the required parameters in the pseudorange multipath model are further calculated; finally, the single-difference pseudorange multipath is obtained, and then the pseudorange after multipath suppression is obtained.

[0014] Optionally, the pseudorange includes the pseudorange of the base station and the pseudorange of the mobile station; the carrier phase observation data includes the carrier phase observation data of the base station and the carrier phase observation data of the mobile station; the carrier-to-noise ratio observation data includes the carrier-to-noise ratio observation data of the base station and the carrier-to-noise ratio observation data of the mobile station.

[0015] Optionally, the received data also includes received ephemeris data and base station location coordinate data.

[0016] Optionally, the cycle slip repair uses a high-order polynomial fitting method and a cycle slip joint detection method. Specifically, the cycle slip repair is based on the existing high-order polynomial fitting method technology, and a cycle slip joint detection method is designed to jointly detect the high-order polynomial fitting results of the double-difference carrier phase observation and the composite observation obtained by the double-difference carrier phase plus the inter-satellite differential distance of the base station.

[0017] Optionally, the suppression of pseudo-range multipath is specifically: using the property that the carrier-to-noise ratio and multipath have the same frequency characteristics, estimating the parameters in the pseudo-range multipath model to achieve pseudo-range multipath suppression, and outputting pseudo-range observation data after multipath suppression. Here, the pseudo-range multipath model refers to a model that uses the reflection coefficient of the multipath reflection surface and the non-direct path delay to quantify the size of the pseudo-range multipath.

[0018] A double-difference carrier phase cycle slip repair and multipath suppression system comprises an observation input unit, a carrier phase cycle slip repair unit, a carrier-to-noise ratio-assisted multipath suppression unit and an RTK positioning unit; the observation input unit is used to receive pseudorange, carrier phase observation data and carrier-to-noise ratio observation data; the carrier phase cycle slip repair unit is used to generate a double-difference carrier phase according to the carrier phase observation data and perform cycle slip repair; the carrier-to-noise ratio-assisted multipath suppression unit is used to suppress pseudorange multipath according to the pseudorange of a mobile station and a base station, the carrier-to-noise ratio observation data and the repaired double-difference carrier phase; the RTK positioning unit is used to perform positioning solution on the repaired double-difference carrier phase and the pseudorange multipath results and output the positioning result.

[0019] Optionally, the carrier phase cycle slip repair unit includes a double difference carrier phase module, a composite observation module, a fitting and joint detection module, and a cycle slip repair module, and the output of the double difference carrier phase module is respectively input into the composite observation module and the fitting and joint detection module, wherein the output of the composite observation module is input into the fitting and joint detection module, and the detection result of the fitting and joint detection module is input into the cycle slip repair module.

[0020] Optionally, the carrier-to-noise ratio-assisted multipath suppression unit includes a double-difference pseudorange unit, a CMP observation unit, a multipath suppression unit based on a multipath model, and a spectrum analysis unit; the double-difference pseudorange unit, the CMP observation unit, and the multipath suppression unit based on a multipath model are connected in sequence, and the output of the spectrum analysis unit is input into the multipath suppression unit based on a multipath model.

[0021] A computer storage medium stores a computer program, which is a step of implementing a double-difference carrier phase cycle slip repair and multipath suppression method when executed by a processor.

[0022] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a double-difference carrier cycle slip repair and multipath suppression method, system and storable medium, which utilizes the joint detection of double-difference carrier phase and composite observation to reduce the false detection probability of cycle slip repair. In addition, the consistency of the carrier-to-noise ratio and the frequency characteristics of the multipath is utilized, and the estimated values ​​of the parameters in the pseudo-range multipath model are obtained by performing frequency analysis on the carrier-to-noise ratio, thereby achieving the purpose of multipath estimation, and greatly improving the positioning accuracy of low-cost equipment in complex multipath environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0024] Figure 1 It is a system block diagram of carrier phase cycle slip repair and pseudorange multipath suppression in the present invention;

[0025] Figure 2 It is a block diagram of the working principle of the observation input unit in the present invention;

[0026] Figure 3 It is a block diagram of the working principle of the carrier phase cycle slip repair unit in the present invention;

[0027] Figure 4It is a block diagram of the working principle of the carrier-to-noise ratio-assisted multipath suppression unit in the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The embodiment of the present invention discloses a double-difference carrier cycle slip repair and multipath suppression method, system and storable medium, wherein the method comprises the following steps:

[0030] S1: At each epoch, the observation input unit 111 is responsible for receiving pseudorange, carrier phase, carrier-to-noise ratio observation data of the mobile station and the base station, as well as auxiliary data such as ephemeris and base station position coordinates.

[0031] S2: The carrier phase cycle slip repair unit 112 is responsible for receiving the carrier phase observation from the observation input unit 111, generating a double difference carrier phase and performing cycle slip repair, mainly by using a high-order polynomial fitting method and a cycle slip joint detection method to reduce the probability of false repair, and finally outputting the repaired carrier phase observation.

[0032] S3: The carrier-to-noise ratio-assisted multipath suppression unit 113 is responsible for receiving the pseudorange and carrier-to-noise ratio observations from the observation input unit 111 and the repaired carrier phase observations from the carrier phase cycle slip repair unit 112, and suppressing pseudorange multipath. It mainly uses the property that the carrier-to-noise ratio and multipath have the same frequency characteristics, estimates the parameters in the pseudorange multipath model, thereby achieving pseudorange multipath suppression, and finally outputs the pseudorange observations after multipath suppression.

[0033] S4: Finally, the RTK positioning unit 114 receives the repaired carrier phase observation from the carrier phase cycle slip repair unit 112 and the multipath suppressed pseudorange observation from the carrier-to-noise ratio-assisted multipath suppression unit 113, performs positioning solution using the RTK positioning technology, and outputs the positioning result.

[0034] In this embodiment, Figure 1 The overall block diagram of the present invention is given, which mainly includes four parts: observation input unit 111, carrier phase cycle slip repair unit 112, carrier-to-noise ratio-assisted multipath suppression unit 113 and RTK positioning unit 114. The data input comes from the first unit, each unit performs certain processing on the data, and the last unit contains the data output.

[0035] Figure 2The specific implementation details and output of the observation input unit 111 are given. Pseudorange, carrier phase and carrier-to-noise ratio observations are obtained from the base station and the rover, respectively.

[0036] Figure 3 The specific implementation details and output of the carrier phase cycle slip repair unit 112 are given. The double-difference carrier phase module performs differential processing on the carrier phase observations of the base station and the mobile station from the observation input unit 111, and then selects the carrier phase of the reference satellite for differential processing to obtain the double-difference carrier phase observation. The "composite observation" module is obtained by adding the inter-satellite differential distance of the base station to the double-difference carrier phase. The method is as follows

[0037]

[0038] in is the double-difference carrier phase observation, is the inter-satellite difference of the geometric distance between the satellite and the receiver antenna, t b The time when the base station receives the signal.

[0039] The fitting and joint detection modules perform polynomial fitting on the double-difference carrier phase and composite observations, namely:

[0040]

[0041] in is the double difference carrier phase obtained by fitting, a, b, c are fitting coefficients. Then the jump variable can be obtained by the following formula

[0042]

[0043] A cycle slip is considered to have occurred when the jump variables obtained from both observations are not 0.

[0044] The cycle slip repair module performs cycle slip repair on observations with cycle slips based on the detection results of the previous module.

[0045] Figure 4 The specific implementation details and output of the carrier-to-noise ratio-assisted multipath suppression unit 113 are given. The "double-difference pseudorange" module performs double-difference processing on the base station pseudorange and the rover pseudorange from the observation input unit 111 to obtain double-difference pseudorange observations.

[0046] The CMP observation module combines the repaired carrier phase observation from the carrier phase cycle slip repair unit 112 and the double-difference pseudo-range observation from the double-difference pseudo-range module into a CMP observation, that is,

[0047]

[0048] in is the double-difference pseudorange, is the double difference carrier phase.

[0049] The spectrum analysis module analyzes the original carrier-to-noise ratio observation input and extracts the frequency component of the carrier-to-noise ratio using FFT transformation to obtain

[0050]

[0051] Where C / N0 is the carrier-to-noise ratio, is the DC component, is the frequency component The amplitude of is the corresponding phase. Further calculations are performed to obtain the parameters in the pseudo-range multipath model:

[0052]

[0053]

[0054] And make

[0055]

[0056] The above k i (t) can be calculated from the carrier-to-noise ratio of the floating satellite, and k′ can be calculated from the carrier-to-noise ratio of the reference satellite. i (t).

[0057] make

[0058]

[0059]

[0060]

[0061] Get a linear equation

[0062]

[0063] Where λ is the wavelength, is the double-difference carrier phase ambiguity, x and x′ are the parameters required in the pseudo-range multipath model, that is,

[0064] x=[δ1,δ2,...,δ n ]

[0065] x′=[δ′1, δ′2,..., δ′ n ]

[0066] The above linear equation can be solved to As well as x and x′. Finally, the single-difference pseudo-range multipath at the mobile station can be calculated as

[0067]

[0068] If we assume that the pseudo-range multipath at the base station is very small and approximately 0, we can get the pseudo-range after multipath suppression as

[0069]

[0070] in is the original pseudorange observation. Finally, the pseudorange observation after multipath suppression is output

[0071] In the RTK positioning unit 114, the RTK positioning algorithm can be implemented by using the pseudo-range observation after multipath suppression from the carrier-to-noise ratio-assisted multipath suppression unit 113. Compared with the positioning algorithm without multipath suppression, its positioning accuracy can be significantly improved.

[0072] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A double-difference carrier phase cycle slip repair and multipath suppression method, characterized in that: The following steps are involved: Receive pseudorange, carrier phase observation data and carrier-to-noise ratio observation data; Generate double difference carrier phase according to carrier phase observation data and perform cycle slip repair; According to the pseudo-range and carrier-to-noise ratio observation data of the mobile station and the base station and the repaired double-difference carrier phase, pseudo-range multipath suppression is performed; the details are as follows: The double-difference pseudo-range module performs double-difference processing on the base station pseudo-range and the rover pseudo-range from the observation input unit to obtain double-difference pseudo-range observations; The CMP observation module combines the repaired carrier phase observation from the carrier phase cycle slip repair unit and the double-difference pseudo-range observation from the double-difference pseudo-range module into a CMP observation, that is, in is the double-difference pseudorange, is the double difference carrier phase; The spectrum analysis module analyzes the original carrier-to-noise ratio observation input and extracts the frequency component of the carrier-to-noise ratio using FFT transformation to obtain Where C / N0 is the carrier-to-noise ratio, is the DC component, is the frequency component The amplitude of is the corresponding phase; further calculations are performed to obtain the parameters in the pseudorange multipath model: And make The above k i (t) can be calculated from the carrier-to-noise ratio of the meteor, and k' can be calculated from the carrier-to-noise ratio of the reference satellite. i (t); make Get a linear equation Where λ is the wavelength, is the double-difference carrier phase ambiguity, x and x' are the parameters required in the pseudo-range multipath model, that is, x=[δ1,δ2,...,δ n ]; x'=[δ'1,δ'2,...,δ' n ]; The above linear equation can be solved to As well as x and x'; finally, the single-difference pseudo-range multipath at the mobile station can be calculated as If we assume that the pseudo-range multipath at the base station is very small and approximately 0, we can get the pseudo-range after multipath suppression as in is the original pseudorange observation, and finally outputs the pseudorange observation after multipath suppression The repaired double-difference carrier phase and pseudo-range multipath results are used for positioning and the positioning results are output.

2. A double-difference carrier phase cycle slip repair and multipath suppression method according to claim 1, characterized in that: The pseudorange includes the pseudorange of the base station and the pseudorange of the mobile station; the carrier phase observation data includes the carrier phase observation data of the base station and the carrier phase observation data of the mobile station; the carrier-to-noise ratio observation data includes the carrier-to-noise ratio observation data of the base station and the carrier-to-noise ratio observation data of the mobile station.

3. A double-difference carrier phase cycle slip repair and multipath suppression method according to claim 1, characterized in that: The received data also includes received ephemeris data and base station location coordinate data.

4. A double-difference carrier phase cycle slip repair and multipath suppression method according to claim 1, characterized in that: The cycle slip repair uses high-order polynomial fitting method and cycle slip joint detection method.

5. A double-difference carrier phase cycle slip repair and multipath suppression method according to claim 1, characterized in that: The suppression of pseudo-range multipath is specifically as follows: using the property that the carrier-to-noise ratio and multipath have the same frequency characteristics, the parameters in the pseudo-range multipath model are estimated, and the pseudo-range observation data after multipath suppression is output.

6. A double-difference carrier phase cycle slip repair and multipath suppression system, characterized in that: It includes observation input unit, carrier phase cycle slip repair unit, carrier-to-noise ratio-assisted multipath suppression unit and RTK positioning unit; The observation input unit is used to receive pseudorange, carrier phase observation data and carrier-to-noise ratio observation data; the carrier phase cycle slip repair unit is used to generate a double difference carrier phase according to the carrier phase observation data and perform cycle slip repair; the carrier-to-noise ratio-assisted multipath suppression unit is used to suppress pseudorange multipath according to the pseudorange of the mobile station and the base station, the carrier-to-noise ratio observation data and the repaired double difference carrier phase; the RTK positioning unit is used to perform positioning solution on the repaired double difference carrier phase and the pseudorange multipath result and output the positioning result; Specifically, the double-difference pseudorange module performs double-difference processing on the base station pseudorange and the rover pseudorange from the observation input unit to obtain double-difference pseudorange observations; The CMP observation module combines the repaired carrier phase observation from the carrier phase cycle slip repair unit and the double-difference pseudo-range observation from the double-difference pseudo-range module into a CMP observation, that is, in is the double-difference pseudorange, is the double difference carrier phase; The spectrum analysis module analyzes the original carrier-to-noise ratio observation input and extracts the frequency component of the carrier-to-noise ratio using FFT transformation to obtain Where C / N0 is the carrier-to-noise ratio, is the DC component, is the frequency component The amplitude of is the corresponding phase; further calculations are performed to obtain the parameters in the pseudorange multipath model: And make The above k i (t) can be calculated from the carrier-to-noise ratio of the meteor, and k' can be calculated from the carrier-to-noise ratio of the reference satellite. i (t); make Get a linear equation Where λ is the wavelength, is the double-difference carrier phase ambiguity, x and x' are the parameters required in the pseudo-range multipath model, that is, x=[δ1,δ2,...,δ n ]; x'=[δ'1,δ'2,...,δ' n ]; The above linear equation can be solved to As well as x and x'; finally, the single-difference pseudo-range multipath at the mobile station can be calculated as If we assume that the pseudo-range multipath at the base station is very small and approximately 0, we can get the pseudo-range after multipath suppression as in is the original pseudorange observation, and finally outputs the pseudorange observation after multipath suppression 7. A double-difference carrier phase cycle slip repair and multipath suppression system according to claim 6, characterized in that: The carrier phase cycle slip repair unit includes a double difference carrier phase module, a composite observation module, a fitting and joint detection module, and a cycle slip repair module; The outputs of the double-difference carrier phase module are respectively input into the composite observation module and the fitting and joint detection module, wherein the output of the composite observation module is input into the fitting and joint detection module, and the detection result of the fitting and joint detection module is input into the cycle slip repair module.

8. A double-difference carrier phase cycle slip repair and multipath suppression system according to claim 6, characterized in that: The carrier-to-noise ratio-assisted multipath suppression unit includes a double-difference pseudo-range unit, a CMP observation unit, a multipath suppression unit based on a multipath model, and a spectrum analysis unit; The double-difference pseudo-range unit, the CMP observation unit and the multipath suppression unit based on the multipath model are connected in sequence, and the output of the spectrum analysis unit is input to the multipath suppression unit based on the multipath model.

9. A computer storage medium, characterized in that The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of a double-difference carrier phase cycle slip repair and multipath suppression method as described in any one of claims 1 to 5.

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