CN114397684A

CN114397684A - Ambiguity fixing method and related equipment

Info

Publication number: CN114397684A
Application number: CN202210073055.XA
Authority: CN
Inventors: 辛浩浩
Original assignee: Tencent Technology Shenzhen Co Ltd
Current assignee: Tencent Technology Shenzhen Co Ltd
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2022-04-26

Abstract

The application discloses a method for fixing ambiguity and related equipment, wherein the method comprises the following steps: determining an observed value of a dependent variable in a first observation equation according to observation data of two reference stations corresponding to a base line, wherein the first observation equation indicates a functional relation between the dependent variable and an ionosphere-free combined model ambiguity of the base line and a base line coordinate error of the base line; performing Kalman filtering according to a first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined mold ambiguity of the base line; determining a target fixed value of the ionosphere-free combined ambiguity of the base line according to the first fixed value of the ionosphere-free combined ambiguity of the base line and the fixed value of the widelane ambiguity of the base line; the scheme can improve the accuracy of ambiguity fixing; the scheme can be applied to the map field and the automatic driving field.

Description

Ambiguity fixing method and related equipment

Technical Field

The present application relates to the field of positioning technologies, and in particular, to a method for fixing ambiguity and a related device.

Background

With the development of positioning technology, the demand range of high-precision positioning by using a network carrier phase differential technology is more and more extensive, and for example, the fields of measurement and mapping, unmanned driving, auxiliary driving, automatic operation robots, equipment positioning, map updating and the like all need higher-precision position information.

An important link for positioning based on the network carrier phase difference technology is the ambiguity of a fixed base line, and the accuracy of the ambiguity fixation of the base line directly influences the accuracy of positioning. In the related art, there is a problem that the accuracy of fixing the ambiguity of the baseline is not high.

Disclosure of Invention

In view of the foregoing problems, embodiments of the present application provide a method and related apparatus for fixing ambiguity, so as to improve the foregoing problems.

According to an aspect of an embodiment of the present application, there is provided a method for fixing an ambiguity, including: determining an observed value of a dependent variable in a first observation equation according to observation data of two reference stations corresponding to a base line, wherein the first observation equation indicates a functional relation between the dependent variable and an ionosphere-free combined model ambiguity of the base line and a base line coordinate error of the base line; performing Kalman filtering according to the first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined mold ambiguity of the baseline; and determining a target fixed value of the ionosphere-free combined ambiguity of the base line according to the first fixed value of the ionosphere-free combined ambiguity of the base line and the fixed value of the widelane ambiguity of the base line.

According to an aspect of an embodiment of the present application, there is provided an ambiguity fixing apparatus including: the observation value determining module is used for determining the observation value of the dependent variable in a first observation equation according to the observation data of the two reference stations corresponding to the base line, wherein the first observation equation indicates the functional relation between the dependent variable and the non-ionosphere combined model ambiguity of the base line and the base line coordinate error of the base line; the first Kalman filtering module is used for carrying out Kalman filtering according to the first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined model ambiguity of the base line; and the target fixed value determining module is used for determining the target fixed value of the ionosphere-free combined ambiguity of the baseline according to the first fixed value of the ionosphere-free combined ambiguity of the baseline and the fixed value of the widelane ambiguity of the baseline.

In some embodiments, the target fixed value determination module comprises: the fixing module is used for fixing the L1 ambiguity and the L2 ambiguity according to the fixed value of the widelane ambiguity of the base line and the first fixed value of the ionosphere-free combined ambiguity of the base line to obtain the fixed value of the L1 ambiguity of the base line and the fixed value of the L2 ambiguity of the base line; a calculation module for calculating a first value of ionospheric-free combined-mold ambiguity for the baseline from the fixed value of L1 ambiguity for the baseline and the fixed value of L2 ambiguity for the baseline; the second Kalman filtering module is used for carrying out Kalman filtering according to a second observation equation and the first numerical value of the ionosphere-free combined mold ambiguity of the baseline, and determining a target fixed value of the ionosphere-free combined mold ambiguity of the baseline; wherein the state variables in the second observation equation include an ionospheric-free combined mode ambiguity for the baseline and a baseline coordinate error for the baseline.

In some embodiments, the observation data comprises carrier observations and pseudorange observations corresponding, over a plurality of epochs, to dual-frequency carriers comprising an L1 carrier and an L2 carrier; in this embodiment, the ambiguity fixing device further includes: a first value determining module, configured to calculate, according to a MW combination manner, a first value of widelane ambiguity of a baseline at each epoch in the epochs, according to carrier observations and pseudo-range observations of two reference stations corresponding to the baseline at the L1 carrier in the epochs and carrier observations and pseudo-range observations of two reference stations corresponding to the baseline at the L2 carrier in the epochs; a second value determining module, configured to calculate, according to a double-difference observation equation that ignores ionospheric delay, a second value of the widelane ambiguity of the baseline in each epoch among the epochs, according to carrier observations of the two reference stations corresponding to the baseline in the epochs corresponding to the L1 carrier in the epochs and carrier observations of the two reference stations corresponding to the baseline in the epochs corresponding to the L2 carrier in the epochs; and the fixed value determining module of the widelane ambiguity is used for determining the fixed value of the widelane ambiguity of the baseline according to the first value of the widelane ambiguity of the baseline in each epoch in the epochs and the second value of the widelane ambiguity of the baseline in each epoch in the epochs.

In some embodiments, the fixed value of widelane ambiguity determination module comprises: a widelane ambiguity mean value determining unit, configured to perform mean value calculation on a first value of the widelane ambiguity of the baseline under the epoch and a historical epoch before the epoch for each epoch in the multiple epochs, to obtain a widelane ambiguity mean value corresponding to the baseline at each epoch; a difference calculation unit, configured to calculate a difference between a target widelane ambiguity mean value corresponding to a target epoch and a second value of widelane ambiguity of the baseline under the target epoch if it is determined that a convergence condition is reached according to widelane ambiguity mean values corresponding to the baseline respectively at the multiple epochs; the target epoch is an epoch corresponding to the mean value of ambiguity of the finger width lane reaching the convergence condition; the target widelane ambiguity mean value is the widelane ambiguity mean value of the baseline when the convergence condition is reached; a fixed value determining unit, configured to determine, if the difference is smaller than a difference threshold and a first integer value and a second integer value are equal to each other, the first integer value as the fixed value of the widelane ambiguity of the baseline, where the first integer value is an integer value obtained by rounding a target widelane ambiguity mean value of the baseline, and the second integer value is an integer value obtained by rounding a second value of the widelane ambiguity corresponding to the baseline under the target epoch.

In some embodiments, the second value determination module comprises: a carrier-phase double-difference observation value determining unit, configured to determine, according to carrier observation values of two reference stations corresponding to a baseline in the plurality of epochs corresponding to the L1 carrier and carrier observation values of two reference stations corresponding to a baseline in the plurality of epochs corresponding to the L2 carrier, a carrier-phase double-difference observation value of each epoch in the plurality of epochs at the L1 carrier and a carrier-phase double-difference observation value at the L2 carrier; and a second value determining unit, configured to calculate, according to a double-difference observation equation in an ionosphere-free combination manner, a carrier-phase double-difference observation value of the baseline in the L1 carrier corresponding to each epoch and a carrier-phase double-difference observation value of the baseline in the L2 carrier, a second value of the widelane ambiguity of the baseline in each epoch in the multiple epochs, respectively.

In some embodiments, the first value determination module comprises: an obtaining unit, configured to obtain a frequency of the L1 carrier, a frequency of the L2 carrier, and a wide-lane combined wavelength; a first value determining unit, configured to calculate a first value of the widelane ambiguity of the baseline in each epoch in the epochs according to a MW combination manner, according to the frequency of the L1 carrier, the frequency of the L2 carrier, the widelane combination wavelength, the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline in the epochs corresponding to the L1 carrier, and the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline in the epochs corresponding to the L2 carrier.

In some embodiments, a first kalman filtering module, comprising: the first initial value determining unit is used for determining an initial value of the ionosphere-free combined double-difference ambiguity of a baseline under an initial epoch according to the observation data; a second initial value acquisition unit configured to acquire an initial value of a baseline coordinate error of the baseline; and the first Kalman filtering unit is used for carrying out Kalman filtering according to the first observation equation based on the observed value of the dependent variable in the first observation equation, the initial value of the ionospheric-free combined double-difference ambiguity of the baseline under the initial epoch and the initial value of the baseline coordinate error of the baseline, and determining a first fixed value of the ionospheric-free combined ambiguity of the baseline.

In some embodiments, the observation data includes pseudo-range observations and carrier observations of two reference stations under a carrier corresponding to a baseline; a first initial value determination unit comprising: the third double-difference unit is used for performing inter-station double-difference according to pseudo-range observed values of the two reference stations corresponding to the baseline, which correspond to the initial epoch under the carrier wave, so as to obtain pseudo-range double-difference observed values of the baseline, which correspond to the initial epoch under the initial epoch; the fourth double-difference unit is used for performing inter-station double-difference according to the carrier observed values of the two reference stations corresponding to the baseline, which correspond to the initial epoch under the carrier, so as to obtain the carrier double-difference observed values of the baseline, which correspond to the initial epoch under the initial epoch; and the initial value determining unit is used for calculating the initial value of the ionosphere-free combined double-difference ambiguity of each baseline according to the pseudo-range double-difference observed value corresponding to the baseline, the carrier double-difference observed value corresponding to the baseline and the frequency corresponding to the carrier.

In some embodiments, an observation determination module, comprising: the first calculation unit is used for calculating the carrier double-difference observation value of the base line under the combination without the ionized layer according to the observation data of the two base stations corresponding to the base line; the second calculation unit is used for calculating the station-satellite double-difference distance corresponding to the base line according to the position information and the position information of the two reference stations corresponding to the base line; and the observation value determining unit is used for determining the observation value of the dependent variable in the first observation equation according to the carrier double-difference observation value of the base line under the combination without the ionosphere and the station-satellite distance double difference corresponding to the base line.

In some embodiments, the observation data includes carrier observations at L1 carrier and carrier observations at L2 carrier for the two reference stations corresponding to the baseline; in this embodiment, the first calculation unit includes: the first double-difference unit is used for carrying out inter-station inter-satellite double differences according to carrier wave observed values of two reference stations corresponding to the base line under the L1 carrier waves to obtain carrier wave double-difference observed values of the base line under the L1 carrier waves; the second double-difference unit is used for performing inter-station inter-satellite double differences according to carrier observed values of two reference stations corresponding to the baseline under the L2 carrier to obtain carrier double-difference observed values of the baseline under the L2 carrier; and a carrier double-difference observation value calculation unit, configured to calculate a carrier double-difference observation value of the baseline under the ionosphere-free combination according to the frequency of the L1 carrier, the frequency of the L2 carrier, the carrier double-difference observation value of the baseline under the L1 carrier, and the carrier double-difference observation value of the baseline under the L2 carrier.

In some embodiments, the means for fixing the ambiguity further comprises: and the positioning service providing module is used for providing positioning services according to the target fixed values of the non-ionized layer combined model ambiguity of the baselines.

In some embodiments, a location services provision module, comprising: a receiving unit for receiving the approximate location information transmitted by the terminal; a target reference station determining unit for determining a plurality of target reference stations for the terminal based on the approximate location information; an observation data determination unit configured to determine observation data of a virtual observation station from the observation data of the plurality of target reference stations and the target fixed value of the ionospheric-free combination ambiguity for each target baseline; the target base line refers to a base line formed between any two target base stations in the plurality of target base stations; and the sending unit is used for sending the observation data of the virtual observation station to the terminal, and the observation data of the virtual observation station is used for the terminal to determine the position information of the terminal.

According to an aspect of an embodiment of the present application, there is provided an electronic device including: a processor; a memory having computer readable instructions stored thereon which, when executed by the processor, implement a method of fixing ambiguities as described above.

According to an aspect of embodiments of the present application, there is provided a computer-readable storage medium having stored thereon computer-readable instructions which, when executed by a processor, implement a fixing method of ambiguities as described above.

According to an aspect of embodiments of the present application, there is provided a computer program product comprising computer instructions which, when executed by a processor, implement the method of fixing ambiguity as described above.

In this application, the state variable in the first observation equation includes the ionospheric-free combined model ambiguity of the baseline and the baseline coordinate error of the baseline, and thus, in the process of performing kalman filtering according to the observation data, it can be avoided to superimpose the influence of the reference station coordinate offset on the observed value onto the ionospheric-free combined ambiguity, in other words, the ionospheric-free combined model ambiguity of the baseline determined by performing the kalman filtering does not include the error due to the reference station coordinate offset, and thus the accuracy of the obtained first fixed value of the ionospheric-free combined model ambiguity of the baseline can be improved.

Furthermore, the target fixed value of the baseline ionospheric-free combined ambiguity is determined on the basis of the higher-accuracy fixed value of the baseline widelane ambiguity and the first fixed value of the baseline ionospheric-free combined ambiguity, so that the accuracy of the determined target fixed value of the baseline ionospheric-free combined ambiguity can be further improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application. It is obvious that the drawings in the following description are only some embodiments of the application, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is a schematic diagram illustrating a positioning system according to an embodiment of the present application.

Fig. 2 is a flow chart illustrating a fixing method of ambiguity according to an embodiment of the present application.

Fig. 3A is a flowchart illustrating step 230 of fig. 2 according to an embodiment of the present application.

Fig. 3B is a flow chart illustrating a fixing method of ambiguity according to another embodiment of the present application.

Fig. 4 is a flowchart illustrating step 210 of fig. 2 according to an embodiment of the present application.

Fig. 5 is a flowchart illustrating step 230 of fig. 2 according to an embodiment of the present application.

FIG. 6 is a flowchart illustrating steps prior to step 230 according to one embodiment of the present application.

FIG. 7 is a flowchart illustrating step 630 according to an embodiment of the present application.

Fig. 8 is a flow chart illustrating providing location services according to an embodiment of the present application.

FIG. 9 is a block diagram illustrating an ionosphere-free combined mold paste fixture, according to one embodiment of the present application.

FIG. 10 illustrates a schematic structural diagram of a computer system suitable for use in implementing the electronic device of an embodiment of the present application.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the subject matter of the present application can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the application.

The block diagrams shown in the figures are functional entities only and do not necessarily correspond to physically separate entities. I.e. these functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor means and/or microcontroller means.

The flow charts shown in the drawings are merely illustrative and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.

It should be noted that: reference herein to "a plurality" means two or more. "and/or" describe the association relationship of the associated objects, meaning that there may be three relationships, e.g., A and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

Before making the detailed description, terms referred to in the present application are explained as follows:

ambiguity (ambiguities of recent cycles): the integer ambiguity is also called integer ambiguity and integer unknown, and is the integer unknown corresponding to the first observed value of the phase difference between the carrier phase and the reference phase when the carrier phase is measured in the global positioning system technology. Since the ambiguity is the number of whole cycles corresponding to the transmission of a carrier in space, the ambiguity is theoretically a positive integer.

The non-ionospheric combination ambiguity refers to an ambiguity calculated in a non-ionospheric combination manner. The ionospheric-free combination is a combination method for eliminating the ionospheric first order, which is to eliminate the ionospheric first order by utilizing the property that the ionospheric first order is inversely proportional to the square of the frequency of the carrier wave. The mode of no ionosphere combination eliminates the influence of ionosphere first-order terms, and has wide application in practice, especially in the scene of long baseline (i.e. the distance between two reference stations is long). However, the ambiguity calculated by the combination method loses the integer characteristic, and still includes some errors, so that the ambiguity of the non-ionosphere combination mold needs to be fixed. RTK technology (Real-time kinematic, Real-time dynamic carrier-phase differential technology): the method is a difference method for processing the carrier phase observed quantities of two stations in real time, and comprises the following steps: and the carrier phase acquired by the reference station is sent to a user receiver (such as a mobile terminal and the like), and the user receiver calculates the difference of the observed values of the carrier phases of the local machine and the reference station and calculates the coordinates. Because most errors of the user receiver and the reference station have time and space correlation, most errors can be offset or reduced, and the carrier phase difference can enable the positioning accuracy to reach centimeter level under the condition that the distance between the user receiver and the reference station is short, so that the method is widely applied to the field of dynamic high-precision position. That is, two receivers (a reference station, a rover station (i.e., a user receiver)) are observing the satellite, and the reference station transmits the received carrier phase signal (or carrier phase difference correction signal) through its transmitting station; then, the rover receives the signal of the reference station at the same time of receiving the signal; on the basis of the two signals, the rover can realize differential calculation so as to accurately determine the spatial relative position relationship of the reference station and the rover.

Network rtk (network rtk): a small number of multiple base stations (at this time, the base stations can be called as reference stations) are uniformly distributed in an area, networking among the base stations covers the area, various errors in the area are calculated, RTK service is provided for users in the area, and the RTK service can complete precise relative positioning on dynamic users in real time. In general, network RTK can be divided into 3 processes: acquiring data of a reference station; the data processing center processes data to obtain error correction information; and broadcasting the correction information. Network RTK mainly has the following modes: a single reference station network mode, a Virtual Reference Station (VRS) technique, a region correction parameter method, a main and auxiliary station technique, and a comprehensive error interpolation method.

Double differences between the stations: firstly, differentiating observed values of the same receiver (the receiver can be a reference station, a mobile terminal and the like) facing different satellites to obtain a single-difference observed value between the satellites; and then, differentiating the single-difference observed values between the satellites of different receivers.

In the related technology, the network RTK technology is more and more widely applied, and the basic principle is that the atmospheric delay error between reference stations is separated through the ambiguity of a fixed base line by utilizing the atmospheric error spatial correlation, then the atmospheric delay error is subjected to spatial modeling, the atmospheric delay error in the coverage area range of the reference station is fitted, the information such as the atmospheric delay correction number and the like is calculated according to the position of a user, and the user terminal is assisted to fix the double-difference ambiguity, so that the precise positioning is realized. From the above, it can be seen that the first link in the network RTK technology is the ambiguity of the fixed baseline, where a baseline is formed between two reference stations, and it can also be understood that the baseline is a connection line between two reference stations, and the ambiguity of the baseline can also be understood as the ambiguity between the reference stations.

Since the network RTK service is based on ambiguity through a fixed baseline, the accuracy of the baseline ambiguity directly affects the positioning accuracy of the network RTK service. The inventor of the present application finds, through research, that in the related art, the influence of a baseline coordinate error of a baseline (i.e., a coordinate deviation between two reference stations) on the ambiguity of the baseline is not considered in the process of fixing the ambiguity, and thus the ambiguity error of the baseline fixed in the related art is large. In view of this, the solution of the present application is proposed.

In practice, the influence of a first-order ionosphere can be eliminated by considering the ionosphere-free combination, so that the ionosphere-free combination model ambiguity is widely applied.

FIG. 1 is a schematic diagram illustrating a positioning system according to an embodiment of the present application. As shown in fig. 1, the positioning system includes a plurality of reference stations 110, a data processing center 120, a terminal 130, and a plurality of satellites 140. Wherein, the reference station 110 is in communication connection with the data processing center 120, and the terminal 130 is in communication connection with the data processing center 120; the reference station 110 and the terminal 130 are each provided with a GPS (Global Positioning System) receiver, and thus, can receive signals transmitted from the satellites 140.

The terminal 130 may be a vehicle-mounted device, an unmanned aerial vehicle, a smart phone, a tablet computer, a portable computer, a desktop computer, a wearable device, a virtual reality device, a smart home, and other devices provided with a GPS receiver, and the like, and is not particularly limited herein.

The reference station 110 and the terminal 130 may perform satellite observations in real time, obtain observation data, and transmit the observation data to the data processing center 120, and the data processing center 120 may fix ambiguities according to the method of the present application. Wherein the observed data may include data observed over a plurality of epochs.

The reference station 110 (or the terminal 130) performs satellite observation, that is, the reference station 110 (or the terminal 130) receives a signal transmitted by a satellite, and based on the received signal, carrier phase observation and pseudo range observation can be performed, so as to determine a pseudo range observation value and a carrier observation value, where the carrier observation value may be a carrier phase observation value determined based on the carrier phase observation or a station-to-satellite distance calculated based on the carrier phase observation value. In this application, the observation data may include carrier observations and pseudorange observations.

The data processing center 120 may be an independent physical server, a server cluster or a distributed system formed by a plurality of physical servers, or a cloud server providing basic cloud computing services such as a cloud service, a cloud database, cloud computing, a cloud function, cloud storage, a Network service, cloud communication, a middleware service, a domain name service, a security service, a CDN (Content Delivery Network), a big data and artificial intelligence platform, and the like.

The data processing center 120 may further provide location services to the terminal after performing ambiguity fixing according to the method of the present application. Wherein the provided positioning service may be a network RTK service. Specifically, the terminal may perform single-point positioning according to signals received from a plurality of satellites to obtain approximate location information of the terminal, and transmit the approximate location information to the data processing center 120; the data processing center 120 calculates differential information of the terminal using the observation data of the reference station, and then transmits the differential information to the terminal 130; the terminal 130 performs differential positioning according to the satellite signal received by the terminal 130 and the received differential information, and finally obtains high-precision position information of the terminal 130.

In some embodiments, a high precision positioning service may be provided for autonomous vehicles, or in assisted driving, map updating, survey mapping, robots, after ambiguity fixing according to the method of the present application by the data processing center 120.

Fig. 2 is a flowchart illustrating a fixing method of an ionosphere-free combination degree of paste according to an embodiment of the present application, which may be performed by an electronic device with processing capability, such as a server, and the like, and is not limited in detail herein. Referring to fig. 2, the method includes at least steps 210 to 230, which are described in detail as follows:

and step 210, determining the observed value of the dependent variable in a first observation equation according to the observation data of the two reference stations corresponding to the base line, wherein the first observation equation indicates the functional relation between the dependent variable and the ionosphere-free combined model ambiguity of the base line and the base line coordinate error of the base line.

A base line is formed between the two reference stations, and the two reference stations forming the base line are called as two reference stations corresponding to the base line. The reference station may be oriented for satellite observation to a plurality of satellites to obtain observation data from the plurality of satellites. In this application, the satellite from which the observation data in step 210 is derived is a satellite that can be observed by both the two reference stations corresponding to the baseline, and the satellite that can be observed by both the two reference stations can also be referred to as a co-view satellite of the two reference stations corresponding to the baseline.

The observation data may include pseudo-range observations and carrier observations, where the carrier observations may be carrier-phase observations or station-to-satellite distances between satellites and reference stations calculated from the carrier-phase observations. The two reference stations corresponding to the base line can carry out satellite observation in real time, so that pseudo-range observation values and carrier observation values of the satellite under a plurality of epochs are obtained.

The pseudo-range observation value is a measured distance between the satellite and the reference station, which is obtained by multiplying the propagation time of the ranging code signal transmitted by the satellite to the reference station by the speed of light. The measured distance obtained is called pseudorange, because of the errors of the satellite clock and the base station clock and the delay of the radio signal through the ionosphere and the troposphere, and the difference between the actually measured distance and the geometric distance from the satellite to the receiver.

The reference station locks the satellite carrier phase, can obtain the carrier signal after the time delay from the satellite to the reference station, if carry on the phase comparison with reference signal produced in the reference station with the carrier signal, can obtain carrier phase observed value and carrier distance observed value. The wavelength of the carrier is multiplied by the carrier phase observed value, so that a carrier distance observed value can be obtained. In a specific embodiment, the signal transmitted by the satellite may include carriers of various frequencies, such as L1 carrier, L2 carrier, and the like, and of course, carriers of other frequencies may also be included.

First, the first observation equation is explained. Assume that the two reference stations corresponding to the baseline are reference station i and reference station b. The first observation equation may be determined according to the following procedure:

the carrier observations of a reference station i to a satellite j under an epoch can be described by the following equation 1:

wherein the content of the first and second substances,

representing the carrier observations of the reference station i facing the satellite j,

representing the actual distance between the reference station i and the satellite j;

the delay in the troposphere is indicated,

indicating ionospheric delay; λ is the wavelength of the carrier;

represents the ambiguity of the reference station i facing the satellite j; dt_iRepresents the clock difference of the reference station i; dt^jRepresents the clock difference for satellite j; and c represents the speed of light.

Similarly, the carrier observation value of the reference station b facing the satellite j is;

the carrier observation value of the reference station i facing the satellite k is;

the carrier observed value of the reference station b facing the satellite k is as follows:

based on the above formulas 1 to 4, the inter-reference station difference and the inter-satellite difference (in this application, the inter-reference station difference and the inter-satellite difference are referred to as inter-station inter-satellite double difference) are performed, so that the following double-difference observation equation can be obtained:

in the above-mentioned formula 5, the above-mentioned formula,

represents a double difference sign;

representing the carrier double-difference observed values of the base station i and the base station b facing the satellite k and the satellite j;

representing the station-satellite double-difference distance of the base station i and the base station b facing the satellite k and the satellite j;

the ionospheric delay double differences of the base station i and the base station b facing the satellite k and the satellite j are represented;

representing the tropospheric delay double differences of base station i and base station b facing satellite k and satellite j;

representing the double-difference ambiguities of base station i and base station b facing satellite k and satellite j.

As can be seen from equation 5, the reference station clock difference and the satellite clock difference are eliminated during the inter-satellite double difference between the stations. Considering that the ionospheric delay is large and the fluctuation is severe when the baseline is long, model calculation cannot be used, and therefore, ionospheric-free combination is adopted to eliminate the influence of the ionosphere. Ignoring ionospheric delays, equation 5 above can be transformed to:

wherein, since the formula 6 is obtained by neglecting the ionospheric delay, the formula 6

And the carrier double-difference observation values of the base station i and the base station b facing the satellite k and the satellite j under the ionosphere-free combination are shown.

Taking the first order term of the linear equation 6 developed by taylor series, the following equation 7 can be obtained:

in the above-mentioned formula 7,

representing an approximation of the double-differenced distances of the reference station i and the reference station b towards the satellite k and the satellite j,

can be approximately equal to

Representing an approximation of the double difference of tropospheric delays for reference station i and reference station b towards satellite k and satellite j,

is approximately equal to

δr₁Denotes the coordinate difference, δ r, of the reference station i₂Represents the coordinate difference of the reference station b; delta delta T_ibDenotes k^kjIs the difference between the projection coefficients of satellite k and satellite j.

In a long baseline scenario (i.e. the distance between two base stations in the baseline is long), the distance between two base stations corresponding to the baseline is generally within 100km, the satellite height is generally about 20000km, and the included angle formed by the connection line between the same satellite and two base stations corresponding to the baseline is small, and at this time:

substituting the above equation 8 into equation 7 can obtain:

it can be seen that formula 9 above shows the functional relationship between the carrier observed values (carrier double-difference observed values) of the two reference stations corresponding to the baseline and the ionosphere-free combined ambiguity of the baseline, the coordinate error of the baseline, and the zenith troposphere delay residual error, and it can be seen that the carrier double-difference observed values corresponding to the baseline are affected by the ionosphere-free combined double-difference ambiguity of the baseline, the coordinate error of the baseline, and the zenith troposphere delay residual error.

It is to be understood that the functional relationship between the carrier observations constructed by the reference station i and reference station b planes from the satellite observations from satellite k and from satellite j and the ionosphere-free combined ambiguity, the baseline coordinate error, and the zenith troposphere delay residual is shown above, in particular embodiments, the satellites that are commonly viewed by reference station i and reference station b are three or more and are not limited to satellite k and from satellite j, and the equation similar to equation 9 can be constructed for the satellites that are commonly viewed by reference station i and reference station b based on the satellite observations of any two satellites according to the similar procedure above.

Based on equation 9 above, a first observation equation is constructed. Specifically, the formula is shown

The term is taken as a state variable, and a first observation equation is constructed as follows:

z is Hx; (formula 10)

δr₁-δr₂＝(δΔx_ib，δΔy_ib，δΔz_ib) (ii) a (formula 13)

δΔx_ibA base line coordinate error of a base line formed by the base station i and the base station b in the x-axis direction is represented; delta y_ibA base line coordinate error of a base line formed by the base station i and the base station b in the y-axis direction is represented; delta z_ibA base line coordinate error of a base line formed by the base station i and the base station b in the z-axis direction is represented;

indicating the double-difference ambiguity that the base line formed by the reference station i and the reference station b corresponds to the satellite k and the satellite 1; h is a state transition matrix, which can be determined from the coefficients of the terms to the right of the equal sign in equation 9 above.

As can be seen based on equations 10-12 above, the state variables in the first observation equation include the baseline coordinate error (i.e., δ Δ x in equation 11)_ib、δΔy_ib、δΔz_ib) No ionospheric combined blur (i.e., as in equation 11 above)

It can also be understood that the required fixed ambiguities are ionospheric-free combined double-difference ambiguities), zenith tropospheric delay residuals (i.e. δ Δ T in equation 11 above)_ib) (ii) a The dependent variable in the first observation equation comprises z (i.e., z

). The ionospheric-free combined ambiguity of the baseline shown in equation 11 includes ionospheric-free combined double-difference ambiguities of any two satellites of the satellites 1 to n facing the baseline, and in a specific embodiment, the number of satellites facing the ionospheric-free combined double-difference ambiguity of the baseline can be determined according to actual needs, for example, assuming that only two satellites face, the ionospheric-free combined double-difference ambiguity of the baseline in equation 11 can be ionospheric-free combined double-difference ambiguities of the baseline facing the satellite k and the satellite j.

It is worth mentioning that the above formula 11 only shows the expression of the state variable corresponding to the baseline formed by the first observation equation for the reference station i and the reference station b, and in other embodiments, the expression of the first observation equation may be determined according to a similar process for other baselines facing other satellites. In the solution of the present application, in step 220, kalman filtering is required, where the kalman filtering is an algorithm that performs optimal estimation on a state variable of a system by inputting observed quantities of a dependent variable to the system at multiple times by using a linear system state equation, and since the observed value of the dependent variable is affected by noise and interference of the system, an optimal estimation process can also be regarded as a filtering process. Since the kalman filter process estimates the value of the state variable from the observed value of the dependent variable, the observed value of the dependent variable needs to be determined first. The observed value of the dependent variable can be understood as the actual measured value of the dependent variable.

Therefore, in order to perform kalman filtering according to the first observation equation, it is necessary to determine the observed values of the dependent variable in the first observation equation under a plurality of epochs. The dependent variable in the first observation equation is z in the above equation 10, and the parameters on the right side in the above equation 11 are referred to as state variables in the first observation equation.

The observed values of the dependent variables in the first observation equation can be obtained by correspondingly calculating the obtained observed data of the two reference stations corresponding to the baseline according to the above formula 12, and the process of specifically determining the dependent variables in the first observation equation is described below.

In a specific embodiment, since it is necessary to estimate the estimated value of the state variable in multiple epochs to determine whether the state variable converges, the observed value of the dependent variable determined in step 210 is also the observed value of the dependent variable corresponding to each epoch in multiple epochs.

And step 220, performing Kalman filtering according to a first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined mold ambiguity of the baseline.

In the kalman filtering process, the value of each state variable is estimated, and the estimated value of the dependent variable calculated based on the estimated value of the state variable is brought close to the observed value of the dependent variable.

In the above formula 11, the delay of the reference station with respect to the troposphere of the zenith is a time variable, and considering that the reference station may have displacement with the ground, the coordinate error with respect to the reference station is also a time variable, both of the two time variables are modeled by using a random walk model, and the ambiguity is a fixed quantity and does not change with time. The state equation for the kalman filtering process is therefore written as:

x (t) ═ Ix (t-1); (formula 14)

Wherein I is an identity matrix.

In order to perform kalman filtering, a state noise input matrix needs to be further set, specifically, the state noise input matrix R may be:

wherein, P_r＝(0.0001Δt)²；P_ΔT＝(0.001Δt)²；P_rIs a covariance matrix of coordinates, P_ΔTIs a covariance matrix of the troposphere delay relative to the zenith, and delta represents the difference between different reference stations, wherein R is an identity matrix; i is_3×3Is a 3 x 3 identity matrix due to P_rIs a covariance matrix corresponding to the coordinates of the base station,since the base station coordinates are 3-dimensional vectors, the unit matrix is set to a 3 × 3 matrix.

Kalman filtering may be performed based on the first observation equation, the state equation, and the state noise input matrix as described above.

Wherein the equations of Kalman filtering include:

a ═ z (t +1) -H (t +1) x (t +1| t); (formula 16)

K＝P(t+1|t)H(t+1)(H(t+1)P(t+1|t)H^T(t+1)+R(t+1))^-1(ii) a (formula 17)

x (t +1| t +1) ═ x (t +1| t) + Ka; (formula 18)

P (t +1) ═ I-KH (t +1)) P (t +1| t); (formula 19)

Wherein z (t +1) represents an observed value of z in (t +1) epoch, wherein the observed value of z in each epoch is predetermined, i.e., the observed value of the dependent variable determined in step 210; x (t +1| t) represents the predicted value of x at (t +1) epoch predicted based on the values of x at t epoch and previous epochs; p (t +1| t) represents the error variance of x in (t +1) epoch estimated using the values of P in t epoch and the previous epoch; k is a Kalman gain matrix; x (t +1| t +1) represents the optimal estimate for x in the (t +1) epoch.

In a specific embodiment, for kalman filtering, an observed value of each state variable in the first observation equation at an initial epoch (hereinafter, an initial value), an initial value of a variance of each state variable, and an observed value of a dependent variable in the first observation equation at a plurality of epochs in succession are given, and thereby, in the kalman filtering process, the predicted value of the state variable at the next epoch may be predicted based on the value of the state variable at the previous epoch, and predicting the variance of the state variable of the next epoch based on the variance of the state variable of the previous epoch, and further determining the predicted value of the dependent variable based on the predicted value of the state variable, then, determining Kalman gain by combining the variance of the state variable and the state transition matrix, and correcting the predicted value of the state variable through the Kalman gain, so that the predicted value of the dependent variable approaches to the observed value of the dependent variable (namely the true value of the dependent variable) when the state variable is the optimal estimated value.

In a specific embodiment, the variance of the ionospheric-free combined ambiguity of the baseline in the initial epoch can be determined according to pseudo-range observations of different satellites and the prior double-difference ionospheric accuracy, and the initial value of the ionospheric-free combined ambiguity in the initial epoch can be directly calculated through the pseudo-range observations and the carrier observations in the existing observation data. The initial value and variance of the baseline coordinate error at the initial epoch may be set empirically. The initial value and variance of the zenith tropospheric delay residual at the initial epoch may also be set empirically.

It is worth mentioning that a fixed value is determined for each state variable in equation 10 by kalman filtering, that is, a fixed value is determined for the baseline coordinate error of the baseline and the zenith tropospheric delay residual in step 220. For ease of distinction, the fixed value of each state variable determined in accordance with step 220 is referred to as a first fixed value.

In step 220, the ionospheric-free combination ambiguities are initially fixed by Kalman filtering. At the end of the Kalman filtering process in step 220, the ionospheric-free combination ambiguity may be considered substantially fixed, and thus, a first fixed value of ionospheric-free combination ambiguity may be determined.

In the kalman filtering process, the state variables in the first observation equation include the ionospheric-free combined ambiguity of the baseline and the baseline coordinate error of the baseline, so that the first fixed value of the ionospheric-free combined ambiguity determined in step 220 is less affected by the baseline coordinate error, thereby improving the accuracy of the first fixed value of the ionospheric-free combination degree of the determined baseline. As described above, if the state variables in the first observation equation also include zenith versus flow delay residuals, it can be determined that the first fixed value determined in step 220 without ionospheric combination ambiguities is also less affected by zenith versus flow delay residuals. As described above, the ionospheric-free combined blur degree of the baseline in equation 11 is the ionospheric-free double-difference blur degree of the baseline, and in the actual positioning process, a differential positioning method is adopted, and the required blur degree of the baseline is also the double-difference blur degree of the baseline, so that the first fixed value of the ionospheric-free combined blur degree determined in step 220 can also be understood as the first fixed value of the ionospheric-free combined double-difference blur degree of the baseline. Of course, in other embodiments, the value of the baseline ionosphere-free combined ambiguity may be further calculated based on the first fixed value of the baseline ionosphere-free combined double-difference ambiguity, and the corresponding double-difference observation equation.

And step 230, determining a target fixed value of the ionosphere-free combined ambiguity of the base line according to the first fixed value of the ionosphere-free combined ambiguity of the base line and the fixed value of the widelane ambiguity of the base line.

Since the first fixed value of the base-line ionosphere-free combined ambiguity is obtained by initial fixation, compared with the first fixed value of the base-line ionosphere-free combined ambiguity, and the fixed value of the base-line widelane ambiguity is also obtained by fixing the base-line widelane ambiguity, the fixed value of the base-line widelane ambiguity is also higher in accuracy, therefore, in step 230, the target fixed value of the base-line ionosphere-free combined ambiguity is determined based on the first fixed value of the base-line ionosphere-free combined ambiguity obtained by initial fixation and the fixed value of the base-line widelane ambiguity, and the accuracy of the target fixed value of the base-line ionosphere-free combined ambiguity can be ensured.

In some embodiments, as shown in FIG. 3A, step 230 includes:

and 231, fixing the L1 ambiguity and the L2 ambiguity according to the fixed value of the widelane ambiguity of the base line and the first fixed value of the ionosphere-free combined ambiguity of the base line to obtain a fixed value of the L1 ambiguity of the base line and a fixed value of the L2 ambiguity of the base line.

The wide lane ambiguity refers to ambiguity under wide lane combination. In some embodiments, a fixed value for the widelane ambiguity for a baseline may be determined from observations of two reference stations to which the baseline corresponds.

Specifically, the fixed value of the L1 ambiguity can be calculated according to the relationship between the L1 ambiguity of the baseline and the ionosphere-free combined ambiguity and the widelane ambiguity as shown in the following equation 20.

After determining the fixed value of the L1 ambiguity, the fixed value of the L2 ambiguity is calculated as follows:

N₂＝N_WL-N₁(ii) a (formula 21)

Wherein N1 is L1 ambiguity, N_IFFor combined degree of pasting, N, without ionosphere_WLIs the width lane ambiguity, f₁Frequency, f, of carrier wave L1₂The frequency of the L2 carrier wave; wherein, the L1 carrier and the L2 carrier are known, the frequency of the L1 carrier is 1575.42MHz, and the wavelength of the L1 carrier is 19.03 cm; the frequency of the L2 carrier wave is 1227.60HMz, and the wavelength of the L1 carrier wave is 24.42 cm; n2 is L2 ambiguity.

In the application, after the widelane ambiguity is fixed and the fixed value of the widelane ambiguity is determined, the fixed value of the widelane ambiguity can be approximately considered as the real value of the widelane ambiguity, and the first fixed value of the ionosphere-free combined ambiguity of the baseline determined in the step 220 is also close to the real value of the ionosphere-free combined ambiguity of the baseline, so that the accuracy of the fixed value of the base line L1 ambiguity calculated according to the fixed value of the widelane ambiguity of the baseline and the first fixed value of the ionosphere-free combined ambiguity of the baseline and the fixed value of the baseline L2 ambiguity calculated is relatively high.

Step 232, calculating a first value of the ionospheric-free combined mold blur for the baseline based on the fixed value of the L1 blur for the baseline and the fixed value of the L2 blur for the baseline.

Specifically, the first value of the baseline ionospheric-free combined mold blur may be calculated according to the following formula:

the step 232 corresponds to the back calculation of the ionospheric-free combined ambiguity by the higher accuracy of the L1 ambiguity and the L2 ambiguity, since the accuracy of the fixed value of the L1 ambiguity and the fixed value of the L2 ambiguity is higher, the back calculation yields a first value of ionospheric-free ambiguity with higher accuracy than the first fixed value of the ionospheric-free combined ambiguity.

Step 233, performing Kalman filtering according to the second observation equation and the first numerical value of the ionosphere-free combined mold ambiguity of the baseline, and determining a target fixed value of the ionosphere-free combined mold ambiguity of the baseline; wherein the state variables in the second observation equation include the ionospheric-free combined ambiguity of the baseline and the baseline coordinate error of the baseline.

The second observation equation may be:

wherein the content of the first and second substances,

is the first value of the ionospheric-free combined mold blur calculated to give the baseline according to equation 22. The principle and process of kalman filtering are described above and will not be described herein.

In some embodiments, the first fixed value of the baseline coordinate error and the first fixed value of the zenith troposphere delay residual error determined in the kalman filtering process of step 220 may be determined as initial values of filtering in the second kalman filtering, and the kalman filtering may be performed based on the more accurate first fixed value of the zenith troposphere delay residual error and the first fixed value of the baseline coordinate error, so that accuracy and efficiency of ambiguity fixing may be improved.

In this embodiment, kalman filtering is performed again through the first numerical value and the second observation equation of the ionospheric-free combined pattern ambiguity of the baseline that is higher in accuracy, thereby, fixing of the ionospheric-free combined pattern ambiguity of the baseline can be performed again, and compared to step 220, the accuracy of the first numerical value of the ionospheric-free combined pattern ambiguity used for performing kalman filtering in step 232 is higher, and therefore, the accuracy of the target fixed value of the ionospheric-free combined pattern ambiguity of the baseline can be ensured. After the target fixed value of the ionosphere-free combined mold ambiguity of the baseline is determined, the target fixed value is correspondingly used as the fixed value of the ambiguity, and further, the accurate positioning service can be provided by combining the fixed value of the ambiguity.

In some embodiments, since the observation quality of the satellite with the higher altitude angle is better, the accuracy of the ambiguity of the reference station facing the satellite with the higher altitude angle is higher, and therefore, in step 232, the first value of the ionospheric-free combined ambiguity corresponding to the baseline of the satellite with the higher altitude angle is used for kalman filtering in step 232, so that the accuracy of the target fixed value of the obtained baseline ionospheric-free combined ambiguity can be improved.

In other embodiments, the baseline ionospheric-free combined blur level may be re-fixed as described above in steps 231-232, i.e., the first value of the baseline ionospheric-free combined blur level calculated in step 232 is used as the target fixed value of the ionospheric-free combined blur level.

In this application, the state variable in the first observation equation includes the non-ionosphere assembling die ambiguity of baseline and the baseline coordinate error of baseline to, at the in-process of carrying out kalman filtering according to the observation data, can guarantee that the error of the first fixed value of the non-ionosphere assembling die ambiguity of baseline confirmed does not include the error that the reference station coordinate offset arouses, thereby can promote the accuracy of the non-ionosphere assembling die ambiguity of baseline confirmed by kalman filtering.

Further, after the fixed value of the widelane ambiguity of the base line and the first fixed value of the ionosphere-free combined ambiguity of the base line are obtained, L1 ambiguity fixing and L2 ambiguity fixing are carried out, the first numerical value of the ionosphere-free combined ambiguity of the base line is inversely calculated according to the fixed value of the L1 ambiguity and the fixed value of the L2 ambiguity, and the accuracy of the first numerical value of the ionosphere-free combined ambiguity of the base line determined by inversely calculating based on the fixed value of the widelane ambiguity with higher accuracy is higher compared with the first fixed value of the base line.

The first numerical value of the ionosphere-free combined model ambiguity based on the baseline and the second observation equation perform Kalman filtering again, and because the state variable of the second observation equation is the same as the state variable of the first observation equation, the influence on the observed value caused by the coordinate offset of the reference station and the influence on the observed value caused by zenith troposphere delay can still be avoided being superposed to the ionosphere-free combined model ambiguity of the baseline in the process of performing Kalman filtering twice. Therefore, the method and the device for fixing the ambiguity can effectively improve the accuracy of the ambiguity fixing.

In the related art, a method for fixing the ambiguity includes: by using a partial fuzzy fixing mode with a cut-off satellite altitude angle, a fuzzy search prior success rate and a Ratio value as main parameters, however, firstly, the fuzzy fixing mode does not consider the error of an initial baseline coordinate, so that the accuracy of fixed fuzzy degree is low, and the quantity of fixable fuzzy degree can be reduced; secondly, in the method, the Ratio value is used as a basis for fixing the ambiguity, and because the correlation of the base line corresponding to the ambiguity of each satellite is low, the Ratio value cannot well reflect the precision of the ambiguity fixing; thirdly, the problem of coordinate offset of the reference station in the long-term operation process is not considered in the method. Therefore, the ambiguity fixed by the ambiguity fixing mode has low accuracy. In the scheme of the application, the influence of the reference station coordinates on the ambiguity (the ionosphere-free combined ambiguity) is considered, and in the Kalman filtering process, the ionosphere-free combined ambiguity of the base line and the base line coordinate error of the base line are both used as state variables of the first observation equation, so that the influence of the base line coordinate error on the ambiguity can be prevented from being superposed on the ionosphere-free combined ambiguity, and the accuracy of the determined ionosphere-free combined ambiguity is ensured.

When the base stations are constructed on a large scale, due to condition limitation, the position of the base stations is difficult to be ensured to be constant all the time, displacement drift phenomena exist in a plurality of base stations, if the coordinate error of the base station is not estimated, the coordinate of the base station needs to be solved at regular time and updated in network RTK service, the method is time-consuming and labor-consuming, a system needs to be initialized again, and positioning service is interrupted. In the scheme, the baseline coordinate error is estimated in the process of ambiguity fixing, so that the coordinates of the reference station can be corrected according to the estimated baseline coordinate error without the need of calculating the coordinates of the reference station at regular time and initializing a system, and the problem of positioning service interruption caused by coordinate drift of the reference station can be solved.

In the present application, in the process of fixing the ambiguity, the ambiguity of multiple baselines may be fixed synchronously, or the ambiguity of each baseline may be estimated individually, which is not specifically limited herein.

Fig. 3B is a flowchart illustrating a fixing method of ambiguity according to an embodiment of the present application. As shown in fig. 3B, includes:

at step 310, the system initializes. The purpose of system initialization is to set an initial filtered value in the kalman filtering process, for example, to set an initial value of the baseline coordinate error of the baseline, an initial value of the variance of the baseline coordinate error, an initial value of the zenith versus flow delay, an initial value of the variance of the zenith versus tropospheric delay, and the like.

Further, the initial value of the ionospheric-free combined double-difference ambiguity of the baseline and the variance of the ionospheric-free combined ambiguity can be calculated based on the existing observation data.

And step 320, forming a double-difference non-ionized layer combined observation equation. The established double-difference ionosphere-free combined observation equation is the first observation equation in the above. The derivation process for specifically constructing the first observation equation is described above. After acquiring the observation data from the reference station, the observation value of the dependent variable in the first observation equation is calculated from the observation data.

And step 330, filtering and resolving. In this process, i.e. based on the first observation equation, kalman filtering is performed, determining a first fixed value for each state variable in the first observation equation.

And 340, fixing the ambiguity of the widelane. A fixed value for the widelane ambiguity is determined, via step 340.

And step 350, fixing the L1 ambiguity and the L2 ambiguity. In this step, a fixed value for L1 ambiguity and a fixed value for L2 ambiguity are determined from the first fixed value for ionospheric-free combined ambiguity determined in step 330 and the initial fixed value for widelane ambiguity obtained in step 340.

Step 360, the ambiguity back-substitution constraint is fixed. In the step, the ionospheric-free combined model ambiguity of the baseline is inversely calculated through the fixed value of the L1 ambiguity with higher accuracy of the baseline and the fixed value of the L2 ambiguity, and the first numerical value of the ionospheric-free combined model ambiguity of the baseline with higher accuracy is obtained.

After determining the baseline first value of ionospheric-free combined ambiguity, return to step 320 to perform kalman filtering again based on the first value of ionospheric-free combined ambiguity, and determine the target fixed value of ionospheric-free combined ambiguity by performing step 320 again.

In some embodiments, each baseline may be calculated separately, or the ambiguities corresponding to multiple baselines may be calculated simultaneously. Further, in order to improve the precision, the coordinate error of a certain reference station corresponding to the baseline can be initially set to be zero, then the coordinate error of another reference station corresponding to the baseline is estimated, and then the coordinate error is jointly solved by a plurality of baselines.

In some embodiments, as shown in FIG. 4, step 210 comprises:

and step 410, calculating a carrier double-difference observation value of the base line under the combination without the ionized layer according to the observation data of the two base stations corresponding to the base line.

Non-ionosphere combination refers to the linear combination of similar observed values among different frequencies. The ionospheric delay error is related to the carrier frequency, with an order term inversely proportional to the square of the carrier frequency. The effect of ionospheric delay errors can be eliminated by ionospheric-free combining.

Specifically, the observation data includes a carrier observation value of two reference stations corresponding to the baseline under the L1 carrier, and a carrier observation value of two reference stations corresponding to the baseline under the L2 carrier; in this embodiment, step 410 includes: performing inter-station inter-satellite double difference according to carrier observed values of two reference stations corresponding to the base line under the L1 carrier to obtain carrier double difference observed values of the base line under the L1 carrier; performing inter-station inter-satellite double difference according to carrier observed values of two reference stations corresponding to the base line under the L2 carrier to obtain carrier double difference observed values of the base line under the L2 carrier; and calculating the carrier double-difference observation value of each base line under the non-ionosphere combination according to the frequency of the L1 carrier, the frequency of the L2 carrier, the carrier double-difference observation value of the base line under the L1 carrier and the carrier double-difference observation value of the base line under the L2 carrier.

Under the combination without ionosphere, the observation equation of the carrier observation value of the reference station i facing the satellite j is shown in the following formula 24:

wherein the content of the first and second substances,

representing the combined carrier observations of base station i facing satellite j without ionospheric combination,

representing the carrier observations of base station i facing satellite j under carrier L1,

the carrier observed value of the base station i facing the satellite j under the L2 carrier is represented;

frequency f representing an L1 carrier wave₁Square of (d); in the same way, the method for preparing the composite material,

frequency f representing an L2 carrier wave₂Square of (d).

Similarly, under the ionosphere combination, the carrier observation equation of the reference station b facing the satellite j is shown in the following formula 25:

the observation equation of the carrier wave of the reference station i facing the satellite k under the combination without the ionosphere is as follows under the following formula 26:

under the combination without ionosphere, the observation equation of the carrier wave of the reference station b facing the satellite k is as follows as shown in the following formula 27:

based on the above formulas 24-27, inter-station double differences are performed to obtain the following double difference observation equation:

representing carrier double-difference observed values of a base line formed between a reference station i and a reference station b facing a satellite k and a satellite j under the ionosphere-free combination;

a carrier double-difference observation value of a base line formed between the reference station i and the reference station b facing the satellite k and the satellite j under the L1 carrier wave is represented;

indicating the base formed between reference station i and reference station bThe line faces the carrier double-difference observations of satellite k and satellite j under the L2 carrier.

Thus, the carrier double-difference observation value of the base line under the combination without the ionized layer can be calculated based on the formula.

And step 420, calculating the satellite double-difference distance corresponding to the base line according to the position information of each satellite and the position information of the two reference stations corresponding to the base line.

It should be noted that the position information of the two reference stations corresponding to the baseline in step 420 is theoretical position information of the reference stations, and for example, the position information may be initial arrangement coordinates of the reference stations. In practice, although the reference station is fixedly disposed on the ground, the reference station may have a coordinate offset with the passage of time, and thus, there is a coordinate error. Therefore, in the present application, the coordinate error is integrated to fix the ambiguity, and the addition of the error caused by the coordinate error of the reference station to other error terms is avoided.

In step 420, a satellite distance between each reference station corresponding to the baseline and the observed satellite is calculated according to the position information of the satellite and the position information of the two reference stations in each baseline; and then, according to the station-to-satellite distance between each reference station corresponding to the base line and the observed satellite, performing station-to-station double difference to obtain the station-to-satellite double difference distance corresponding to the base line.

The description is also made above with reference to satellite j, satellite k, reference station i and reference station b as examples: according to the position information of the reference station i and the position information of the satellite j, the station-to-satellite distance between the reference station i and the satellite j can be calculated

Similarly, the station-satellite distance between the reference station b and the satellite j can be calculated according to the position information of the reference station b and the position information of the satellite j

According to the position information of the reference station i and the position information of the satellite k, the station-satellite distance between the reference station i and the satellite k can be calculated

According to the position information of the reference station b and the position information of the satellite k, the station-satellite distance between the reference station b and the satellite k can be calculated

On the basis, the station-satellite distance between the reference station i and the satellite j is determined

And the station-to-satellite distance between the reference station b and the satellite j

Performing station single difference to obtain station satellite distance single difference of the base line formed by the reference station i and the reference station b facing the satellite j

Namely:

similarly, the station-to-satellite distance between the reference station i and the satellite k can be determined

And the station-satellite distance between the reference station b and the satellite k

Performing station single difference to obtain station satellite distance single difference of a base line formed by the reference station i and the reference station b facing the satellite k

Namely:

then, the base line formed by the reference station i and the reference station b faces the station satellite distance single difference of the satellite j

And the station-satellite distance single difference of the base line formed by the reference station i and the reference station b facing the satellite k

Carrying out inter-satellite difference to obtain the station-satellite double-difference distance of the reference station i and the reference station b facing the satellite j and the satellite k

Namely:

according to the above process, the station-satellite double-difference distance of each baseline facing any two satellites can be calculated.

And 430, determining the observed value of the dependent variable in the first observation equation according to the carrier double-difference observed value of the base line under the combination without the ionized layer and the station-satellite double-difference distance corresponding to the base line.

As shown in equation 11 above, the state variables in the first observation equation also include the zenith tropospheric delay residual. Therefore, the observed value of the zenith tropospheric delay residual also needs to be determined in step 530. The base station satellite-oriented tropospheric delay can be calculated by means of a tropospheric delay correction model. Tropospheric delay correction models such as The Hopfield model, The saataminonin model, The EGNOS model (The European Geo-Stationary Navigation system), etc., are not particularly limited herein.

After the troposphere delay of each base station facing the satellite is obtained through calculation, inter-station inter-satellite double differences are carried out, and the troposphere delay double differences of two base stations facing two satellites in common view in the base line can be obtained.

Determining carrier double-difference observed values and base line correspondence of base lines under non-ionosphere combinationAfter the satellite double-difference distance and the base-line tropospheric delay double-difference, according to the above formula 12, that is

The observed value of the dependent variable in the first observation equation is obtained through calculation.

As described above, before kalman filtering, the observed values of the dependent variable in the first observation equation at multiple epochs need to be given in advance, and the observed values of the dependent variable in the first observation equation at each epoch can be calculated according to the process of step 410-430 as described above.

In some embodiments, as shown in FIG. 5, step 230 includes:

and step 510, determining an initial value of the ionospheric-free combined double-difference ambiguity of the baseline in the initial epoch according to the observation data.

Specifically, the observation data includes pseudo-range observation values and carrier observation values of two reference stations corresponding to the baseline under the carrier; step 510, comprising: performing inter-station double difference according to pseudo-range observed values of two reference stations corresponding to the baseline, which correspond to the initial epoch under the carrier, to obtain pseudo-range double-difference observed values corresponding to the baseline under the initial epoch; according to the carrier observed values of the two reference stations corresponding to the baseline under the carrier corresponding to the initial epoch, inter-station double-difference is carried out to obtain the carrier double-difference observed values of the baseline under the initial epoch; and calculating an initial value of the ionospheric-free combined double-difference ambiguity of the baseline under the initial epoch according to the pseudo-range double-difference observed value corresponding to the baseline under the initial epoch, the carrier double-difference observed value corresponding to the baseline under the initial epoch and the frequency corresponding to the carrier.

The carrier may be an L1 carrier, an L2 carrier, or a carrier of another frequency. Specifically, the initial value of the ionospheric-free combined double-difference ambiguity of the baseline may be calculated using the pseudo-range observed value and the carrier observed value of each of the two reference stations corresponding to the baseline under the L1 carrier, or the initial value of the ionospheric-free combined double-difference ambiguity of the baseline may be calculated using the pseudo-range observed value and the carrier observed value of each of the two reference stations corresponding to the baseline under the L2 carrier.

As described above, to perform kalman filtering, initial values of the state variables need to be given in advance, thereby facilitating prediction of estimated values of the state variables in subsequent processes in the kalman filtering process. Step 510 is to determine the value of equation 11

The baseline faces the initial value of the ionospheric-free combined double-difference ambiguity of any two satellites under the initial epoch.

It is understood that the initial epoch is related to a target epoch phase corresponding to observation data used for kalman filtering, where the initial epoch may be the first epoch in the target epoch phase, or may be one epoch selected from the target epoch phase as the initial epoch, and then only data corresponding to the initial epoch and data after the initial epoch in the observation data are used for kalman filtering.

In a specific embodiment, the initial value of the ionospheric-free combined double-difference ambiguity of the baseline facing any two co-view satellites at the initial epoch can be calculated according to the following formula:

wherein the content of the first and second substances,

the pseudo-range double-difference observed values of the reference station i and the reference station b facing the satellite k and the satellite j are represented;

representing carrier double-difference observed values of the reference station i and the reference station b facing the satellite k and the satellite j; λ is the frequency of the carrier wave; to be calculated according to equation 32

Approximated as a combined double-difference ambiguity without ionosphere.

At step 520, an initial value of the baseline coordinate error of the baseline is obtained.

The initial value of the baseline coordinate error of each baseline may be empirically set in advance. In one embodiment, the mean of the baseline coordinate errors may be set to an initial value of the baseline coordinate errors, and the mean of the baseline coordinate errors may be set to 0.

As shown in the above equation 11, the state variable in the first observation equation further includes the zenith troposphere residual, and therefore, it is further necessary to obtain an initial value of the zenith troposphere residual for kalman filtering. Specifically, a mean value of the zenith troposphere delay residual errors may be preset, and the mean value of the zenith troposphere delay residual errors may be set as an initial value of the zenith troposphere delay residual errors, for example, the mean value of the zenith troposphere delay residual errors is set to 0.

In the kalman filtering process, the variance value of each state variable in the initial epoch needs to be further set as the initial filtering value. The variance of the baseline coordinate error in the initial epoch and the variance of the zenith troposphere delay residual in the initial epoch can also be set empirically. In a particular embodiment, the variance of the baseline coordinate error at the initial epoch and the variance of the zenith tropospheric delay residual at the initial epoch may both be set to 0.01.

And 530, performing Kalman filtering according to a first observation equation based on the observed value of the dependent variable, the initial value of the ionosphere-free combined double-difference ambiguity of the baseline under the initial epoch and the initial value of the baseline coordinate error of the baseline, and determining a first fixed value of the ionosphere-free combined ambiguity of the baseline.

After determining an initial value of the ionosphere-free combined double-difference ambiguity of the baseline under an initial epoch, an initial value of a baseline coordinate error of the baseline and an initial value of a zenith troposphere delay residual error, a filtering initial value in a Kalman filtering process is correspondingly determined, so that Kalman filtering is performed according to the above formula 16-19 based on the filtering initial value and an observed value of a dependent variable in a first observation equation, and then a first fixed value of each state variable in the first observation equation is determined, so that a first fixed value of the ionosphere-free combined ambiguity of the baseline is correspondingly determined.

In some embodiments, the observation data includes carrier observations and pseudorange observations corresponding to dual-frequency carriers at a plurality of epochs, the dual-frequency carriers including an L1 carrier and an L2 carrier; the fixed value of the widelane ambiguity may be calculated according to the procedure shown in fig. 6, as shown in fig. 6, before step 240, the method further comprising:

and step 610, calculating a first value of widelane ambiguity of the baseline under each epoch in the plurality of epochs according to the carrier observed values and the pseudo-range observed values of the two reference stations corresponding to the baseline under the plurality of epochs, which correspond to the L1 carrier, and the carrier observed values and the pseudo-range observed values of the two reference stations corresponding to the baseline under the plurality of epochs, which correspond to the L2 carrier, in a MW combination mode.

In some embodiments, step 610 includes: acquiring the frequency of an L1 carrier wave, the frequency of an L2 carrier wave and a wide lane combined wavelength; and calculating a first value of the widelane ambiguity of the baseline under each epoch in a plurality of epochs according to the frequency of the L1 carrier, the frequency of the L2 carrier, the combined wavelength of the widelane, the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline under the L1 carrier under a plurality of epochs, and the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline under the L2 carrier under a plurality of epochs.

In this application, the value of the widelane ambiguity of the baseline calculated in the form of the MW combination is referred to as the first value of the widelane ambiguity of the baseline.

MW combining is proposed by melbourbe and Wubbena in the form of linear combinations of pseudorange observations and carrier observations at different frequencies. Specifically, the first value of the widelane ambiguity of the baseline at each epoch can be calculated according to the following formula 32:

wherein λ is_WLFor combining the wavelength of the wide laneThe combined wavelength is 80 cm;

a carrier observation value of a reference station i facing a satellite j under an L1 carrier;

a carrier observation value of a reference station i facing a satellite j under an L2 carrier;

a pseudo-range observation value of a reference station i facing a satellite j under an L1 carrier;

pseudorange observations are made for reference station i facing satellite j under the L2 carrier.

And step 620, calculating a second value of the widelane ambiguity of the baseline under each epoch in the plurality of epochs according to the carrier observed values of the two reference stations corresponding to the baseline under the plurality of epochs corresponding to the L1 carrier and the carrier observed values of the two reference stations corresponding to the baseline under the plurality of epochs corresponding to the L2 carrier and a double-difference observation equation under the condition of neglecting ionospheric delay. In the present application, the value of widelane ambiguity calculated according to the equation of double-difference observation under neglecting ionospheric delay is referred to as the second value of widelane ambiguity.

In some embodiments, step 620 includes: determining a carrier phase double-difference observed value of the baseline under the L1 carrier and a carrier phase double-difference observed value of the baseline under the L2 carrier, which correspond to each epoch in a plurality of epochs, according to a carrier observed value of the two reference stations corresponding to the baseline under the L1 carrier in the plurality of epochs and a carrier observed value of the two reference stations corresponding to the baseline under the L2 carrier in the plurality of epochs; and respectively calculating a second value of the widelane ambiguity of the baseline under each epoch in a plurality of epochs according to a double-difference observation equation under the condition of neglecting the ionospheric delay, and the carrier-phase double-difference observation value of the baseline under the L1 carrier wave and the carrier-phase double-difference observation value of the baseline under the L2 carrier wave corresponding to each epoch.

As described above, equation 6 results from ignoring ionospheric effectsTo the carrier observation equation, in this embodiment, equation 6 as above can be used as a double-difference observation equation under the condition of neglecting ionospheric delay, and correspondingly, equation 6 is used at this time

The carrier double-difference observed value under the wide lane combination can be correspondingly replaced, and the double-difference ambiguity in the formula 6 is

Correspondingly replacing double-difference widelane ambiguity, and replacing the wavelength in the formula 6 with a widelane combined wavelength; that is, the above equation 6 is transformed into:

under the wide lane combination, the wide lane carrier phase observed value is:

Φ_WL＝Φ₁-Φ₂(ii) a (formula 33)

The wide lane carrier phase observed value and the wide lane carrier phase observed value have the following relationship:

L_wL＝λ_WL·Φ_WL(ii) a (formula 34)

Wherein phi_WLCombining phases for the wide lane; phi₁Is a carrier phase observation at the L1 carrier; phi₂Is a carrier phase observation at the L2 carrier; l is_wLAnd the observed value is a wide-lane carrier observed value.

Performing inter-station double difference on wide-lane carrier phase observed values of two base stations (assumed as a base station i and a base station b) facing two satellites in common view (assumed as a satellite j and a satellite k), and obtaining:

wherein the content of the first and second substances,

represents base stations i andthe base station b faces to the double-difference wide-lane combined phase of the satellite k and the satellite j;

the carrier phase double-difference observation values of the base station i and the base station b facing the satellite k and the satellite j under the L1 carrier wave are represented;

the carrier phase double-difference observed values of the base station i and the base station b facing the satellite k and the satellite j under the L2 carrier are shown.

In conjunction with the above equations 32, 34, and 35, one can obtain:

performing double-difference wide-lane ambiguity back calculation according to a formula 36, namely calculating the double-difference wide-lane ambiguity according to the following formula:

according to the formula 37, the double-difference widelane ambiguity corresponding to the baseline can be calculated, and further, the carrier phase equation of the same baseline facing a plurality of satellites can be associated, so that the second numerical value of the widelane ambiguity corresponding to the baseline can be correspondingly calculated, and further, the second numerical value of the widelane ambiguity corresponding to the lower baseline of each epoch in a plurality of epochs can be obtained.

Step 630, determining a fixed value of the widelane ambiguity of the baseline according to the first value of the widelane ambiguity of the baseline in each epoch in the epochs and the second value of the widelane ambiguity of the baseline in each epoch in the epochs.

The errors in widelane ambiguity calculated by step 620 above include ionospheric delay and tropospheric delay residuals, but since widelane ambiguity wavelength is 80cm, the effect generally does not reach above 0.5 weeks.

The MW combination may eliminate the effects of tropospheric and ionospheric delays, and therefore the error in widelane ambiguity calculated as the MW combination does not include ionospheric and tropospheric delay residuals. However, in the process of calculating the widelane ambiguity according to the MW combination form, the widelane ambiguity is calculated by using the pseudo-range observation value, and the pseudo-range observation value has large noise, so that the calculated widelane ambiguity has a large error. Therefore, in the present application, the widelane ambiguity of the baseline is fixed by combining the first value of the widelane ambiguity of the baseline in each epoch and the second value of the widelane ambiguity of the baseline in each epoch in a plurality of epochs, so as to improve the accuracy of the fixed value of the widelane ambiguity of the baseline.

In some embodiments, as shown in fig. 7, step 630, comprises:

and step 710, for each epoch in the plurality of epochs, performing mean calculation on a first value of widelane ambiguity of the baseline under the historical epoch before the epoch and the epoch to obtain a widelane ambiguity mean value corresponding to the baseline under each epoch.

For example, if the first values of widelane ambiguities of the baseline at t1, t2, t3, t4. are calculated sequentially, let N be assumed to be N, respectively_WL，t1、N_WL，t2、N_WL，t3、N_WL，t4.., for t1 epoch, N will be_WL，t1As a wide lane ambiguity mean value corresponding to t1 epoch; for the t2 epoch, N will be at t1 epoch_WL，t1And N in t2 epoch_WL，t2Performing mean value calculation to obtain

Namely the wide lane ambiguity mean value corresponding to t2 epoch; for t3 epoch, carrying out mean value calculation on a first value of widelane ambiguity under t1-t3 epoch to obtain

Namely the wide lane ambiguity mean value corresponding to t3 epoch; by analogy, the wide lane ambiguity mean value corresponding to each epoch can be calculated.

Step 720, if the convergence condition is determined to be reached according to the widelane ambiguity mean values respectively corresponding to the baseline in the plurality of epochs, calculating a difference value between the target widelane ambiguity mean value corresponding to the target epoch and a second value of the widelane ambiguity of the baseline in the target epoch; the target epoch is the epoch corresponding to the mean value of ambiguity of the widelane reaching the convergence condition; the target widelane ambiguity mean is the widelane ambiguity mean of the baseline when the convergence condition is reached.

In some embodiments, a variance of the widelane ambiguity mean may be calculated based on the widelane ambiguity mean corresponding to the baseline over a plurality of epochs, and it may be determined that a convergence condition is reached if the variance is less than a variance threshold.

In other embodiments, it may be determined that widelane ambiguity mean values corresponding to M consecutive epochs are all within a mean value range according to widelane ambiguity mean values corresponding to a baseline under multiple epochs, and it is determined that an iteration end condition is reached, where M is a positive integer, and M and the mean value range may be set according to actual needs.

Step 730, if the difference is smaller than the difference threshold and the first integer value is equal to the second integer value, determining the first integer value as an initial fixed value of the widelane ambiguity of the baseline, where the first integer value is an integer value obtained by rounding a target widelane ambiguity mean value of the baseline, and the second integer value is an integer value obtained by rounding a second value of the widelane ambiguity corresponding to the baseline in the target epoch.

As described above, the ambiguity is theoretically an integer, and correspondingly, the widelane ambiguity is also theoretically an integer, so in this embodiment, the target widelane ambiguity mean value and the second value of the widelane ambiguity corresponding to the target epoch are both rounded; on the basis, when the difference value is smaller than the difference threshold value and the first integer value is equal to the second integer value, the first integer value is determined as an initial fixed value of the widelane ambiguity.

Through the process, the fixing of the widelane ambiguity of the base line is realized, and the fixed value of the widelane ambiguity is correspondingly determined. Because the different methods calculate the different error sources in the widelane ambiguity of the baseline, in this embodiment, the widelane ambiguity is fixed by combining the widelane ambiguity values of the baseline calculated by the two methods, so that the accuracy of the fixed value of the widelane ambiguity of the determined baseline can be improved, and the fixed value of the widelane ambiguity of the baseline is ensured to be close to the true value of the widelane ambiguity.

In this embodiment, after determining that the widelane ambiguity mean value of the baseline reaches the convergence condition, the second value of the widelane ambiguity corresponding to the target epoch is compared with the target widelane ambiguity mean value corresponding to the target epoch, and since it is determined that the widelane ambiguity mean value reaches the convergence condition, it indicates that the error of the widelane ambiguity mean value is small, and the fixed value of the widelane ambiguity is determined based on the widelane ambiguity mean value with a small error, so that the problem that the fixed value of the widelane ambiguity has a large error can be avoided. On the contrary, if the widelane ambiguity mean value does not reach the convergence condition, the widelane ambiguity mean value is compared with the second value of the widelane ambiguity, and the error of the widelane ambiguity mean value is larger at this moment, so that the error of the fixed value of the determined widelane ambiguity is easily caused to be larger.

In some embodiments, after step 230, the method further comprises: and providing positioning service according to the target fixed value of the ionosphere-free combined ambiguity of the multiple baselines.

Specifically, the positioning service provided may be a differential positioning service, or may be a network RTK service, which is not limited herein. If the provided positioning service is a network RTK service, the mode of the network RTK service may be according to a single reference station network mode, a Virtual Reference Station (VRS) technique, a regional correction parameter method, a master-slave station technique, and a synthetic error interpolation method.

After the target fixed value of the ionosphere-free combined model ambiguity of the baseline is determined, error correction information can be determined by combining error information of other error items, such as ionosphere delay, troposphere delay, base station coordinate error and the like, so that the observation value is corrected based on the error correction information in the process of providing the positioning service, and high-precision position information of the terminal is obtained.

In some embodiments, as shown in fig. 8, providing location services according to target fixed values of ionosphere-free combined ambiguity for multiple baselines includes:

step 810, receiving the approximate location information transmitted by the terminal.

As described above, the GPS receiver in the terminal can receive the signal transmitted from the satellite, so that the terminal determines its own position information from the received signal from the satellite, wherein the accuracy of its own position information determined by the terminal directly from the signal from the satellite is low, and therefore, the position information determined by the terminal directly from the signal transmitted from the satellite is referred to as approximate position information.

In step 820, a plurality of target reference stations are determined for the terminal based on the approximate location information.

In some embodiments, at least one of the following reference stations may be determined as the target reference station for the terminal: the base station has a signal strength greater than a signal strength threshold value with respect to the terminal, and the base station has a distance less than a distance threshold value with respect to a position indicated by the approximate position information of the terminal.

Step 830, determining the observation data of the virtual observation station according to the observation data of the plurality of target reference stations and the target fixed value of the ionosphere-free combined mold ambiguity of each target base line; the target baseline refers to a baseline formed between any two target reference stations in the plurality of target reference stations.

It is understood that, after determining the fixed value of the ionospheric-free combination blur degree of each base line and determining the target reference station according to the above procedure, corresponding to the target base line formed between any two target reference stations, the fixed value corresponding to the ionospheric-free combination blur degree of the target base line can be obtained.

And 840, sending the observation data of the virtual observation station to the terminal, wherein the observation data of the virtual observation station is used for the terminal to determine the position information of the terminal.

In this embodiment, a virtual reference station technique is employed to provide network RTK positioning services to the terminal. And integrally correcting errors according to the observation data of a plurality of target reference stations, the determined target fixed value without the ionosphere combination ambiguity and error information of other error items to obtain differential information, and sending the differential information to a terminal, wherein the differential information is equivalent to a virtual reference station generated near the terminal, and therefore, the differential signal is the observation data of the virtual observation station.

After the terminal receives the observation data of the virtual observation station, the carrier phase difference is carried out by combining the observation data received by the terminal, so that the position information of the terminal with higher precision can be determined, and real-time RTK is realized. In this embodiment, because the determined target fixed value without the ionosphere combined mold ambiguity has high accuracy, the accuracy of the determined observation data of the virtual observation station is ensured, and the accuracy of the terminal in positioning according to the observation data of the virtual observation station with higher accuracy is further ensured.

Embodiments of the apparatus of the present application are described below, which may be used to perform the methods of the above-described embodiments of the present application. For details which are not disclosed in the embodiments of the apparatus of the present application, reference is made to the above-described embodiments of the method of the present application.

Fig. 9 is a block diagram illustrating an ionosphere-free combination mold ambiguity fixing apparatus according to an embodiment of the present application, the ambiguity fixing apparatus including, as shown in fig. 9: an observation value determining module 910, configured to determine an observation value of a dependent variable in a first observation equation according to observation data of two reference stations corresponding to a baseline, where the first observation equation indicates a functional relationship between an ionospheric-free combined ambiguity of the dependent variable and the baseline and a baseline coordinate error of the baseline; the first kalman filtering module 920 is configured to perform kalman filtering according to a first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined mold ambiguity of the baseline; and a target fixed value determining module 930, configured to determine a target fixed value of the ionosphere-free combined ambiguity of the baseline according to the first fixed value of the ionosphere-free combined ambiguity of the baseline and the fixed value of the widelane ambiguity of the baseline.

In some embodiments, the target fixed value determination module 930 includes: the fixing module is used for fixing the L1 ambiguity and the L2 ambiguity according to the fixed value of the widelane ambiguity of the base line and the first fixed value of the ionosphere-free combined ambiguity of the base line to obtain the fixed value of the L1 ambiguity of the base line and the fixed value of the L2 ambiguity of the base line; a calculation module for calculating a first value of ionospheric-free combined blur for the baseline based on the fixed value of L1 blur for the baseline and the fixed value of L2 blur for the baseline; the second Kalman filtering module is used for carrying out Kalman filtering according to a second observation equation and the first numerical value of the ionosphere-free combined mold ambiguity of the base line to determine a target fixed value of the ionosphere-free combined mold ambiguity of the base line; wherein the state variables in the second observation equation include the ionospheric-free combined ambiguity of the baseline and the baseline coordinate error of the baseline.

In some embodiments, the observation data includes carrier observations and pseudorange observations corresponding to dual-frequency carriers at a plurality of epochs, the dual-frequency carriers including an L1 carrier and an L2 carrier; in this embodiment, the ambiguity fixing device further includes: the first value determining module is used for calculating a first value of the widelane ambiguity of the baseline under each epoch in the plurality of epochs according to a MW combination mode according to the carrier observed value and the pseudo-range observed value of the L1 carrier wave corresponding to the two reference stations corresponding to the baseline under the plurality of epochs and the carrier observed value and the pseudo-range observed value of the L2 carrier wave corresponding to the two reference stations corresponding to the baseline under the plurality of epochs; the second numerical value determining module is used for calculating a second numerical value of the widelane ambiguity of the baseline under each epoch in the plurality of epochs according to a double-difference observation equation under the condition of neglecting ionospheric delay according to the carrier observation values of the two reference stations corresponding to the baseline under the plurality of epochs corresponding to the L1 carrier and the carrier observation values of the two reference stations corresponding to the baseline under the plurality of epochs corresponding to the L2 carrier; and the fixed value determining module of the widelane ambiguity is used for determining the fixed value of the widelane ambiguity of the baseline according to the first value of the widelane ambiguity of the baseline under each epoch in the epochs and the second value of the widelane ambiguity of the baseline under each epoch in the epochs.

In some embodiments, the fixed value of widelane ambiguity determination module comprises: the widelane ambiguity mean value determining unit is used for carrying out mean value calculation on a first numerical value of widelane ambiguity of a baseline under historical epochs before the epochs and the epochs for each epoch in the multiple epochs to obtain a widelane ambiguity mean value corresponding to the baseline at each epoch; a difference calculation unit, configured to calculate a difference between a target widelane ambiguity mean value corresponding to the target epoch and a second value of widelane ambiguity of the baseline under the target epoch, if it is determined that a convergence condition is reached according to widelane ambiguity mean values corresponding to the baseline respectively at the multiple epochs; the target epoch is the epoch corresponding to the mean value of ambiguity of the widelane reaching the convergence condition; the target widelane ambiguity mean value is the widelane ambiguity mean value of the baseline when the convergence condition is reached; and the fixed value determining unit is used for determining the first integer value as the fixed value of the widelane ambiguity of the baseline if the difference value is smaller than the difference threshold value and the first integer value is equal to the second integer value, wherein the first integer value is an integer value obtained by rounding a target widelane ambiguity mean value of the baseline, and the second integer value is an integer value obtained by rounding a second value of the widelane ambiguity corresponding to the baseline in the target epoch.

In some embodiments, the second value determination module comprises: a carrier phase double-difference observation value determining unit, configured to determine, according to carrier observation values of two reference stations corresponding to the baseline and corresponding to the L1 carrier under multiple epochs and carrier observation values of two reference stations corresponding to the baseline and corresponding to the L2 carrier under multiple epochs, a carrier phase double-difference observation value of each epoch of the baseline and the carrier phase double-difference observation value of each epoch under the L1 carrier and the carrier phase double-difference observation value of each epoch under the L2 carrier in the multiple epochs; and the second numerical value determining unit is used for respectively calculating a second numerical value of the widelane ambiguity of the baseline under each epoch in a plurality of epochs according to a double-difference observation equation under the condition of neglecting the ionospheric delay, and the carrier-phase double-difference observation value of the baseline under the L1 carrier wave and the carrier-phase double-difference observation value of the baseline under the L2 carrier wave corresponding to each epoch.

In some embodiments, the first value determination module comprises: an obtaining unit, configured to obtain a frequency of an L1 carrier, a frequency of an L2 carrier, and a wide lane combination wavelength; and the first numerical value determining unit is used for calculating a first numerical value of the widelane ambiguity of the baseline under each epoch in a plurality of epochs according to the frequency of the L1 carrier, the frequency of the L2 carrier, the widelane combined wavelength, the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline under the L1 carrier under a plurality of epochs, and the carrier observed value and the pseudo-range observed value of the two reference stations corresponding to the baseline under the L2 carrier under a plurality of epochs.

In some embodiments, a first kalman filtering module, comprising: the first initial value acquisition unit is used for determining the initial value of the ionosphere-free combined double-difference ambiguity of the baseline under the initial epoch according to the observation data; a second initial value acquisition unit configured to acquire an initial value of a baseline coordinate error of the baseline; and the first Kalman filtering unit is used for carrying out Kalman filtering according to the first observation equation based on the observed value of the dependent variable in the first observation equation, the initial value of the ionosphere-free combined double-difference ambiguity of the baseline under the initial epoch and the initial value of the baseline coordinate error of the baseline, and determining the ionosphere-free combined ambiguity of the baseline.

In some embodiments, the observation data includes pseudo-range observations and carrier observations of two reference stations under a carrier corresponding to a baseline; a first initial value determination unit comprising: the third double-difference unit is used for carrying out inter-station double-difference according to pseudo-range observed values of two reference stations corresponding to the base line, which correspond to the initial epoch under the carrier wave, so as to obtain pseudo-range double-difference observed values of the base line, which correspond to the initial epoch under the initial epoch; the fourth double-difference unit is used for carrying out inter-station double-difference according to the carrier observed values of the two reference stations corresponding to the baseline, which correspond to the initial epoch under the carrier, so as to obtain the carrier double-difference observed values of the baseline, which correspond to the initial epoch under the initial epoch; and the initial value determining unit is used for calculating the initial value of the ionospheric-free combined double-difference ambiguity of the baseline under the initial epoch according to the pseudo-range double-difference observed value corresponding to the baseline under the initial epoch, the carrier double-difference observed value corresponding to the baseline under the initial epoch and the frequency corresponding to the carrier.

In some embodiments, the observation determination module 910 includes: the first calculation unit is used for calculating the carrier double-difference observation value of the base line under the combination without the ionized layer according to the observation data of the two reference stations corresponding to the base line; the second calculation unit is used for calculating the station-satellite double-difference distance corresponding to the base line according to the position information and the position information of the two reference stations corresponding to the base line; and the observation value determining unit is used for determining the observation value of the dependent variable in the first observation equation according to the carrier double-difference observation value of the base line under the combination without the ionosphere and the station-satellite double-difference distance corresponding to the base line.

In some embodiments, the observation data includes carrier observations at L1 carrier and carrier observations at L2 carrier for the two reference stations corresponding to the baseline; in this embodiment, the first calculation unit includes: the first double-difference unit is used for carrying out inter-station inter-satellite double differences according to carrier observed values of two reference stations corresponding to the base line under the L1 carrier waves to obtain carrier double-difference observed values of the base line under the L1 carrier waves; the second double-difference unit is used for carrying out inter-station inter-satellite double differences according to carrier observed values of two reference stations corresponding to the base line under the L2 carrier, so as to obtain carrier double-difference observed values of the base line under the L2 carrier; and the carrier double-difference observation value calculation unit is used for calculating the carrier double-difference observation value of the base line under the non-ionosphere combination according to the frequency of the L1 carrier, the frequency of the L2 carrier, the carrier double-difference observation value of the base line under the L1 carrier and the carrier double-difference observation value of the base line under the L2 carrier.

In some embodiments, the means for fixing the ambiguity further comprises: and the positioning service providing module is used for providing positioning service according to the target fixed value of the ionosphere-free combined module ambiguity of the baselines.

In some embodiments, a location services provision module, comprising: a receiving unit for receiving the approximate location information transmitted by the terminal; a target reference station determining unit for determining a plurality of target reference stations for the terminal based on the approximate location information; the observation data determining unit is used for determining the observation data of the virtual observation station according to the observation data of the plurality of target reference stations and the target fixed value of the ionosphere-free combined mold ambiguity of each target base line; the target base line refers to a base line formed between any two target base stations in the plurality of target base stations; and the sending unit is used for sending the observation data of the virtual observation station to the terminal, and the observation data of the virtual observation station is used for the terminal to determine the position information of the terminal.

FIG. 10 illustrates a schematic structural diagram of a computer system suitable for use in implementing the electronic device of an embodiment of the present application. It should be noted that the computer system 1000 of the electronic device shown in fig. 10 is only an example, and should not bring any limitation to the functions and the scope of use of the embodiments of the present application. As shown in fig. 10, the computer system 1000 includes a Central Processing Unit (CPU)1001 that can perform various appropriate actions and processes, such as performing the methods in the above-described embodiments, according to a program stored in a Read-Only Memory (ROM) 1002 or a program loaded from a storage portion 1008 into a Random Access Memory (RAM) 1003. In the RAM 1003, various programs and data necessary for system operation are also stored. The CPU1001, ROM1002, and RAM 1003 are connected to each other via a bus 1004. An Input/Output (I/O) interface 1005 is also connected to the bus 1004.

The following components are connected to the I/O interface 1005: an input section 1006 including a keyboard, a mouse, and the like; an output section 1007 including a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), and a speaker; a storage portion 1008 including a hard disk and the like; and a communication section 1009 including a Network interface card such as a LAN (Local Area Network) card, a modem, or the like. The communication section 1009 performs communication processing via a network such as the internet. The driver 1010 is also connected to the I/O interface 1005 as necessary. A removable medium 1011 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 1010 as necessary, so that a computer program read out therefrom is mounted into the storage section 1008 as necessary.

In particular, according to embodiments of the application, the processes described above with reference to the flow diagrams may be implemented as computer software programs. For example, embodiments of the present application include a computer program product comprising a computer program embodied on a computer readable medium, the computer program comprising program code for performing the method illustrated by the flow chart. In such an embodiment, the computer program may be downloaded and installed from a network through the communication part 1009 and/or installed from the removable medium 1011. When the computer program is executed by a Central Processing Unit (CPU)1001, various functions defined in the system of the present application are executed.

It should be noted that the computer readable medium shown in the embodiments of the present application may be a computer readable signal medium or a computer readable storage medium or any combination of the two. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples of the computer readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a Read-Only Memory (ROM), an Erasable Programmable Read-Only Memory (EPROM), a flash Memory, an optical fiber, a portable Compact Disc Read-Only Memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present application, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. In this application, however, a computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the foregoing.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present application. Each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The units described in the embodiments of the present application may be implemented by software, or may be implemented by hardware, and the described units may also be disposed in a processor. Wherein the names of the elements do not in some way constitute a limitation on the elements themselves.

As another aspect, the present application also provides a computer-readable storage medium, which may be contained in the electronic device described in the above embodiments; or may exist separately without being assembled into the electronic device. The computer readable storage medium carries computer readable instructions which, when executed by a processor, implement the method of any of the embodiments described above.

According to an aspect of the present application, there is also provided an electronic device, including: a processor; a memory having computer readable instructions stored thereon which, when executed by the processor, implement the method of any of the above embodiments.

According to an aspect of an embodiment of the present application, there is provided a computer program product or a computer program comprising computer instructions stored in a computer readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions to cause the computer device to perform the method of any of the above embodiments.

It should be noted that although in the above detailed description several modules or units of the device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the application. Conversely, the features and functions of one module or unit described above may be further divided into embodiments by a plurality of modules or units.

Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which can be a personal computer, a server, a touch terminal, or a network device, etc.) to execute the method according to the embodiments of the present application.

Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains.

It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims

1. A method for fixing an ambiguity, comprising:

determining an observed value of a dependent variable in a first observation equation according to observation data of two reference stations corresponding to a base line, wherein the first observation equation indicates a functional relation between the dependent variable and an ionosphere-free combined model ambiguity of the base line and a base line coordinate error of the base line;

performing Kalman filtering according to the first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the ionosphere-free combined mold ambiguity of the baseline;

and determining a target fixed value of the ionosphere-free combined ambiguity of the base line according to the first fixed value of the ionosphere-free combined ambiguity of the base line and the fixed value of the widelane ambiguity of the base line.

2. The method of claim 1, wherein determining the target fixed value for ionospheric-free combined ambiguity for the baseline from the first fixed value for ionospheric-free combined ambiguity for the baseline and the fixed value for widelane ambiguity for the baseline comprises:

according to the fixed value of the widelane ambiguity of the base line and the first fixed value of the ionosphere-free combined ambiguity of the base line, fixing L1 ambiguity and L2 ambiguity to obtain a fixed value of the L1 ambiguity of the base line and a fixed value of the L2 ambiguity of the base line;

calculating a first value of the ionospheric-free combined mold ambiguity of the baseline from the fixed value of the L1 ambiguity of the baseline and the fixed value of the L2 ambiguity of the baseline;

performing Kalman filtering according to a second observation equation and the first numerical value of the ionosphere-free combined mold ambiguity of the base line, and determining a target fixed value of the ionosphere-free combined mold ambiguity of the base line; wherein the state variables in the second observation equation include an ionospheric-free combined mode ambiguity for the baseline and a baseline coordinate error for the baseline.

3. The method of claim 1 or 2, wherein the observation data comprises carrier observations and pseudorange observations corresponding to dual-frequency carriers over a plurality of epochs, the dual-frequency carriers comprising an L1 carrier and an L2 carrier;

before determining the target fixed value of the ionospheric-free combined ambiguity of the baseline according to the first fixed value of the ionospheric-free combined ambiguity of the baseline and the fixed value of the widelane ambiguity of the baseline, the method further includes:

calculating a first value of widelane ambiguity of the baseline at each epoch in the epochs according to carrier observations and pseudo-range observations of the two reference stations corresponding to the baseline at the L1 carrier under the epochs and carrier observations and pseudo-range observations of the two reference stations corresponding to the baseline at the L2 carrier under the epochs, and according to a MW combination form;

calculating a second value of the widelane ambiguity of the baseline at each epoch in the epochs according to a double-difference observation equation under the condition of neglecting ionospheric delay according to carrier observations of the two reference stations corresponding to the baseline at the L1 carrier in the epochs and carrier observations of the two reference stations corresponding to the baseline at the L2 carrier in the epochs;

and determining a fixed value of the widelane ambiguity of the baseline according to a first value of the widelane ambiguity of the baseline in each epoch in the epochs and a second value of the widelane ambiguity of the baseline in each epoch in the epochs.

4. The method of claim 3, wherein determining the fixed value for the widelane ambiguity for the baseline based on a first value for the widelane ambiguity for the baseline at each of the plurality of epochs and a second value for the widelane ambiguity for the baseline at each of the plurality of epochs comprises:

for each epoch in the plurality of epochs, performing mean calculation on a first value of the widelane ambiguity of the baseline under the epoch and a historical epoch before the epoch to obtain a widelane ambiguity mean value corresponding to the baseline in each epoch;

if the convergence condition is determined to be reached according to the widelane ambiguity mean values respectively corresponding to the base line in the plurality of epochs, calculating a difference value between a target widelane ambiguity mean value corresponding to a target epoch and a second value of the widelane ambiguity of the base line in the target epoch; the target epoch is an epoch corresponding to the mean value of ambiguity of the finger width lane reaching the convergence condition; the target widelane ambiguity mean is the widelane ambiguity mean of the baseline when a convergence condition is reached;

and if the difference is smaller than a difference threshold value and a first integer value is equal to a second integer value, determining the first integer value as a fixed value of the widelane ambiguity of the baseline, wherein the first integer value is an integer value obtained by rounding a target widelane ambiguity mean value of the baseline, and the second integer value is an integer value obtained by rounding a second value of the widelane ambiguity of the baseline under the target epoch.

5. The method of claim 3, wherein calculating the second value of the widelane ambiguity for the baseline at each epoch in the plurality of epochs based on carrier observations of the two reference stations corresponding to the baseline at the plurality of epochs corresponding to the L1 carrier and carrier observations of the two reference stations corresponding to the baseline at the plurality of epochs corresponding to the L2 carrier according to a double-difference observation equation that ignores ionospheric delay comprises:

determining a carrier-phase double-difference observation value of each epoch of the baseline in the plurality of epochs under the L1 carrier and a carrier-phase double-difference observation value of each epoch of the baseline under the L2 carrier according to carrier observations of the two reference stations corresponding to the baseline under the plurality of epochs under the L1 carrier and carrier observations of the two reference stations corresponding to the baseline under the plurality of epochs under the L2 carrier;

and respectively calculating a second value of the widelane ambiguity of the baseline under each epoch in the epochs according to a double-difference observation equation under the condition of ignoring ionospheric delay, and the carrier-phase double-difference observation value of the baseline under the L1 carrier wave and the carrier-phase double-difference observation value of the baseline under the L2 carrier wave corresponding to each epoch.

6. The method of claim 3, wherein the computing the first value of the widelane ambiguity for the baseline at each epoch in the plurality of epochs from carrier observations and pseudorange observations of the baseline for the two reference stations corresponding to the L1 carrier at the plurality of epochs and carrier observations and pseudorange observations of the baseline for the two reference stations corresponding to the L2 carrier at the plurality of epochs in MW combinations comprises:

acquiring the frequency of the L1 carrier, the frequency of the L2 carrier and a wide lane combined wavelength;

and calculating a first value of the widelane ambiguity of the baseline at each epoch in the epochs according to the frequency of the L1 carrier, the frequency of the L2 carrier, the combined wavelength of the widelane, the carrier observed values and the pseudo-range observed values of the two reference stations corresponding to the baseline under the L1 carrier under the epochs and the carrier observed values and the pseudo-range observed values of the two reference stations corresponding to the baseline under the L2 carrier under the epochs, in a MW combination mode.

7. The method of claim 1, wherein performing Kalman filtering according to the first observation equation based on the observed values of the dependent variables to obtain a first fixed value of the ionospheric-free combined ambiguity for the baseline comprises:

determining an initial value of the ionospheric-free combined double-difference ambiguity of the baseline under an initial epoch according to the observation data;

acquiring an initial value of the baseline coordinate error of the baseline;

and performing Kalman filtering according to the first observation equation based on the observed value of the dependent variable, the initial value of the ionosphere-free combined double-difference ambiguity of the baseline under the initial epoch and the initial value of the baseline coordinate error of the baseline, and determining a first fixed value of the ionosphere-free combined ambiguity of the baseline.

8. The method of claim 7, wherein the observation data comprises pseudorange observations and carrier observations of two reference stations under a carrier for the baseline;

the determining an initial value of the ionospheric-free combined double-difference ambiguity for the baseline at an initial epoch from the observation data comprises:

according to pseudo-range observed values of two reference stations corresponding to the baseline under the carrier wave and corresponding to the initial epoch, inter-station inter-satellite double differences are carried out, and pseudo-range double-difference observed values corresponding to the baseline under the initial epoch are obtained;

according to the carrier observed values of the two reference stations corresponding to the baseline under the carrier corresponding to the initial epoch, inter-station double-difference is carried out to obtain the carrier double-difference observed values of the baseline under the initial epoch;

and calculating an initial value of the ionospheric-free combined double-difference ambiguity of the baseline under the initial epoch according to the pseudo-range double-difference observed value corresponding to the baseline under the initial epoch, the carrier double-difference observed value corresponding to the baseline under the initial epoch and the frequency corresponding to the carrier.

9. The method of claim 1, wherein determining the observed value of the dependent variable in the first observation equation based on the observed data of the two reference stations corresponding to the baseline comprises:

calculating a carrier double-difference observation value of the base line under the combination without the ionized layer according to the observation data of the two base stations corresponding to the base line;

calculating the satellite double-difference distance of the station corresponding to the base line according to the position information of each satellite and the position information of the two reference stations corresponding to the base line;

and determining the observed value of the dependent variable in the first observation equation according to the carrier double-difference observed value of the baseline under the combination without the ionized layer and the satellite double-difference distance corresponding to the baseline.

10. The method of claim 9, wherein the observation data comprises carrier observations at L1 carrier and carrier observations at L2 carrier for the two reference stations corresponding to the baseline;

the calculating the carrier double-difference observation value of the base line under the combination without the ionized layer according to the observation data of the two base stations corresponding to the base line comprises the following steps:

performing inter-station inter-satellite double difference according to the carrier observed values of the two reference stations corresponding to the baseline under the L1 carrier to obtain a carrier double-difference observed value of the baseline under the L1 carrier;

performing inter-station inter-satellite double difference according to the carrier observed values of the two reference stations corresponding to the baseline under the L2 carrier to obtain a carrier double-difference observed value of the baseline under the L2 carrier;

and calculating the carrier double-difference observation value of the baseline under the non-ionospheric combination according to the frequency of the L1 carrier, the frequency of the L2 carrier, the carrier double-difference observation value of the baseline under the L1 carrier and the carrier double-difference observation value of the baseline under the L2 carrier.

11. The method of claim 1 or 2, wherein after determining the target fixed value of ionospheric-free combined ambiguity for the baseline from the first fixed value of ionospheric-free combined ambiguity for the baseline and the fixed value of widelane ambiguity for the baseline, the method further comprises:

and providing positioning service according to the target fixed values of the ionosphere-free combined template ambiguity of the baselines.

12. The method of claim 11, wherein providing location services according to the target fixed values of ionosphere-free combined ambiguity for the plurality of baselines comprises:

receiving approximate position information sent by a terminal;

determining a plurality of target reference stations for the terminal based on the approximate location information;

determining observation data of a virtual observation station according to the observation data of the plurality of target reference stations and the target fixed value of the ionospheric-free combined ambiguity of each target base line; the target base line refers to a base line formed between any two target base stations in the plurality of target base stations;

and sending the observation data of the virtual observation station to the terminal, wherein the observation data of the virtual observation station is used for the terminal to determine the position information of the terminal.

13. An ambiguity fixing apparatus, comprising:

the observation value determining module is used for determining the observation value of the dependent variable in a first observation equation according to the observation data of the two reference stations corresponding to the base line, wherein the first observation equation indicates the functional relation between the dependent variable and the non-ionosphere combined model ambiguity of the base line and the base line coordinate error of the base line;

the first Kalman filtering module is used for carrying out Kalman filtering according to the first observation equation based on the observed value of the dependent variable to obtain a first fixed value of the non-ionosphere combined model ambiguity of the baseline;

and the target fixed value determining module is used for determining the target fixed value of the ionosphere-free combined ambiguity of the baseline according to the first fixed value of the ionosphere-free combined ambiguity of the baseline and the fixed value of the widelane ambiguity of the baseline.

14. An electronic device, comprising:

a processor;

a memory having computer-readable instructions stored thereon which, when executed by the processor, implement the method of any of claims 1-12.

15. A computer readable storage medium having computer readable instructions stored thereon which, when executed by a processor, implement the method of any one of claims 1-12.

16. A computer program product comprising computer instructions, characterized in that the computer instructions, when executed by a processor, implement the method of any of claims 1-12.