CN114355419A - Distributed Beidou position service center RTK product positioning method and positioning device - Google Patents
Distributed Beidou position service center RTK product positioning method and positioning device Download PDFInfo
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Abstract
The invention relates to a distributed Beidou position service center RTK product positioning method and a positioning device, wherein the positioning method comprises the following steps: selecting an observation time period, and observing n satellites from m monitoring stations under L observation epochs in the observation time period to obtain observation data on L multiplied by m multiplied by n puncture points; calculating the total electron content in the zenith direction on each puncture point according to the observation data; establishing a low-density network region quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points, and calculating a model coefficient; predicting ionospheric correction parameters of a target time period after an observation time period according to the ionospheric correction model and the model coefficients; and (4) combining the ionosphere correction parameters, and carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology to obtain a positioning result. The positioning method establishes the regional ionosphere correction model through the ground observation network, reduces the transmission distance between the control center and the base station and between the control center and the rover station, realizes short-distance transmission and ensures real-time RTK.
Description
Technical Field
The invention belongs to the technical field of satellite positioning, and particularly relates to a distributed Beidou position service center RTK product positioning method and a positioning device.
Background
The Beidou position service center is a Beidou integrated service platform which takes a Beidou satellite navigation technology as a core and provides high-precision position information service for the whole industry universe based on a cloud computing technology. By utilizing a System architecture opened and shared by cloud technology, infrastructure, data resources and service platforms related to position and time services such as a Global Navigation Satellite System (GNSS), a Geographic Information System (GIS), a Remote Sensing technology (RS) and the like are integrated into one System, so that comprehensive services based on position Information are provided for government departments, major industries, enterprises and individual consumers. The whole Beidou high-precision position service center adopts a hierarchical design, and is provided with a regional position service data sub-center and a provincial position service data application center. The expansion is strong, the structure is complete, the layout is reasonable, and the standard data, service, safety, storage and other technical standards are provided.
Real-time carrier-phase differential positioning (RTK) is a technique for performing Real-time dynamic relative positioning using carrier-phase observations. When RTK measurement is carried out, at least 2 receivers are required to be equipped, one receiver is installed on the reference station, the other receiver carries out real-time relative positioning near the reference station, and then the three-dimensional coordinates of the other receiver are obtained according to the coordinates of the reference station. The conventional single-machine RTKs are very limited in working distance because the spatial correlation of various errors will rapidly decrease as the distance between the rover station and the base station increases. In order to overcome the drawbacks of the conventional RTK techniques, network RTK has been proposed in which a single-point error model of linear attenuation is replaced by a regional network error model, i.e., a network composed of a plurality of reference stations is used to estimate an error model of a region and provide correction data for users in a network-covered region.
In order to continuously and quickly obtain a fixed solution in the network RTK, an RTK mobile station needs to continuously, reliably and quickly receive a data link signal sent by a reference station, so that the selection of a data link transmission frequency and a transmission mode is a great key factor influencing the performance of the network RTK, besides, the ionospheric delay of a region where the mobile station is located is also one of main errors influencing the positioning accuracy of the network RTK, and an empirical ionospheric correction model cannot be well adapted to the ionospheric delay correction of each region. Aiming at the problem that a data chain and an observation environment are greatly influenced due to different regions of a mobile station, a technology is needed to solve the regional problem of network RTK, the network RTK and a distributed deployment mode of a Beidou high-precision position service center are closely combined, a regional ionosphere correction model is established according to the regional characteristics of the sub-centers of each position service center, and data transmission frequency between a reference station and the mobile station is reasonably selected according to the regional characteristics, so that the RTK high-precision positioning service of the distributed Beidou high-precision position service center is realized.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a distributed Beidou position service center RTK product positioning method and a positioning device. The technical problem to be solved by the invention is realized by the following technical scheme:
the embodiment of the invention provides a distributed Beidou position service center RTK product positioning method, which comprises the following steps:
selecting an observation time period, and observing n satellites from m monitoring stations under L observation epochs in the observation time period to obtain observation data on L multiplied by m multiplied by n puncture points;
calculating the total electron content in the zenith direction on each puncture point according to the observation data;
establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points, and calculating a model coefficient;
predicting ionospheric correction parameters of a target time period after the observation time period according to the quasi-real-time ionospheric correction model of the low-density network region and the model coefficient;
and (4) combining the ionospheric correction parameters, and carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology to obtain a positioning result.
In one embodiment of the invention, calculating zenith direction total electron content on each puncture site from the observation data comprises:
calculating a first total electron content under double-frequency observation when code measurement pseudo-range observation is utilized according to the observation data;
calculating a second total electron content under the dual-frequency observation when the carrier phase is observed according to the observation data;
and calculating the zenith direction total electron content on each puncture point by combining the first total electron content, the second total electron content and the satellite altitude angle.
In one embodiment of the present invention, calculating a first total electron content under dual frequency observation using code-measuring pseudorange observation according to the observation data comprises:
calculating a first geometric distance from the satellite to the receiver when observed with the code-measuring pseudorange:
wherein ρ' is a pseudo range, f is an observation frequency, s is a signal propagation path, and Ne is an electron density;
calculating the first total electron content using the first frequency, the second frequency and the first geometric distance under dual frequency observation:
TECG＝9.52437(ρ′1-ρ′2)
wherein ,TECGIs the first total electron content, ρ'1Is a pseudo range, rho ', during observation at a first frequency'2Is the pseudorange observed using the second frequency.
In one embodiment of the invention, calculating a second total electron content under the dual-frequency observation using carrier phase observation from the observation data comprises:
calculating a second geometric distance from the satellite to the receiver when observed using the carrier phase:
wherein ρ' is a pseudo range, f is an observation frequency, s is a signal propagation path, and Ne is an electron density;
calculating the second total electron content using the first frequency, the second frequency, and the second geometric distance under the dual-frequency observation:
wherein ,N1Is the integer ambiguity of the first carrier observation,
is a first carrier observation, N2Is the integer ambiguity of the second carrier observation,
is a second carrier observation.
In one embodiment of the present invention, the zenith direction total electron content on each puncture point is:
VTEC＝TEC·cosZ
wherein, TEC is the combined value of the first total electron content and the second total electron content, Z is the zenith distance of the satellite on the puncture point, and cosZ is the satellite altitude angle.
In one embodiment of the present invention, establishing a low density network region quasi-real-time ionospheric correction model based on the zenith direction total electron content on the L × m × n puncture points comprises:
selecting a surface fitting model VTEC ═ f (B, L, t), according to the L multiplied by m multiplied by nConstructing latitude by total electron content in zenith direction on puncture point
And sun angle difference S-S0Forming a near real-time ionospheric correction model of the low-density grid region:
wherein ,EijIn order to be the coefficients of the first model,
is the geographical latitude of the survey area,
is the geographical latitude of the central point of the measuring area, S is the difference of the solar time angles, S0Is the center point of the measuring region
Angular difference of sun at central time of observation period, (S-S)0)＝(λ-λ0)+(t-t0) λ is the geographic longitude of the puncture point, λ0Is the geographical longitude of the central point of the measuring area, t is the observation time, t0For reference time, m is the number of monitoring stations and n is the number of satellites.
In one embodiment of the invention, calculating the first model coefficients comprises:
the first model coefficients are calculated using a least squares method.
In an embodiment of the present invention, predicting an ionospheric correction parameter of a target time period after the observation time period according to the near-real-time ionospheric correction model of the low-density grid region and the model coefficient includes:
predicting the total electron content in the zenith direction of the target time period according to the quasi-real-time ionosphere correction model of the low-density network region and the model coefficient;
establishing a prediction model according to the total electron content in the zenith direction obtained by prediction:
wherein ,
mfjfor mapping functions, DCBrIs a receiver differential code bias, beta is a receiver differential code bias coefficient factor, a0,a1,a2For ionospheric correction parameters, j is the jth satellite, latjTo calculate the latitude of the point at the ionospheric puncture point,
is the latitude, lon, of the regional net reference point at the ionosphere puncture pointjTo calculate the longitude of a point at the ionospheric puncture point,
longitude of a regional network reference point at an ionosphere puncture point;
and calculating the ionospheric correction parameters according to the prediction model.
In an embodiment of the present invention, in combination with the ionospheric correction parameters, a real-time carrier phase differential positioning technique is used to perform real-time positioning, so as to obtain a positioning result, where the positioning result includes:
constructing an RTK carrier interplanetary double-difference observation equation according to a basic difference principle:
wherein ,tiDenotes the observation time, λLiIndicating frequency point LiV represents a interstation single difference, Δ represents an interstellar double difference, φ represents a carrier phase observation, R represents a station separation between a satellite and a station, N represents an ambiguity, i, j represents the ith and jth satellites, p1,2 represents 1,2, two different satellitesThe station(s) of (a) is (are) connected,
the delay in the troposphere is indicated,
indicating frequency point LiThe delay of the ionospheric layer above,
indicating frequency point LiOf the multipath effect, ε (φ)Li) Representing residual noise;
calculating the frequency point L by using the ionosphere correction parametersiIonospheric delay above
And solving the RTK carrier interplanetary double-difference observation equation to obtain the positioning result.
Another embodiment of the present invention provides a distributed big dipper position service center RTK product positioning device, including:
the data acquisition module is used for acquiring observation data on L multiplied by m multiplied by n puncture points obtained by performing double-frequency observation on n satellites from m monitoring stations under L observation epochs in an observation period;
the data processing module is used for calculating the total electron content in the zenith direction on each puncture point according to the observation data;
the model establishing module is connected with the data processing module and used for establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points and calculating a model coefficient;
the parameter prediction module is connected with the model establishing module and used for predicting the ionospheric correction parameters of a target time period after the observation time period according to the near-real-time ionospheric correction model of the low-density network area and the model coefficients;
and the real-time positioning module is connected with the parameter prediction module and used for carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology in combination with the ionosphere correction parameters to obtain a positioning result.
Compared with the prior art, the invention has the beneficial effects that:
according to the distributed Beidou position service center RTK product positioning method, satellites are observed from the monitoring station in the ground observation network, the low-density network area quasi-real-time ionosphere correction model is established for ionosphere delay correction through the ground observation network, and the transmission distance between the control center and the base station and between the control center and the mobile station is reduced, so that the cost is greatly saved, the real-time performance of the RTK is guaranteed while the short-distance transmission is realized, the user experience is improved, and the large-area popularization cost is reduced.
Drawings
Fig. 1 is a schematic flowchart of a distributed big dipper position service center RTK product positioning method provided by an embodiment of the present invention;
FIG. 2 is a schematic diagram of a process for ionospheric delay correction according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a real-time carrier phase differential positioning technique for real-time positioning according to an embodiment of the present invention;
fig. 4 is a schematic processing flow chart of performing real-time positioning by using a real-time carrier phase differential positioning technique according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a distributed big dipper position service center RTK product positioning device provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Example one
Referring to fig. 1 and fig. 2, fig. 1 is a schematic flowchart of a positioning method for a distributed beidou location service center RTK product according to an embodiment of the present invention, and fig. 2 is a schematic flowchart of a ionospheric delay correction according to an embodiment of the present invention.
The satellite signal is an electromagnetic wave transmitted in the ionosphereThe phase velocity (propagation velocity of the phase of a satellite signal of a single frequency) V of the broadcastpWith refractive index n of phase in ionospherePThe following relationships exist between:
where c is the speed of light in vacuum, nPIs the refractive index of the phase in the ionosphere.
And the phase refractive index nPCan be expressed as:
np＝1-K1Nef-2±K2Ne(H0cosθ)f-3-K3Ne3f-4 (2)
in the formula (2), the reaction mixture is,
in the formulae (2) and (3), Ne is an electron density, i.e., the number of electrons contained in a unit volume, the number of common electrons/m3To represent; m is the mass of the electron, m is 9.1096 × 10-31kg; e is the charge value of the electron, e is 1.6022 × 10-19c；ε0Is the dielectric coefficient in vacuum, epsilon0＝8.8542×10-12F/m；H0Is the magnetic field strength of the earth magnetic field; mu.s0Is the magnetic permeability in vacuum; theta is an included angle between the direction of the geomagnetic field and the propagation direction of the satellite signals; f is the frequency of the satellite signal.
Substituting the above values into equations (2) and (3), and substituting the third term (f) on the right side of the medium sign in equation (2)-3Term) is less than or equal to 10-9Item four (f)-4Term) is less than or equal to 10-10Generally, they are all negligible. The following approximate formula is then obtained:
the phase velocity V propagating in the ionosphere is thus obtainedp：
The second term (containing f) in the formula (5)-2Term) generally has a value of 10-6～10-7。
In the formula, V ispNot the material propagation velocity but the propagation velocity of the phase of the satellite signal (electromagnetic wave) in the ionosphere. In carrier phase measurement, the carrier phase is simply the phase velocity VpPropagating in the ionosphere. Similarly, the propagation velocity V of a set of electromagnetic wave signals of different frequencies in the ionosphere as a wholeGReferred to as group velocity. VGAnd group refractive index n in ionosphereGThe following relationships exist between:
as with a single frequency, ignoring f-3Terms and f-4In the case of items:
thus, we obtain:
when the satellite is used for distance measurement, the distance measuring code transmitted by the satellite is at group velocity VGPropagating in the ionosphere. Outside the ionosphere, the signal still propagates at the speed of light c in vacuum (no other error is estimated) because the electron density Ne is zero.
Based on the theory, firstly, the system utilizes the base station resources under the reference station network to construct the reference station networks with different scales according to the distance between different stations; wherein, the distance between different stations can be set according to actual requirements. Then, for each reference station network, establishing a low-density network area quasi-real-time ionosphere correction model, and forming the low-density network area quasi-real-time ionosphere correction models in different areas by different reference station networks, so as to solve and obtain a plurality of model coefficients, further obtain ionosphere correction parameters by using the model coefficients, and perform positioning by combining an RTK product positioning method.
Referring to fig. 2, the procedure of ionospheric delay correction is: for the observation data file, data in the data file is extracted, and then carriers of all frequency bands are extracted through the original observation data file to calculate the TEC value. For the navigation data file, data in the data file are extracted firstly, then the satellite position is calculated by using the extracted data, and then the satellite altitude is calculated through the satellite position and the observation station coordinates. When all the satellites are not calculated, calculating the VTEC value of a certain satellite according to the TEC value and the satellite altitude; if all the satellites are completely calculated, model coefficients (namely conversion parameters) of the same satellite of each observation station are calculated, and therefore ionospheric correction parameters are obtained by means of the model coefficients and issued.
The positioning method specifically comprises the following steps:
and S1, selecting an observation time period, and performing double-frequency observation on n satellites from m monitoring stations under L observation epochs in the observation time period to obtain observation data on L multiplied by m multiplied by n puncture points.
For each reference station network, assuming that there are L observation epochs in the observation period, each epoch performs double-frequency observation on n satellites from m detection stations, thereby obtaining observation data on L × m × n puncture points.
Specifically, the length of the observation period is generally 2 to 4 hours. The source data in ionospheric delay modification is derived from observation data files and navigation data files, which may be in a Rinex format, as shown in fig. 2.
And S2, calculating the total electron content in the zenith direction on each puncture point according to the observation data.
The method specifically comprises the following steps:
and S21, calculating the first total electron content under the double-frequency observation when the code-measuring pseudo range is observed according to the observation data.
S211, calculating a first geometric distance from the satellite to the receiver when the code-measuring pseudo-range is used for observation.
Specifically, if the propagation time of the ranging code from the satellite to the receiver is Δ t', the geometric distance ρ from the satellite to the receiver is:
let c · Δ t 'be ρ', where ρ 'is the pseudorange, and convert the integration variable of the second term in equation (9) to ds ═ cdt, and then the integration interval Δ t' also becomes the signal propagation path s accordingly. Finally, the first geometric distance from the satellite to the receiver when the code-measuring pseudo-range is observed can be obtained:
the second term in equation (10) is the tropospheric delay correction that should be applied when using the ranging code for range measurements:
s212, calculating the first total electron content by using the first frequency, the second frequency and the first geometric distance under the double-frequency observation.
Specifically, when a code measurement pseudo range observation is adopted, a dual-frequency observation value (the dual-frequency observation value refers to two observation values with different frequencies, signals B1, B2 and B3 in a Beidou satellite navigation system respectively correspond to different frequencies, and the dual-frequency is a combination of the two signals with different frequencies) is utilized to determine ionospheric delay suffered by the observation values with different frequencies so as to eliminate the influence of the ionospheric delay, and a zenith direction total electron content VTEC value on a puncture point (an intersection point of a satellite signal propagation path and a central ionospheric layer) can be determined.
When code-measuring pseudo-range observation is adopted, under double-frequency observation, the method comprises the following steps according to the formula (10):
wherein ,TECGIs the first total electron content, ρ'1Is a pseudo range, rho ', during observation at a first frequency'2To observe pseudo-range using the second frequency, f1Is a first frequency, f2Is the second frequency, f1 and f2Are all fixed numerical values.
Further, f is1 and f2The numerical value of (2) is taken into the formula (12) to obtain:
TECG＝9.52437(ρ′1-ρ′2) (13)
wherein ,TECGAt 1016Electron/m2Is a unit; rho'1 and ρ′2In units of m.
Thereby obtaining a first total electron content observed using the code-measuring pseudorange.
And S22, calculating a second total electron content under the dual-frequency observation when the carrier phase is used for observation according to the observation data.
And S221, calculating a second geometric distance from the satellite to the receiver when the carrier phase is used for observation.
Specifically, a second geometric distance from the satellite to the receiver at the time of the carrier phase measurement is calculated by a method similar to the calculation of the first geometric distance, resulting in:
wherein ρ' is a pseudo range, f is an observation frequency, s is a signal propagation path, and Ne is an electron density; the second term in equation (14) is the tropospheric delay correction that should be applied when using carrier phase measurements:
in the formula (14), the compound represented by the formula (I),
wherein ：
is an observed value in carrier phase measurement, and consists of a whole-week count lnt (phi) and a fraction Fr (phi) less than one week; n is the integer ambiguity; λ is the carrier wavelength calculated from the speed of light c in vacuum.
As is clear from the formulae (11) and (15), only f is considered2Under the condition (1), tropospheric delay corrections of the code-measurement pseudorange observed value and the carrier phase observed value are the same in magnitude and opposite in sign.
S222, calculating the second total electron content by using the first frequency, the second frequency and the second geometric distance under the double-frequency observation.
Specifically, the frequency of the dual-frequency observation observed with the carrier phase coincides with the frequency of the dual-frequency observation observed with the code measurement pseudo-range.
The same method as that for calculating the first total electron content can be used to obtain:
wherein ,N1Is the integer ambiguity of the first carrier observation,
is a first carrier observation, N2Is the integer ambiguity of the second carrier observation,
is a second carrier observation.
And S23, calculating the zenith direction total electron content on each puncture point by combining the first total electron content, the second total electron content and the satellite altitude angle.
Specifically, after obtaining a first total electron content observed by using a code measurement pseudorange and a second total electron content observed by using a carrier phase, the zenith direction total electron content on each puncture point is obtained by using the following formula:
VTEC＝TEC·cosZ (17)
wherein, TEC is the combined value of the first total electron content and the second total electron content, Z is the zenith distance of the satellite on the puncture point, and cosZ is the satellite altitude angle.
S3, establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points, and calculating a model coefficient.
Specifically, a low-density network area quasi-real-time ionosphere correction model is established according to the VTEC value obtained through calculation.
The modeling method of the VTEC value is to select a surface fitting model VTEC ═ f (B, L, t) to fit the VTEC values, so as to establish a VTEC model of the area (coverage area of observed values of m monitoring stations) in the period. The model is that VTEC is regarded as latitude
And sun angle difference (S-S)0) As a function of (c). The specific expression is as follows:
wherein ,EijIn order to be the coefficients of the first model,
is the geographical latitude of the survey area,
is the geographical latitude of the central point of the measuring area, S is the difference of the solar time angles, S0Is the center point of the measuring region
Angular difference of sun at central time of observation period, (S-S)0)＝(λ-λ0)+(t-t0) λ is the geographic longitude of the puncture point, λ0Is the geographical longitude of the central point of the measuring area, t is the observation time, t0For reference time, m is the number of monitoring stations and n is the number of satellites.
The method for solving the model coefficient is to estimate the undetermined coefficient E in the formula (18) by using the least square method according to the VTEC value measured in the step S2ijThereby obtaining the model coefficient of the quasi-real-time ionosphere correction model in the low-density network area.
And S4, predicting the ionospheric correction parameters of the target time interval after the observation time interval according to the quasi-real-time ionospheric correction model of the low-density network area and the model coefficient.
And S41, predicting the total electron content in the zenith direction of the target time period according to the quasi-real-time ionosphere correction model of the low-density network area and the model coefficient.
Specifically, the total electron content in the zenith direction of a target time interval after an observation time interval is predicted according to the low-density network region quasi-real-time ionosphere correction model in the formula (18), wherein the target time interval is generally 20-30 minutes, namely, the total electron content VTEC value in the zenith direction of 20-30 minutes after the observation time interval is predicted according to the model and is used for navigation and user positioning.
And S42, establishing a prediction model according to the total electron content in the zenith direction obtained through prediction.
Specifically, the prediction model is:
wherein ,
mfjfor mapping functions, DCBrIs a receiver differential code bias, beta is a receiver differential code bias coefficient factor, a0,a1,a2For ionospheric correction parameters, j isThe jth satellite, latjTo calculate the latitude of the point at the ionospheric puncture point,
is the latitude, lon, of the regional net reference point at the ionosphere puncture pointjTo calculate the longitude of a point at the ionospheric puncture point,
the longitude of the regional network reference point at the ionosphere puncture point.
And S43, calculating the ionospheric correction parameters according to the prediction model.
Specifically, according to the prediction model, a third-order polynomial is constructed, so that the model coefficient is solved, and the ionosphere correction parameter a is obtained0,a1,a2。
The quasi-real-time ionosphere correction model in the low-density network region is fit by a certain mathematical model according to the VTEC value actually measured in a certain region in a certain time period, so that the change rule and the reason of the ionosphere delay are not required to be thoroughly understood. The main factors influencing the accuracy of the model are as follows: the number and the geographical distribution of the monitoring stations, the accuracy of the observed value and whether the adopted mathematical model is appropriate or not; some short-time, small-scale irregular changes in the ionosphere (long-time, large-scale changes can be observed and reflected into the model). Because the ionospheric delay can be accurately measured by using the dual-frequency observation value, the number of the satellites is small and the distribution is generally uniform, so that a more ideal result can be obtained by adopting the method.
And S5, combining the ionosphere correction parameters, and carrying out real-time positioning by using a real-time carrier phase differential positioning technology to obtain a positioning result.
Referring to fig. 3 and 4, fig. 3 is a schematic diagram of a real-time carrier phase differential positioning method for real-time positioning according to an embodiment of the present invention, and fig. 4 is a schematic diagram of a processing flow of the real-time carrier phase differential positioning method for real-time positioning according to an embodiment of the present invention.
The concrete method for carrying out real-time positioning by utilizing the real-time carrier phase differential positioning technology in combination with the ionosphere correction parameters comprises the following steps:
and S51, constructing an RTK carrier interplanetary double-difference observation equation according to the basic difference principle.
a) A reference station and a monitoring station are determined.
After the modeling of the ionosphere low-density area is completed, each reference station forming each reference station network becomes a reference station, the selection principle of the reference stations is determined by the distance, and generally, the closest distance reference station is preferably selected as a reference station P1(X, Y, Z), the station to be measured being a monitoring station P2(X, Y, Z) as shown in FIG. 3.
b) And (4) public satellite screening.
Due to the RTK technology requirements, it is necessary to determine the common satellite sequence observed simultaneously between the reference station and rover station as data preparation for the next solution.
c) The non-differential carrier phase corrects for flow errors.
Before a double-difference variance calculation model is constructed between a reference station and a mobile station, some errors need to be calculated, such as flow errors, and the errors cannot be ignored due to the relatively long distance between the reference station and the mobile station; when the distance between the reference station and the mobile station is relatively close, tropospheric error calculation values under the same satellite of the two stations are very close to 0, so that the error is selected to be calculated for the uniformity of the calculation model and the calculation method regardless of the distance between the reference station and the mobile station under the low-density base station network.
d) A reference star is selected.
In order to construct an optimal intersatellite double-difference model, the altitude angles of the public satellites constructed in the previous step are sequenced, the satellite with the highest altitude angle is selected as a reference satellite, and the other public satellites and the reference satellite construct intersatellite double-difference observation values.
e) And (5) constructing an observation equation.
By using a plurality of double-difference observation values, an RTK carrier interplanetary double-difference observation equation can be constructed according to a basic difference principle through a basic carrier observation equation of the GNSS:
wherein ,tiDenotes the observation time, λLiIndicating frequency point LiV represents interstation single difference, Δ represents interstellar double difference, Φ represents a carrier phase observation, R represents the station separation between a satellite and a station, N represents ambiguity, i, j represents the ith and jth satellites, p1,2 represents 1,2 two different stations,
the delay in the troposphere is indicated,
indicating frequency point LiThe delay of the ionospheric layer above,
indicating frequency point LiOf the multipath effect, ε (φ)Li) Representing residual noise.
S52, calculating the frequency point L by using the ionosphere correction parametersiIonospheric delay above
In general terms, the amount of the solvent to be used,
and
the value after the interstation interplanetary double difference is substantially 0,
since there is a strong correlation with space, when the distance between the reference station and the mobile station is close (less than 10Km), the value thereof is also substantially 0, but increases as the distance between the reference station and the mobile station increasesThe value of the sum cannot be 0, so that the ionospheric correction parameter a can be used0,a1,a2The prediction model of the sum formula (19) calculates the non-difference ionospheric delay of each station and each satellite
Then, to
Making a difference twice between the interstellar stations to obtain
And will be
And (3) solving the position in an RTK carrier interplanetary double-difference observation equation of an equation (20).
And S53, solving the RTK carrier interplanetary double-difference observation equation to obtain a positioning result.
Specifically, firstly, the solution is carried out to obtain the floating ambiguity, and the ambiguity is completely fixed once, so that a partial ambiguity fixing strategy is required to be adopted, the ambiguity is partially fixed under the combined action of the satellite noise ratio and the satellite observation continuous counting according to the criterion of partially fixing the satellite ambiguity, then the fixed ambiguity is substituted into the original equation to carry out constraint solution, other ambiguity fixing can be achieved through precision evaluation, then constraint information is updated, and finally, the ambiguity is fixed through a plurality of cycles, substituted into the normal equation of the original observation equation, and finally, the solution is carried out to obtain a result, so that a positioning result is obtained.
The embodiment provides a distributed Beidou position service center RTK product positioning method, which aims at the problems that the traditional centralized position service center is high in calculation pressure and high in cost caused by the fact that a large amount of data is transmitted, and the traditional RTK is limited by the length of a base line, an empirical ionosphere correction model cannot be well adapted to ionosphere delay correction in each area, and the like.
Example two
Referring to fig. 5, fig. 5 is a schematic structural diagram of a distributed big dipper position service center RTK product positioning device provided in an embodiment of the present invention, where the positioning device includes:
and the data processing module is used for calculating the total electron content in the zenith direction on each puncture point according to the observation data.
And the model establishing module is connected with the data processing module and used for establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points and calculating the model coefficient.
And the parameter prediction module is connected with the model establishing module and used for predicting the ionospheric correction parameters of a target time period after the observation time period according to the near-real-time ionospheric correction model of the low-density network area and the model coefficients.
And the real-time positioning module is connected with the parameter prediction module and used for carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology in combination with the ionosphere correction parameters to obtain a positioning result.
Please refer to embodiment one for specific execution steps of each module in the apparatus, which is not described in detail in this embodiment.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (10)
1. A distributed Beidou position service center RTK product positioning method is characterized by comprising the following steps:
selecting an observation time period, and observing n satellites from m monitoring stations under L observation epochs in the observation time period to obtain observation data on L multiplied by m multiplied by n puncture points;
calculating the total electron content in the zenith direction on each puncture point according to the observation data;
establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points, and calculating a model coefficient;
predicting ionospheric correction parameters of a target time period after the observation time period according to the quasi-real-time ionospheric correction model of the low-density network region and the model coefficient;
and (4) combining the ionospheric correction parameters, and carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology to obtain a positioning result.
2. The method of claim 1, wherein calculating zenith direction total electron content on each puncture point from the observation data comprises:
calculating a first total electron content under double-frequency observation when code measurement pseudo-range observation is utilized according to the observation data;
calculating a second total electron content under the dual-frequency observation when the carrier phase is observed according to the observation data;
and calculating the zenith direction total electron content on each puncture point by combining the first total electron content, the second total electron content and the satellite altitude angle.
3. The distributed big Dipper position service center RTK product positioning method of claim 2, wherein calculating a first total electron content under dual frequency observation using code-finding pseudorange observation from said observation data comprises:
calculating a first geometric distance from the satellite to the receiver when observed with the code-measuring pseudorange:
wherein ρ' is a pseudo range, f is an observation frequency, s is a signal propagation path, and Ne is an electron density;
calculating the first total electron content using the first frequency, the second frequency and the first geometric distance under dual frequency observation:
TECG＝9.52437(ρ′1-ρ′2)
wherein ,TECGIs the first total electron content, ρ'1Is a pseudo range, rho ', during observation at a first frequency'2Is the pseudorange observed using the second frequency.
4. The method of claim 2, wherein calculating a second total electron content under the dual-frequency observation using carrier phase observation from the observation data comprises:
calculating a second geometric distance from the satellite to the receiver when observed using the carrier phase:
wherein ρ' is a pseudo range, f is an observation frequency, s is a signal propagation path, and Ne is an electron density;
calculating the second total electron content using the first frequency, the second frequency, and the second geometric distance under the dual-frequency observation:
wherein ,N1Is the integer ambiguity of the first carrier observation,
is a first carrier observation, N2Is the integer ambiguity of the second carrier observation,
is a second carrier observation.
5. The method for positioning a distributed Beidou position service center RTK product according to claim 2, characterized in that the zenith direction total electron content on each puncture point is:
VTEC＝TEC·cosZ
wherein, TEC is the combined value of the first total electron content and the second total electron content, Z is the zenith distance of the satellite on the puncture point, and cosZ is the satellite altitude angle.
6. The method of claim 1, wherein establishing a low density network area quasi-real time ionosphere correction model based on the zenith direction total electron content over the L x m x n puncture points comprises:
selecting a surface fitting model VTEC (v-f (B, L, t)), and constructing a latitude according to the zenith direction total electron content on the Lxmxn puncture points
And sun angle difference S-S0Forming a near real-time ionospheric correction model of the low-density grid region:
wherein ,EijIn order to be the coefficients of the first model,
is the geographical latitude of the survey area,
is the geographical latitude of the central point of the measuring area, S is the difference of the solar time angles, S0Is the center point of the measuring region
Angular difference of sun at central time of observation period, (S-S)0)＝(λ-λ0)+(t-t0) λ is the geographic longitude of the puncture point, λ0Is the geographical longitude of the central point of the measuring area, t is the observation time, t0For reference time, m is the number of monitoring stations and n is the number of satellites.
7. The distributed Beidou position service center RTK product positioning method of claim 1, wherein calculating the first model coefficients comprises:
the first model coefficients are calculated using a least squares method.
8. The method of claim 1, wherein predicting ionospheric correction parameters for a target time period after the observation time period based on the low density network area near real-time ionospheric correction model and the model coefficients comprises:
predicting the total electron content in the zenith direction of the target time period according to the quasi-real-time ionosphere correction model of the low-density network region and the model coefficient;
establishing a prediction model according to the total electron content in the zenith direction obtained by prediction:
wherein ,
mfjfor mapping functions, DCBrFor receiver differential codesOffset, beta is a receiver differential code offset coefficient factor, a0,a1,a2For ionospheric correction parameters, j is the jth satellite, latjTo calculate the latitude of the point at the ionospheric puncture point,
is the latitude, lon, of the regional net reference point at the ionosphere puncture pointjTo calculate the longitude of a point at the ionospheric puncture point,
longitude of a regional network reference point at an ionosphere puncture point;
and calculating the ionospheric correction parameters according to the prediction model.
9. The method of claim 1, wherein the positioning of the RTK product by the distributed Beidou position service center is performed in real time by using a real-time carrier phase differential positioning technique in combination with the ionosphere correction parameters to obtain a positioning result, and comprises:
constructing an RTK carrier interplanetary double-difference observation equation according to a basic difference principle:
wherein ,tiDenotes the observation time, λLiIndicating frequency point Li(ii) a wavelength of (c) or (c),
representing interstation single differences, delta representing interstellar single differences,
representing interplanetary double differences, phi representing carrier phase observations, R representing station-to-station separation between satellites and stations, N representing ambiguities, i, j representing the i and j satellites, p1,2 representing 1,2 two different stations,
the delay in the troposphere is indicated,
indicating frequency point LiThe delay of the ionospheric layer above,
indicating frequency point LiOf the multipath effect, ε (φ)Li) Representing residual noise;
calculating the frequency point L by using the ionosphere correction parametersiIonospheric delay above
And solving the RTK carrier interplanetary double-difference observation equation to obtain the positioning result.
10. The utility model provides a distributing type big dipper position service center RTK product positioner, its characterized in that includes:
the data acquisition module is used for acquiring observation data on L multiplied by m multiplied by n puncture points obtained by performing double-frequency observation on n satellites from m monitoring stations under L observation epochs in an observation period;
the data processing module is used for calculating the total electron content in the zenith direction on each puncture point according to the observation data;
the model establishing module is connected with the data processing module and used for establishing a low-density network area quasi-real-time ionosphere correction model according to the total electron content in the zenith direction on the Lxmxn puncture points and calculating a model coefficient;
the parameter prediction module is connected with the model establishing module and used for predicting the ionospheric correction parameters of a target time period after the observation time period according to the near-real-time ionospheric correction model of the low-density network area and the model coefficients;
and the real-time positioning module is connected with the parameter prediction module and used for carrying out real-time positioning by utilizing a real-time carrier phase differential positioning technology in combination with the ionosphere correction parameters to obtain a positioning result.
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