CN118091718A - Method for improving UT1 calculation accuracy through low orbit satellite downlink navigation signal - Google Patents
Method for improving UT1 calculation accuracy through low orbit satellite downlink navigation signal Download PDFInfo
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Abstract
The invention discloses a method for improving UT1 resolving precision through a low-orbit satellite downlink navigation signal, which comprises the steps of preprocessing data of a pseudo-range observation value and a carrier phase observation value which are respectively corresponding to a GNSS satellite and a low-orbit satellite; then, double-difference processing is carried out between the satellites of the stations to obtain double-difference pseudo-range observed values and double-difference carrier phase observed values which correspond to the GNSS satellites and the low-orbit satellites respectively; and solving a global network solution product according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, and acquiring UT1-UTC from the global network solution product, and further acquiring UT1 from UT 1-UTC. According to the invention, the GNSS satellite and the low orbit satellite are combined to be used in the resolving process of the UT1, so that the accuracy of the global network resolving product resolved by the method is higher, and the resolving accuracy of the UT1 is improved.
Description
Technical Field
The invention belongs to the field of communication navigation remote sensing, and particularly relates to a method for improving the resolving precision of UT1 through a low-orbit satellite downlink navigation signal.
Background
The precise measurement of the earth rotation parameters is an important precondition for realizing the conversion between the celestial sphere reference system and the earth reference system, and plays an indispensable important role in the fields of aerospace measurement and control, deep space exploration, precise time service, satellite navigation and the like. The rotation parameters of the earth mainly comprise polar motion parameters、/>And UT1 (universal time) -UTC (coordinated universal time), where UT1-UTC represents the difference between universal time and coordinated universal time. There are various means of determining earth rotation parameters, and there are very long baseline interferometry techniques (Very Long Baseline Interfere, VLBI), satellite laser ranging techniques (SATELLITE LASER RANGING, SLR), combination satellite-based doppler orbit determination and radio positioning techniques (Doppler Orbitography and Radiopositioning Integrated by Satellite, DORIS), and global satellite navigation system techniques (Global Navigation SATELLITE SYSTEM, GNSS) that are relatively common at present. The earth rotation parameter measurement technology based on GNSS observation has unique advantages, and can provide stable routine earth rotation parameter products, which are mainly beneficial to relatively low cost of GNSS ground stations, wide ground station distribution, continuous observation and gradual increase of the number of satellites of each GNSS system nowadays. The UT1 solution is often performed simultaneously with GNSS satellite orbit determination and other series of parameter solutions, which is one of the fixed output products of global large GNSS analysis centers, including the international GNSS monitoring and evaluation system (international GNSS Monitoring & ASSESSMENT SYSTEM, IGMAS) in China, when performing GNSS global network solutions.
However, since the GNSS satellites are medium-high orbit satellites, the flying speed is limited, and the geometric variation with respect to each ground station on the earth is slow, which results in lower resolution of the GNSS world wide web solution product. Correspondingly, the resolution of UT1-UTC is lower.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a method for improving UT1 resolution by using low-orbit satellite downlink navigation signals.
The technical problems to be solved by the invention are realized by the following technical scheme:
the invention provides a method for improving UT1 resolving precision through a low orbit satellite downlink navigation signal, which comprises the following steps:
performing data preprocessing on pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellites and the low-orbit satellites respectively;
Respectively carrying out inter-station inter-satellite double-difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite;
According to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, calculating a global network solution product, acquiring UT1-UTC from the global network solution product, and acquiring UT1 from the UT 1-UTC; the global solution product includes a plurality of global solution parameters including the UT1-UTC.
Optionally, calculating a global network solution product according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value corresponding to the GNSS satellite and the low-orbit satellite respectively, and acquiring UT1-UTC from the global network solution product, including:
Under the condition of no fixed ambiguity, calculating a global network solution product according to the double-difference pseudo-range observed value and the double-difference carrier phase observed value which correspond to the GNSS satellite and the low-orbit satellite respectively;
taking a global solution product under the condition of unfixed ambiguity as an initial value, and performing integer ambiguity fixing processing on the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively to obtain the integer ambiguity of the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively;
Substituting the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite;
And re-calculating a global network solution product under the condition of fixed ambiguity according to the double-difference pseudo-range observation value corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation value, and acquiring UT1-UTC from the calculated global network solution product.
Optionally, the data preprocessing is performed on the pseudo-range observed value and the carrier phase observed value corresponding to each of the GNSS satellite and the low-orbit satellite, including:
and carrying out data preprocessing on pseudo-range observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an ionosphere-free combined single-point positioning method, and carrying out data preprocessing on carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an inter-station single-difference processing method.
Optionally, inter-station inter-satellite double-difference processing is performed on the pseudo-range observed value and the carrier phase observed value corresponding to each of the GNSS satellite and the low-orbit satellite after data preprocessing, to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value corresponding to each of the GNSS satellite and the low-orbit satellite, including:
For each GNSS satellite, obtaining a first inter-station single difference of pseudo-range observation values of the GNSS satellite on different ground stations;
For each two GNSS satellites, calculating the difference of single differences between the two GNSS satellites for the first stations of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two GNSS satellites;
For each GNSS satellite, obtaining a second inter-station single difference of carrier phase observed values of the GNSS satellite on different ground stations;
for every two GNSS satellites, calculating the difference of single differences between the two GNSS satellites and the second stations of the same ground station group, and taking the difference as a double-difference carrier phase observation value corresponding to the two GNSS satellites;
for each low-orbit satellite, calculating a third inter-station single difference of pseudo-range observation values of the low-orbit satellite to different ground stations;
For each two low-orbit satellites, calculating the difference of single differences between the two low-orbit satellites and a third station of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two low-orbit satellites;
for each low-orbit satellite, obtaining a fourth inter-station single difference of carrier phase observed values of the low-orbit satellite for different ground stations;
For each two low-orbit satellites, the difference of single differences between the two low-orbit satellites and a fourth station of the same ground station group is obtained and is used as a double-difference carrier phase observation value corresponding to the two low-orbit satellites.
Optionally, the global solution product specifically includes: ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock biases, low-orbit satellite clock biases, and the UT1-UTC.
According to the method for improving the UT1 resolving precision through the downlink navigation signals of the low-orbit satellite, data preprocessing is carried out on pseudo-range observed values and carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively; respectively carrying out inter-station inter-satellite double-difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite; according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, calculating a global network solution product, acquiring UT1-UTC from the global network solution product, and acquiring UT1 from UT 1-UTC; the global solution product includes a plurality of global solution parameters including UT1-UTC.
Compared with the prior art, the method has the advantages that the number of satellites is obviously increased in the process of resolving the UT1-UTC by combining the GNSS satellites and the low-orbit satellites, the GNSS satellites can be used for covering the earth in a large range, continuous observation values can be provided, and the low-orbit satellites and the ground station have the characteristics of quick relative geometric change and more observation values, so that the accuracy of the global network resolving product resolved by the method is higher, the UT1-UTC with higher accuracy can be obtained from the global network resolving product, and the UT1 with higher accuracy can be obtained from the UT1-UTC, and the resolving accuracy of the UT1 is improved.
The present invention will be described in further detail with reference to the accompanying drawings.
Drawings
Fig. 1 is a flowchart of a method for improving UT1 resolution by using a low-orbit satellite downlink navigation signal according to an embodiment of the present invention;
Fig. 2 is a flowchart of another method for improving UT1 resolution by using a low-orbit satellite downlink navigation signal according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
Accurate measurement of UT1-UTC variation is an important precondition for realizing conversion between a celestial sphere reference system and an earth reference system, and the difference between UT1 and UTC is caused by factors such as instability of earth rotation speed, perturbation factors and the like. UT1 represents the world time, is the time determined according to the earth rotation period, can accurately reflect the angular position of the earth in space, and is the time scale used by astronomical world. UTC represents coordinated universal time, and is a time metering system that is as close to universal time as possible in time. Therefore, the accuracy of the UT1-UTC change is obtained by examining the resolution accuracy of UT 1. In order to solve the problem of lower resolving precision of UT1, the embodiment of the invention provides a method for improving the resolving precision of UT1 through a downlink navigation signal of a low-orbit satellite.
Referring to fig. 1, fig. 1 is a schematic flow chart of a method for improving UT1 resolving precision by low-orbit satellite downlink navigation signals, which is provided by the embodiment of the invention, and includes the following steps:
step S101, data preprocessing is performed on pseudo-range observed values and carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites respectively.
In the embodiment of the invention, the GNSS satellites are medium-high orbit satellites, and the orbit period is long, so that the GNSS satellites can cover the earth in a large range, and the ground station has better tracking and communication capabilities. The low-orbit satellites have a low satellite orbit, have a fast relative geometry with respect to the ground station, and can provide more observations due to the high number of low-orbit satellites.
The pseudorange observations refer to the distances calculated by the propagation time of the satellite transmitted pseudorange signals to the ground station, which measured distances contain errors, i.e. the distances represented by the observations are not true distances, and thus the observations are pseudorange observations.
In an embodiment of the present invention, for a GNSS satellite, the pseudorange observations of the GNSS satellite are determined by the propagation time of the GNSS satellite pseudorange signals transmitted by the GNSS satellite to the ground station. For a low-orbit satellite, the pseudorange observations for the low-orbit satellite are determined by the propagation time of the low-orbit satellite downlink pseudorange signal transmitted by the low-orbit satellite to the ground station.
The carrier phase observations are measures of the phase difference between the carrier signal transmitted by the satellite and the local oscillator signal of the ground station receiver after the ground station has locked the satellite.
In the embodiment of the present invention, for a GNSS satellite, the carrier phase observation value is a measured value of the phase difference between the carrier signal transmitted by the GNSS satellite and the local oscillation signal of the ground station receiver after the GNSS satellite is locked by the ground station receiver. For a low-orbit satellite, the carrier phase observation is a measurement of the phase difference between the carrier signal transmitted by the low-orbit satellite and the local oscillator signal of the ground station after the low-orbit satellite is locked by the ground station receiver.
Performing data preprocessing on pseudo-range observed values and carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites respectively, wherein the data preprocessing comprises the following steps:
and preprocessing the pseudo-range observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an ionosphere-free combined single-point positioning method, and preprocessing the carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an inter-station single-difference processing method.
In the embodiment of the invention, the ionosphere-free combination technology refers to a linear combination technology for eliminating first-order ionosphere delay by using double-frequency observation, and can greatly reduce the influence of the ionosphere delay on the propagation of signals of GNSS satellites and low-orbit satellites. Single point positioning is a basic positioning method, which refers to a method for determining the position of a ground station according to satellite broadcast ephemeris and pseudo-range observations of the ground station, and is used for performing rough navigation positioning.
In the embodiment of the invention, the step of preprocessing data of pseudo-range observation values corresponding to GNSS satellites and low-orbit satellites by adopting an ionosphere-free combined single-point positioning method comprises the following steps:
(1) And preprocessing GNSS pseudo-range observation by using GNSS satellite broadcast ephemeris, GNSS satellite pseudo-range signals and ground station priori coordinates and adopting a ionosphere-free combined single-point positioning method.
The broadcast ephemeris of the GNSS satellites is determined and provided by a ground control part of the global positioning system, and is a data format in which the satellite navigation system broadcasts relevant information of the GNSS satellites to a ground station through radio signals so that a user can accurately position and navigate. The GNSS satellite broadcast ephemeris includes GNSS satellite related information such as GNSS satellite number, GNSS satellite count, GNSS satellite clock bias, etc.
(2) And preprocessing the low-orbit satellite downlink pseudo-range observation by using the low-orbit satellite primary orbit, the low-orbit satellite downlink pseudo-range signal and the prior coordinates of the ground station and adopting a method of combining single-point positioning without an ionosphere.
The low-orbit satellite initial orbit refers to a low-orbit satellite orbit with slightly poorer accuracy used for calculation by initial substitution.
In the embodiment of the invention, the pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite respectively are subjected to data preprocessing by adopting an ionosphere-free combined single-point positioning method, and the pseudo-range observation can be subjected to coarse difference elimination by calculating residual errors.
In the embodiment of the invention, the data preprocessing of the carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite by adopting the inter-station single difference processing method comprises the following steps:
And respectively carrying out inter-station single difference processing on carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite. The single difference between stations refers to the primary difference between observations of the same satellite at a single time by two ground stations. The satellite clock error can be eliminated through the single difference between stations, and delay errors of an ionosphere, a troposphere and the like can be greatly reduced.
After single difference processing among stations, carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites are preprocessed by using priori GNSS satellite orbits, priori low-orbit satellite orbits and priori ground station coordinates, cycle slip detection is carried out, and outliers and unreasonable values in the carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites are removed.
In the embodiment of the invention, poor-quality observations can be removed by carrying out data preprocessing on the pseudo-range observation values and the carrier phase observation values corresponding to the GNSS satellites and the low-orbit satellites, and a more stable and reliable data base is provided for subsequent data processing.
Step S102, inter-station inter-satellite double-difference processing is respectively carried out on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing, and the double-difference pseudo-range observed value and the double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite are obtained.
In the embodiment of the invention, the single difference between stations refers to the difference between the observed values of two ground stations on the same satellite, and the observed value refers to a pseudo-range observed value or a carrier phase observed value. After two satellites are observed on two different ground stations, two inter-station single differences are formed, and the process of performing group difference on the two inter-station single differences is called inter-station inter-satellite double differences.
Performing inter-station inter-satellite double-difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite, wherein the method comprises the following steps:
For each GNSS satellite, obtaining a first inter-station single difference of pseudo-range observation values of the GNSS satellite on different ground stations; for every two GNSS satellites, the difference of single differences between the two GNSS satellites and the first station of the same ground station group is obtained and is used as a double-difference pseudo-range observation value corresponding to the two GNSS satellites.
For each GNSS satellite, obtaining a second inter-station single difference of carrier phase observed values of the GNSS satellite on different ground stations; for every two GNSS satellites, the difference of single differences between the two GNSS satellites and the second station of the same ground station group is obtained and is used as a double-difference carrier phase observation value corresponding to the two GNSS satellites.
For each low-orbit satellite, calculating a third inter-station single difference of pseudo-range observation values of the low-orbit satellite to different ground stations; and solving the difference of single differences between the two low-orbit satellites for the third stations of the same ground station group aiming at each two low-orbit satellites, and taking the difference as a double-difference pseudo-range observation value corresponding to the two low-orbit satellites.
For each low-orbit satellite, obtaining a fourth inter-station single difference of carrier phase observed values of the low-orbit satellite for different ground stations; for each two low-orbit satellites, the difference of single differences between the two low-orbit satellites and a fourth station of the same ground station group is obtained and is used as a double-difference carrier phase observation value corresponding to the two low-orbit satellites.
In the embodiment of the invention, errors such as satellite clock error, ground clock error, satellite hardware delay, receiver hardware delay and the like can be eliminated by respectively carrying out inter-station inter-satellite double difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing.
Step S103, calculating a global network solution product according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, acquiring UT1-UTC from the global network solution product, and acquiring UT1 from UT1-UTC.
Specifically, the global solution product includes a plurality of global solution parameters, and the global solution product includes ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock biases, low-orbit satellite clock biases, and UT1-UTC. Therefore, UT1-UTC may be obtained from the Global solution product, and UT1 may be obtained from UT1-UTC.
Wherein, the ground station coordinates refer to the coordinates of the reference point of the ground station in a ground fixed coordinate system.
Tropospheric parameters refer to zenith tropospheric parameters.
Satellite orbit is the coordinates of a satellite in a fixed ground coordinate system.
Satellite clock skew refers to the difference between an atomic clock on a satellite and a reference time scale (e.g., GPST). Correspondingly, the GNSS satellite clock difference is the difference between an atomic clock on the GNSS satellite and a reference time scale; the low orbit satellite clock difference is the difference between the atomic clock on the low orbit satellite and the reference time scale.
According to the method, initial values calculated according to various models are substituted in the calculation process according to the double-difference pseudo-range observed value and the double-difference carrier phase observed value which correspond to the GNSS satellite and the low-orbit satellite respectively, and then the global network solution product is calculated step by step according to a least square method. The models comprise an earth gravity field model, a Saastamoinen troposphere model, a relativistic effect model and the like.
For a specific resolving procedure, reference is made to the prior art.
The calculated global network solution product can obtain UT1-UTC from the global network solution product, and then UT1 can be obtained from the UT 1-UTC.
Compared with the prior art, the method and the device have the advantages that the number of satellites is remarkably increased in the process of resolving the UT1-UTC by combining the GNSS satellites and the low-orbit satellites, the GNSS satellites can be used for covering the earth area in a large range, continuous observation values and relative geometric changes of the low-orbit satellites and the ground station are fast, more observation values can be provided, and therefore the global network resolving product resolved by the method and the device is higher in precision, UT1-UTC with higher precision can be obtained from the global network resolving product, UT1 with higher precision is obtained from the UT1-UTC, and therefore resolving precision of UT1 is improved.
In the embodiment of the invention, the specific steps of calculating the global network solution product according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which are respectively corresponding to the GNSS satellite and the low-orbit satellite and obtaining the UT1-UTC from the global network solution product comprise the following steps:
and 1, under the condition of no fixed ambiguity, calculating a global network solution product according to the double-difference pseudo-range observed value and the double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite.
In the embodiment of the invention, the ambiguity is whole-cycle ambiguity. Integer ambiguity refers to the number of integer periods of carrier phase measured from the satellite to the ground station, and is an unknown quantity. Unfixed ambiguity can be understood as floating ambiguity. In particular, the floating ambiguity, i.e., the integer ambiguity of the carrier phase, is not fixed to an integer, but is replaced by an estimate of floating point.
Under the condition of no fixed ambiguity, according to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which are respectively corresponding to the GNSS satellite and the low-orbit satellite, substituting the initial value calculated according to various models in the resolving process, calculating the difference between the double-difference pseudo-range observation value and the double-difference carrier phase observation value which are respectively corresponding to the GNSS satellite and the low-orbit satellite and the initial value calculated by various models, and resolving step by step according to a least square method to obtain an initial global network solution product. Compared with the prior art that only the related data of the GNSS satellite is used for solving the global network solution product, the accuracy of each parameter in the initial global network solution product obtained at the moment is improved compared with the accuracy of each parameter in the global network solution product under the condition of unfixed ambiguity in the prior art because the double-difference pseudo-range observation value and the double-difference carrier phase observation value of the low-orbit satellite are introduced, but in order to further improve the accuracy, the following operation can be performed.
And 2, performing integer ambiguity fixing processing on the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite by taking a global solution product under the condition of unfixed ambiguity as an initial value, so as to obtain the integer ambiguity of the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite.
In the embodiment of the invention, the global solution product under the condition of no fixed ambiguity is taken as an initial value to carry out the fixed processing of the integer ambiguity. For the integer ambiguity fixing process, floating ambiguity is mapped to the integer domain. The specific operation manner of the integer ambiguity fixing process may be implemented by a kalman algorithm or an LAMBDA algorithm (an iterative algorithm for solving the problem of function optimization), and the like, and may be specifically referred to the prior art, which is not limited herein.
In the embodiment of the invention, the integer ambiguity of the double-difference carrier phase observed value corresponding to the GNSS satellite and the low-orbit satellite is obtained, namely, the fixed solution of the integer ambiguity of the double-difference carrier phase observed value corresponding to the GNSS satellite and the low-orbit satellite is obtained. The fixed solution indicates that the integer ambiguity of the double-difference carrier phase observations corresponding to the GNSS satellite and the low-orbit satellite respectively has been solved, and is the most accurate solution type of the integer ambiguity.
And 3, substituting the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite.
In the embodiment of the invention, because the integer ambiguity is already resolved, the integer ambiguity of the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite can be substituted into the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite, and the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite can be updated to more correct values.
And 4, re-calculating a global network solution product under the condition of fixed ambiguity according to the double-difference pseudo-range observation value corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation value, and acquiring UT1-UTC from the calculated global network solution product.
In the embodiment of the invention, the whole-cycle ambiguity is substituted into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, so that the global solution product under the condition of fixed ambiguity can be recalculated according to the double-difference pseudo-range observation values corresponding to the GNSS satellite and the low-orbit satellite and the double-difference carrier phase observation values substituted with the whole-cycle ambiguity, thereby obtaining the global solution product under the condition of fixed ambiguity with higher parameter accuracy. And then obtaining the UT1-UTC from the global network solution products with higher parameter precision, thereby improving the precision of the UT1-UTC solution.
In the embodiment of the invention, the whole-cycle ambiguity is solved by using the global solution product under the condition of not fixing the ambiguity, and because the fixed solution of the whole-cycle ambiguity is the most accurate solution type of the whole-cycle ambiguity, the precision of each parameter of the global solution product under the condition of the fixed ambiguity calculated based on the solved whole-cycle ambiguity is further improved. Therefore, according to the global network solution product under the condition of fixed ambiguity, the UT1-UTC with higher precision can be obtained.
It will be appreciated that the accuracy of the parameters in the global solution product without fixed ambiguity is lower than the accuracy of the parameters in the global solution product with fixed ambiguity.
In order to further explain how to improve the UT1 resolution by using the low-orbit satellite downlink navigation signal, another method for improving the UT1 resolution by using the low-orbit satellite downlink navigation signal is provided in the embodiment of the present invention, referring to fig. 2, fig. 2 is a flowchart of another method for improving the UT1 resolution by using the low-orbit satellite downlink navigation signal, which is provided in the embodiment of the present invention, and includes the following steps:
in step S201, data preprocessing is performed on pseudo-range observations corresponding to the GNSS satellites and the low-orbit satellites.
The specific data preprocessing process is described in step S101, and will not be described herein.
In step S202, GNSS satellite carrier phase pre-processing and low orbit satellite carrier phase pre-processing are performed.
Specifically, the inter-station single difference processing method is adopted to respectively perform data preprocessing on carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite, so that satellite clock differences can be eliminated, and delay errors of an ionosphere, a troposphere and the like can be greatly reduced.
Step S203, floating ambiguity global solution.
In the embodiment of the present invention, floating ambiguity can be understood as a non-fixed ambiguity, i.e. a resolving global net solution product in case of non-fixed ambiguity.
Firstly, inter-station inter-satellite double difference processing is needed to be carried out on pseudo-range observed values and carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites respectively so as to eliminate errors such as satellite clock differences, ground clock differences, satellite hardware delays, receiver hardware delays and the like, and double-difference pseudo-range observed values and double-difference carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites are obtained.
The meaning of inter-station inter-star double difference is as described above and will not be described in detail herein.
After obtaining the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, under the condition of not fixing the ambiguity, resolving a global network solution product according to the obtained double-difference pseudo-range observation value and the obtained double-difference carrier phase observation value to obtain a preliminary global network solution product, and completing the floating ambiguity global network solution.
In step S204, GNSS satellite integer ambiguity is fixed and low orbit satellite integer ambiguity is fixed.
In the embodiment of the present invention, the initial global solution product obtained in step S203 performs the integer ambiguity fixing process on the dual-difference carrier phase observations corresponding to the GNSS satellite and the low-orbit satellite, so as to obtain the integer ambiguity of the dual-difference carrier phase observations corresponding to the GNSS satellite and the integer ambiguity of the dual-difference carrier phase observations corresponding to the low-orbit satellite.
Step S205, fix the global solution of ambiguity.
After the integer ambiguity of the double-difference carrier phase observation value corresponding to the GNSS satellite and the integer ambiguity of the double-difference carrier phase observation value corresponding to the low-orbit satellite are obtained, the integer ambiguity is respectively substituted into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite, so that the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite are updated.
In order to further improve the precision of each parameter in the global network solution product, the global network solution product under the condition of fixed ambiguity can be recalculated according to the double-difference pseudo-range observation value corresponding to each of the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation value, so that the global network solution product under the condition of fixed ambiguity can be obtained, and further, UT1-UTC with higher precision can be obtained according to the global network solution product under the condition of fixed ambiguity, and then UT1 with higher precision is obtained from UT 1-UTC.
In the embodiment of the invention, the downlink navigation signals of the low-orbit satellites and the signals of the GNSS satellites are integrated into the resolving process of the UT1, so that the number of the observation values is greatly increased, the GNSS satellites can be utilized to cover the earth in a large range, the characteristics of continuous observation values and the characteristics of rapid relative geometric change of the low-orbit satellites and the ground station can be provided, and more observation values can be provided, so that the resolving precision of the resolved global network is higher, and therefore, the UT1-UTC with higher precision can be obtained from the global network resolving product, and the UT1 with higher precision can be obtained from the UT1-UTC, thereby improving the resolving precision of the UT 1.
It should be noted that the terms "first," "second," and the like are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. The implementations described in the following exemplary examples do not represent all implementations consistent with the invention. Rather, they are merely examples of methods consistent with aspects of the invention.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Further, one skilled in the art can engage and combine the different embodiments or examples described in this specification.
Although the invention is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings and the disclosure. In the description of the present invention, the word "comprising" does not exclude other elements or steps, the "a" or "an" does not exclude a plurality, and the "a" or "an" means two or more, unless specifically defined otherwise. Moreover, some measures are described in mutually different embodiments, but this does not mean that these measures cannot be combined to produce a good effect.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (5)
1. A method for improving UT1 resolution via low-orbit satellite downlink navigation signals, the method comprising:
performing data preprocessing on pseudo-range observation values and carrier phase observation values corresponding to the GNSS satellites and the low-orbit satellites respectively;
Respectively carrying out inter-station inter-satellite double-difference processing on the pseudo-range observed value and the carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite after data preprocessing to obtain a double-difference pseudo-range observed value and a double-difference carrier phase observed value which are respectively corresponding to the GNSS satellite and the low-orbit satellite;
According to the double-difference pseudo-range observation value and the double-difference carrier phase observation value which correspond to the GNSS satellite and the low-orbit satellite respectively, calculating a global network solution product, acquiring UT1-UTC from the global network solution product, and acquiring UT1 from the UT 1-UTC; the global solution product includes a plurality of global solution parameters including the UT1-UTC.
2. The method of claim 1, wherein resolving a global solution product from the double-differential pseudorange observations and the double-differential carrier-phase observations corresponding to each of the GNSS satellites and the low-orbit satellites, and obtaining UT1-UTC from the global solution product, comprises:
Under the condition of no fixed ambiguity, calculating a global network solution product according to the double-difference pseudo-range observed value and the double-difference carrier phase observed value which correspond to the GNSS satellite and the low-orbit satellite respectively;
taking a global solution product under the condition of unfixed ambiguity as an initial value, and performing integer ambiguity fixing processing on the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively to obtain the integer ambiguity of the double-difference carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively;
Substituting the integer ambiguity of the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite into the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite so as to update the double-difference carrier phase observation values corresponding to the GNSS satellite and the low-orbit satellite;
And re-calculating a global network solution product under the condition of fixed ambiguity according to the double-difference pseudo-range observation value corresponding to the GNSS satellite and the low-orbit satellite and the updated double-difference carrier phase observation value, and acquiring UT1-UTC from the calculated global network solution product.
3. The method of claim 1, wherein the data preprocessing of the pseudorange observations and the carrier phase observations for each of the GNSS satellites and the low-orbit satellites comprises:
and carrying out data preprocessing on pseudo-range observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an ionosphere-free combined single-point positioning method, and carrying out data preprocessing on carrier phase observed values corresponding to the GNSS satellite and the low-orbit satellite respectively by adopting an inter-station single-difference processing method.
4. The method of claim 1, wherein performing inter-station inter-satellite double difference processing on the pseudo-range observed values and the carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites after the data preprocessing respectively to obtain double-difference pseudo-range observed values and double-difference carrier phase observed values corresponding to the GNSS satellites and the low-orbit satellites respectively, comprises:
For each GNSS satellite, obtaining a first inter-station single difference of pseudo-range observation values of the GNSS satellite on different ground stations;
For each two GNSS satellites, calculating the difference of single differences between the two GNSS satellites for the first stations of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two GNSS satellites;
For each GNSS satellite, obtaining a second inter-station single difference of carrier phase observed values of the GNSS satellite on different ground stations;
for every two GNSS satellites, calculating the difference of single differences between the two GNSS satellites and the second stations of the same ground station group, and taking the difference as a double-difference carrier phase observation value corresponding to the two GNSS satellites;
for each low-orbit satellite, calculating a third inter-station single difference of pseudo-range observation values of the low-orbit satellite to different ground stations;
For each two low-orbit satellites, calculating the difference of single differences between the two low-orbit satellites and a third station of the same ground station group, and taking the difference as a double-difference pseudo-range observation value corresponding to the two low-orbit satellites;
for each low-orbit satellite, obtaining a fourth inter-station single difference of carrier phase observed values of the low-orbit satellite for different ground stations;
For each two low-orbit satellites, the difference of single differences between the two low-orbit satellites and a fourth station of the same ground station group is obtained and is used as a double-difference carrier phase observation value corresponding to the two low-orbit satellites.
5. The method according to claim 1, characterized in that said global solution product comprises in particular: ground station coordinates, tropospheric parameters, GNSS satellite orbits, low-orbit satellite orbits, GNSS satellite clock biases, low-orbit satellite clock biases, and the UT1-UTC.
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