A low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solution

Abstract

The invention provides a low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solutions. The low-orbit enhanced GNSS PPP user terminal comprises a data receiving module, an information enhancement solution module and a precise single-point positioning solution module. Satellite-borne GNSS observation data and ground station network GNSS observation data are sent to the information enhancement solution module, and GNSS observation data and LEO observation data are sent to the precise single-point positioning solution module; the information enhancement solution module performs information enhancement solution; the obtained solution result is sent to the precise single-point positioning solution module; the precise single-point positioning solution module completes the joint PPP positioning solution of the GNSS observation data and the LEO observation data, and uses the multi-information enhancement solution result to perform error correction on PPP, thereby obtaining a low-orbit enhanced GNSS PPP positioning result.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite navigation enhancement, and in particular relates to a low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solution. Background Art

[0002] PPP technology uses the precise satellite orbits and satellite clock errors calculated from GNSS observation data from global reference stations to perform positioning and calculation on the phase and pseudo-range observations collected by a single GNSS receiver, thus providing reliable centimeter-level positioning accuracy services to users anywhere in the world. However, due to the slow convergence speed of PPP and the problem that the signal is easily blocked and interfered in motion or complex environments, its real-time, continuity and reliability are poor.

[0003] In recent years, the idea of ​​using low earth orbit (LEO) satellites to enhance GNSS PPP has been proposed. The enhancement of GNSS PPP by low earth orbit can be divided into information enhancement and signal enhancement. Information enhancement refers to the use of satellite-based observation data provided by low earth orbit satellites, and the enhanced correction information is calculated jointly with ground-based observation data, and broadcast to users to correct the errors of PPP positioning to improve navigation positioning accuracy and reliability. Signal enhancement refers to the method of transmitting navigation signals through low earth orbit satellites, and users receiving GNSS navigation signals and low earth orbit satellite navigation signals at the same time, thereby improving PPP positioning accuracy and availability. Summary of the invention

[0004] In view of this, the present invention provides a low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solutions, which takes into account multiple information enhancements and completes the solution of enhanced information at the user end to reduce the load burden on the satellite.

[0005] The technical solution for implementing the present invention is as follows:

[0006] A low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solutions, comprising a data receiving module, an information enhancement solution module and a precise single-point positioning solution module;

[0007] The data receiving module completes the reception of satellite data and onboard and ground receiver data, including GNSS observation data, LEO observation data, onboard GNSS observation data and ground station network GNSS observation data. The onboard GNSS observation data and ground station network GNSS observation data are sent to the information enhancement solution module, and the GNSS observation data and LEO observation data are sent to the precise single point positioning solution module;

[0008] The information enhancement solution module mainly performs information enhancement solution, including satellite-ground joint precise orbit determination, satellite-ground joint earth self-propagation parameter estimation, satellite-ground joint GNSS satellite PCV calibration, satellite-ground joint GNSS satellite DCB estimation solution, and sends the obtained solution results to the precise single point positioning solution module;

[0009] The precise single point positioning solution module mainly completes the joint PPP positioning solution of GNSS observation data and LEO observation data, and uses the information enhancement solution result to correct the PPP error, thereby obtaining the low-orbit enhanced GNSS PPP positioning result.

[0010] Furthermore, the satellite-ground joint precise orbit determination combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data, and simultaneously solves the precise orbits and clock errors of low-orbit satellites and GNSS satellites, and utilizes the advantages of satellite-borne receiver data in information quantity, information quality and distribution to achieve enhanced precise orbit and clock error parameter estimation.

[0011] Furthermore, the Earth's rotation parameters are estimated jointly by the satellite and the ground. Parameters related to the Earth's rotation are introduced into the observation equation and estimated together with the orbit and clock error parameters during the satellite-ground precise orbit determination to obtain enhanced Earth's rotation parameters.

[0012] Furthermore, the joint satellite-ground GNSS satellite PCV calibration combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data to provide observation data with a larger elevation range for the calibration of GNSS satellite PCV, thereby realizing enhanced GNSS satellite PCV solution.

[0013] Furthermore, the satellite-ground joint GNSS satellite DCB estimation combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data, making up for the uneven distribution of ground stations and providing high-quality observation data. Two different sets of spherical harmonic function parameters are used to represent the ionospheric delay terms of satellite-borne and ground pseudorange observations, achieving enhanced GNSS satellite DCB estimation.

[0014] Beneficial effects:

[0015] 1. The terminal of the present invention completes the solution of multiple information enhancements, and corrects the PPP error based on the information enhancement solution results combined with GNSS and LEO observation data to achieve low-orbit enhanced GNSS PPP positioning solution.

[0016] 2. The present invention takes into account various information enhancements and completes the calculation of the enhanced information at the user end to reduce the load burden on the satellite.

[0017] 3. The present invention uses the GNSS observation data of the satellite receiver to perform DCB estimation, which can solve the impact of uneven distribution of ground stations and poor observation accuracy on DCB, improve DCB estimation accuracy, and enhance DCB correction information. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a schematic diagram of the structure of a low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solution according to an embodiment of the present invention.

[0019] Figure 2 The present invention is a schematic diagram of an information enhancement module of a low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solutions according to an embodiment of the present invention.

[0020] Figure 3 The present invention is a schematic diagram of a low-orbit enhanced GNSS PPP user terminal precise single-point positioning solution module integrating multi-information enhanced solution according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0022] The present invention provides a low-orbit enhanced GNSS PPP user terminal with integrated multi-information enhancement solutions. The low-orbit enhanced GNSS PPP user terminal completes the reception and storage of satellite-borne and ground receiver data, as well as the satellite-ground joint precise orbit determination, satellite-ground joint earth self-propagation parameter estimation, satellite-ground joint GNSS satellite PCV calibration, satellite-ground joint GNSS satellite DCB estimation and other information enhancement solutions, improving the performance of low-orbit enhanced PPP positioning services while reducing the burden of on-board data storage and calculation.

[0023] like Figure 1 As shown, the low-orbit enhanced GNSS PPP user terminal includes a data receiving module, an information enhancement solution module and a precise single-point positioning solution module.

[0024] The data receiving module receives satellite data and onboard and ground receiver data, including GNSS observation data, LEO observation data, onboard GNSS observation data, and ground station network GNSS observation data. The onboard GNSS observation data and ground station network GNSS observation data are sent to the information enhancement solution module, and the GNSS observation data and LEO observation data are sent to the precise point positioning solution module.

[0025] like Figure 2 As shown, the information enhancement solution module mainly performs information enhancement solution, including:

[0026] 1) Satellite-ground joint precise orbit determination

[0027] By combining the observation data of the onboard GNSS receiver of the low-orbit satellite and the observation data of the ground station network, the precise orbit and clock error of the low-orbit satellite and the GNSS satellite are solved at the same time. The observation model of the satellite-ground joint precise orbit determination is as follows:

[0028]

[0029]

[0030]

[0031]

[0032] Where P, L represent pseudorange and carrier phase observations respectively; g, Leo represent ground station and LEO satellite respectively, j represents frequency; ρ is the geometric distance between the center of mass of navigation satellite and the center of mass of LEO satellite; c is the speed of light in vacuum; δt g ,δt leo Represent the clock errors of the ground receiver and the satellite receiver, δt s represents the navigation satellite clock error; λ j represents the signal wavelength at the jth frequency; b s,j , b leo,j are the pseudorange hardware delays at the ground and satellite receiver ends, represents the pseudorange hardware delay of the satellite end; B g,j and B leo,j represent the phase delays at the ground and satellite receiver ends, respectively, Indicates the phase delay at the satellite end; and represents the ionospheric delay corresponding to the jth frequency on the path from the ground and spaceborne receivers to the GNSS satellite; represents the tropospheric slant delay at the ground station; are the integer ambiguities of the carrier phase observations of the ground and satellite receivers in weeks, respectively; and Represent the sum of multipath effect and observation noise on the pseudorange of ground and satellite receivers respectively; and Represent the sum of multipath effect and observation noise on the carrier phase of ground and satellite receivers respectively;

[0033] In order to eliminate the influence of the first-order ionospheric term in the observation model, an ionospheric-free combination is used, and the following is obtained:

[0034]

[0035]

[0036]

[0037]

[0038] For the tropospheric delay of the ground station, the dry and wet components are corrected using the a priori model. Since the wet component can only be partially corrected using the a priori model, the wet component is estimated as a piecewise constant parameter in the joint orbit determination process.

[0039] Then the above ionosphere-free combined observation model is linearized to obtain

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] in, and They are the unit vectors in the directions from the ground station to the GNSS satellite and from the low-orbit satellite to the navigation satellite. and They are the state transfer matrices of GNSS satellites and low-orbit satellites respectively. Represents the initial state of the GNSS satellite, mainly including the position of the GNSS satellite at the initial epoch speed And the light pressure parameters to be estimated O leo,0 represents the state transfer matrix of the low-orbit satellite, including the initial position of the low-orbit satellite (x leo,0 ,y leo,0 ,z leo,0 )、initial velocity (v leo,x ,v leo,y ,,v leo,z ) and force model parameters (p leo,1 ,p leo,2 ,…,p leo,n ). is the tropospheric parameters to be estimated at the ground station, including the tropospheric wet component Z g , north-south tropospheric gradient parameter G ns and the east-west tropospheric gradient parameter G ew . Represents the projection function of the tropospheric wet component, represents the projection function of the tropospheric gradient part. a represents the azimuth. The estimated parameters of joint orbit determination can be expressed as

[0048]

[0049] The Kalman filter is used to iteratively solve the above parameters to be estimated and obtain enhanced precise orbit and clock errors.

[0050] 2) Joint satellite-ground Earth rotation parameter estimation

[0051] The distance between the satellite and the ground station is expressed as follows

[0052] ρ=|R s -R r ∣

[0053] Where R s , R r They represent the three-dimensional coordinates of the satellite and the ground station in the inertial system, R r It can be obtained by converting the coordinates of the measuring station in the ground-fixed coordinate system as follows:

[0054]

[0055] in The coordinates of the station in the Earth-fixed coordinate system, P(t), N(t), U(t) and W(t) represent the rotation matrices corresponding to precession, nutation, earth rotation and polar motion correction respectively. Among them, the P(t) and N(t) matrices are calculated using model values, the LOD parameters are required to calculate the U(t) matrix, and the XPOLE and YPOLE parameters are required to calculate the W(t) matrix. Therefore, ERP is introduced in the observation equation.

[0056] The estimation of the Earth's rotation parameters by satellite-ground joint orbit determination is carried out by introducing the estimated parameters of ERP into the observation model of joint orbit determination through the above process, and then linearizing and using Kalman filter estimation to obtain enhanced Earth's rotation parameter estimation results.

[0057] 3) Joint GNSS satellite PCV calibration

[0058] Using the onboard GNSS data of low-orbit satellites for GNSS satellite PCV calibration can effectively provide observation data with a lower elevation range for GNSS satellite PCV calibration. By establishing a GNSS satellite PCV calibration model related to the elevation angle, the estimated parameters related to PCV can be introduced into the satellite-ground joint observation equation, and then by fixing the GNSS satellite orbit and the LEO satellite orbit, the enhanced GNSS satellite PCV can be fixed.

[0059] 4) Joint GNSS satellite DCB estimation

[0060] Using the GNSS observation data of the satellite receiver for DCB estimation can solve the impact of uneven distribution of ground stations and poor observation accuracy on DCB, improve the DCB estimation accuracy, and enhance DCB correction information. By subtracting the inter-frequency pseudorange observation values ​​of the GNSS observation data, we can get:

[0061]

[0062] Where ΔP represents the pseudorange difference; Indicates the frequency of 1 and 2 bands; STEC s Represents the ionospheric delay on the slant path; DCB r,12 , Represent the inter-frequency DCB of the receiver and the satellite respectively; is the difference in noise between frequencies and is negligible.

[0063] The ionospheric delay of a GNSS satellite can be expressed by the product of the vertical ionospheric delay model and the projection function, where the ionospheric projection function can be expressed by the single layer projection model (SLM):

[0064]

[0065] in, represents the projection function; Z′ represents the zenith distance; R represents the radius of the earth; H represents the height of a single layer of ionosphere; is the satellite altitude angle.

[0066] In global ionosphere modeling, the vertical ionospheric delay is represented by a 15th-order spherical harmonic function:

[0067]

[0068] Among them, S, They represent the latitude and longitude of the puncture point in the solar-solid geomagnetic system; n and m represent the maximum order and number respectively; P mn represents the regularized Legendre function; a mn , b mn They represent the estimated parameters of the spherical harmonics.

[0069] LEO satellite receivers have a certain altitude, and their ionospheric delay is different from that of ground stations, which completely pass through the ionosphere. They partially pass through the ionosphere, and different spherical harmonic functions need to be used to express them when estimating.

[0070] According to the above process, the DCB estimation equations of the satellite receiver and the ground receiver can be established. For the joint settlement of a large number of station data, the normal equation superposition method is used to solve it. Finally, the enhanced DCB estimation can be completed by least squares.

[0071] like Figure 3 The figure shows the flow chart of the precise point positioning solution module. It mainly completes the joint PPP positioning solution of GNSS observation data and LEO observation data, and uses the information enhancement solution results to correct the PPP errors, so as to obtain the low-orbit enhanced GNSS PPP positioning results. This module first preprocesses the received GNSS and LEO observation data, including the detection of cycle slips, clock jumps and gross errors. Then, according to the received information enhancement solution results and the precise point positioning data processing related files provided by some IGS organization official websites, various error terms that need to be considered for precise point positioning are calculated, and the pseudorange and carrier phase observations are corrected. The fusion positioning function model is constructed using the corrected GNSS and LEO pseudorange carrier observations.

[0072] The GNSS / LEO fusion positioning function model is as follows:

[0073]

[0074]

[0075]

[0076]

[0077] Wherein: superscript C denotes GNSS satellite, superscript L denotes low-orbit satellite, superscript s denotes satellite-related items, subscript r denotes receiver-related items, and subscript j denotes signal frequency; P denotes pseudorange, L denotes carrier, ρ denotes the distance between satellite stations, c denotes the speed of light, dt denotes clock error, T denotes tropospheric delay, I denotes ionospheric delay, N denotes integer ambiguity, d denotes pseudorange hardware delay, b denotes phase hardware delay, e denotes pseudorange noise, and ξ denotes phase noise.

[0078] The parameter vector to be estimated after reparameterizing the observation model is:

[0079]

[0080] Then, the Kalman filter is used to iteratively calculate the estimated parameters to obtain the multi-information enhanced low-orbit enhanced GNSSPPP positioning result and output it.

[0081] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-orbit enhanced GNSS PPP user terminal integrating multi-information enhancement solution, characterized in that: The low-orbit enhanced GNSS PPP user terminal includes a data receiving module, an information enhancement solution module and a precise single-point positioning solution module; The data receiving module completes the reception of satellite data and onboard and ground receiver data, specifically including the reception of GNSS observation data, LEO observation data, onboard GNSS observation data and ground station network GNSS observation data; and sends the onboard GNSS observation data and ground station network GNSS observation data to the information enhancement solution module, and sends the GNSS observation data and LEO observation data to the precise point positioning solution module; The information enhancement solution module performs information enhancement solution, including solution of satellite-ground joint precise orbit determination, satellite-ground joint earth self-propagation parameter estimation, satellite-ground joint GNSS satellite PCV calibration, and satellite-ground joint GNSS satellite DCB estimation; and sends the obtained solution result to the precise single point positioning solution module; The precise point positioning solution module completes the joint PPP positioning solution of GNSS observation data and LEO observation data, and uses the information enhancement solution result to correct the PPP error, thereby obtaining the low-orbit enhanced GNSS PPP positioning result.

2. The low-orbit enhanced GNSS PPP user terminal with integrated multi-information enhancement solution according to claim 1, characterized in that: The satellite-ground joint precise orbit determination combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data, and simultaneously solves the precise orbits and clock errors of the low-orbit satellite and the GNSS satellite, and utilizes the advantages of the satellite-borne receiver data in terms of information quantity, information quality and distribution to achieve enhanced precise orbit and clock error parameter estimation.

3. The low-orbit enhanced GNSS PPP user terminal with integrated multi-information enhancement solution according to claim 1 or 2, characterized in that: The satellite-ground joint Earth rotation parameter estimation introduces parameters related to the Earth's rotation into the observation equation, and estimates them together with the orbit and clock error parameters during the satellite-ground precise orbit determination to obtain enhanced Earth's rotation parameters.

4. The low-orbit enhanced GNSS PPP user terminal with integrated multi-information enhancement solution according to claim 3, characterized in that: The joint satellite-ground GNSS satellite PCV calibration combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data to provide observation data with a larger elevation range for the calibration of GNSS satellite PCV, thus realizing enhanced GNSS satellite PCV solution.

5. The low-orbit enhanced GNSS PPP user terminal with integrated multi-information enhancement solution according to claim 3, characterized in that: The joint satellite-ground GNSS satellite DCB estimation combines the LEO satellite-borne GNSS observation data and the ground station network GNSS observation data, making up for the defect of uneven distribution of ground stations and providing high-quality observation data; two sets of different spherical harmonic function parameters are used to represent the ionospheric delay terms of satellite-borne and ground pseudorange observations, realizing enhanced GNSS satellite DCB estimation.

Images