75 results about "Precise Point Positioning" patented technology

The invention discloses a global ionosphere modeling method and device based on Beidou single-frequency ionosphere weighted PPP, and belongs to the technical field of GNSS navigation positioning and atmosphere modeling. The method comprises the following steps: acquiring real-time precise orbit and clock error information of a Beidou satellite and an initial ionospheric delay correction value; a single-frequency ionosphere weighted precision single point positioning (SF-IW-PPP) observation equation is constructed; establishing a space-time correlation constraint model of the ionized layer delay error and determining a prior variance; carrying out combined calculation by taking the previous variance as a constraint to obtain an ionosphere delay residual error, and further obtaining the total delay of the high-precision inclined ionosphere; and finally generating a global ionosphere grid model. According to the invention, high-precision and real-time global ionosphere modeling is realized by only needing a low-cost single-frequency receiver and combining Beidou real-time enhancement service, the hardware threshold and data processing delay are remarkably reduced, and the method is suitable for the fields of public navigation, intelligent transportation, space weather monitoring and the like.

The invention relates to an unmanned aerial vehicle high-precision positioning method based on micro-centimeter space low-orbit constellation and Beidou PPP-B2b fusion enhancement, and the method comprises the steps: obtaining a precise orbit correction number and a precise clock correction number of a GPS and a BDS system based on a Beidou PPP-B2b signal; calculating a precise orbit and a precise clock error of the GNSS satellite based on the precise orbit correction and the precise clock error correction; on the basis of the precise orbit and the precise clock error of the GNSS satellite, an observation value of a micro-centispace low-orbit satellite is fused, and a GNSS / LEO combined PPP observation model is constructed; and based on extended Kalman filtering, precise point positioning calculation is carried out on the GNSS / LEO combined PPP observation model, and the real-time high-precision position of the unmanned aerial vehicle is obtained. According to the invention, the real-time high-precision position of the unmanned aerial vehicle can be rapidly and stably obtained, and a reliable position reference is provided for autonomous operation of the unmanned aerial vehicle in a network-free environment.

Described herein are solutions for real-time precise ionosphere corrections. An integrate and dump (I&D) server can receive a Networked Transport of Radio Technical Commission For Maritime Services (RTCM) via Internet Protocol (NTRIP) bit stream of a spherical harmonic model for precise point positioning (PPP). The model can be a vertical total electron content (VTEC) spherical harmonic expansion model and / or can include a set of ionosphere coefficients for correcting errors in satellite signals due to ionospheric conditions. The I&D server can generate a file of ionosphere coefficients, according to a refresh timer, and can send the file to a content delivery network (CDN) for distribution to user equipment (UEs) upon request. These and many other features and examples are described herein.

The invention discloses a joint correction method and system for GNSS (Global Navigation Satellite System) non-structural deformation and a storage medium. According to the method, GNSS pseudo-range and carrier phase observation data and precise products such as a precise orbit and clock correction are obtained, a three-component displacement time sequence caused by a non-tidal atmospheric load, a non-tidal ocean load and a land hydrological load and a temperature-driven thermoelastic displacement time sequence are constructed, and the three-component displacement time sequence and the temperature-driven thermoelastic displacement time sequence are unified to a reference frame and a time system consistent with GNSS calculation. After interpolating the non-structural displacement vector to an observation epoch according to time, converting the non-structural displacement vector to a geocentric rectangular coordinate system from a site local coordinate system ENU, and projecting the non-structural displacement vector to a sight line direction from a satellite to an observation station reference point to form an equivalent geometric distance correction item; the correction terms are respectively applied to pseudo-range observation and carrier phase equivalent meter domain observation in the form of the same domain as observation, and then GNSS daily arc precise calculation is performed to output a coordinate time sequence, and preferably, the method can be used for a precise single-point positioning integer ambiguity fixing technology.

The invention provides a troposphere anisotropy-considered real-time PPP positioning method, and relates to the technical field of satellite navigation and positioning, and the method comprises the following steps: S01, receiving real-time GNSS observation data, broadcast ephemeris data and precision correction data, carrying out detection and restoration of clock slip and cycle slip, data quality control and preprocessing of antenna phase correlation errors on the data to obtain a preprocessed data set; s02, calculating the solar altitude after atmospheric refraction correction according to each preprocessed data set and the geographic position and observation time of the observation station corresponding to each data set; and S03, based on the solar altitude and the satellite altitude. According to the method, solar altitude parameters are introduced, the troposphere anisotropy effect caused by solar radiation is effectively modeled, and the precision and convergence speed of real-time precise single-point positioning are remarkably improved.

A mobile device positioning method, a mobile device, and a storage medium. The positioning method comprises: when a positioning system is powered on and started, determining first position information by means of a self-differential positioning mode, and performing calculation by means of a precise point positioning mode to obtain second position information. Because the calculation speed of the self-differential positioning mode is relatively fast, when the precise point positioning mode has not yet successfully completed the calculation, the first position information calculated by means of the self-differential positioning mode is used as target position information of a mobile device, thereby ensuring the positioning efficiency of the mobile device; and when the precise point positioning method successfully completes the calculation, position processing is performed on the basis of the second position information, thereby achieving high-precision positioning and high-precision operations in a no-network or weak network environment.

The invention discloses an unmanned aerial vehicle cluster autonomous decision-making method and system fusing Beidou enhancement service and multi-source perception, and the method comprises the steps: enabling each unmanned aerial vehicle to receive a satellite-based enhancement signal, carrying out the real-time calculation of the satellite-based enhancement signal through employing a precise single-point positioning technology, and obtaining precise PVT information; each unmanned aerial vehicle synchronously collects sensor information, carries out space-time alignment on the sensor information and the precise PVT information, and processes local sensing features and wide-area geographic information by using an information fusion model to generate a global environment situation tensor; inputting the global environment situation tensor into a deep reinforcement learning strategy network to obtain a task instruction set; carrying out consensus confirmation on key instructions in the task instruction set by utilizing a Beidou global short message to obtain a task instruction after consensus; and each unmanned aerial vehicle performs collaborative operation based on the task instruction after consensus, performs real-time fusion on new perception data generated in the execution process and precise PVT information, and inputs the fused data into the information fusion model again to complete an autonomous decision closed loop.

An example method for updating global navigation satellite system (GNSS) error correction data for global navigation satellite system (GNSS)-based positioning. The method performed by a server may include obtaining a plurality of GNSS measurements crowdsourced from one or more GNSS devices across a plurality of measurement periods; determining a GNSS measurement residual using the plurality of GNSS measurements and existing GNSS error correction data; and transmitting updated GNSS error correction data for GNSS-based positioning, wherein the updated GNSS error correction data is determined using the determined GNSS measurement residual and the existing GNSS error correction data.

Methods and apparatus are provided for propagating a time-tag signal (T2) from at least one server site to at least one client site. The method comprises: at each server site, running a server global navigation satellite system GNSS process (202(i)) configured to generate a server GNSS output raw data signal (R7(T2); R7(T2(i))) based on at least one or more first satellite signals; generating a precise orbit and clock signal (C8(T2); C10(T2); T4(T PPP -T2); T9(T PPP -T2)) embedding said time-tag signal (T2) based on all server GNSS output signals (T2(i); T7(T2(i))), and broadcasting said precise orbit and clock signal (C8(T2); C10(T2); T4(T PPP -T2); T9(T PPP -T2)) via a telecommunications network (206); at each client site, running a client global navigation satellite system GNSS process (201(c)) configured to generate a client GNSS output raw data signal (R5(T1(c))) based on a client clock signal (T1(c)) and based on one or more second satellite signals; running a client precise point positioning PPP process (203(c)) configured to receive said client GNSS output raw data signal (R5(T1(c))) and said precise orbit and clock signal (C8(T2); C10(T2); T4(T PPP -T2); T9(T PPP -T2)), and generate a difference signal (T1(c)-T2) between said client clock signal (T1(c)) and the time-tag signal (T2).

This invention discloses a real-time dynamic relative positioning method, system, and device based on state domain correction information. The method involves: a server receiving real-time GNSS observation data streams from the entire network of reference stations and real-time precise orbit clock correction streams to perform real-time precise single-point positioning calculations, and broadcasting network-wide floating-point ambiguity information; then performing real-time phase deviation estimation and broadcasting it; further, combining the network-wide reference station observation data streams and real-time precise orbit clock errors to perform real-time precise single-point positioning fixed-solution calculations, and broadcasting network-wide atmospheric delay information; performing atmospheric modeling and broadcasting the model information; and a user terminal receiving the precise orbit clock correction information, phase deviation information, and model information broadcast by the server in real-time, generating virtual observation values ​​at its approximate coordinates, and performing real-time dynamic relative positioning calculations. This invention can significantly reduce the algorithm complexity of current precise positioning servers and is compatible with existing relative positioning user terminals while ensuring one-way communication and privacy protection.

The present application belongs to the global navigation positioning technology field, disclose a kind of phase deviation generation and application method for multi-frequency PPP-AR.For the problems of insufficient real-time stability, higher system implementation complexity and avoiding the influence of inter-frequency clock bias deviation by weakening the model strength in the process of inter-frequency clock bias deviation processing in existing multi-frequency precise point positioning ambiguity fixing technology, in the phase deviation generation stage of the server, the time-varying IFCB component in the third frequency is absorbed into the corresponding floating ambiguity state by parameterization, and on this basis, the multi-frequency uncalibrated phase delay parameter is estimated, which is further converted into the phase OSB product corresponding to each frequency for direct use by the user side. The method of the present application realizes the stable fixing of multi-frequency ambiguity and high-precision positioning without introducing additional independent IFCB product and without weakening the overall constraint ability of the user-side PPP-AR model.

The application discloses a joint correction method and system of GNSS non-tectonic deformation and a storage medium. The method obtains GNSS pseudo-range and carrier phase observation data and precise orbit, clock error and other precise products, constructs three-component displacement time series caused by non-tidal atmospheric load, non-tidal ocean load and land hydrology load and temperature-driven thermal elastic displacement time series, and unifies to a reference frame and a time system consistent with GNSS solution. The non-tectonic displacement vector is interpolated to the observation epoch by time, converted from the local coordinate system ENU to the geocentric rectangular coordinate system, and projected to the line-of-sight direction of the satellite to the reference point of the station to form an equivalent geometric distance correction term; the correction term is applied to the pseudo-range observation and the carrier phase equivalent meter domain observation in the same domain as the observation, and then GNSS daily arc segment precise solution is performed to output the coordinate time sequence, which is preferably used for precise point positioning integer ambiguity fixing technology.

The invention relates to a fast convergence satellite clock error resolving method under regional station distribution, which belongs to the field of satellite navigation, and comprises the following steps: in a regional monitoring network, constructing a normal equation by using an ionosphere-free combination pseudo range and a carrier phase by using a known precise orbit and a station coordinate; in the Kalman filtering stage, covariance forecasting is carried out on satellite clock correction, receiver clock correction and troposphere delay, cycle slip detection and covariance forecasting are carried out on ambiguity, when the ambiguity has no cycle slip and converges, the forecasting covariance is reset to be a minimum value so as to apply reinforced constraint, and the reinitialization time is remarkably compressed; performing parameter estimation to obtain an optimal value and a pseudo-range post-test residual error; the satellite clock error constant deviation is calculated through multi-station multi-epoch residual errors in a combined mode, and the satellite clock error constant deviation is fused into the original code deviation to form extended code deviation parameter broadcasting; the user side only needs to add the extension correction in the pseudo-range observation value to realize instantaneous centimeter-level positioning. According to the invention, high-precision and high-availability real-time precise single-point positioning service under the regional network condition is realized.

The invention belongs to the technical field of unmanned aerial vehicle navigation and path planning, and discloses an unmanned aerial vehicle intelligent path planning method and system based on a KOA algorithm and a Beidou system, and the method comprises the steps: achieving the centimeter-level precise single-point positioning of an unmanned aerial vehicle through a Beidou PPP-B2b technology; constructing a three-dimensional environment and constraint model; a KOA algorithm is utilized to encode path points into planet individuals, multi-objective optimization planning is carried out by simulating planet motion under universal gravitation, and global exploration and local development are effectively balanced; smoothing and dynamically re-planning the path; and finally, carrying out precise tracking control by combining high-precision positioning feedback. The system correspondingly comprises a positioning module, a sensing module, a planning module, a control module and the like. According to the method, high-precision navigation and an intelligent algorithm are deeply fused, and the path optimality, safety and autonomy of the unmanned aerial vehicle in a complex environment are remarkably improved.

The application discloses a kind of receiving galileo HAS service and positioning performance evaluation method and device, belong to satellite positioning and navigation technical field.The method includes: through USRP device, galileo E6B frequency band signal is captured, after being separated by biasing device radio frequency and direct current signal, by GNSS-SDR software, adaptive hierarchical processing is carried out, including the dynamic sampling and interference suppression of radio frequency adaptation layer, the double-domain cooperative synchronization and adaptive decoding of baseband intelligent processing layer, and the multidimensional feature mapping and robustness check of HAS correction number extraction layer, finally output standardization HAS correction number.Combining real-time precise point positioning technology, realize centimeter level dynamic positioning, and positioning performance is evaluated by comparing with reference station data.The application improves the robustness and precision of signal reception and processing, and is suitable for high-precision positioning demand under complex environment.

This invention discloses a satellite navigation enhancement method and system based on inertial navigation data. To address the problems of slow convergence, frequent cycle slips, easy loss of fixed solutions, and discontinuous or abrupt navigation outputs in real-time dynamic differential positioning and precise single-point positioning under highly dynamic and complex obstruction environments, this invention aligns the inertial measurement unit data with carrier phase and Doppler observation data in time, constructs a continuous-time state trajectory, establishes a Gaussian process prior, and performs tight-coupled joint estimation of trajectory state and carrier phase integer ambiguity within a sliding time window. Based on the carrier phase residual, it performs change point detection to determine cycle slips, triggers ambiguity reset, and performs re-initialization constraints based on inertial prediction state and uncertainty to complete the update estimation. This achieves the technical effects of robust cycle slip detection and rapid recovery, improved fixed solution preservation capability and switching smoothness, and enhanced continuity and stability of navigation solutions.

The invention relates to a real-time estimation method and a real-time estimation device for GNSS (Global Navigation Satellite System) satellite clock correction of an air-to-ground-based united network, and belongs to the technical field of satellite communication. The method comprises the following steps: preprocessing regional ground network data to obtain preprocessed regional ground network data; preprocessing the LEO satellite-borne data, and carrying out cycle slip detection, pseudo-range single-point positioning and precise single-point positioning to obtain an LEO satellite orbit coordinate; a function model and a random model of GNSS real-time satellite clock error estimation are constructed based on regional ground network data, LEO satellite orbit coordinates and LEO satellite-borne observation values, and priori information of multiple epochs of non-white noise parameters in a sliding window is superposed with a normal equation of current epoch parameters based on the function model and the random model. Obtaining an expanded normal equation; and obtaining a GNSS satellite precision clock error, an LEO satellite precision clock error and an LEO satellite orbit based on the extended normal equation. According to the invention, real-time full-arc precise estimation of the GNSS satellite clock error under a small number of ground stations in a region is realized.

The invention discloses a precise point positioning method, system and device under limited satellite communication resources, a medium and a product, and relates to the field of advanced precise positioning of satellite navigation, the method comprises the following steps: receiving user data and a precise satellite correction product in real time at a system end, generating correction data matched with a user end positioning model, carrying out lightweight coding on the precision satellite correction product, and broadcasting to a user side; at a user side, analyzing a lightweight coded precise satellite correction product, determining ultra-wide lane comprehensive deviation correction information, determining a fixed EWL integer ambiguity, and determining a fixed WL integer ambiguity in combination with a wide lane integer ambiguity fixing model; in combination with a narrow lane integer ambiguity fixed model, determining a user position under a narrow lane fixed solution and updating the current user position; the PRN number of the current user visible satellite and the updated user position are sent to the system end, precise point positioning is completed, the convergence time is shortened, and the positioning precision is improved.

The invention discloses a multi-satellite-based enhanced precision single-point positioning service real-time fusion method, which belongs to the technical field of navigation positioning, is used for real-time precision single-point navigation positioning, and comprises the following steps of: eliminating abnormal corrections according to the consistency of adjacent epoch corrections of the same service; unifying coordinate frames of different services by using a Helmert seven-parameter coordinate transformation model, and carrying out weighted average on the track product to obtain a high-precision fused track product; after orbital change compensation and broadcast ephemeris unified compensation of the clock correction number are calculated, constraint conditions are introduced to construct an improved clock correction Kalman filtering fusion model to obtain a high-precision fusion clock correction product; and the two products are applied to real-time precise single-point positioning of a receiver end. According to the invention, by unifying coordinate frames of different services and introducing constraint conditions to construct an improved clock correction Kalman filtering fusion model, real-time and rapid multi-service ephemeris orbit and clock correction high-precision fusion is realized, and a fused product can be effectively applied to real-time precise single-point positioning of a receiver end.

The invention discloses a booster station slope automatic monitoring and early warning system based on the Beidou technology, and relates to the technical field of booster station slope monitoring, and the system comprises a monitoring terminal module, a preprocessing module, a positioning calculation module, a trend prediction module, an abrupt change detection module, an early warning decision module, and a sampling regulation and control module. The monitoring terminal module is used for arranging a plurality of Beidou receiving terminals on a booster station slope and collecting original observation data; the preprocessing module is used for performing cycle slip repair and quality evaluation on original observation data to generate an observation data sequence; the positioning resolving module is used for acquiring high-precision three-dimensional coordinates of each monitoring point of the booster station slope by adopting a precise single-point positioning and real-time difference mixed resolving method fused with multi-system information according to the observation data sequence output by the preprocessing module, and converting the high-precision three-dimensional coordinates into a real-time displacement sequence under a local coordinate system; and the trend prediction module is based on a displacement sequence.

The invention provides a service message abnormity monitoring method and system based on a satellite-based augmentation system, and belongs to the field of satellite navigation and satellite-based augmentation. The method comprises the following steps: firstly, acquiring an enhanced message generated by a master control station based on observation station observation data calculation, and performing static inspection on the enhanced message; if the static check is passed, uploading an enhanced message; receiving the broadcasted enhanced telegraph text, sequentially comparing the satellite-ground consistency in real time, performing observation quality evaluation based on the O-C residual error to verify the enhancement effectiveness of the enhanced telegraph text, and performing PPP integrity test based on the monitoring station; if the test is passed, the service message is normal; and if the static check is not passed and static abnormity exists, or satellite-ground consistency comparison abnormity exists, or O-C residual verification is not passed, or positioning check is not passed and monitoring station PPP positioning abnormity is determined, fault association and positioning are carried out according to a determination result by constructing a rule base or an algorithm model. According to the invention, the abnormal monitoring capability of the telegraph text is enhanced.

The application discloses an ionosphere time delay compensation method for real-time precise point positioning, and the method comprises the following steps: constructing an ionosphere prediction polynomial fitting model, using STEC historical data of ionosphere products to solve polynomial fitting coefficients in the ionosphere prediction polynomial fitting model, and obtaining a polynomial fitting prediction ionosphere product; using ionosphere product historical data, combining double-frequency phase observation values, constructing ionosphere residual combination observation, calculating ionosphere variation between epoch moments, and generating residual combination observation prediction ionosphere products; and according to satellite states observed by a terminal, automatically selecting the polynomial fitting prediction ionosphere product or the residual combination observation prediction ionosphere product to predict the ionosphere. According to the application, ionosphere product historical information and double-frequency phase observation value information are used to predict the ionosphere slant delay at the current moment, so that the ionosphere product time delay compensation is achieved, the product precision loss is reduced, and the PPP-RTK positioning performance is improved.

This invention discloses a method for fixing ambiguity in precise single-point positioning based on phase deviation accuracy factor, belonging to the field of Global Navigation Satellite System (GNSS) technology. The method includes: calculating the fractional-cycle portions of ultra-wide lane ambiguity, wide lane ambiguity, and narrow lane ambiguity based on GNSS reference station phase observations; sequentially selecting stations according to the number of observed satellites, and using the whole-network phase deviation solution method and the fractional-cycle portions of ultra-wide lane ambiguity, wide lane ambiguity, and narrow lane ambiguity, iteratively calculating the receiver-side UPD value and the satellite-side UPD value and extracting the residual vector of phase deviation; calculating the UPD accuracy factor based on the phase deviation residual vector; updating the ambiguity variance-covariance matrix at the user end using the UPD accuracy factor, and fixing the ambiguity at the user end based on the LAMBDA algorithm. This invention solves the problem of inconsistency between the ambiguity and the accuracy of the ambiguity variance-covariance matrix in existing technologies.

The application discloses a kind of based on low orbit fixed enhancement Beidou PPP-B2b positioning method and device, belong to GNSS positioning technical field. Including: obtaining Beidou and low orbit satellite observation data;Decoding PPP-B2b enhancement signal, utilize its precise correction number to correct satellite orbit and clock error;Based on the data after modification constructs Beidou / low orbit fusion's precise point positioning model;In model solution, using low orbit ambiguity priority fixing strategy, utilize the advantage that low orbit satellite geometry changes fast, first its carrier phase integer ambiguity is fixed as integer;Fixed low orbit ambiguity is regarded as known constraint back substitution to fusion model, re-solution obtains receiver precise positioning result.The application effectively overcomes the problem that traditional PPP-B2b signal is easy to shield, and convergence time is long, significantly improves the continuity of positioning, convergence speed and accuracy.

The present application relates to a kind of navigation satellite orbit determination precision promotion method based on pseudo-range deviation correction, belong to satellite navigation field, the method is combined with global distribution ground station dual-frequency pseudo-range observation value and external precise orbit clock difference product constructs ionosphere-free combination observation equation, through precise point positioning calculation receiver coordinate and constructs posteriori pseudo-range residual equation;According to the grouping of receiver model and the application of zero-sum constraint, align receiver clock difference, through multi-epoch joint network least square batch processing each type receiver is solved to each navigation satellite dual-frequency ionosphere-free combination pseudo-range deviation value;According to the receiver model of ground station, select the pseudo-range deviation value of corresponding type, deduct from dual-frequency ionosphere-free combination pseudo-range observation, obtain the pseudo-range observation of correction;Using the pseudo-range observation of correction and carrier phase observation, joint solution navigation satellite precise orbit parameter.The present application has significantly improved the navigation satellite orbit determination precision and spatial reference consistency level.

The invention relates to a Beidou single-frequency precise point positioning method considering inter-satellite delay. The method comprises the following steps: receiving a Beidou satellite single-frequency signal; constructing a pseudo-range and carrier phase observation equation of the Beidou satellite and a receiver in a non-difference and non-combination form based on the Beidou satellite single-frequency signal; correcting a satellite clock error in the observation equation based on relative satellite hardware delay between different frequency points; deriving the coordinate of the receiver based on the corrected satellite clock error through the observation equation; according to the method, additional hardware delay of a clock correction product is introduced, the influence of inter-satellite delay is considered when Beidou single-frequency PPP calculation is carried out, and the high-precision characteristic of Beidou single-frequency PPP is guaranteed; non-difference and non-combination observation value calculation is adopted, the high-precision characteristic of a Beidou single-frequency terminal is guaranteed, and for Beidou terminal equipment supporting multi-frequency point calculation, the problems that original characteristics of observation values are damaged and noise is amplified by adopting a traditional ionosphere-free combination or other observation value combination mode are solved.

The invention discloses a non-modular error correction method and system for satellite high-precision navigation positioning and a storage medium. The method comprises the following steps: extracting an original observation value of a satellite receiver, and obtaining a residual sequence by using a non-difference and non-combination precision single-point positioning method; calculating a non-modular error feature vector of the residual error sequence according to the time domain and frequency domain features, and constructing an environment recognition model according to the non-modular error feature vector; calculating a correlation coefficient between each error factor and the residual sequence according to the pseudo-range and the carrier phase observation value; establishing a non-modeling error correction model according to the correlation coefficient of each error factor and the residual error sequence, and performing fine adjustment on parameters of the non-modeling error correction model according to a deep transfer learning algorithm; and outputting a corrected result according to the adjusted non-modular error correction model. According to the method, the problem that the existing high-precision navigation positioning non-modular error processing method is insufficient in universality and precision in a complex and changeable environment is solved.

The invention discloses a multi-level integrity monitoring method based on LEO / GNSS independent solution, and belongs to the technical field of satellite navigation and high-precision positioning. According to the method, firstly, independent precise single-point positioning and standard single-point positioning calculation is carried out on a GNSS and an LEO, and key parameters such as the position, the ambiguity state and the geometric accuracy factor are obtained; secondly, dynamically constructing a geometric configuration reference value based on historical PDOP and GDOP, and calculating a normalized position deviation and a geometric risk factor; next, fault recognition and reliability evaluation are dynamically executed according to the positioning calculation state, NPD, GRF and ambiguity reliability indexes are fused, and a comprehensive risk value (Risk) is calculated through a weighting model; and finally, according to the Risk value, outputting three-level integrity state identifiers of "available", "degraded" or "unavailable", and executing a targeted degradation strategy when an abnormality is detected. The reliability, availability and robustness of the positioning system are remarkably improved, and the method is suitable for safety key scenes such as automatic driving and emergency rescue.

A method and apparatus are provided for propagating a time-stamped signal from at least one server site to at least one client site. The method includes: at each server site, running a server GNSS process configured to generate a server GNSS output raw data signal based on at least one or more first satellite signals; generating a precise orbit and clock signal embedded with the time-stamped signal based on all server GNSS output signals, and broadcasting the precise orbit and clock signal via a telecommunications network; at each client site, running a client GNSS process configured to run a client precise point positioning (PPP) process based on a client clock signal and generating a client GNSS output raw data signal based on one or more second satellite signals, the PPP process being configured to receive the client GNSS output raw data signal and the precise orbit and clock signal, and generate a difference signal between the client clock signal and the time-stamped signal.