| The key to the enhancement of the LEO navigation is the real-time and high precision positioning of the LEO navigation enhancement satellite.Usually,real-time satellite positioning uses spaceborne GNSS pseudo-range positioning algorithm,the accuracy is better than 10 meters.However it cannot meet the accuracy requirements of the enhanced navigation submeter.The paper tskes the LEO satellite navigation augmentation into consideration,in oder to reach real-time and high precision positioning,takes the advantages of the ability of LEO satellite,which can receive the high-density precise ephemeris data and has the advantage of combining the characteristic of carrier phase positioning precision and low orbit satellite fast motion.The paper proposed high precision positioning method based on dual frequency GNSS receiver carrier phase in orbit.Theoretical modeling and simulation show that the accuracy of satellite positioning is increased by an order of magnitude and the location time is also reduced by half after improving the measurement noise and ephemeris accuracy.The algorithm is verified on the enhanced load of the "DT-1" microsatellite navigation,which launched in November 15,2017.The main work of this article includes:1.An adaptive noise estimation algorithm for non differential precision single point positioning is designed.The general location estimation algorithm considers the observation noise as a linear white noise,but the actual situation shows that this is not the case and it results the model error,which affects the improvement of positioning accuracy.To solve this problem,the method of adaptive estimation of measurement noise based on M-W combined observations is presented in this paper.The key is that the noise covariance matrix is determined by real-time estimation of observed noise.The ground static tests show that the algorithm can effectively improve the positioning accuracy and reduce the positioning time.The result achieves decimeter level positioning accuracy,and solves the problem by noise mutation model of environmental impact,meets the high precision positioning and orbit orbit demand.2.A real-time and high precision positioning method based on multi ephemeris data flow is proposed.The high accuracy positioning of GNSS receiver is based on the precise ephemeris from high precision navigation star.In this paper,the GPS satellite orbit data is corrected by combining the GPS broadcast ephemeris,the ephemeris products provided by IGS organization and the SSR real-time track data flow.From the accuracy,the highest precision ephemeris can achieve centimeter level,and the broadcast ephemeris usually in meters,after the track data SSR correction,the accuracy of the broadcast ephemeris can get submeter accuracy.From the perspective of access convenience,the broadcast ephemeris is acquired from the GNSS signal,which is received by the spaceborne GNSS receiver,and the precise ephemeris and SSR correction data are downloaded from the ground network ahead of time and then injected onto the LEO satellite.The three kinds of ephemeris have their own advantages and disadvantages.Therefore,from the feasibility of practical application,this paper combines the three kinds of ephemeris products to achieve the best results.The algorithm is fully tested in the on orbit dynamic environment,which has been simulated by the ground GPS signal generator,and the feasibility is verified.At present,the navigation augmentation load of the algorithm is being tested on the rail. |
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