Research And Implementation Of Real-time High-precision Differential Positioning Algorithm For Smart Phone

In recent years,Location Based Services(LBS)based on smart terminals has gradually become a research hotspot in the field of navigation and positioning.In August 2016,Google announced to users the original observation interface of the Global Navigation Satellite System(GNSS).Since then,high-precision positioning technology based on smart terminals has become the focus of attention of domestic and foreign researchers.At present,there are many smart phones on the market that can support BDS/GPS/GLONASS/Galileo four-system observation data acquisition,and some of them already support dual-frequency or even tri-frequency data acquisition.In May 2018,Xiaomi released the world's first dual-band smartphone-Xiaomi 8,which can track GPS/Galileo/QZSS L5/E5 bands.In April 2020,the P40 smartphone released by Huawei supports Beidou tri-band(B1I+B1C+B2a)data acquisition for the first time.In this context,many scholars have done smart phone related experiments,most of which are based on the carrier phase observation value of Precise Point Positioning(PPP),real-time dynamic(Real Time Kinematic,RTK)carrier phase difference technology,and There are few and incomplete researches on the pseudorange positioning of smart phones.This paper uses smart phone pseudo-range observations and grid pseudo-range difference technology to improve the positioning accuracy of smart phones and fill the gaps in the neighborhood of smart phone pseudo-range difference.It provides a reference for studying the characteristics of the pseudo-range observation value of smart phones and the use of pseudo-range for navigation and positioning,which has certain reference significance.The main research content and contributions of the thesis are as follows:(1)A smart phone data preprocessing method based on double-difference limit error is proposed.First,the Xiaomi 8,Huawei P30 dual-band smart phone and the TRIMBLE NET R9 measurement receiver are used for simultaneous observation in the same environment,in terms of satellite navigation tracking capability,multipath effect error,observation noise,signal-to-noise ratio,clock stability,etc.Data analysis was carried out,and then based on the observation noise extracted by the epoch double difference,the original pseudorange observation data preprocessing strategy based on the limit error was proposed,which realized the effective elimination of most errors and greatly improved the smart phone positioning accuracy.(2)Research and analyze the single point positioning(SPP)performance of smart phones based on Doppler and carrier phase smoothing pseudorange.After Doppler smoothing,the MI8 single-point positioning plane has a unidirectional outer coincidence accuracy of less than 1m,while the accuracy of P30 in the N and U directions has been improved,but the improvement is not obvious,and the E direction is reduced.This is due to the P30 Doppler observation.The accuracy of the value is not high,and part of the Doppler error is related to the pseudorange error.After carrier phase smoothing,the single-point positioning accuracy of MI8 and P30 is less than 1m.Among them,the single-point positioning accuracy of MI8 is improved by 71.8%,65.2%,and 67.8% in the N,E,and U directions after carrier phase smoothing;P30 After carrier phase smoothing,the single-point positioning accuracy is increased by 42.3%,38.3%,41.5% in the N,E,and U directions respectively.Although there are a lot of gross errors in the pseudorange,carrier phase,and Doppler observations of P30,after data preprocessing,the integrity of the data is significantly improved.Combined with the smoothing algorithm,the accuracy is improved.From the results,the carrier Phase smoothing is more applicable,and the effect is improved significantly.(3)Research and realize the BDS/GPS/GLONASS/Galileo four-system grid pseudo-range differential service system compatible with BDS3/Galileo.Based on the Continuously Operating Reference Stations(CORS)in Hunan and Nanjing,this paper implements a four-system grid pseudorange differential service system,and develops related terminal programs.After testing,it is found that the pseudorange of the measurement receiver is smoothed,which will increase the correlation of the singlepoint positioning results and make the randomness worse.Through the grid pseudorange difference,the correlation can be reduced.Multi-system fusion can improve positioning accuracy when the accuracy difference between systems is small,but not when the accuracy difference is large,but multi-system fusion can increase the stability of the system.(4)Research and realize the grid pseudorange difference algorithm based on extended Kalman filter.After testing,it is found that using the data of the reference station to do the simulation dynamic experiment,the result is slightly improved compared with the least square algorithm,but the accuracy improvement is limited.Judging from the dynamic test results in the complex environment of urban areas,the Kalman filter algorithm has greater advantages,and the results have better continuity.(5)The study achieved the acquisition of real-time observations of smartphones,and analyzed the performance of real-time high-precision differential positioning algorithms for smartphones.Using the developed software,the MI8 and P30 smart phones have been tested for single point positioning(SPP)under the conditions of pseudorange unsmoothing,Doppler smoothing,and carrier phase smoothing,and grid pseudorange differential positioning based on least squares(GRID Least Square).,GRID?LS)algorithm and grid pseudo-range differential positioning(GRID Extended Kalman Filter,GRID?EKF)algorithm based on extended Kalman filter,and use carrier phase smoothing GRID?EKF algorithm for related dynamic experiments.The results show that pseudo-range differential can effectively improve the positioning accuracy of smart terminals;in static and dynamic conditions,the pseudo-range differential positioning accuracy of the smart phone grid smoothed by pseudo-range can reach the meter level.