Research On GNSS Raw Data And Positioning Performance For Android Smart Phone

With the continuous development of mobile communication and satellite navigation technology and the popularization of smart phone,users have increasingly higher requirements for the positioning of smart phone.After the Google I/O conference in May 2016,Android 7.0 and later versions support the output of GNSS raw observation data through the application program interface.With the opening of GNSS raw observation data,the positioning of Android smart phone has become a research hotspot in the subject of surveying and mapping..Therefore,based on the GNSS observation data of the Android smart phone,this paper studies and analyzes the quality of the GNSS raw observation data of the Android smart phone;studies the positioning accuracy of the Android smart phone in a static and dynamic environment;optimizes and improves the GNSS raw observation data of the Android smart phone;Finally,the accuracy of the PPP positioning model of the Android mobile smart phone is explored.The main content and results of the paper are as follows:(1)Briefly introduce the principle of GNSS positioning and various errors encountered in the process of GNSS positioning,and the specific methods to eliminate each error;the parameter estimation method of GNSS positioning;the current common precision single-point positioning model;Android intelligent phone system and The basic structure of the application program interface;the time and coordinate system used by the Android smart phone when positioning;the method of obtaining the original GNSS observation data of the Android smart phone;the preprocessing method of the GNSS raw observation data of the Android smart phone and the random model in the positioning.(2)The system analyzes the data quality of the original GNSS observation data of the Android smart phone.From the aspects of signal-to-noise ratio,data integrity,satellite visibility and continuity,pseudorange observation noise and multipath error,pseudorange change rate,Duty Cycle and cycle slip,the quality of GNSS raw observation data of Android smart phone is analyzed.Experimental results show that under the same observation environment,the signal-to-noise ratio of the single-frequency smart phone is lower than that of the dual-frequency smart phone,and the correlation with the altitude angle is not strong.The data integrity of the two smart phone under GPS satellites is better than the data integrity under BDS satellites;the number of satellites and continuity observed by the single-frequency smart phone is not as good as the dual-frequency smart phone;the pseudo-range observation of the single-frequency smart phone Noise and multi-path error can reach about 10 meters,and the pseudo-range observation noise and multi-path error of dual-frequency smart phone can reach about 7 meters;the pseudo-range change rate of single-frequency and dual-frequency smart phone fluctuates sharply;research and analysis Duty Cycle and cycle slips show that there are frequent cycle slips in single-frequency and dual-frequency smart phone.(3)The positioning accuracy of Android smart phone is studied.Research on the positioning accuracy of single-frequency and dual-frequency smart phone in different environments.Experiments show that the positioning accuracy of dual-frequency smart phone is better than that of single-frequency smart phone in a static environment,whether in a single GPS,BDS or GPS+BDS system.In a dynamic environment,the positioning accuracy of the two smart phone under a single system is not ideal,and the received data is unstable,resulting in unsatisfactory positioning accuracy.Under multiple systems,the dual-frequency intelligent phone is better than the single-frequency The intelligent phone can receive more L5 frequency data,and the positioning performance of the dual-frequency intelligent phone is better than that of the single-frequency intelligent phone.(4)Optimization has improved the GNSS data quality of Android smart phone.The positioning accuracy error of the two smart phone using the original pseudorange observations fluctuates greatly.The GNSS data of the Android smart phone is optimized and improved by the Doppler smoothing pseudorange method.The experimental results show that: before Doppler smoothing,Perform data preprocessing to eliminate gross errors.The two smart phone can filter out some of the noisy original pseudorange observations through the Doppler smoothing pseudorange filtering algorithm,and the positioning results show a smoother accuracy curve.The positioning accuracy of the smart phone is also better than that when the original pseudorange observation value is used,and it can meet general positioning requirements in real life.(5)The precise single-point positioning model of Android smart phone is studied.Design and study the applicability of the three PPP models in Android smart phones.The experimental results show that the PPP positioning accuracy under the Uofc model is the best,and the dual-frequency smart phone has a shorter convergence time than the single-frequency smart phone,and PPP positioning is performed The accuracy of the Android smart phone is also better;due to the poor quality of the carrier data of the Android smart phone,the conventional traditional model and the positioning accuracy without ambiguity are poor;the Uofc model is preferred for the PPP positioning of the Android smart phone.