Research On GPS/Galileo Dual-frequency Positioning Based On Android Smartphone

Recent years,with the rapid development of GNSS,multi-GNSS combination positioning has some advantages in convergence time and positioning accuracy,and the update of android system and the emergence of dual-frequency GNSS chip enabled smartphones to acquire GPS/Galileo dual-frequency GNSS observations.In this paper,PPP Algorithm of dual-frequency smartphone was studied,and the performance of PPP was evaluated by making static,kinematic and real-time experiments:(1)This paper summarized the advantages of PPP and the main research methods and difficulties of multi-GNSS PPP.The methods commonly used by low-cost receivers to improve the positioning accuracy was introduced,the applications and algorithms of GNSS positioning for smartphones in recent years were summarized.(2)This paper introduced the GPS and Galileo,studied the smartphone GPS/Galileo L1/L5 dual-frequency PPP algorithm,analyzed the main error sources and the correction method of the PPP,and introduced the EKF parameter estimation method.(3)This paper introduced the method of acquiring the raw GNSS measurement by android platform and the advantage of the update of android system to the smartphone precision positioning.(4)In this paper,the GPS L1/L5 and Galileo E1/E5 a dual-frequency PPP algorithm based on RTKLIB and GAMP was applied to analyze the positioning performance of the Xiaomi Mi 8 dual-frequency smartphone in static and kinematic modes.The results showed that in the static mode,the RMS position errors of the dualfrequency smartphone PPP solutions in the E,N,and U directions were 21.8 cm,4.1 cm,and 11.0 cm,respectively,after convergence to 1 m within 102 minutes.The PPP of dual-frequency smartphone showed similar accuracy with geodetic receiver in single-frequency mode,while geodetic receiver in dual-frequency mode has higher accuracy.In the kinematic mode,the positioning track of the smartphone dualfrequency data had severe fluctuations,the positioning tracks derived from the smartphone and the geodetic receiver showed approximately difference of 3-5 m.(5)Considering smartphone in daily use,the experiment of real-time positioning of dual-frequency smartphone in different environments was carried out.Compared with the devices of different price and different use,dual-frequency smartphones did not show better positioning accuracy than single-frequency smartphones,with a positioning accuracy of 3.389 m in the horizontal direction,while in a masking environments,because of the anti-jamming capabilities of L5 frequency data,dual-frequency smartphones show better positioning performance than singlefrequency smartphones.In heavily shaded environments,the smartphone's positioning performance is poor,while the Trimble Catalyst,an external antenna system for smartphone,expressed the best positioning performance.