| Global navigation satellite system(GNSS)can realize all-weather positioning,navigation and timing(PNT)functions all over the world,and has been widely used in many industries.With the popularity of smart terminals,location-based services have greatly promoted the development of information dissemination,transportation and logistics,engineering construction and other industries.Users are increasingly dependent on smartphone location services,but also put forward higher requirements for them,which makes the research on GNSS high precision positioning of Android smartphones become a current research hotspot.This thesis evaluates the GNSS data quality of Android smartphones,and studies the Standard Point Positioning(SPP)and single-frequency Precise Point Positioning(PPP)based on the original GNSS data of Android smartphones,which is of great significance to improve the GNSS positioning accuracy of Android smartphones and meet the high-precision positioning needs of the mass market.Based on the GNSS positioning theory,this thesis studies the high-precision positioning of Android smartphones based on the original GNSS data,including the quality assessment of the original GNSS data of Android smartphones,the quality control algorithms of GNSS data based on Android smartphones and Android smartphones’ SPP and PPP algorithms.The main work and results are as follows:(1)The GNSS observations of Android smartphones,the main error sources of GNSS positioning of smartphones and the common correction measures are studied.The quality of GNSS raw observation data of Android smartphones is systematically analyzed.Compared with the geodesic receiver,the GNSS raw data of Android smartphones is analyzed from many aspects.The results showed that the quality of GNSS raw observation data from Android smartphones is poor compared with that of the receiver,with a low number of visible satellites and missing data.The carrier-tonoise ratio is 10-15 Db-Hz lower than that of the receiver,and the correlation with the elevation angle is low.The multipath error of two dual-band smartphones in the L1 band is about 2～4 m,and the multipath error of model B smartphone in the L5 band is small,while the multipath error of model A smartphone is still large.These results provide the basis for data quality control algorithms later.(2)The mathematical model of SPP for Android smartphones is studied,and the SPP positioning performance of GPS,BDS and GRCE(GPS + GLONASS + BDS +Galileo)quad systems is analyzed respectively.The GNSS data quality control algorithm is proposed for the data characteristics of Android smartphones,which effectively improves the positioning accuracy.The results showed that,derived from the use of Doppler-Smoothed-Code(DSC)and signal-to-noise ratio stochastic models,the SPP positioning accuracy of Android smartphones can be within 3 m for the GPS,within 4.5 m for the BDS,and sub-meter for the GRCE quad systems,which is a significant improvement compared with the results of the combination of no smoothing and height angle model.(3)The model and data processing strategy of single-frequency PPP for Android smartphones are studied,and the static and static imitation dynamic positioning performance of PPP in GPS and GRCE systems are analyzed.The results are illustrated that in the PPP static positioning,the positioning accuracy can only reach the meter level and the convergence time is long under the GPS,while the positioning accuracy can reach the sub-meter level and converge in the E and N directions within40 min under the GRCE systems.In the PPP dynamic positioning,the positioning accuracy of smartphone single-frequency PPP can only reach the meter level.The relevant research results of this thesis provide technical support for the application of GNSS high-precision positioning technology in the field of Android smartphone location services,and have certain application value. |
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