| With the rapid development of science and technology,almost every smart terminal is equipped with a Global Navigation Satellite System(GNSS)chip.The Location Based Services(LBS)it provides can be used in travel,social networking and shopping.It greatly enriches and facilitates people's daily life.In 2016,the Android 7.0 operating system opened the interface for obtaining raw observation data of GNSS on Android smart terminals.Therefore,it has become a new possibility to achieve high-precision GNSS positioning on Android smart terminals.At the same time,developers can also further improve and optimize the GNSS positioning performance of Android smart terminals.On this basis,this article combines the current domestic and foreign research status and related results to systematically evaluate the quality of the original GNSS observation data of the Android smart terminal,and explore the GNSS positioning performance of the Android smart terminal.The main work and conclusions of this paper are as follows:(1)The current situation of the Android smart terminal hardware platform and the acquisition method of GNSS observations under the Android platform are described,and the positioning solution method based on the observations of pseudorange,carrier phase,Doppler,etc.is given.In terms of signal-to-noise ratio,multipath effect,number of observable satellites,and DOP value,a comprehensive and in-depth analysis of the GNSS observations of the Android smart terminal is carried out.The experimental results show that the signal-to-noise ratio of GNSS observations in the Android smartphone L1/L5 band is about 20-40dB,which is about 10-15dB lower than that of geodetic receivers,and the signal-to-noise ratio of the Android smartphone GNSS observations in the L5 band is about 20-40dB.The L1 band is higher.The multipath effect of Android smartphones is significantly higher than that of geodesic receivers.The L5 band has stronger antimultipath interference capability than the L1 band,and is more suitable for GNSS positioning in a complex environment with tall buildings and severe multipath effects.(2)To explore the static positioning accuracy of Android smart terminals.When the smart phone adopts the pseudo-range single-point positioning algorithm,the three multi-system combination methods are used for positioning calculation,which can achieve meter-level positioning accuracy in the horizontal direction.In the vertical direction,only the Mi 8 mobile phone has an accuracy of more than ten meters when using a single BDS system for positioning;when Mi 8 uses carrier phase di fferential positioning,the positioning accuracy of the single BDS system can only reach the meter level,and the other two systems are combined.The positioning accuracy has reached the decimeter level.In addition,the positioning accuracy of the Huawei P40 using three multi-system combinations can reach the decimeter level.Because Xiaomi 8 mobile phone observes fewer BDS satellites and the quality of BDS data is low,the positioning solution accuracy of the two positioning algorithms of the Xiaomi 8 single BDS system is poor.Analyzing the combined positioning performance of the three systems,it is found that the BDS+GPS dual-system positioning can improve the positioning accuracy compared to the single-system positioning,and can shorten the convergence time to a certain extent.For static precision single-point positioning,the overall positioning error curves of the two mobile phones decrease over time and tend to stabilize.The horizontal positioning accuracy can reach the decimeter level,and the vertical positioning accuracy is about 1m.For Android smart phones,precise single-point positioning can greatly improve positioning accuracy,and can fully meet the positioning needs of ordinary users and users in low-demand professional fields.Compared with geodetic receivers,the positioning accuracy of Android smartphones is always an order of magnitude different.(3)To study the dynamic positioning performance of Android smart terminals in different environments.In an open environment,smart phones use three GNSS positioning technologies for positioning calculations,and both phones can achieve meterlevel positioning accuracy.Among them,the accuracy of differential positioning is the highest,and the accuracy of pseudo-range single-point positioning is similar to that of precision single-point positioning;in complex environments,the equipment is mostly in obscured areas,and the number of observable satellites decreases sharply,and the influence of GNSS signal multipath effects is aggravated.Therefore,smart phones and geodetic receivers have a lot of large errors in positioning and solving,and some of them even exceed 100m.In summary,the overall positioning accuracy of the two mobile phones in a complex environment can only reach ten meters.Figure[57]Table[14]Reference[80]... |
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