不同环境下手机GNSS数据质量及PPP性能分析

Comparative analysis on GNSS data quality and PPP performance of smartphones under different environments

为了进一步提高智能手机的定位精度,提出一种不同环境下智能手机全球卫星导航系统(GNSS)数据质量及精密单点定位(PPP)性能的分析方法:通过可见卫星数、数据完整率、数据中断次数、载波噪声密度比(C/N0,文中简称为载噪比)、多路径5个指标对小米8手机在开阔、信号塔、河边、树荫和高楼5种不同环境下的GNSS数据质量进行对比分析;随后测试其在不同环境下的PPP性能。结果表明:在可见卫星数方面,全球定位系统(GPS)与北斗卫星导航系统(BDS)观测卫星数明显较多;在数据完整率方面,L5/E5a频率信号相对L1/E1频率信号更易受环境因素的影响;对于数据中断情况,L5/E5a频率信号发生中断的次数在开阔、信号塔、河边和树荫4个不同环境下分别比L1/E1频率信号增加了95%、89%、54%和32%;对于载噪比,不同环境下的L1/G1/B1/E1频率信号C/N0均与高度角呈明显正相关关系,而L5/E5a频率信号C/N0与高度角无明显相关关系;在多路径方面,小米8手机的多路径均方根误差是天宝大地型接收机的5倍多,表明手机内置的线性极化天线对多路径的抑制能力较差;另外,河边和高楼环境下的多路径误差明显增大;在定位性能方面,使用单双频混合PPP模型在静态开阔环境下小米8手机三维定位精度可达1.45 m,相比信号塔、河边、树荫和高楼环境分别提高了6%、42%、44%和94%,动态PPP三维定位精度相比静态下降到2.35 m。

In order to further improve the positioning accuracy of smartphones,the paper proposed a method of analyzing global navigation satellite system(GNSS)data quality and precise point positioning(PPP)performance of smartphones under different environments:the GNSS data quality of Xiaomi Mi8 smartphones in the enviroments of open lands,signal transmitting towers,riversides,shades and urban canyons was comparatively analyzed by the indexes of the number of visible satellites,data integrity rate,data interruption times,carrier-to-noise density(C/N0)and multipath effect;afterward,the performance of precise point positioning(PPP)on a Xiaomi Mi8 smartphone under different environments was tested.Results showed that:the number of global positioning system(GPS)satellites and BeiDou satellite navigation system(BDS)satellites could be both significantly more than that of other constellations;in terms of data integrity rate,the L5/E5a frequency signals could be more susceptible to environmental changes;the data interruption times at L5/E5a frequency signals could be 95%,89%,54%and 32%,respectively,more than that at L1/E1 frequencies in open land,signal transmitting tower,riverside,and shade environments;the C/N0 at L1/G1/B1/E1 frequencies in different environments would have a significant positive correlation with the elevation angle,while the C/N0 at L5/E5a frequencies could have no obvious correlation with the elevation angle;the root mean square error of the multipath effect of the Xiaomi Mi8 smartphone would be more than 5 times that of a geodetic receiver named Trimble R9,indicating that the linear polarization antenna built-in Xiaomi Mi8 could have poor multipath suppression ability;in addition,the multipath effect would be relatively large in riverside and urban canyon environments;in the case of positioning performance,in the static mode,the three-dimensional positioning accuracy of the Xiaomi Mi8 smartphone in the open environment could reach 1.45 m using mixed single-frequency and dual-frequency PPP model,which would improve by 6%,42%,44%and 94%over that in the signal transmitting tower,riverside,shade and urban canyon environments,respectively,while in the kinematic mode,the three-dimensional PPP accuracy could decrease to 2.35 m.