非差非组合电离层加权PPP-RTK/INS紧组合模型

Undifferenced and Uncombined ionospheric-weighted PPP-RTK/INS tightly integration model

PPP-RTK是一种可实现快速模糊度固定的精密单点定位(PPP)技术,它的组成包括由多个接收机构成的网端用于生成各类精密改正产品,以及单站构成的用户端以实现快速高精度定位.当网端是中等尺度参考网,即参考站之间的站间距在百余公里,有必要引入电离层加权模型,其优势在于能够增强PPP-RTK函数模型.此外,从非差非组合观测值层面出发,其能够兼容单/双频用户.然而,单凭卫星导航定位技术很难在复杂环境下提供连续导航定位服务.本文从理论到应用,基于非差非组合电离层加权PPP-RTK模型,构建了单/双频PPP-RTK/INS紧组合模型.在距离最近参考站约70 km的区域进行了两次车载实验,并分别利用单/双频PPP-RTK以及PPP-RTK/INS紧组合模型的实时处理结果进行分析.结果表明,双频PPP-RTK/INS紧组合在半城市环境能从分米级定位提升至厘米级定位,重收敛时间从11 s提升至3.6 s.以水平偏差小于0.2 m评估定位可用率,双频PPP-RTK/INS紧组合模型在半城市环境和复杂城市环境中分别可实现100%和96.97%.考虑车道级定位,单频PPP-RTK/INS紧组合模型在半城市和复杂城市环境内分别可实现分米以及亚米级定位,其在水平偏差在0.5 m内的可用率分别为98.97%和76.1%.

PPP-RTK,otherwise known as integer ambiguity resolution enabled precise point positioning,its implementation requires a network consisting of multiple receivers to generate corrections,and a user equipped with a standalone receiver to be positioned.In case of a medium-scale network with inter-station distances of a few hundreds of kilometers,it is sensible to turn to the ionosphere-weighted(IW)PPP-RTK,in which,GNSS observation equations formulated at undifferenced and uncombined level have been further strengthened by imposing constraints on the stochastic characteristics of the ionosphere,besides making the model compatible for multi-frequency and single-frequency users.Nevertheless,the vulnerability of satellite signals severely limits the application in challenging environments.In this contribution,we integrate the IW-PPP-RTK with the inertial navigation system(INS)through setting up a tightly-coupled(TC)model with dual-and single-frequency observations.We evaluate the performance of this TC model with two sets of vehicle-based data collected in GNSS-deprived environments that are approximately 70 km from the nearest reference station.The results indicate that,the positioning accuracy of dual-frequency PPP-RTK can be improved from decimeter level to centimeter level in a semi-urban environment with INS augmentation,and the refixed time is reduced from 11 s to 3.6 s in a typical signal interruption scenario.Moreover,in semi-urban and urban environments,the availability of dual-frequency PPP-RTK/INS TC is 100%and 96.9%,respectively,when the horizontal error is less than 0.2 m.Besides,taking the lane-level navigation with single-frequency PPP-RTK/INS TC into consideration,evaluating the availability that the horizontal error less than 0.5 m,the single-frequency PPP-RTK/INS TC are 98.97%and 76.1%in semi-urban and urban environments,respectively.