面向北斗单历元分米级定位的ARAIM保护水平计算方法

ARAIM protection level calculation method for BeiDou decimeter level single epoch point positioning

精密定位的质量控制和完好性评估是实时全球卫星导航系统(GNSS)导航应用不可或缺的环节,尤其是在GNSS易受损害的城市峡谷等场景下,这种需求更加迫切.广域精密单点定位(PPP)瞬时分米级定位,利用GNSS三频信号形成的两个宽巷观测值可以实现单点单历元分米级定位.然而,在城市复杂环境中,反射信号、严重多路径以及其他信号干扰对定位造成的影响无法准确评估与识别,限制了PPP瞬时分米级单点定位的应用.完好性概念中的高级接收机自主完好性监测(ARAIM)可以计算用户定位误差最小置信区间的上限保护水平(PL)以评估定位有效性,可经过一定改进用于PPP瞬时定位的质量控制.针对当前ARAIM中计算PL的误差模型难以适应高精度定位需求的问题,提出了一种改进的ARAIM PL算法,称其为BARAIM(Back Advanced Receiver Autonomous Integrity Monitoring).使用PPP三频组合观测值残差对ARAIM权与误差模型进行修正以计算PL.基于不同复杂程度的环境下采集的车载数据对算法进行了验证,对PL的改进情况以及导航的可用性提升情况进行评估.结果表明:在不同环境下,基于改进的B-ARAIM算法得到的PL,相比传统方法得到的PL更符合城市定位的需要,将PL降低了30%~70%.此方法有助于将ARAIM算法应用在高精度GNSS定位领域.

Precision positioning quality control and integrity assessment is an integral part of real-time Global Navigation Satellite System(GNSS)navigation applications,especially in GNSS vulnerable urban canyon scenarios.Wide-area precise point positioning(PPP)instantaneous decimeter level positioning can be realized by using the observation values of two wide lanes formed by GNSS three-frequency signal.However,in the complex urban environment,the impact of reflected signals,serious multipath and other signal interference on positioning cannot be accurately evaluated and identified,which limits the application of PPP instantaneous decimeter-level point positioning.advanced receiver autonomous integrity monitoring(ARAIM)in the concept of integrity can calculate the upper limit protection level(PL)of the minimum confidence interval of user positioning error to evaluate the positioning effectiveness,which can be used for quality control of PPP instantaneous positioning after some improvement.Aiming at the problem that the error model used to calculate the PL in ARAIM is difficult to meet the requirements of high-precision positioning,an improved ARAIM PL algorithm which is called B-ARAIM is proposed in this paper.The residual of PPP three-frequency combination observation value is used to modify the ARAIM weight and error model to calculate the PL.This paper verifies the algorithm based on on-board data collected in environments with different complexity levels,and evaluates the improvement of PL and the improvement of navigation availability.The results show that the PL obtained by the improved B-ARAIM algorithm is more in line with the needs of city positioning than that obtained by the traditional method,and the PL is reduced by 30%to 70%in different environments.This method is helpful to the application of ARAIM algorithm in GNSS positioning.