三种典型低轨增强星座与北斗系统联合应用的RAIM性能分析

接收机自主完好性监测(receiver autonomous integrity monitoring,RAIM)是终端用户高可靠导航定位的保障,低轨卫星的发展为完好性监测带来新的机遇,然而不同低轨星座增强下的终端RAIM性能可能会存在显著差异。基于高轨道倾角(80颗)、中轨道倾角(120颗)和混合轨道倾角(168颗)3种典型的低轨星座,系统评估了低轨卫星增强下的北斗卫星导航系统（BeiDou navigation satellite system,BDS）RAIM可用性及故障检测效果。仿真计算结果表明：对于高纬区域,高轨道倾角增强下的RAIM可用性效果最好,而在中、低纬区域,中轨道倾角星座增强下的RAIM可用性效果最优;在全球范围内,高轨道倾角、中轨道倾角和混合轨道倾角星座增强下非精密进近阶段的RAIM可用性较BDS分别提升30.5%、29.0%和41.0%。由此可知,由不同轨道倾角组成的混合星座可较好地弥补可视卫星在空间覆盖上的缺陷,其全球RAIM可用性增强效果最优,增强下的RAIM可检测到的最小伪距偏差较之前平均减小33.3 m。     

基于IGGⅢ权函数的GNSS/INS组合导航RAIM模型

将IGGⅢ权函数引入GNSS/INS组合导航中,提出基于IGGⅢ权函数的GNSS/INS组合导航RAIM模型,根据Kalman残差平方和服从x2分布,论证运用IGGⅢ权函数探测粗差星的可行性.开发模拟平台生成GPS、Galileo、GLONASS和BeiDou卫星星座,卫星观测值加入单粗差和多粗差,测试RAIM模型的粗差探测能力.算例表明,RAIM模型能够准确定位粗差星,剔除粗差星后,可提高GNSS/INS组合导航精度.     

接收机自主完好性监测的算法分析

RAIM技术在接收机端实现卫星完好性监测,因此,监测算法的原理、正确性和灵敏度值得分析与研究。文中给出了RAIM故障检测和识别的数学模型,同时给出了两者的完好性保证算法。对告警门限值、误警率、漏检率之间的关系进行了较为全面的分析,分析了故障检测和故障识别功能与误警率、漏检率之间的关系。分析结果表明:可视卫星数相同时,误警概率越低,FD和FI的精度越低;误警概率相同时,可视卫星数越多,FD的灵敏度越高,FI的灵敏度越低;RAIM可用性一定时,同时满足低漏检率和低误警率是不可能的。     

RAIM算法研究

用户自主完备性监测RAIM算法是广域差分GPS的关键和核心技术之一。在已有RAIM算法的基础上，讨论了粗差探测和定位的方法，并给出了Parity方法中剔除多个粗差的算法，最后用‘99南海实测数据进行了验证。     

GPS接收机基于奇偶矢量的RAIM算法研究

RAIM是指用户接收机利用多余观测量为定位解自主地提供完善性监测,其基本功能包括故障检测（FD）及故障排除（FE）两个部分。文中对基于奇偶矢量法的GPS接收机自主完善性监测（RAIM）算法进行分析与研究,并以具体数据为例,对该算法进行验证分析。     

观测量非等权模型RAIM可用性算法研究

针对基于最小二乘残差估计的接收机自主完好性监测(RAIM)算法,结合伪距单点定位多采用观测量非等权模型,提出一种观测量非等权模型RAIM可用性算法,对实际计算具有借鉴意义。通过实测数据,分析了等权模型和非等权模型RAIM可用性算法对卫星几何分布的估计情况,验证了观测量非等权模型RAIM可用性算法的可行性。     

基于定位误差估计减少RAIM误警的方法

在GPS接收机自主完好性监测（RAIM）中，卫星出现伪距偏差可能导致检测量超限而实际定位误差不超限的误警。我们提出一种减少误警的方法，该方法是在检测和识别故障后，估计定位误差并将其与误差告警限值比较。用一组实测GPS星历数据进行仿真试验，试验结果表明，这种方法减少误警的能力和伪距偏差有关。当伪距偏差较小时此方法的误警率小于传统RAIM算法，当伪距偏差较大时和传统RAIM算法的误警率相当。     

LPV-200下中国区域内 ARAIM 可用性评估

随着GNSS星座的增多以及多频技术的发展,基于解分离的高级接收机自主完好性监测算法被广泛研究。本文介绍了该算法的基本原理,并结合多星座特点,对中国区域内ARAIM算法能力进行评估,利用仿真数据分析了用户测距精度对算法可用性的影响;探讨了不同星座数据在中国区域的完好性性能。仿真结果表明：双频条件下,系统完好性性能很大程度上取决于用户测距精度,在中国区域内,仅GPS单星座不足以满足LPV-200进近对完好性的要求,GPS与Galileo双星座下,ARAIM 算法覆盖率可达100％。     

基于多模GNSS接收机的卫星系统完好性监测

为了满足多卫星系统完好性监测的需要,本文通过对比不同卫星系统定位结果的方法来监测各个卫星系统的可用性。利用上述方法对实测的三模(GPS、GLONASS和COMPASS)数据进行了处理,结果表明该方法具有可行性,可为多模GNSS接收机的自主完好性监测提供参考信息。     

GPS和Galileo系统下RAIM算法可用性分析

介绍了RAIM算法中故障检测及其完好性保证的原理,采用STK仿真得到GPS和Galileo系统的卫星坐标及中国区域内的格网点坐标,结合航空用户对完好性需求,比较了GPS和Galileo系统下、不同类型导航性能需求的RAIM算法的可用性结果,分析了截止高度角、可视卫星数对故障检测可用性的影响.结果表明:当截止高度角越低、可视卫星数越多,故障检测的可用性越高;相同截止高度角条件时,Galileo系统下的RAIM可用性要高于GPS系统;单一的GPS导航系统难以满足垂直引导进近和精密进近等高等级的航空需求.     

GPS和Galileo系统下RAIM算法可用性分析

介绍了RAIM算法中故障检测及其完好性保证的原理,采用STK仿真得到GPS和Galileo系统的卫星坐标及中国区域内的格网点坐标,结合航空用户对完好性需求,比较了GPS和Galileo系统下、不同类型导航性能需求的RAIM算法的可用性结果,分析了截止高度角、可视卫星数对故障检测可用性的影响。结果表明:当截止高度角越低、可视卫星数越多,故障检测的可用性越高;相同截止高度角条件时,Galileo系统下的RAIM可用性要高于GPS系统;单一的GPS导航系统难以满足垂直引导进近和精密进近等高等级的航空需求。     

基于圆概率误差的RAIM可用性算法研究

把导航领域、军事领域和导航电子地图中广泛应用的圆概率误差(circular error probable,CEP)引入到HPL(horizontal protection level)的计算中,在最小二乘残差法基础上构建了基于圆概率误差的RAIM(receiver autonomous integrity monitoring)可用性算法。首先计算了在一定误警率、漏警率条件下多颗卫星发生故障时的水平定位偏差和一定置信度下的圆概率误差;然后以GPS导航星座为例,探讨了相关观测下计算HPL的新方法;最后把HPL与水平告警限差(horizontal alert limit,HAL)相比较,得到了基于圆概率误差的RAIM可用性,并通过算例验证了此方法的有效性和可行性。     

GNSS接收机自主完备性监测高级算法的有效性验证

针对RAIM的高级算法———ARAIM,使之应用于对GNSS完备性和生命安全要求更高的领域,基于GNSS实测数据对ARAIM算法下的垂直保护水平、精度、有效监测阈值、连续性风险进行了研究,并对ARA-IM算法下GNSS的可用性进行了评估。结果表明,相对于GPS系统而言,GPS/GLONASS系统下的垂直保护水平、精度、有效监测阈值、连续性风险及可用性完全满足LPV-200阶段的导航性能要求,验证了ARAIM算法在预测垂直保护水平、精度、有效监测阈值、连续性风险方面的有效性。     

Modeling and assessment of combined GPS/GLONASS precise point positioning

A combination of GPS and GLONASS observations can offer improved reliability, availability and accuracy for precise point positioning (PPP). We present and analyze a combined GPS/GLONASS PPP model, including both functional and stochastic components. Numerical comparison and analysis are conducted with respect to PPP based on only GPS or GLONASS observations to demonstrate the benefits of the combined GPS/GLONASS PPP. The observation residuals are analyzed for more appropriate stochastic modeling for observations from different navigation systems. An analysis is also made using different precise orbit and clock products. The performance of the combined GPS/GLONASS PPP is assessed using both static and kinematic data. The results indicate that the convergence time can be significantly reduced with the addition of GLONASS data. The positioning accuracy, however, is not significantly improved by adding GLONASS data if there is a sufficient number of GPS satellites with good geometry.     

GNSS receiver autonomous integrity monitoring (RAIM) performance analysis

The availability of GPS signals is a major concern for many existing and potential applications. Fortunately, with the development of Galileo by the European Commission (EC) and European Space Agency (ESA) and new funding for the restoration of the Russian GLONASS announced by the Russian Federation (Revnivykh et al., in European Navigation Conference 2005, Munich, Germany, July 19–22), the future for satellite-based positioning and navigation applications is extremely promising. With the complete cooperation from all these global navigation satellite systems (GNSS), greater levels of satellite visibility and therefore integrity can be expected. In this paper, a receiver autonomous integrity monitoring (RAIM) scheme along with reliability and separability measures are used to assess integrity performance levels of standalone GPS and integrated GPS/GLONASS, GPS/Galileo and GPS/GLONASS/Galileo systems where the clock offsets for each of the additional systems are estimated. It is shown, herein, that a minimum of three satellites must be visible in an additional system in order to provide a full integrity contribution when the system’s clock offset is to be estimated within the adjustment. A comparison of the integrity results obtained via system clock offsets estimated in the adjustment versus the case where the offsets are known and the measurements are corrected prior to the adjustment is also made for a high elevation mask scenario. Global simulation results for combined GPS/GLONASS/Galileo show that, theoretically, for the time of simulation and for any point on the globe, an outlier of 20 m can be detected with 80% probability at the 0.5% significance level and then separated from any other measurement with 90% probability. Corresponding values for the GPS only and combined GPS/GLONASS and GPS/Galileo systems, respectively, are approximately 435, 110 and 28 m, respectively, for the maximum MSBs and 312, 50 and 26 m, respectively, for the maximum MDBs. Temporal 24 h simulations for the GPS/GLONASS/Galileo scenario delivered agreeable results with the global snapshots for a 15° elevation mask. For the case where system clock offsets are estimated within the adjustment, it was shown that only the reliability measure was available for 100% of the time, with horizontal external reliability values of no more than about 12 m when a 30° masking angle was used. By assuming the clock offsets were determined and corrected for prior to the adjustment, the separability measure was markedly improved and was also available 100% of the time.     

GPS/BDS/GLONASS多系统组合定位分析

可见卫星数是评价导航系统定位性能的一个重要指标,也是系统可用性的基本要求。均方根差(亦称中误差)是观测精度的数据标准。本文通过实验分析了不同环境下的多系统组合的可见星数以及中误差,进而研究了多系统组合在不同环境中的可用性及定位精度。实验结果表明:在相同环境下,系统组合的可用性大幅提高,精度高于单GPS系统的精度,其中GPS/BDS/GLONASS三系统组合测量精度最高,GPS/BDS组合精度次之,GPS/GLONASS组合精度略低于GPS/BDS组合。     

Preliminary evaluation of the Russian GLONASS system as a potential geodetic tool

By the beginning of 1996 the Russian Global Navigation Satellite System (GLONASS) constellation was completely deployed, although several satellites have already been decommissioned since then. With 17 satellites in operation (status as of 21 December 1997, although two of them are unusable and one is a non-operative spare), GLONASS is now an alternative and a complement to GPS. We present an evaluation of the current status of the GLONASS system, paying particular attention to its possible geodetic applications. Data from several receivers were used for this evaluation, including data from GPS receivers in order to allow for a comparison between GLONASS and GPS. We tested the quality of the geodetic observables, the consistency of the broadcast orbits, the single-point positioning results, and we also looked at multipath errors and cycle slips in our GLONASS data. In general the GLONASS performance has been found to be very satisfactory, even better than GPS in aspects such as single-receiver positioning or in the quality of the second-frequency pseudo-ranges due to the degradation of the GPS measurement quality under selective availability and anti-spoofing. Received: 26 November 1996 / Accepted: 16 January 1998     

基于漏检概率的RAIM可用性分析方法

描述了通常基于单故障假设相应的HPL，或VPL，的计算模型，针对WAAS用户在应用RAIM时需要顾及多故障的情况，提出了基于漏检概率的可用性分析方法，并通过模拟计算得到一些结论。