惯导辅助的无电离层与宽巷组合周跳探测与修复方法

由于卫星信号被遮挡、低信噪比或接收机运动等原因,载波相位观测值较正常值会发生周跳。为解决这一问题,基于精密单点定位与惯导组合系统,提出了一种有效的惯导辅助周跳探测与修复方法。该方法基于无电离层（ionospheric free,IF）组合与宽巷（wide lane,WL）组合,利用惯导短时高精度信息代替伪距消除站星几何距离,结合历元间差、星间差等建立惯导辅助的IF组合模型和惯导辅助的WL组合模型。惯导辅助的IF组合模型不受电离层延迟影响,但无法探测特殊比例周跳,惯导辅助的WL组合模型波长较长,却无法探测双频等周周跳,两者的综合使用实现了优势互补。实验结果表明,该方法不仅能有效探测出各种大、小、双频等周和特殊比例周跳,而且在一定卫星信号中断时间内能实现周跳瞬时校正。     

一种INS辅助的PPP周跳探测方法

PPP/INS组合导航系统中,接收机载波相位观测值由于接收机高动态、卫星低仰角、信号被遮挡等原因,往往发生周跳。周跳不仅会影响PPP定位精度,而且可能会导致模糊度参数重新初始化以致数十分钟才能重新收敛。针对以上问题,本文提出利用惯性导航系统（INS）辅助PPP宽巷周跳探测的新策略,通过具有短时高精度的INS信息,消除宽巷组合中的站星几何位置,克服传统MW方法中码伪距噪声及多路径误差的影响。试验表明,INS辅助的宽巷周跳探测方法能够精确识别各种宽巷小周跳。将该方法与无几何距离（GF）组合方法相结合,可以实现对双频等周周跳和特殊周跳（5/4、9/7等）的探测,具有较高探测精度,并可应用于实时周跳探测。     

利用历元间差分观测值进行参考站周跳探测与修复

载波观测量是高精度卫星导航定位及其相关应用的基础，其整周模糊度的正确解算是实现厘米级导航定位和纳米级授时的关键。周跳探测与修复直接影响整周模糊度解算的性能，尤其对于连续运行参考站网等高精度位置服务的核心基础设施，保证连续可靠的模糊度解算是实现高精度位置服务的重要保障。参考站接收机具有观测值精度高、静止等特点，且采样频率较高（一般为1 Hz），在较短的时间间隔内，电离层延迟、对流层延迟、硬件延迟等误差相关性较强。基于以上特点，本文将历元间差分法应用于参考站周跳探测与修复，结合参考站静止的特性，提出了一种适用于参考站的周跳探测与修复的方法。该方法无需进行观测值组合，同时避免了伪距噪声的影响，探测精度高，且单站各个频率可以单独探测，在周跳修复的过程中，考虑非整周粗差并进行剔除。试验表明，该方法可以准确地探测和修复1周的整周周跳，可以探测小数偏差大于0.1周的非整周粗差。     

惯性辅助强多径环境中的北斗三频周跳探测与修复

针对北斗三频信号,引入了惯性信息辅助周跳探测与修复,建立了北斗/INS松组合模型,提高了多径误差严重影响下的BDS周跳探测成功率和修复率。在常规伪距-相位组合与几何无关组合探测三频周跳的基础上,提出了INS定位辅助的北斗三频组合法,构建了INS辅助的周跳决策量,分析了INS定位误差对周跳探测的影响。该方法克服了周跳探测受伪距观测值精度影响的不足,实现了北斗系统多径环境中的小周跳探测。试验采用船载INS/BDS三频组合系统进行数据实测分析,结果表明,在水面强多径噪声环境导致传统三频探测模型失效的情况下,该方法显著提高了探测成功率与修复率,并适用于低频北斗观测数据。     

高轨飞行器精确导航的载波相位时间差分/捷联惯导紧组合算法

提出了基于载波相位时间差分与捷联惯导紧组合的方法对高轨飞行器进行自主导航,其中捷联惯导主要在飞行器进行轨道机动时使用,分析了载波相位观测方程中的误差因素,通过SRUKF建立了组合导航非线性滤波模型,研究了周跳检测与修复策略。研究表明,提出的导航方法避免了整周模糊度的求解和周跳的影响,因而可使导航系统具有高精度和高可靠性...     

GNSS/INS组合导航系统初始对准及其故障修复研究

正全球卫星导航系统可在无遮蔽环境中为用户提供高精度、低频率的导航定位服务,但在复杂环境中,GNSS信号易被遮挡或干扰。惯性导航系统经过初始化后,能够独立自主提供高频率、连续的位置、速度和姿态信息。通过二者合理结合,能够在遮蔽或半遮蔽环境中为用户提供连续且可靠的导航解。本文重点研究了GNSS/INS组合导航系统初始化及其故障修复方法,内容包括高精度惯导快速自对准技术、大失准角故障处理、磁力计辅助MEMS IMU抗差自适应姿态融合、神经网络辅助GNSS/INS组合导航系统故障识别与修复和惯导辅助BDS三频周跳探测与修复技术等,主要研究成果如下:     

GPS/INS紧组合的INS辅助周跳探测与修复

建立了GPS/INS紧组合定位模型,改正惯性器件误差及电离层折射误差,对不同组合观测量的误差影响进行了分析,构造不同观测值组合,提出了基于惯性信息辅助的GPS周跳自适应探测方法,分析了INS定位误差对周跳探测的影响,给出了周跳探测误报率及修复成功率评价指标,提出了一种周跳检测阈值自适应确定方法。利用实测组合导航试验数据验证本文的算法,文中模拟了不同的单历元多周跳及信号失锁条件,结果表明,在GPS信号完全失锁20 s内,该方法能准确检测和修复所有周跳,中断时间的延长降低了周跳修复的成功率;GPS信号部分失锁时,在模拟的90 s中断时段内仍能修复所有周跳;模拟了170历元的5 s间隔密集周跳,周跳探测成功率为100%,正确修复率为99.41%。     

利用双频载波相位观测值求差的方法探测与修复周跳

周跳的探测与修复,特别是小周跳的探测是GPS高精度实时定位的热点问题.分析两种载波相位观测值的关系,提出一种利用两种载波相邻相位观测值求差的方法探测与修复周跳.通过实例分析,证明该方法能够有效地探测并修复周跳.     

北斗三号卫星的周跳探测与修复算法

在高精度GNSS应用中,载波相位观测值中出现周跳问题直接影响到整周模糊度的解算及最终定位精度,针对北斗卫星导航系统三代卫星密集发射的现状,该文提出一种联合采用码伪距与相位伪距组合、MW组合和电离层残差组合进行北斗三号卫星双频数据周跳探测和修复的算法。该算法可以发挥单个组合优势有效进行周跳探测且能避免各自的探测盲区,联合3种组合观测量进行周跳值求解时,计算方法简单,可以直接取整得到周跳值。通过对北斗三号卫星双频实测数据的处理分析,验证了该算法能够准确地探测出所有周跳,并能够有效修复。     

摄影/惯导组合定位技术在GNSS动态定位性能测试中的应用

在分析现有GNSS动态定位精度评估方法不足的基础上,提出区别于传统组合导航滤波算法的摄影/惯导组合定位技术。将多个摄影节点的位置观测量作为基准,利用最小二乘最优估计法统一解算捷联惯导误差参数。摄影/惯导组合定位方法的基本观测量、工作模式与卫星导航定位方法有本质区别;同时又具备高精度定位、高动态定位、高数据刷新率和差异数据观测量4个条件,十分适合作为GNSS动态定位性能测试的评估技术。通过在标志场内进行的摄影测量试验和摄影/惯导组合定位性能仿真试验,验证了摄影/惯导组合定位方法的可行性。该方法为首次提出,具有一定的科学价值。     

Instantaneous re-initialization in real-time kinematic PPP with cycle slip fixing

The network-based real-time kinematic (RTK) positioning has been widely used for high-accuracy applications. However, the precise point positioning (PPP) technique can also achieve centimeter to decimeter kinematic positioning accuracy without restriction of inter-station distances but is not as popular as network RTK for real-time engineering applications. Typically, PPP requires a long initialization time and continuous satellite signals to maintain the high accuracy. In case of phase breaks or loss of signals, re-initialization is usually required. An approach of instantaneous cycle slips fixing using undifferenced carrier phase measurements is proposed, which leads to instantaneous re-initialization for real-time PPP. In the proposed approach, various errors such as real-time orbit and clock errors, atmosphere delay and wind-up effects are first refined and isolated from integer cycle slips. The integer values of cycle slips can then be estimated and fixed with the LAMBDA technique by applying a cascade cycle slip resolution strategy. Numerical experiments with different user dynamics are carried out to allow a comprehensive evaluation of efficiency and robustness of the cycle slip fixing algorithm. The results show that the cycle slips can be fixed correctly in all cases considered and that data gaps of up to 300?s can be connected with high confidence. As a result, instantaneous re-initialization is achieved in the real-time PPP processing.     

GNSS精密单点定位中的实时质量控制

提出了一套适用于GNSS精密单点定位(PPP)的实时质量控制方法,重点研究了钟跳探测与修复、周跳探测与标记、抗差估计方法,并在现有质量控制方法的基础上进行了改进。对比分析了不同质量控制方案对PPP的影响,结果表明,钟跳不利于周跳探测,严重影响非差PPP的精度和效率,必须对其进行探测与修复;联合MW、GF组合可以探测出绝大多数周跳,且较使用单一方法更为准确、可靠;采用改进的抗差估计有效抑制了残余粗差对精密定位的影响,显著提高了PPP的精度和可靠性。     

Cycle slip detection and repair of undifferenced single-frequency GPS carrier phase observations

Cycle slip detection and repair is an important issue in the GPS data processing. Different methods have been developed to detect and repair cycle slips on undifferenced , single- or double-differenced observations. The issue is still crucial for high-precision GPS positioning, especially for the undifferenced GPS observations. A method is proposed to fix cycle slips based on the generalized likelihood ratio (GLR) test. The method has a good performance on cycle slip fixing of undifferenced carrier phase observations on individual frequencies, either on L1 or on L2, without making a linear combination among the observables. The functional model is a piecewise cubic curve fitted to a number of consecutive data using the least squares cubic spline approximation (LS-CSA). For fixing the cycle slips, an integer estimation technique is employed to determine the integer values from the float solution. The performance of the proposed method is then compared with the existing two methods using simulated data. The results on a few GPS data sets with sampling rate of 1 Hz or higher confirm that this method can detect and correct all simulated cycle slips regardless of the size of the cycle slip or the satellite elevation angle. The efficacy of the method is then investigated on the GPS data sets with lower sampling rates of 5, 10, and 30 s. The results indicate that the proposed method always performs the best for the data sets considered. This is thus an appropriate method for cycle slip detection and repair of single-frequency GPS observations.     

双频相位求差法与多普勒法探测与修复周跳的比较

介绍产生周跳和常用的探测与修复周跳方法,并通过用双频相位求差法和多普勒方法对周跳进行探测和修复,算例结果表明两种方法均能准确地锁定发生小周跳的历元,且能高效地修复观测值。两种方法执行效率高,实用性强,适合RTK等动态导航定位的应用。     

A cycle slip fixing method with GPS + GLONASS observations in real-time kinematic PPP

A key limitation of precise point positioning (PPP) is the long convergence time, which requires about 30 min under normal conditions. Frequent cycle slips or data gaps in real-time operation force repeated re-convergence. Repairing cycle slips with GPS data alone in severely blocked environments is difficult. Adding GLONASS data can supply redundant observations, but adds the difficulty of having to deal with differing wavelengths. We propose a single-difference between epoch (SDBE) method to integrate GPS and GLONASS for cycle slip fixing. The inter-system bias can be eliminated by SDBE, thus only one receiver clock parameter is needed for both systems. The inter-frequency bias of GLONASS satellites also cancels in the SDBE, so cycle slips are preserved as integers, and the LAMBDA method is adopted to search for cycle slips. Data from 7 days of 20 globally distributed IGS sites were selected to test the proposed cycle slip fixing procedure with artificial blocking of the signal; cycle slips were introduced for all un-blocked satellites at each epoch. For a 30-s sampling interval, the average success rate of fixing can be improved from 73 to 98 % by adding GLONASS. Even for a 180-s sampling interval, GPS + GLONASS can achieve a success rate of 81 %. A real-time kinematic PPP experiment was also performed, and the results show that using GPS + GLONASS can achieve continuous high-accuracy real-time PPP without re-convergence.     

A double-differenced cycle slip detection and repair method for GNSS CORS network

The difficulty to detect and repair cycle slip of carrier phase measurements is a key limit for continuously high accuracy of GNSS positioning and navigation services. We propose an automated cycle slip detection and repair method for data preprocessing of a CORS network. The method jointly uses double-differenced (DD) geometry-free (GF) combination and ionospheric-free observation corrected for the computed geometrical distance (IF-OMC) to estimate the cycle slips in dual-frequency observations. The DD GF combination, which is only affected by the ionospheric residual, can be used to detect cycle slips with high reliability except for special pairs such as (77, 60) on GPS L1/L2 frequencies. The detection principle of the IF-OMC observable is such that there is a large discontinuity related to the previous epoch when cycle slips occur at the present epoch. The disadvantages of these two combinations can be overcome employing the proposed detection method. The cycle slip pair (77, 60) has no effect on the GF combination, while a change of 14.65 m is derived from GPS L1/L2 observations using the IF-OMC algorithm. Using pre-determined station coordinates as precise values, we found that the accuracy of the DD IF-OMC combination was 18 mm for a 200-km CORS baseline. Therefore, cycle slips in dual-frequency observations can be correctly and uniquely determined using DD GF and IF-OMC equations. The proposed method was verified by adding simulated cycle slips in observations collected from the CORS network under a quiet ionosphere and shown to be effective. Moreover, the method was assessed with observations made during intense ionospheric activity, which generated extensive cycle slips. The results show that the algorithm can detect and repair all cycle slips apart from two exceptions relating to long data gaps.     

实时精密单点定位中周跳探测与修复的算法研究

提出了一种适用于实时GPS精密单点定位的周跳探测与修复的新算法。该算法步骤为：①利用M-W组合和电离层残差组合初步确定没有发生周跳和可能发生周跳的卫星;②利用当前历元与前一（或几个）历元的L1、L2和Lw观测值和第一步得出的没有发生周跳的卫星信息,采用基于历元间差分观测值的周跳处理模型对可能发生周跳的卫星进行周跳探测;③对第二步中周跳处理失败的卫星进行进一步的精化处理,以尽可能修复周跳。实验表明,新算法在实时GPS精密单点定位中可以准确地探测并修复周跳。     

一种基于多项式拟合的单频周跳探测改进方法

提出了一种基于多项式拟合的单频周跳探测的改进方法,综合利用了星间单差载波相位观测数据和非差载波相位观测数据,实现了单频载波相位周跳的准确定位。