State transformation extended Kalman filter for GPS/SINS tightly coupled integration

Extended Kalman filter (EKF) is a widely used estimator for integrated navigation systems, and it works well in general situations. However, in adverse conditions such as partially observable environments and highly dynamic maneuvers, the performance of the traditional EKF-based strap-down inertial navigation system (SINS)/GPS integrated navigation system is easily to be affected by the dynamic changes of the specific force, thus leading to the problem of error covariance inconsistency. Though the inconsistency problem can be overcome to some extent if the system matrix, the states and the error covariance matrix are propagated as fast as possible in the SINS calculation rate, the problem cannot be fully solved. State transformation extended Kalman filter (ST-EKF) mechanization, with a new converted velocity error model for the SINS, is proposed, which can also be used to solve the inconsistency problem. In the ST-EKF, the specific force vector in the system error model is replaced by the nearly constant gravity vector for local navigation. Since the propagation and the updating of the ST-EKF can be executed simultaneously in the updating interval, the computation cost is greatly reduced compared with the traditional EKF. Experiments for the GPS/SINS tightly coupled navigation, including linear vibration Monte Carlo test and an unmanned aerial vehicle flight test, are implemented to evaluate the performance of the proposed ST-EKF. The results show that the proposed ST-EKF has superior performance to the traditional EKF, especially in partially observable situations.     

GNSS/SINS/视觉多传感器融合的精密定位定姿方法与关键技术EI北大核心CSCD

全球导航卫星系统作为国家重要的空间信息基础设施,具备全球、全天候、高精度连续定位、导航和授时的功能,然而,到达地面的GNSS卫星信号非常微弱,存在遮挡、干扰和欺骗三大脆弱性问题,无法在电磁干扰、物理遮蔽等复杂环境下使用,为了保障国家PNT系统的坚韧性,提升导航与位置服务的能力,我国开始推进以北斗为核心的国家综合PNT体系建设,其中多传感器集成、多源异质信息融合是未来PNT技术的重要发展方向,也是从根本上解决单一导航系统局限性和脆弱性的有效途径,为了实现连续可用,精准可靠的PNT服务体系,迫切需要解决多传感器融合的精密定位定姿关键技术。论文主要工作如下。     

Robust GPS/BDS/INS tightly coupled integration with atmospheric constraints for long-range kinematic positioning

GPS Solutions - The combination of new global navigation satellite system (GNSS) has brought great benefits to reliable positioning and ambiguity resolution (AR), especially in restricted...     

Hybrid derivative-free extended Kalman filter for unknown lever arm estimation in tightly coupled DGPS/INS integration

Differential carrier phase observations from GPS (Global Positioning System) integrated with high-rate sensor measurements, such as those from an inertial navigation system (INS) or an inertial measurement unit (IMU), in a tightly coupled approach can guarantee continuous and precise geo-location information by bridging short outages in GPS and providing a solution even when less than four satellites are visible. However, to be efficient, the integration requires precise knowledge of the lever arm, i.e. the position vector of the GPS antenna relative to the IMU. A previously determined lever arm by direct measurement is not always available in real applications; therefore, an efficient automatic estimation method can be very useful. We propose a new hybrid derivative-free extended Kalman filter for the estimation of the unknown lever arm in tightly coupled GPS/INS integration. The new approach takes advantage of both the linear time propagation of the Kalman filter and the nonlinear measurement propagation of the derivative-free extended Kalman filter. Compared to the unscented Kalman filter, which in recent years is typically used as a superior alternative to the extended Kalman filter for nonlinear estimation, the virtue of the new Kalman filter is equal estimation accuracy at a significantly reduced computational burden. The performance of the new lever arm estimation method is assessed with simulated and real data. Simulations show that the proposed technique can estimate the unknown lever arm correctly provided that maneuvers with attitude changes are performed during initialization. Field test results confirm the effectiveness of the new method.     

GPS/INS紧耦合系统提高GPS失锁后解算精度的方法

在GPS/INS辅助航空摄影测量作业过程中,如果GPS失锁时间过长将会影响到整个机载POS数据后处理精度,从而影响制图效果。文章旨在研究解决传统基于位置、速度组合的松耦合导航系统在GPS失锁情况下后处理精度不高的问题,提出基于伪距、伪距率的紧耦合导航系统:在保证外符合精度前提下,后处理后的位置内符合精度达到0.05m、航向角内符合精度约为0.005deg,各项指标均满足国外GPS/INS辅助航空摄影测量系统解算精度要求。研究结果可以为解决相关问题提供参考。     

Accuracy and reliability of tightly coupled GPS/ultra-wideband positioning for surveying in urban environments

A tightly coupled filter integrating GPS and ultra-wideband (UWB) observations for high-precision position applications is implemented and tested to survey several external corner points of an eight story building. The filter uses GPS pseudoranges, GPS carrier-phase measurements, and UWB ranges and includes in-run estimation of UWB bias and scale factor states. The filter employs inequality constraints and innovation testing to mitigate the effects of unmodeled errors. The tightly coupled solution is compared to GPS-only, UWB-only, and loosely coupled solutions. The ability of each solution to detect measurement blunders is compared. Sub-meter level position solutions are maintained using tight-coupling in conditions where the solutions from the other three approaches are either unavailable or unreliable.     

改进的GNSS/水准点优化选择的逐步剔除法

GNSS/水准联测点的合理选择对GNSS高程拟合至关重要,剔除法是一种较好的优化选点方法,传统的剔除法是以高程异常拟合误差最小为目标函数进行优化选点,可能会出现选点不均匀情况。鉴于此,提出根据GNSS/水准点生成的泰森多边形面积大小进行优化选点,并在此基础上对传统优化选点的方法进行改进,即同时考虑高程异常拟合误差大小及由泰森法生成的多边形面积大小进行优化选点（称为综合法）。以1~3次多项式拟合模型为研究对象,实验结果表明,GNSS/水准点优化选择的综合法可在改善点分布的同时获得稳定性好、精度较高的高程异常拟合结果。     

InSAR与北斗/GNSS综合方法监测地表形变研究现状与展望

作为蓬勃发展的空间大地测量技术,InSAR和北斗/GNSS在地表形变监测中具有独特优势。应用两种手段开展综合测量,可充分利用其互补性,实现北斗/GNSS高时间分辨率与InSAR高空间分辨率的有机统一。本文首先介绍了InSAR与北斗/GNSS监测地表形变的基本原理,重点探讨了InSAR研究在20余年内的理论发展;其次综述了InSAR与北斗/GNSS技术集成及数据融合研究的最新进展;然后总结分析了当前地表形变监测应用所面临的关键问题及挑战;最后对InSAR与北斗/GNSS综合测量方法的发展趋势进行了展望。     

一种低动态高抖动环境下的GPS/INS紧组合方法

针对低动态高抖动环境下,影响GPS/INS紧组合精度的重要因素——惯性测量单元(IMU)数据中的噪声,该文提出利用小波降噪方法分离IMU数据中的噪声和有用信号以提高GPS/INS紧组合的精度。首先对IMU数据进行小波分解后得到的高频系数进行阈值量化处理,然后将GPS观测数据与降噪后的IMU数据进行GPS/INS紧组合解算,最终得到载体的导航信息。实例结果表明,该方法可以大幅提升GPS/INS紧组合的精度和稳定可靠性。     

An intelligent and autonomous MEMS IMU/GPS integration scheme for low cost land navigation applications

An intelligent scheme to integrate inertial navigation system/global positioning system (GPS) is proposed using a constructive neural network (CNN) to overcome the limitations of current schemes, namely Kalman filtering (KF). The proposed CNN technique does not require prior knowledge or empirical trials to implement the proposed architecture since it is able to construct its architecture “on the fly,” based on the complexity of the vehicle dynamic variations. The proposed scheme is implemented and tested using Micro-electro-mechanical systems inertial measurement unit data collected in a land-vehicle environment. The performance of the proposed scheme is then compared with the multi-layer feed-forward neural networks (MFNN) and KF- based schemes in terms of positioning accuracy during GPS signal outages. The results are then analyzed and discussed in terms of positioning accuracy and learning time. The preliminary results presented in this article indicate that the positioning accuracy were improved by more than 55% when the MFNN and CNN-based schemes were implemented. In addition, the proposed CNN was able to construct the topology by itself autonomously on the fly and achieve similar prediction performance with less hidden neurons compared to MFNN-based schemes.     

PPP/PPP-RTK新进展与北斗/GNSS PPP定位性能比较

首先简要回顾了精密单点定位（PPP）技术在最近几年的发展现状,重点总结了高采样率钟差实时快速估计、多系统组合PPP模糊度固定、多频GNSS PPP模型及其模糊度固定、PPP快速初始化、PPP-RTK等若干热点方向的最新研究进展。在此基础上,利用目前四大卫星导航系统（GPS、GLONASS、Galileo、北斗）最新的实际观测数据,全面比较分析了各系统及多系统组合PPP定位性能,重点给出了北斗二号+北斗三号PPP浮点解和固定解的定位精度、收敛时间和首次固定时间。结果表明：我国北斗导航卫星系统已经可以实现与其他导航卫星系统基本相当的PPP定位性能。北斗二号+北斗三号组合PPP的收敛时间/首次固定时间20~30 min;静态解的东、北、天方向定位精度在毫米到厘米级;动态解水平方向约5 cm,高程方向约7 cm;多系统组合可显著提高PPP定位精度、收敛时间和首次固定时间：固定解定位精度比浮点解在东、北、天方向分别提升了14.8%、12.0%和12.8%;相比单GPS,多系统组合PPP浮点解的收敛时间和固定解首次固定时间分别缩短了36.5%和40.4%。     

基于SINS／GPS的无人机组合导航系统建模与仿真

根据无人机的飞行特点以及SINS(捷联惯导)和GPS(全球定位系统)的优缺点,利用轨迹发生器设计无人机的飞行轨迹,建立基于SINS/GPS的无人机组合导航系统,依据卡尔曼滤波的相关原理对系统进行数学建模和计算仿真,验证无人机SINS/GPS组合导航系统的可靠性。     

A network distance and graph-partitioning-based clustering method for improving the accuracy of urban hotspot detection

Clustering is an important approach to identifying hotspots with broad applications, ranging from crime area analysis to transport prediction and urban planning. As an on-demand transport service, taxis play an important role in urban systems, and the pick-up and drop-off locations in taxi GPS trajectory data have been widely used to detect urban hotspots for various purposes. In this work, taxi drop-off events are represented as linear features in the context of the road network space. Based on such representation, instead of the most frequently used Euclidian distance, Jaccard distance is calculated to measure the similarity of road segments for cluster analysis, and further, a network distance and graph-partitioning-based clustering method is proposed for improving the accuracy of urban hotspot detection. A case study is conducted using taxi trajectory data collected from over 6500 taxis during one week, and the results indicate that the proposed method can identify urban hotspots more precisely.     

GPS/GNSS卫星定位原理与应用双语课程建设初探

主要介绍GPS/GNSS导航定位双语教学课程建设的设计思想和体会。针对测绘类专业卫星导航定位课程教学大纲内容,选取一些主要的GPS/GNSS英文原版参考书和网络资料,对其涵盖的主要内容及其更新性、读者对象、可读性等方面进行详细分析。对于采用原版教材、自编教材等方式进行讨论,提出采用以Internet网络资源为主、原版参考书为辅的GPS/GNSS双语教材选取模式。     

GNSS联合全站仪在新农村建设中实现地面数字测图

介绍了在新农村建设测图中采用GPS静态模式进行首级控制测量,采用GPS RTK模式进行图根控制测量,以及采用GPS RTK模式联合全站仪进行地形数据采集,利用计算机成图软件快速、高效地实现新农村测图的一种全新的测图方法.     

GPS/IMU组合定位定向系统设计

介绍了一种组合低成本的GPS和IMU(Inertial Measurement Unit)来获得高精度姿态、位置和速度信息的方法。文中介绍了GPS／IMU组合系统的设计方案及系统的硬件和软件设计，并给出了实验结果。该组合系统将来安装于炮兵测地车后，不仅可以提高测地的精度，而且在采样率、可靠性等方面比单独采用GPS定位的方法更有优势。     

New jump trajectory determination method using low-cost MEMS sensor fusion and augmented observations for GPS/INS integration

Objective information on athletic maneuvers for performance evaluation has become highly desired in sports such as skiing, snowboarding, and mountain biking. Body-mounted devices, incorporating low-cost microelectromechanical, inertial navigation units, and global positioning system (GPS) receivers, to calculate sport-specific key performance variables (KPVs) and provide real-time feedback, are now commercially available. However, algorithms implemented for such purposes still lack accuracy and power efficiency. A new GPS/INS (inertial navigation system) integration algorithm is proposed to determine the trajectory of an athlete executing jumps while skiing, snowboarding, mountain biking etc. KPVs, such as jump horizontal distance, vertical height, and drop, are calculated from the trajectory. A new sensor error compensation scheme is developed using sensor fusion and linear Kalman filters (LKF). The LKF parameters are varied to address the fluctuating dynamics of the athlete during a jump. The extended Kalman filter used for GPS/INS integration has an observation vector augmented with sensor error measurements derived from sensor fusion. The performance of the proposed algorithm is evaluated through experimental field tests. For the determination of jump horizontal distance, height, and drop, the proposed algorithm has errors of 14.3 cm (5.5 %), 1.6 cm (38 %), and 6.7 cm (9.4 %), respectively. Errors in KPVs for a set of jumps were first determined with respect to the true KPVs, and then the errors for all the jumps were averaged to calculate the absolute and percentage errors. The accuracy achieved is deemed to fulfill the expectations of both recreational and professional athletes.     

北斗GEO/IGSO/MEO卫星定轨地面站构型影响分析及其优化

GNSS卫星定轨精度主要取决于卫星动力学模型精度和GNSS几何观测信息。由于北斗GEO/IGSO卫星静地、高轨特性,以及力学模型不精确等原因,地面几何观测信息对轨道改进至关重要。本文讨论了北斗GEO/IGSO/MEO卫星定轨地面站分布影响及优化改进方法。在简化动力学定轨模型基础上,探讨多历元几何观测信息累积对轨道的改进;研究了北斗导航卫星定轨理想几何构型条件,得到影响定轨精度的几何因子,包括测站数量、覆盖范围、分布密度;利用离散概率密度方法研究地面站构型,分析了3类卫星轨道改进机理和优化方法。通过算例,讨论了增加5个中国区域基准站改善离散概率密度指标,优化全球北斗卫星定轨构型,发现GEO和IGSO卫星精度改善最为明显,MEO卫星改善最小;其中GEO卫星提高了10%,IGSO卫星提高了16%,MEO卫星提高了4%。     

"北斗+"新形态下GNSS原理与方法课程教学改革实践

全球卫星导航定位技术在各行各业的应用已步入高速发展的新时代,"北斗+"新形态下对卫星导航定位相关的创新型人才培养提出了更高要求.本文针对课程教学中学生主动学习积极性不高、创新实践能力锻炼不足等问题,构建了线上线下混合教学模式,整合线上线下学习资源,同时优化教学内容,改进教学方法,建立了多元化考核机制.通过课程改革实践,进一步提升学生学习的主动性和积极性,拓展学生在卫星导航应用方面的就业领域,提高服务社会的能力.     

GNSS/地磁组合的室内外无缝定位平滑过渡方法

针对室内外无缝定位在室内外过渡点精度低、不能平滑自动切换等问题,结合GNSS定位技术以及室内地磁指纹节点的组合方法来实现室内外无缝定位及导航。由于从室外至室内时接收机接收到的卫星星数减少、GDOP值逐渐增加、定位的误差增大,因此室内地磁定位精度逐渐优于GNSS定位精度,在两个定位精度临界点通过分析计算得出GDOP最优转化范围值,进行平稳切换。此次试验仿真结果表明,GDOP在3~3.5进行切换与单一GNSS或地磁方法定位的精度相比,分别提高85.7%和82.6%,从而达到了室内外的高精度无缝定位,填补了国内外在室内外无缝定位上没有合适的切换界定的空白。