Aiming at the problem that during the data preprocessing for high-precision global navigation satellite system（GNSS）, it is liable to inaccurate small cycle slip detection and threshold diffusion after cycle slip detection failure for MelbourneWübbena（MW） linear combination, one of the most commonly used methods in non-differential cycle slip detection, due to the influence of pseudo range noise, the paper proposed a detection algorithm of BeiDou navigation satellite system（BDS） cycle slips:in order to reduce the influence of pseudo range noise and improve the detection success rate, the total variation denoising algorithm was introduced to denoise the MW combined observation; and the cycle slip detection was carried out by using the difference between adjacent epochs of MW combined observation after denoising; then the selection of regularization parameter value and cycle slip detection threshold of total variational denoising algorithm were analyzed, knowing that when the regularization parameter is 5 and the threshold is set to 0.45, cycle slips greater than 1 cycle（including） can be detected.Experimental result showed that the regularization parameters and cycle slip detection threshold selected could be reasonable, and small cycle slips would be detected through the difference between adjacent epochs in the denoised MW combined observations with a success rate of 100% and no wrong detection and missed detection, which could make up for the deficiency of insensitive cycle slip detection in the MW combined observations.

针对北斗三号卫星导航系统(BDS-3)五频点观测数据和非差非组合精密定轨理论,介绍了非差非组合观测模型和参数估计方法,提出了利用K均值聚类算法(K-means)进行测站选取的策略,分析并讨论了非差非组合方法的优势.通过K-means和人工经验选取两种测站选取方案,分别使用BDS-3 五频,B1C+B2a、B1I+B3I三种频率选择方式,利用 30 个观测站,对BDS-3 中轨道地球卫星(MEO)和倾斜地球同步轨道卫星(IGSO)进行精密定轨处理.结果表明:当接收B1C+B2a频点观测数据测站不足时,非差非组合方法可以通过利用五频观测数据增加观测数据数量、优化测站布局,提高定轨精度,与B1C+B2a频率组合相比,五频定轨结果切向(A)、法向(C)、径向(R)和三维(3D)方向均方根(RMS)月均值分别提升 0.003 m、0.004 m、0.003 m和 0.007 m;K-means算法选取的测站与人工经验选取相比,分布更加合理,定轨精度更高,三种频率选择方案MEO卫星 3D RMS月均值精度分别提升 0.009 m、0.017 m和 0.009 m.

In order to analsis the applicability and accuracy of TEC modelling for regional ionosphere from observations at a single station, the TEC models of 16 single-station regions in Europe are established and the TEC grids of the region are generated based on the spherical harmonic function of order from 2 to 15. The products are compared with the authoritative ionospheric products such as CODE, iGMAS and IGS. The results show that the single station regional ionospheric TEC model based on low order spherical harmonic function (2×2 or 3×3) has the same accuracy as that of global ionospheric TEC such as CODE, iGMAS and IGS, which is about 1.0TECU in the longitude and latitude range of 10×10 (radius < 600km) centered on a single station. Thus, the global ionospheric TEC model can be replaced by the ionospheric TEC model established by a single station in a certain region (radius less than 600 km), and the high-precision ionospheric delay correction can be efficiently provided for the single frequency users in the region.

北斗三号卫星导航系统(BDS-3)开通已一年有余,通过研究2019-08—2021-08共2 a的北斗卫星导航系统(BDS)广播星历数据,采用事后精密星历对北斗二号卫星导航系统(BDS-2)和BDS-3卫星的轨道、钟差和空间信号测距误差(SISRE)进行分析.结果表明:BDS-3系统开通后,卫星轨道精度比BDS-2提升明显,径向(R)误差均方根(RMS)值从0.87 m左右提升至优于0.23 m,精度提升约74％,3D误差RMS值从1.63 m以内提升到优于0.75 m,精度提升约54％;氢原子钟和铷原子钟精度相当,BDS-3钟差误差RMS值精度提升与BDS-2提升基本相同,精度提升约1 ns;SISRE精度比对中,BDS-2 SISRE的RMS值从0.9 m提升到0.7 m,BDS-3从0.8 m提升到0.5 m.综合比较,BDS-3系统性能提升较大.

基于iGMAS与武汉大学提供超快速轨道产品,以Geoscience Australia机构开源的GNSS处理软件ACS为平台,进行了BDS实时钟差估计实验,并对生成的产品进行了分析.实验结果表明,使用全球具有实时数据流的监测站,在以武汉大学最终钟差产品为参考钟差进行评估的情况下,基于武汉大学小时轨道估计的BDS实时钟差精度为0.25/0.67 ns(MEO/IGSO),而使用iGMAS超快速产品估计的钟差的精度为0.37/2.51 ns(MEO/IGSO),MEO卫星优于IGSO卫星,BDS-2与BDS-3均无明显分群差异.两类实时钟差产品的差异主要来自于轨道切换时产生的跳变.

It has a good outlier detection effect and satellite clock error prediction accuracy based on the time series model to eliminate the influence of AO (Additive Outlier) and carry out the satellite clock error prediction. However, there are difference, inverse difference and model order determination operations when a time series model is used. In this paper, the AR model with trend item is combined with the EM algorithm, and an algorithm for AO detection and satellite clock error prediction are proposed to avoid difference, inverse difference and model order determination operations. When the AO in the clock error is successfully detected, the algorithm can obtain an accurate AR model with trend item, and then fit the growth or decline trend of the satellite clock error accurately. The algorithm also has good satellite clock error prediction accuracy. Finally, using the measured data of the BDS satellite clock error to calculate and analyze, the results verify the correctness and effectiveness of the algorithm.

导航星座性能直接决定着系统性能指标的实现,不同的星座构型和轨道参数决定了不同的星座性能.为系统评估北斗三号全球卫星导航系统(BDS3)建成开通后四大全球系统星座、BDS3与其他系统组合星座的当前实际性能,利用2020-08-01—2020-08-10的星历数据计算了各星座的全球可见卫星数、星座PDOP(位置精度因子)可用性和全球空间覆盖率,比较分析了各星座在不同用户高度截止角下的性能,探讨了各星座PDOP值在全球的分布规律.结果表明,在5°、15°、30°和45°高度截止角下,北斗系统(BDS)星座性能最优,在30°E～180°E,90°S～90°N区域,单系统中BDS的PDOP值远小于其他系统,用户高度截止角较高时,BDS3+GPS组合能在保证高可用性的条件下提供更高的全球空间覆盖率.所得结论对不同类型的用户使用北斗系统以及将BDS3与其他系统组合使用具有重要的参考价值.

为了分析与评估国际GNSS监测评估系统(iGMAS)全球电离层TEC格网产品精度,该文基于iGMAS及IGS各电离层分析中心发布的全球电离层TEC格网产品,进行了精度比较分析,结果表明:iGMAS与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组发布的全球电离层TEC格网产品,在全球、不同纬度带和欧洲等不同区域均表现出较高的一致性和强相关性,互差为0～2.0 TECU;JPL分析中心GIM的内符合精度约为2.5 TECU,iGMAS、IGS、CODE、ESOC和UPC等分析中心GIM的内符合精度均小于1.5 TECU;在2～8 TECU的精度范围内,iGMAS全球电离层TEC格网产品的精度总体与IGS、CODE、JPL、ESOC、UPC等IGS电离层工作组的精度相当.

卫星导航定位中,电离层延迟是影响用户实时定位精度的重要因素之一.利用全球电离层格网(global ionosphere maps,GIM)提供电离层延迟改正是较为常用的方法,而GIM格网的精度受限于地面GNSS(global navigation satellite system)跟踪站的分布密度.利用区域内少量或1个GNSS跟踪站建立实时区域电离层总电子含量(total electron content,TEC)模型,生成高精度的实时区域电离层格网,为用户提供区域电离层延迟改正显得尤为重要.基于CODE (Center for Orbit Determination in Europe)分析中心2016-2018年995 d的GIM格网数据,分析了相邻格网点TEC的变化范围以及不同时间间隔同一格网点TEC的变化范围.结果 表明,GIM在经度方向上分辨率为5.变化的均值范围为0.2～1.0 TECU,在纬度方向上分辨率为2.5.变化的均值范围为0.4～1.4 TECU,在经度和纬度分辨率均小于1.时,电离层TEC的变化小于1.0 TECU;1h内同一格网点电离层TEC的变化均值约为1.28 TECU,30 min内同一格网点电离层TEC的变化小于1.0 TECU.该研究为小范围内(半径小于100 km)实时区域电离层TEC模型的建立及电离层格网的时间适用范围提供了有效的数据支撑和理论验证,同时对区域电离层TEC时空变化的研究、电离层TEC预报、电离层异常监测和磁暴监测等具有一定的参考意义.

为研究中国陆态网区域电离层TEC在空间小尺度、高分辨率情况下的变化特性及适用精度范围，利用陆态网260个GNSS连续运行观测站数据，解算并生成2016-2017年731天陆态网区域电离层RIM格网，并进行精度验证.在同一RIM格网中，分别在经度和纬度方向上对间隔不同经纬度的TEC格网点作差分析.结果表明：陆态网区域内经度方向上TEC最大变化率和平均变化率分别为0.30TECU·（°）-1和0.11TECU·（°）-1；经度间隔1°时，TEC差值小于2TECU，且随着经度间隔的增大，其TEC差值也随之增大，并表现出一定的半年和周年变化规律；纬度方向上TEC最大变化率和平均变化率分别为1.7TECU·（°）-1和0.46TECU·（°）-1；陆态网区域内电离层TEC随纬度减小而增大，纬度间隔1°时，99.4%的TEC差值小于4TECU，且随着纬度间隔的增大，其TEC差值也随之增大，并表现出一定的半年和周年变化规律；间隔相同情况下，纬度方向上TEC的变化比经度方向上大.

Centre National d’Etudes Spatiales (CNES) now provides real-time correction information such as orbits/clock correction, code/phase bias, and ionospheric spherical harmonic coefficients, which are so-called SSR corrections, and it can better support real-time precise point positioning (RTPPP) compared to ultra-rapid products. In order to assess the performance of RTPPP using SSR corrections, this paper performed static experiments and Unmanned Arial Vehicle (UAV) flight experiments. The experimental results show that PPP using SSR corrections can achieve the performance similar to PPP using the final product, and the ionospheric correction of SSR corrections is better than that of the final ionospheric grid product, but the correction of orbit and clock is slightly worse. There is still a gap between the actual positioning performance of dual-frequency PPP and real-time accurate positioning requirement, and single-frequency PPP still has a long way to go before it can be practically used.

卫星导航信号模拟源为用户终端设备的设计、验证、测试提供输入信号源,是用户终端设备研发和卫星导航信号系统验证的重要工具.早期的射频合成技术产生的信号的精度和通道一致性较差,随后的模拟中频合成技术存在通道间偏差的问题,而目前常用的数字中频合成技术存在相位抖动问题,所以本文基于PXI Express(PXIe)总线的软件无线电架构,设计并实现了一款采用数字基带合成技术的软硬件结合模拟源.模拟源上位机数学仿真软件采用图形化编程语言LABVIEW开发,实现简单,开发效率高,最终生成数字基带合成信号;模拟源硬件则使用美国国家仪器公司(NI)模块化的虚拟仪器,接收并处理上位机产生的数字基带合成信号,最终产生用户终端设备可以接收的全球定位系统(GPS)射频信号.利用频谱分析仪观察模拟源输出信号的频率和带宽,验证了GPS模拟源仿真信号的正确性;利用商用接收机进行定位解算,分析静态和动态场景下的信号质量、定位结果及三轴定位误差,验证了GPS模拟源仿真信号的准确性和有效性.

Global Navigation Satellite System (GNSS), once dedicated to military and geodetic applications, is entering civilian life with the development of low-cost internal multi-GNSS chips in mass-market smart devices. The recently enabled Application Programming Interface (API) to GNSS raw measurement in Android Nougat operating system, make it possible to implement precise positioning technology on Android smart devices, such as Real-Time Kinematic Positioning (RTK) and Precise Point Positioning (PPP). An optimized kinematic positioning approach on Android smart devices with Doppler-Smoothed-Code (DSC) filter and Constant Acceleration (CA) model is assessed in this paper. In this optimized approach, DSC filter is used to reduce the code measurement noise, which is extremely high on smart devices and CA model is used to accurately predict the kinematic state of smart devices. The optimized approach is named Smart-RTK for its applicability to smart devices, respectively. The performance of the Smart-RTK approach is validated by two Google/HTC Nexus 9 tablets separately under stationary, walking, and vehicular condition. The numerical experiments show the significant improvement on positioning accuracy and continuity. The positioning Root Mean Square Error (RMSE) in horizontal component reaches about 0.3-0.6 m in stationary condition and 0.4-0.7 m in walking condition, improved by about 85% compared with that of chipset original solutions. In the subsequent vehicular experiment, the horizontal positioning RMSE is about 0.85 m, 50% better than that of chipset solutions. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.

电离层延迟误差是卫星导航和定位中不可忽略的重要误差,全球电离层总电子含量(TEC)格网数据因其将全球按规则的经纬度格网化,并给出了相应格网点的电离层TEC值,从而为用户使用提供了极大的便利.本文基于Linux Shell脚本编写简单、快速和容易维护等优点,利用Shell脚本对电离层TEC格网数据进行提取和分析处理,主要包括全球和自定义区域电离层TEC数据提取、均值计算、格网经纬度互差计算、最值提取等应用,可为基于全球电离层格网(GIM)数据对全球或区域电离层TEC周年变化、季节变化、周日变化规律以及时空变化特性等相关规律的分析研究提供一定的参考.

目前,普通智能终端的平面定位精度在5m左右.2016年,Google公司推出Android系统7.0版本,开始支持输出GNSS(global navigation satellite system)原始观测值.通过改正和计算,可以获得Android智能终端的伪码和载波相位观测值,从而实现较高精度的GNSS定位.研究采用华为P9手机进行,在观测条件良好的情况下,采集静态的GNSS原始观测数据,并采用多种方式分别进行定位解算,并分析其定位精度.同时,在相邻观测点放置NovAtel DL-V3-L1型接收机进行对比.实验表明通过静态下精密单点定位或者载波相位差分定位的方式,可以显著提升智能终端的定位精度,达到分米级水平.

随着卫星导航系统的飞速发展,卫星导航定位技术正朝着实时、高精度和高可靠性的方向发展.在实现实时PPP和多系统网络RTK等技术中,高效准确地实时解码原始数据能够为后续的数据分析和处理提供可靠的保障.本文系统地介绍了u-blox M8接收机原始数据流的内容和格式,分析每种数据格式中的信息组织结构,给出了相关电文解析方法,实现了多系统原始GNSS数据流的实时解析.作为应用实例,基于解码后的数据分别进行了伪距单点定位和差分定位等,进一步证明了解码后数据的有效性和正确性.

Android, the most popular smart operating system with an approximately 86

为了进一步研究磁暴对电离层总电子含量变化的影响,基于2017年9月6日太阳爆发X9.3级特大耀斑并引发磁暴现象,文中将iGMAS提供的全球电离层总电子含量格网数据与中国科学院空间环境预报中心(SEPC)提供的磁暴环电流指数进行相关性分析,并重点分析了磁暴过程中不同阶段磁暴环电流指数与全球不同纬度带电离层总电子含量变化的相关性及影响,结果表明:1)此次特大耀斑爆发13小时后发生大磁暴,磁暴主相阶段磁暴环电流指数与滞后1h的电离层总电子含量相关系数为-0.999 7,即随着磁暴加剧电离层总电子含量迅速增加,恢复相阶段迅速减少并趋于稳定;2)电离层总电子含量变化随磁暴环电流指数变化而变化,两者变化趋势一致,磁暴强度与电离层总电子含量变化呈强负相关性,磁暴对不同纬度带的电离层总电子含量影响趋于一致,影响程度大小由高纬至低纬逐渐递减;3)磁暴对不同纬度带的电离层总电子含量变化影响不同步,其影响存在由高纬逐渐延伸至低纬,磁暴主相阶段对不同纬度带的影响时延约为1h,恢复相阶段时延逐渐消失,电离层电离层总电子含量变化趋于稳定;4)此次磁暴恢复相阶段出现的电离层总电子含量异常变化,还有待进一步研究分析.

针对目前精密单点定位技术主要基于PC端事后解算或采用静态模拟动态的技术模式,在实际工程应用中难以满足对实时性和动态性的需求.文中采用T rimble BD970 OEM板和Raspberry Pi单板计算机搭建嵌入式接收机平台,将实时精密单点定位程序移植到该平台上,通过无线网络获取信息工程大学iGM AS分析中心提供的实时轨道产品和实时钟差产品,进行实时精密单点定位实验.结果表明,X、Y、Z平均统计精度分别为0.22 m、0.32 m、0.33 m,实现分米级定位,结果与目前已知嵌入式终端产品精度相当,能够满足接收机测量要求.

在全球卫星导航系统的研究和应用中,高质量的GNSS观测数据能为后续的数据分析和处理提供可靠的保障.以iGMAS和MGEX跟踪站采集的四系统多频点观测数据为研究对象,从数据处理角度深入分析了数据质量评估的相关指标,并按照不同系统间的频点差异,对各类型GNSS采集设备进行了对比分析.