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类型 基础研究 预答辩日期 2018-03-04
开始(开题)日期 2016-04-01 论文结束日期 2017-12-25
地点 九龙湖校区教学楼J3-300室 论文选题来源 国家自然科学基金项目     论文字数 8.5 (万字)
题目 多系统多频GNSS融合快速精密定位关键技术研究
主题词 GNSS,紧组合,精密相对定位,差分系统间偏差,模糊度解算
摘要 随着我国BDS的运行,Galileo、IRNSS等建设推进以及GPS、GLONASS的提升完善,卫星导航已进入多系统并存的时代,多系统多频观测信息为卫星定位精度、可靠性等性能提升提供了新的技术条件。与此同时,卫星导航与移动通信、互联网技术融合极大拓展了高精度卫星定位技术应用的深度和广度,各行业对其技术模式和性能指标的需求也在发生深刻变化,利用多系统多频数据融合,对现有精密定位技术的提升和创新,是保障GNSS进一步拓展应用的迫切需求。 基于上述需求,本文围绕多系统多频融合精密相对定位中的关键问题展开研究,主要涉及多GNSS观测质量分析、不同系统间观测值融合处理模型、多系统多频模糊度解算策略以及基于三频观测值的多尺度定位模型四个方面,通过相关算法和模型的创新或改进,提升了定位的可靠性、实时性、连续性以及多样性等性能,论文的主要工作和贡献如下: 1. 系统分析了GNSS各系统的数据质量以及数据融合中的若干特性问题 (1)阐述了基于站间单差模型计算观测值残差的原理,针对GLONASS系统,提出了通过两次选取解算基准的单差载波残差估计模型,从而无需考虑由各卫星频率不同导致的单差模糊度问题。基于各系统的单差残差结果,建立了各接收机、各系统观测数据随高度角变化的随机模型。 (2)对BDS的星端伪距偏差、GLONASS的频间伪距偏差及其对相对定位的影响进行了分析和验证,结果表明,在250km内,BDS的星端伪距偏差改正值小于10cm,因此在中长基线情况下可以忽略;对于GLONASS的频间伪距偏差,即使是对于相同类型的接收机,其影响依然无法消除。对于存在线性关系的接收机组合,设置IFB变化率参数能有效吸收伪距IFB的影响。 (3)系统研究了三频观测值组合中的载波多路径效应影响,对几种典型的三频组合进行了具体的分析。结果表明,当组合系数较大时,载波多路径误差会被显著放大,且难以在短时间内通过平滑或取平均的方法予以有效削弱,尤其是对于BDS GEO卫星,多路径误差显示出更显著的系统误差特性。 2. 提出了不同频率系统间差分观测值的紧组合融合模型 针对GPS和BDS系统间不同频率观测值的融合处理,提出了差分系统间偏差的估计和分析方法。结果表明,当接收机类型不同时,载波DISB序列呈现出一定的低频变化,但其趋势非常平滑和缓慢,数小时至数天内的变化也仅在0.1周内。总体上,载波和伪距DISB较为稳定,利用这一特性,分别提出了短基线和中长基线情况下GPS和BDS共用参考卫星的紧组合定位模型,通过在多历元模式下实时估计DISB参数,实现定位模型强度的提升。实验结果表明,相比常规的系统内差分模型,该模型能有效提升定位的精度和可靠性,尤其是对遮挡等可视卫星数较少的情况改进明显。 3. 优化了多系统多频融合模糊度快速解算策略 (1)详细分析了三频无几何模式下各模糊度解算模型受观测噪声及电离层延迟的影响,重点分析了电离层无偏以及有偏两类模型的解算性能,结果表明电离层有偏模型虽然残留了电离层延迟的影响,但其影响系数较小,在中等基线情况下依然具有较高的求解精度,通过控制模糊度取整的小数区间能进一步减小模糊度固定的纳伪概率。 (2)针对窄巷模糊度解算,建立了三频和双频融合的几何相关解算模型,并针对模糊度和观测值维数大的问题,提出了相应的运算优化策略。基于实测数据对模糊度解算和定位性能进行了测试和评估,结果表明,在短基线情况下,三频相比双频、多系统相比单系统具有明显优势,特别是对于遮挡观测环境,多系统能显著提高模糊度的固定率;中长基线情况下,三频相比双频对窄巷模糊度解算的贡献不大,BDS系统受制于GEO和IGSO的空间构型变化缓慢,导致模糊度固定的速度总体上慢于GPS,甚至长时间无法固定,而组合系统能显著提升模糊度固定的速度及定位精度。 (3)针对长距离参考站间的三频超宽巷/宽巷模糊度解算,利用参考站间基线已知的特性,提出了一种分步无电离层解算模型,利用模糊度容易固定的(0,-1,1)载波观测值与第二个宽巷/超宽巷组成无电离层组合,实现模糊度的快速求解。实验结果表明,该模型能够有效解决长基线电离层延迟的影响,同时受观测值噪声的影响较小。 4. 建立了基于三频观测值的多尺度定位模型,并对不同基线长度下的定位性能进行了评估 利用三频观测值超宽巷/宽巷模糊度易于固定的优势,建立了忽略(Ionosphere-fixed)以及顾及(Ionosphere-float)电离层延迟影响的两类多尺度快速定位模型,并采用基线长度不等的BDS三频实测数据对定位性能进行了测试和评估,结果表明: (1)在Ionosphere-fixed模式下,依托超宽巷解基本可实现单历元分米级定位;对于宽巷解,当基线较短时能够实现亚分米级的平面精度和亚分米至分米级的高程精度,对于基线长度更长的基线,平面和高程方向精度均为分米级。比较来看,使用三频超宽巷和宽巷观测值相比使用伪距,相对定位的精度能够得到显著提升,对于80km以内的中长基线能够实现单历元分米级甚至亚分米级的定位精度。 (2)在Ionosphere-float模式下,单历元超宽巷/宽巷解的平面精度在分米级,高程方向介于分米级至亚米级之间;而使用伪距观测值时,平面和高程定位精度均为米级,显著大于超宽巷/宽巷解。在多历元模式下,通过引入窄巷观测方程能有效削弱观测噪声的影响,同时通过融合GPS双频观测值也能显著提升定位解的收敛速度。但受限于放大的载波多路径影响,在短时间内难以收敛到亚分米或厘米级的精度,且通过增加采样间隔难以有效提高定位的收敛速度和精度。
英文题目 STUDY ON THE KEY TECHNOLOGIES OF FAST PRECISE POSITIONING BASED ON THE FUSION OF MULTI-SYSTEM AND MULTI-FREQUENCY GNSS
英文主题词 GNSS, tight combination, precise relative positioning, differential inter-system biases (DISB), ambiguity resolution
英文摘要 With the gradual operation of BDS and the development of GPS, GLONASS Galileo, IRNSS, etc., the satellite navigation and positioning has entered an era of multi-system co-existence. The multi-system and multi-frequency observations bring the new opportunities for the improvement of positioning accuracy, reliability and other performance. At the same time, the integration of satellite navigation, mobile communication and internet technologies has greatly expanded the application of high-precision satellite positioning. The positioning demands in various industries are undergoing profound changes. Therefore, it is necessary to improve the existing precise positioning technology based on the abundant observations, so that the further demands of GNSS precise positioning can be met better. Based on the above requirements, this thesis is intended to study the key technologies in precise relative positioning with the fusion of multi-system multi-frequency, which mainly involves: (1) the quality analysis of multi-GNSS observations, (2) the fusion model of observations between different systems, (3) the ambiguity resolution (AR) strategy with multi-system and multi-frequency observations, and (4) the multi-scale positioning model using triple-frequency observations. Based on the innovation or improvement of some algorithms and models, the positioning reliability, real-time, continuity and diversity have been improved. The main work and contributions are listed as follows: 1. The data quality of each GNSS system and some special problems in observation fusion are analyzed systematically. (1) The principle of calculating the observation residuals based on the between-station single-difference (SD) model is expounded. For GLONASS which adopts frequency division multiple access (FDMA), a single-difference carrier residual estimation model is proposed by choosing the bases twice. Then the SD carrier residuals can be calculated without considering the SD ambiguity caused by the difference of satellite frequencies. Based on the results of SD residuals from each system, the stochastic models with the elevation for each receiver and each system are established. (2) The satellite pseudorange bias variation of BDS, the pseudorange inter-frequency bias (IFB) of GLONASS and their effect on the relative positioning are analyzed and verified. The results show that within 250km, the correction of BDS pseudorange bias is less than 10cm, and thus can be neglected for medium baselines. For the GLONASS pseudorange IFB, the results show that even for the receivers with the same type, the effect still cannot be eliminated. For receiver combinations with linear relationship between pseudorange IFB and channel number, the effect of the pseudorange IFB can be absorbed effectively by setting the parameter of IFB rate. (3) The carrier-phase multipath in triple-frequency observation combinations is studied systematically. Several typical triple-frequency combinations including extra-wide-lane (EWL) combination, ionosphere estimation with ambiguity-corrected EWL/wide-lane (WL) combinations and the geometry-free and ionosphere-free (GIF) combination for narrow-lane (NL) AR, are analyzed in detail. The results show that the multipath-caused errors will increase with the absolute values of combination coefficients and cannot be effectively mitigated in short time, especially for BDS GEO satellites, which shows more systematic characteristics. 2. The tightly combined model between the inter-system observations with different frequencies is proposed. Aiming at the fusion of different-frequency observations between GPS and BDS system, a method of estimating and analyzing the differential inter-system biases (DISB) is proposed. The results show that when the receiver types are different, the carrier DISB presents a certain low-frequency variation. Fortunately, this variation is very smooth and slow, and changes within 0.1 cycles in a few hours to several days. In general, the carrier and pseudorange DISB are relatively stable. Using this feature, the tightly combined positioning models of GPS and BDS with a common reference satellites are proposed for short and medium baselines respectively. Through the real-time estimation of DISB parameters in multi-epoch mode, the strength of positioning model can be enhanced. Experimental results show that compared with the conventional intra-system differential model, the tightly combined model can effectively improve the positioning accuracy and reliability, especially for the obstructed environments with a small number of satellites available. 3. The AR strategy using multi-system and multi-frequency is optimized. (1) The influences of the observation noise and the ionospheric delay on each triple-frequency geometry-free (GF) model are analyzed in detail. The properties of the ionosphere-unbiased and biased models for wide-lane (WL) and extra-wide-lane (EWL) are analyzed and compared particularly. The results show that although ionospheric delay remains in the ionosphere-biased models, the influence coefficient is small, so that a high accuracy still can be obtained for medium baselines. The control of the fractional interval can further reduce the probability of the wrong ambiguity fixing. (2) For the narrow-lane (NL) AR, a geometry-based model with the fusion of triple- and dual-frequency observations is established. In order to solve the problem of large dimension of ambiguities and observations, some optimization strategies are proposed. The performance of AR and positioning is tested and evaluated with real observations. Results show that for short baselines, the triple-frequency performs better than dual-frequency and multi-system performs better than single system, especially for the obstructed environments. In the case of medium baselines, the triple-frequency mode only contributes a little to the NL AR compared with the dual-frequency mode. Generally, the NL AR of BDS is slower than that of GPS due to the slow change of satellite geometry of GEO and IGSO satellites. The combination of BDS and GPS can significantly improve the AR and positioning performance compared with the single system. (3) Aiming at the triple-frequency WL and EWL AR between long-range reference stations of BDS, a new stepwise ionosphere-free (SIF) method is proposed based on the characteristic that the baseline components are precisely known. Firstly, the (0,-1,1) ambiguity can be solved reliably with single epoch. Then the ambiguity-fixed (0,-1,1) observation are used to form a ionosphere-free carrier observation together with the second wide-lane combination. The results indicate that the proposed SIF method can avoid the influence of ionosphere delay in long-range baselines with smaller observation noises. 4. The multi-scale positioning model based on triple-frequency observations is established and the positioning performance is assessed using baselines with different length. Based on the advantage that the EWL and WL ambiguities can be fixed easily, two types of multi-scale fast positioning models, i.e. Ionosphere-fixed and Ionosphere-float, are established. The positioning performance is evaluated using BDS real observations with different baseline length. The results show that: (1) In Ionosphere-fixed mode, single-epoch decimeter positioning can be achieved by using EWL observations. Using WL observations, sub-meter accuracy and sub-meter to decimeter accuracy can be achieved for horizontal and vertical directions respectively for the baselines under 41.5km. For the longer baselines, decimeter-level accuracy can be achieved for both horizontal and vertical directions. Compared with pseudorange, the positioning accuracy can be significantly improved by using EWL and WL observations. For medium-long baselines within 80 km, single-epoch decimeter-level or even sub-meter level positioning accuracy can be achieved. (2) In Ionosphere-float mode, the single-epoch positioning accuracy with EWL/WL observation is decimeter level for the horizontal direction, and decimeter to sub-meter level for the vertical direction. While for pseudorange observations, the horizontal and vertical accuracies are both meter-level. In multi-epoch mode, the effect of noises and carrier multipath effects can be effectively reduced by introducing NL observations. Adding GPS dual-frequency observations can further speed up the convergence. However, it is difficult to converge to the sub-decimeter or centimeter accuracy in short time due to the existence of amplified carrier multipath effect. It is also hard to improve the convergence speed and positioning accuracy by decreasing the sampling interval.
学术讨论
主办单位时间地点报告人报告主题
ISPRS/IAG/FIG 2015.12.09 悉尼 Dorota A. Brzezinska On multi-sensor PNT technologies applied to mobile mapping and other emerging applications
Nottingham Geospatial Institute 2016.12.07 诺丁汉 高旺 Ambiguity Resolution and Precise RTK Positioning Using Multi-System and Multi-Frequency GNSS
东南大学空间信息与导航定位研究中心 2016.09.23 南京 高旺 GNSS三频载波观测组合中的多路径影响分析
东南大学测绘工程系 2016.06.27 南京 李博峰 网络参考站增强的多频多模RTK理论及应用
东南大学空间信息与导航定位研究中心 2015.11.20 南京 高旺 GNSS/SINS组合导航研发阶段性学习汇报
东南大学空间信息与导航定位研究中心 2016.05.06 南京 高旺 基于分步无电离层组合的北斗三频长距离参考站间宽巷模糊度解算方法
中国测绘学会工程测量分会 2013.11.16 南京 高旺 基于区域参考站网络的精密卫星钟差估计及其在实时PPP中的应用
中国卫星导航系统管理办公室 2014.05.21 南京 陈学庚 卫星导航技术在兵团农业中的应用需求
     
学术会议
会议名称时间地点本人报告本人报告题目
ISPRS/IAG/FIG 2015.12.11 悉尼 Real-Time Precise Point Positioning Augmented with Single GNSS Beacon Station
中国卫星导航系统管理办公室 2014.05.21 南京 Ill-Posedness Analysis of Ambiguity Resolution Using BDS-2 and Its Fusion with GPS
     
代表作
论文名称
北斗三频宽巷组合网络RTK单历元定位方法
基于部分固定策略的多系统长距离基准站间模糊度快速解算方法
Improving Ambiguity Resolution for Medium Baselines Using Combined GPS and BDS Dual/Triple-Frequency
A method of GPS/BDS/GLONASS combined RTK positioning for middle-long baseline with partial ambiguity
Single-Epoch Navigation Performance with Real BDS Triple-Frequency Pseudorange and EWL/WL Observatio
Inter-System Differencing between GPS and BDS for Medium-Baseline RTK Positioning
基于分步无电离层组合的北斗三频长距离参考站间宽巷模糊度解算方法
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
金双根 正高 研究员 博导 中科院上海天文台
史照良 正高 教授级高级工程师 博导 江苏省国土资源厅
王庆 正高 教授 博导 东南大学
胡伍生 正高 教授 博导 东南大学
黄腾 正高 教授 博导 河海大学
      
答辩秘书信息
姓名职称工作单位备注
于先文 副高 副教授 东南大学