【作者】 邹璇；

【导师】 刘经南； 姜卫平； 葛茂荣； Galina Dick；

【作者基本信息】 武汉大学 ， 大地测量学与测量工程， 2010， 博士

【摘要】 自全球卫星导航系统(GNSS)问世以来,由于其具有全球性、全天候、高精度、高效率、保密性强等一系列特点,现已被广泛应用于卫星导航、测量定位、形变监测、大气探测等领域。目前,GNSS精密导航与定位一般都采用双频接收机,其主要原因是为了消除电离层误差的影响。在利用GNSS技术开展区域变形监测、大气探测等研究中,由于需要采集高时空分辨率的信息,不得不布设大量的GNSS接收机。如全部采用GNSS双频接收机进行施测,其成本无疑将非常昂贵,这必然会极大限制GNSS技术在这些领域未来的发展和应用。正因为如此,如何消除电离层误差的影响,利用相对廉价的单频接收机实现大范围、高精度定位是目前国内外卫星大地测量研究的热点和难点问题之一；此外,实现对现有GNSS技术的统一,即：PPP与网络RTK技术的统一,区域与全球数据处理模式的统一,单频与双频数据处理策略的统一也是目前亟待解决的难点问题。本文旨在研究和推进这两个难题的解决,主要内容是深入研究单频接收机进行精密定位的方法,突破解决其关键技术难题,推进GNSS技术统一问题的解决,并研制实用的软件。首先,本文深入研究了现有各类区域误差改正模型构建方法,发展了历元差分电离层模型(SEID),并将其成功应用于大规模参考网内GNSS单频接收机精密定位,取得了不错的实验分析结果。其次,本文研究并提出了一种基于非差改正数的网络RTK方法。虽然,这两种方法都可被有效应用于各类GNSS卫星导航系统的事后、实时或准实时单频接收机精密定位服务。但基于非差改正数的网络RTK方法更体现了对现有各类区域误差融合技术的统一,是更为一般性的模型构建方法。该方法综合了PPP技术与网络RTK技术各自的优点,使用现有的各类卫星轨道和钟差产品,实现了GNSS双频接收机用户采用全球PPP与区域RTK时在技术上的统一和服务上的无缝连接。使网内和网外用户基于同样的精密点定位数据处理模式(PPP模式)获得不同精度需求的精密定位服务：网内接收到区域误差改正信息的用户站可获得与网络RTK模式相等价的快速、精密定位结果,而网外或未接收到该区域误差改正信息的用户则得到PPP模式的定位精度。最后,本文基于以上方法和已有的PANDA软件采用fortran语言开发实现了单频／双频数据逐历元处理功能,并对未来将基于非差改正数的网络RTK方法应用于PPP模式实时精密定位的应用前景进行了有效的模拟分析。论文的主要工作和研究成果包括：1)在广泛查阅文献的基础上,从GNSS数学模型、误差改正技术、精密定位方法、以及软件开发等四个方面全面综述了GNSS精密定位在国内外的研究现状。针对本文的重点研究内容,还对GNSS单频接收机精密定位这个研究热点以及区域误差改正模型构建这个研究难点进行了较为深入的探讨与总结；2)深入研究了GNSS精密定位理论,包括精密定位中涉及到的各种时空框架及其转换关系,观测方程与误差改正,以及最小二乘参数估计算法；3)系统描述和分析了现有各种区域误差改正模型构建方法,是对该类技术的一次全面总结；4)论证了网络RTK与HiRIM方法当电离层薄层高度假定为0时在理论上是一致的,指出其只是具体实现时有细微区别。本文对网络RTK与HiRIM方法进行了理论上的描述和误差改正侧重点上的比较分析,脉络清晰地推导论证了两类方法的等价性和差异,进而得出了一些有益的结论；5)发展了SEID方法,并提出了一套完整的GNSS单频接收机精密定位数据处理策略。对于小于90km的参考网,利用网内单频数据并基于SEID方法,其单天静态测量精度基本可达到双频数据的解算结果,能够满足单频接收机高程方向mm级单天静态精密定位的应用要求；6)提出了基于非差改正数的网络RTK方法,该方法是对现有各类区域误差融合技术的统一,是更为一般性的模型构建方法。该方法有效消除了电离层、对流层、接收机硬件延迟、卫星轨道和卫星钟差等误差影响,实现了对全球PPP与区域RTK在技术上的统一和服务上的无缝连接；7)严密推导论证了历元差分电离层模型和基于非差改正数的网络RTK方法,采用fortran语言开发了两套区域误差模型构建软件；8)研究了GNSS单频数据处理软件的模块组成,描述了数据质量控制、模糊度固定以及最小二乘参数估计方法的原理和公式,给出了单频接收机数据处理算法的实现流程,在此基础上参与了GNSS单频数据处理软件研制,并结合大量算例验证了新方法和软件的解算能力和精度水平,特别是对未来将基于非差改正数的网络RTK方法应用于PPP模式实时精密定位的应用前景进行了有效的模拟分析。更多还原

【Abstract】 Since the development of Global Navigation Satellite System (GNSS), it has been widely applied in many fields, such as satellite navigation, surveying and positioning, deformation monitoring, together with atmospheric detection, thanks to its global coverage, all-weather, high precision and efficiency as well as strong security.At present, dual-frequency receivers have been commonly used in GNSS precise navigation and positioning mainly to eliminate the ionospheric error. When carrying out researches on regional deformation monitoring and atmospheric probing based on GNSS technology, massive GNSS receivers have to be laid out in order to collect information with high spatial and temporal resolution. Under this circumstance, using GNSS dual-frequency receivers for all stations would no doubt be expensive, which will definitely limit the future development and application of GNSS technology greatly in these fields. Because of this, how to eliminate the ionospheric error and realize high-precision positioning using relatively cheaper single-frequency receivers in a wide area has become one of the research hot spot in the present satellite geodesy at home and abroad. In addition, how to realize the unification of existing GNSS technology that:the unification of PPP and network RTK technology, the unification of regional and global data-processing, the unification of single-and dual-frequency data-processing strategy are also the currently difficult problems to be solved. This dissertation paper focuses on investigating and solving the problems, mainly include performing in-depth research on the method of precise positioning using single frequency receivers, breaking through its key technologies, promoting the unification of existing GNSS technology and developing practical software for real application.Firstly, thorough investigations have been done on various kinds of model construction method for current regional error correction. Some improvement has been made to the Satellite-specific Epoch-differenced Ionospheric Delay model (SEID), which then has been applied successfully in the GNSS precise positioning using single-frequency receivers for large-scale reference network, yielding very good results. Secondly, the author has proposed a new network RTK approach based on undifferenced observation corrections. Although both methods could be used effectively in various GNSS single-frequency precise positioning services for post processing, real time or near real time applications, this new network RTK approach based on undifferenced observation corrections exhibits more general characteristics, which is a unification of various regional error fusion technologies. Integrating with advantages of PPP and network RTK, this new method realizes a technological unification and seamless joint service between global PPP and regional RTK by using the existing various kinds of satellite orbit and clock error products. Users inside and outside network could obtain precise positioning service with different accuracy requirements under the same data processing mode (that is PPP mode). Those who could receive regional error correction information inside the network would achieve rapid precise positioning results equivalent with network RTK, while others who haven’t receive error correction from this region or outside the network would achieve PPP positioning accuracy.Finally, based on the existing PANDA software and the above methods, this paper has realized an epoch by epoch processing function for single-frequency data by using fortran programming language, and carried out effective simulation analysis towards the future prospect of this new network RTK approach based on undifferenced observation corrections to be used in real time PPP-mode precise positioning application. Main contributions and innovative achievements of this dissertation paper include:1) Current status of GNSS precise positioning at home and abroad has been thoroughly reviewed from aspects of GNSS mathematical model, error correction technology, precise positioning method as well as software development. Aiming at the key contents of this paper, deep discussion and summarization have been made on the GNSS precise positioning using single-frequency receivers together with model construction for regional error correction;2) Detailed investigation has been done on the theory of GNSS precise positioning, including various spatial-temporal frames involved in precise positioning and their transformation, observation equation and error correction, as well as least square parameter estimation algorithm;3) Various regional error correction model construction methods have been illustrated and analyzed systematically, which could be demonstrated as a comprehensive summary towards this kind of technology;4) Theoretical consistency between network RTK and the HiRIM method has been proved, pointing out that there is only little difference in concrete implementation between them. This paper has conducted theoretical description for network RTK and the HiRIM method, and focused on the comparison of their error correction effects. The equivalence and difference between these two kinds of method have been demonstrated clearly. Then some beneficial conclusions have been drawn;5) The SEID method has been developed, and a complete set of data processing strategy for GNSS precise positioning using single-frequency receivers has been proposed. As for the reference network ranging smaller than 90km, its daily static measuring accuracy could almost achieve the precision obtained by dual-frequency data based on the SEID method by only using single-frequency data inside the network, which could satisfy the requirement of mm-level daily static precise positioning at the vertical component for single-frequency receivers;6) A new network RTK approach based on undifferenced observation corrections has been put forward in this paper, which exhibits a unification of the current regional error fusion technologies, and belongs to a more general model construction method. By effectively eliminating the influences of ionospheric delay, tropospheric delay, receiver hardware delay, as well as satellite orbit and clock error, this method realizes a technological unification and seamless joint service between global PPP and regional RTK;7) Mathematical models for epoch-differenced ionospheric delay correction and network RTK approach based on undifferenced observation corrections have been rigorously deduced. Two sets of software for regional error correction model construction have been developed; 8) Module composition for GNSS single-frequency data processing software has been investigated. Principle and formula for data quality control, ambiguity resolution, as well as least square parameter estimation method has been illustrated. Also the realization flow for data processing algorithm from single-frequency receivers has been given in this paper. Under these backgrounds, the author has participated in the development of GNSS single-frequency data processing software, verified the resolving ability and precision level of the new method as well as the software by using massive numerical examples, and in particular carried out effective simulation analysis towards the future prospect of this network RTK approach based on undifferenced observation corrections to be used in real time PPP-mode precise positioning application.更多还原