GNSS and Global Geodesy

研究计划由三个相互交织的项目组成，受益于我们早期的发展，涵盖了大地测量学的物理和几何方面。******第一个研究项目涉及全球高度系统的基本主题。目前正在努力建立一个位势水平的全球高度系统，即大地水准面，并建立全球高度系统与国家高度系统之间的关系。各国要么使用正交高度，要么使用标准高度。前者与物理表面（大地水准面）有关，而后者与近似的准大地水准面有关。根据Helmert的公式计算正交高度。我们已经开发了一个更严格的公式，严格的正交高度。该项目需要在全球范围内调查地形密度变化对重力和高度的影响，确定全球范围内严格和Helmert的正交高度与正常高度之间的关系，同时考虑到空间变化和精度。设计并实现了一个计算包，以简化严格的正交高度计算，并将这三种常见的高度类型相互转换以用于实际目的。******第二个研究项目涉及使用大地测量学研究气候。其最终目标是为气候界提供一种鲁棒可靠的算法，该算法可用于中性大气参数时间序列在用于气候分析之前的均匀化。这些参数可由全球导航卫星系统观测或数值天气预报模式（NWM）产生。该项目需要在GNSS处理过程中设计、实施和评估光线追踪，通过误差传播对光线追踪操作过程中的不确定性进行全面评估，设计和测试用于中性大气时间序列质量控制的组合算法，以及设计、测试和验证用于GNSS和NWM衍生的中性大气参数均质化的算法，以便向气候界提供。******第三个项目评估实时GNSS精确点定位（PPP）的使用和能力及其在车辆导航中的应用。提出了自主导航中协同定位和车道保持的概念。它增强了地图匹配的概念，并探索了使用Wi-Fi来补充定位中断。它需要优化集成卡尔曼滤波器，该滤波器集成了实时PPP定位、Wi-Fi、惯性和来自地图数据库的信息，对Wi-Fi进行评估以补充定位中断，并评估与实际场景中PPP所需的实时数据流接收相关的问题。

The research program is composed by three interlaced projects, benefiting from earlier developments we have made, covering physical and geometrical aspects of Geodesy. ******The first research project deals with the very fundamental subject of global heights system. There is an effort for establishing a global height system at the geopotential level, the geoid, and to establish relationships between the global height system and national ones. Countries use either orthometric or normal heights. The former relates to a physical surface (geoid) whereas the latter to a close approximation, the quasi-geoid. Orthometric heights are computed based on Helmert's formulation. We have developed a more rigorous formulation, the rigorous orthometric heights. The project entails the investigation of the effect of topo-density variation on gravity and heights on global scale, the determination of relationships between rigorous and Helmert's orthometric heights with normal heights, on a global scale, taking into consideration spatial variations and accuracy, the design and implementation a computational package to simplify the computation of rigorous orthometric height and to convert these three common types of heights to each other to be used for practical purposes. ******The second research project deals with the use of Geodesy for climate. Its final objective is to provide the climate community with a robust and reliable algorithm that can be used in the homogenization of neutral-atmospheric parameters time series before their use in climate analysis. The parameters can be generated from GNSS observations or from numerical weather prediction models (NWM). The project entails the designing, implementation and assessment of ray-tracing inside the GNSS processing, a full evaluation of uncertainties during the ray tracing operation via error propagation, the design and test of combination algorithms for quality control of neutral-atmospheric time series, and the design, test and validation of algorithm for homogenization of GNSS- and NWM- derived neutral-atmospheric parameters to be made available to the climate community. ******The third project assesses the use and capabilities of real-time GNSS precise point positioning (PPP) and its application in vehicle navigation. It advances the concept of cooperative positioning and lane-keeping for autonomous navigation. It enhances the concept of map-matching and explores the use of Wi-Fi to complement positioning outages. It entails the optimization of the integration Kalman Filter that integrates real-time PPP positioning, Wi-Fi, inertial and information from the map database, assessment of Wi-Fi to complement positioning outages and assess problems associated with reception of the real-time data stream necessary for PPP in a real scenario.