GNSS and Global Geodesy

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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.