PhD Thesis Defense: A geodetic approach to precise, accurate, available and reliable navigation
In the cotext of this PhD Thesis defense, M. Eulàlia Parés presents her work realized at CTTC.
The determination of a body position, velocity and attitude is the purpose of the navigation techniques. The most extended navigation systems (INS/GNSS), as any other HW and SW system, provide precise and accurate enough trajectory determinations under the appropriate conditions. However, when those systems acquire data on non-friendly environments the computed navigation solution suffers from unacceptable errors. Since the foundation of the Geodesy and Navigation group of the former Institute of Geomatics, now at CTTC, its researchers have to deal with three fundamental issues: solution performance (precision-accuracy), specially for low-cost systems, reliability and environmentally independent availability.
The main objective of the research presented on this dissertation is to contribute to the adoption of the geodetic method for navigation. The geodetic method is based on a proper problem abstraction, on optimal estimation criteria, on rigorous mathematical modelling, on the use of sufficiently redundant data and on the use of sufficiently heterogeneous data. Since rigorous modelling, redundancy and heterogeneous data have been widely used by the navigation community, this thesis focus on a proper problem abstraction as well as on an optimal estimation criteria.
The first step to prove the geodetic approach suitability has been to design, implement and validate the GEMMA system. The GEMMA system is a set of SW modules allowing the validation of new trajectory determination algorithms. The system is made up of measurement generators, filters and analysers, as well as trajectory generators and analysers and, as its main component, a generic platform for the optimal determination of trajectories (NAVEGA). The main purpose of the signal and trajectory generators and lters is to provide data to test and validate new navigation algorithms. Signal and trajectory analysers are used to characterize the error of data sets. NAVEGA is a software platform for the optimal determination of trajectories or paths of stochastic dynamical systems driven by observations and their associated dynamic or static models. The second step has been the design of a new optimal estimation algorithm that maximise the benefits of redundant systems. Redundancy in the number of available satellites but also redundancy in the number of sensors. The availability of several sensors allows reducing the noise and detecting possible outliers. In this thesis, a new bayesian filter implementation, named Simultaneous Prediction and Filtering (SiPF), providing access to the residuals of redundant measurements is presented. This approach allows to apply all the quality determination geodetic techniques to the navigation solution determination.
The benefits of the previous tools, together with the extended acceptance of the benefit of redundancy, rigorous modelling and heterogeneity lead us to conclude that the geodetic approach is a suitable way to face the navigation problem and to improve its performance, its availability and its reliability.