User-Level Reliability and Quality Monitoring in Satellite-Based Personal Navigation

Abstract

Although high sensitivity receiver technology is necessary to ensure sufficient observation availability of satellite navigation in degraded signal environments, processing of high sensitivity data observed in deteriorated line-of-sight conditions is susceptible to production of inordinately inaccurate navigation observations. Thus, monitoring the reliability and the quality of the obtained user navigation solution is essential when using a satellite navigation system, such as the Global Positioning System (GPS) or the anticipated European Galileo system in poor signal conditions.This thesis assesses reliability testing and quality control procedures at the user level in Global Navigation Satellite Systems (GNSS) with the aim of enhancing accuracy and reliability in poor signal conditions with failure detection and exclusion techniques. Reliability testing, in the form of Receiver Autonomous Integrity Monitoring (RAIM) and Fault Detection and Exclusion (FDE), traditionally rely on statistical tests in order to isolate one erroneous measurement from position estimation. This thesis takes a slightly wider point of view of the quality monitoring problem of both user position and velocity; observation weighting, navigation geometry and accuracy estimation aspects, and statistical reliability theory with applications to personal satellite navigation are also assessed. The principal focus of this thesis involves the development and analysis of different FDE schemes based on recursive statistical testing, particularly in challenging signal environments. The operating environment is therefore different from traditional safety-critical navigation, where the usual problem is the failure of only one satellite, and where the error is not necessarily due to obstructions in the propagation path, as is typically the case in urban areas.Through the application of the FDE and quality control methods developed herein to high sensitivity GPS and simulated GPS/Galileo data, it has been demonstrated that reliability and quality monitoring yield a significant improvement in accuracy and are essential in enhancing the reliability of user navigation solutions.