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

High sensitivity receiver technology is necessary to ensure sufficient observation availability of satellite navigation in degraded signal environments. However, high sensitivity processing in the deteriorated line-of-sight conditions is susceptible to bringing about severely erroneous navigation observations. Therefore, when using a satellite navigation system, such as the Global Positioning System (GPS) or the future European Galileo in poor signal conditions, monitoring the reliability and the quality of the obtained user navigation solution is of great importance. 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, namely 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. In this thesis, a slightly wider point of view is taken to the quality monitoring problem of both user position and velocity, and observation weighting, navigation geometry and accuracy estimation aspects, and statistical reliability theory with applications to personal satellite navigation are assessed. The principal focus of this thesis includes developing and analyzing different FDE schemes based on recursive statistical testing intended for challenging signal environments. The operating environment for the monitoring functions 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 the case in urban areas. The results of applying the developed FDE and quality control methods to highsensitivity GPS data from indoor and urban tests and simulated GPS/Galileo data demonstrate that reliability and quality monitoring yield a significant improvement in accuracy and are essential in enhancing the user navigation solution reliability.